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Chernobyl disaster
Chernobyl Disaster.jpg
The nuclear reactor after the disaster. Reactor 4 (center). Turbine building (lower left). Reactor 3 (center right).
Date 26 April 1986 (1986-04-26)
Time 01:21 a.m. (UTC+3)
Location Pripyat, Soviet Union, now Ukraine
Casualties
56 direct deaths
800,000 (est) suffered radiation exposure, which may result in as many as 4,000 cancer deaths over the lifetime of those exposed, in addition to the approximately 100,000 fatal cancers to be expected from all other causes in this population.[1]
The abandoned city of Pripyat with Chernobyl plant in the distance.
Radio-operated bulldozers being tested prior to use.
Abandoned housing blocks in Pripyat.

The Chernobyl disaster, also alternatively spelled Chornobyl disaster, was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the Ukrainian Soviet Socialist Republic (then part of the Soviet Union), now in Ukraine.

It is considered to be the worst nuclear power plant disaster in history and the only level 7 event on the International Nuclear Event Scale. It resulted in a severe release of radioactivity following a massive power excursion that destroyed the reactor. Most fatalities from the accident were caused by radiation poisoning.

On April 26, 1986 at 01:23 a.m. (UTC+3), reactor number four at the Chernobyl plant, near Pripyat in the Ukrainian Soviet Socialist Republic, had a fatal meltdown. Further explosions and the resulting fire sent a plume of highly radioactive fallout into the atmosphere and over an extensive geographical area, including the nearby town of Pripyat. Four hundred times more fallout was released than had been by the atomic bombing of Hiroshima.[2]

The plume drifted over large parts of the western Soviet Union, Eastern Europe, Western Europe, and Northern Europe. Rain contaminated with radioactive material fell as far away as Ireland. Large areas in Ukraine, Belarus, and Russia were badly contaminated, resulting in the evacuation and resettlement of over 336,000 people. According to official post-Soviet data,[3] about 60% of the radioactive fallout landed in Belarus.

The accident raised concerns about the safety of the Soviet nuclear power industry as well as nuclear power in general, slowing its expansion for a number of years while forcing the Soviet government to become less secretive.[4]

The countries of Russia, Ukraine, and Belarus have been burdened with the continuing and substantial decontamination and health care costs of the Chernobyl accident. It is difficult to accurately quantify the number of deaths caused by the events at Chernobyl, as over time it becomes harder to determine whether a death has been caused by exposure to radiation.

The 2005 report prepared by the Chernobyl Forum, led by the International Atomic Energy Agency (IAEA) and World Health Organization (WHO), attributed 56 direct deaths (47 accident workers and nine children with thyroid cancer) and estimated that there may be 4,000 (questioned, could be higher) extra cancer deaths among the approximately 600,000 most highly exposed people.[1] Although the Chernobyl Exclusion Zone and certain limited areas remain off limits, the majority of affected areas are now considered safe for settlement and economic activity.[5]

Contents

Chernobyl nuclear power plant

Location of the Chernobyl Nuclear Power Plant.

The Chernobyl station is near the town of Pripyat, Ukraine, 18 km (11 mi) northwest of the city of Chernobyl, 16 km (10 mi) from the border of Ukraine and Belarus and about 110 km (68 mi) north of Kiev. The station consisted of four RBMK-1000 nuclear reactors, each capable of producing 1 gigawatt (GW) of electric power, and the four together produced about 10% of Ukraine's electricity at the time of the accident.[6] Construction of the plant began in the late 1970s, with reactor no. 1 commissioned in 1977, followed by no. 2 (1978), no. 3 (1981), and no. 4 (1983). Two more reactors, no. 5 and 6, also capable of producing 1 GW each, were under construction at the time of the disaster.

Reactor design and behavior

RBMK reactor structure
RBMK power plant schematics
Reactor control rod positions at the moment of the explosion; blue=neutron sources (12), yellow=shortened control rods from the reactor bottom (32), grey=pressure tubes (1661), green=control rods (167), red=automatic control rods (12)

The reactor is a cylindrical concrete-lined vessel with core composed of vertically stacked graphite blocks, with zircaloy pressure tubes through their centers. A 350 kg block is located on top of each fuel channel, giving the top of the reactor its characteristic tiled appearance. The blocks and the pressure tubes are affixed to a massive circular complete block, the Upper Biological Shield. Above the reactor top, a gantry crane where the refueling machinery is located; the reactor design allows refueling during on-line, without need to shut down the reactor. The bottom side of the reactor is covered by the Lower Biological Shield. The reactor core is 7 meters high and 11.8 meters in diameter. Partly due to the large size of the reactor, the reactivity of different portions of the core is only loosely coupled and the regulation of spatial power distribution is crucial; the reactor may behave like several semi-independent reactors, especially if there is a non-uniform buildup of nuclear poisons (especially xenon-135) in different parts of the core, which occurs at low power levels when the neutron flux is insufficient to burn the Xe-135. Just before the disaster, the upper and lower part of the core were behaving fairly independently, separated by a heavily xenon-poisoned central region. The possibility of destructive local reactivity feedback had already been demonstrated during the partial core meltdown of the Unit 1 RBMK1000 reactor in the Leningrad Nuclear Power Plant in 1975. The Leningrad plant is of a similar design to the Chernobyl one.[7]

Reactor vessel, moderator and shielding

The reactor pit is made of reinforced concrete and has dimensions 21.6×21.6×25.5 meters. It houses the vessel of the reactor, made of a cylindrical wall and top and bottom metal plates. The vessel contains the graphite stack and is filled with a helium-nitrogen mixture for providing an inert atmosphere for the graphite and for mediation of heat transfer from the graphite to the coolant channels.

The moderator blocks are made of nuclear graphite of dimensions 250×250×500 mm. There are holes with 114 mm diameter through the longitudal axis of the blocks for the fuel and control channels. The blocks are stacked inside the reactor vessel into a cylindrical core 14 m in diameter and 8 m high.[8] The maximum allowed temperature of the graphite is less or equal to 730 °C.[9]

The reactor vessel is a steel cylinder (Schema KZh) with outer diameter of 14.52 m, wall thickness 16 mm, height 9.75 m, and is equipped with a bellows compensator to absorb axial thermal expansion loads.

The moderator is surrounded by a cylindrical water tank (Schema L), a welded structure with 30 mm thick walls, inner diameter of 16.6 m and outer diameter of 19 m, internally divided to 16 vertical compartments. The water is supplied to the compartments from the bottom and removed from the top; the water can be used for emergency reactor cooling. The tank contains thermocouples for sensing the water temperature and ion chambers for monitoring the reactor power.[10] The tank, sand layer, and concrete of the reactor pit serve as additional biological shields.

The top of the reactor is covered by the Upper Biological Shield, also called Schema E, Pyatachok, or, after the explosion, Elena, a 3 m thick cylinder 17 m in diameter. It is penetrated by standpipes for fuel and control channel assemblies. The top and bottom are covered with 40 mm thick steel plates, welded to be helium-tight, and additionally joined by structural supports. The space between the plates and pipes is filled with serpentinite, a rock containing significant amount of bound water. The disk is supported on 16 rollers, located on the upper side of the reinforced cylindrical water tank. The structure of the UBS supports the fuel and control channels, the floor above the reactor in the central hall, and the steam-water pipes.[10][11]

Below the bottom of the reactor core there is the Lower Biological Shield (Schema OR), similar to the UBS, but only 14.5 m in diameter and 2 m thick. It is penetrated by the tubes for the lower ends of the pressure channels and carries the weight of the graphite stack and the coolant inlet piping. A steel structure, two heavy plates intersecting in right angle under the center of the LBS and welded to the LBS, supports the LBS and transfers the mechanical load to the building.[11]

Above the UBS there is the upper shield cover; its top surface is the floor of the central hall. It serves as part of the biological shield and for thermal insulation of the reactor space. Its center area above the reactor channel consists of individual removable steel-graphite plugs, located over the tops of the channels.[11]

Pressure channels

The fuel channels consist of welded zircaloy pressure tubes 80 mm in inner diameter with 4 mm thick walls, led through the channels in the center of the graphite moderator blocks. The top and bottom parts of the tubes are made of stainless steel, and joined with the central zircaloy segment with zirconium-steel alloy couplings. The pressure tube is held in the graphite stack channels with two alternating types of 20 mm high split graphite rings; one is in direct contact with the tube and has 1.5 mm clearance to the graphite stack, the other one is directly touching the graphite stack and has 1.3 mm clearance to the tube; this assembly reduces transfer of mechanical loads caused by neutron-induced swelling, thermal expansion of the blocks, and other factors to the pressure tube, while facilitating heat transfer from the graphite blocks. The tubes are welded to the top and bottom metal plates of the reactor vessel.[11]

It is estimated that about 5.5% of the core thermal power is in the form of graphite heat. About 80-85% of this heat is removed by the fuel rod coolant channels, via the graphite rings. The rest of the heat is removed by the control rod channel coolant. The gas circulating in the reactor plays role of assisting the heat transfer to the coolant channels; itself plays almost no role in heat removal.

There are 1661 fuel channels and 211 control rod channels in the reactor core.

The fuel assembly is suspended in the fuel channel on a bracket, with a seal plug. The seal plug has a simple design, to facilitate its removal and installation by the remotely controlled refueling machine.

The fuel channels may instead of fuel contain fixed neutron absorbers, or be empty and just filled with the cooling water.

The small clearance between the pressure channel and the graphite block makes the graphite core susceptible to damage. If the pressure channel deforms, e.g. by too high internal pressure, the deformation or rupture can cause significant pressure loads to the graphite blocks and lead to their damage, and possibly propagate to neighboring channels.

Fuel

RBMK reactor fuel rod holder 1 - distancing armature; 2 - fuel rods shell; 3 - fuel tablets.

The fuel pellets are made of uranium dioxide powder, sintered with a suitable binder into barrels 11.5 mm diameter and 15 mm long. The material may contain added europium oxide as a burnable nuclear poison to lower the reactivity differences between a new and partially spent fuel assembly.[12] To reduce thermal expansion issues and interaction with the cladding, the pellets have hemispherical indentations. A 2 mm hole through the axis of the pellet serves to reduce the temperature in the center of the pellet and facilitates removal of gaseous fission products. The enrichment level is 2% (0.4% for the end pellets of the assemblies). Maximum allowable temperature of the fuel pellet is 2100 °C.

The fuel rods are zircaloy (1% Nb) tubes 13.6 mm in outer diameter, 0.825 mm thick. The rods are filled with helium at 0.5 MPa and hermetically sealed. Retaining rings help to seat the pellets in the center of the tube and facilitate heat transfer from the pellet to the tube. The pellets are axially held in place by a spring. Each rod contains 3.5 kg of fuel pellets. The fuel rods are 3.64 m long, with 3.4 m of that being the active length. The maximum allowed temperature of a fuel rod is 600 °C.[13]

The fuel assemblies consist of two sets of 18 fuel rods. The rods are arranged along the central carrier rod (13 mm outer diameter) and held in place with 10 stainless steel spacers separated by 360 mm distance. The two sub-assemblies are joined with a cylinder at the center of the assembly; during the operation of the reactor, this dead space without fuel lowers the neutron flux in the central plane of the reactor. The total mass of uranium in the fuel assembly is 114.7 kg. The fuel burnup is 20 MW·d/kg. The total length of the fuel assembly is 10.025 m, with 6.862 m of the active region.

In addition to the regular fuel assemblies, there are instrumented ones, containing neutron flux detectors in the central carrier. In this case, the rod is replaced with a tube with wall thickness of 2.5 mm; and outer diameter of 15 mm.[14]

Unlike the rectangular PWR/BWR fuel assemblies, the RBMK fuel assembly is cylindrical to fit the round pressure channels.

The refueling machine is mounted on a gantry crane and remotely controlled. The fuel assemblies can be replaced without shutting down the reactor, a factor significant for production of weapon-grade plutonium and, in a civilian context, for better reactor uptime. When a fuel assembly has to be replaced, the machine is positioned above the fuel channel, mates to it, equalizes pressure within, pulls the rod, and inserts a fresh one. The spent rod is then placed in a cooling pond. The capacity of the refueling machine with the reactor at nominal power level is two fuel assemblies per day, with peak capacity of five per day.

Control rods

Most of the reactor control rods are inserted from above; 24 shortened rods are inserted from below and are used to augment the axial power distribution control of the core. With the exception of 12 automatic rods, the control rods have a 4.5 meters long graphite section at the end, separated by a 1.25 meters long telescope (which creates a water-filled space between the graphite and the absorber), and a boron carbide neutron absorber section. The role of the graphite section, known as "displacer," is to enhance the difference between the neutron flux attenuation levels of inserted and retracted rods, as the graphite displaces water that would otherwise act as a neutron absorber, although much weaker than boron carbide; a control rod channel filled with graphite absorbs fewer neutrons than when filled with water, so the difference between inserted and retracted control rod is increased. When the control rod is fully retracted, the graphite displacer is located in the middle of the core height, with 1.25 meters of water at its each end. The displacement of water in the lower 1.25 meters of the core as the rod moves down causes a local increase of reactivity in the bottom of the core as the graphite part of the control rod passes that section. This "positive scram" effect was discovered in 1983 at the Ignalina Nuclear Power Plant; however, the matter was soon forgotten. The control rod channels are cooled by an independent water circuit and kept at 40-70 °C. The narrow space between the rod and its channel hinders water flow around the rods during their movement and acts as a fluid damper, which is the primary cause of their slow insertion time (nominally 18–21 seconds for the RCPS rods, or about 0.4 m/s). After the disaster, the control rod servos on other RBMK reactors were exchanged to allow faster rod movements, and even faster movement was achieved by cooling of the control rod tubes by a thin layer of water while letting the rods themselves move in gas.

The division of the control rods between manual and emergency protection groups was arbitrary; the rods could be reassigned from one system to another during reactor operation without technical or organizational problems.

Additional static boron-based absorbers are inserted into the core when it is loaded with fresh fuel. About 240 absorbers are added during initial core loading. These absorbers are gradually removed with increasing burnup. The reactor's void coefficient depends on the core content; it ranges from negative with all the initial absorbers to positive when they are all removed.

The normal reactivity margin is 43-48 control rods.

Gas circuit

The reactor operates in a helium-nitrogen atmosphere (70-90% He, 10-30% N2).[13] The gas circuit is composed of a compressor, aerosol and iodine filters, adsorber for carbon dioxide, carbon monoxide, and ammonia, a holding tank for allowing the gaseous radioactive products to decay before being discharged, an aerosol filter to remove solid decay products, and a ventilator stack, the iconic chimney above the plant building.[15] The gas is injected to the stack from the bottom in a low flow rate, and exits from the standpipe of each channel via an individual pipe. The moisture and temperature of the outlet gas is monitored; an increase of them is an indicator of a coolant leak.[9]

Cooling and steam circuits

The reactor has two independent cooling circuits, each having four main circulating pumps (three operating, one standby). The cooling water is fed to the reactor through lower water lines to a common pressure header (one for each cooling circuit), which is split to 22 group distribution headers, each feeding 38-41 pressure channels through the core, where the feedwater boils. The mixture of steam and water is led by the upper steam lines, one for each pressure channel, from the reactor top to the steam separators, pairs of thick horizontal drums located in side compartments above the reactor top; each has 2800 mm diameter, 31 m length, wall thickness of 100 mm, and weighs 240 t.[8] Steam, with steam quality of about 15%, is taken from the top of the separators by two steam collectors per separator, combined, and led to two turbogenerators in the turbine hall, then to condensers, reheated to 165 °C, and pumped by the condensate pumps to deaerators, where remains of gaseous phase and corrosion-inducing gases are removed. The resulting feedwater is led to the steam separators by feedwater pumps and mixed with water from them at their outlets. From the bottom of the steam separators, the feedwater is led by 12 downpipes (from each separator) to the suction headers of the main circulation pumps, and back into the reactor.[16] There is an ion exchange system included in the loop to remove impurities from the feedwater.

The turbine consists of one high-pressure rotor and four low-pressure ones. Five low-pressure separators-preheaters are used to heat steam with fresh steam before being fed to the next stage of the turbine. The uncondensed steam is fed into a condenser, mixed with condensate from the separators, fed by the first-stage condensate pump to a chemical purifier, then by a second-stage condensate pump to four deaerators where dissolved and entrained gases are removed; deaerators also serve as storage tanks for feedwater. From the deaerators the water is pumped through filters and into the bottom parts of the steam separator drums.[17]

The main circulating pumps have the capacity of 5,500–12,000 m3/h and are powered by 6 kV electric motors. The normal coolant flow is 8000 m3/hour per pump; this is throttled down by control valves to 6000-7000 m3/h when the reactor power is below 500 MWt. Each pump has a flow control valve and a backflow preventing check valve on the outlet, and shutoff valves on both inlet and outlet. Each of the pressure channels in the core has its own flow control valve so that the temperature distribution in the reactor core can be optimized. Each channel has a ball type flow meter.

The nominal coolant flow through the reactor is 46,000-48,000 m3/h. The steam flow at full power is 5440-5600 t/h.[9]

The nominal temperature of the cooling water at the inlet of the reactor is about 265-270 °C and the outlet temperature 284 °C, at pressure of 6.9 MPa (in the drum separator).[9] The pressure and the inlet temperature determine the height at which the boiling begins in the reactor; if the coolant temperature is not sufficiently below its boiling point at the system pressure, the boiling starts at the very bottom part of the reactor instead of its higher parts; the positive void coefficient of the reactor makes the reactor very sensitive to the feedwater temperature. If the coolant temperature is too close to its boiling point, cavitation can occur in the pumps and their operation can become erratic or even stop entirely. The feedwater temperature is dependent on the steam production; the steam phase portion is led to the turbines and condensers and returns significantly cooler (155-165 °C) than the water returning directly from the steam separator (284 °C). At low reactor power, therefore, the inlet temperature may become dangerously high. The water is kept below the saturation temperature to prevent film boiling and the associated drop in heat transfer rate.[8]

The reactor is tripped in case of too high or low water level in the steam separators (with two selectable low-level thresholds), high steam pressure, low feedwater flow, or loss of two main coolant pumps on either side. These trips can be manually disabled.[10]

The level of water in the steam separators, the percentage of steam in the reactor pressure tubes, the level at which the water begins to boil in the reactor core, the neutron flux and power distribution in the reactor, and the feedwater flow through the core have to be carefully controlled. The level of water in the steam separator is mainly controlled by the feedwater supply, with the deaerator tanks serving as a water reservoir.

The maximum allowed heat-up rate of the reactor and the coolant is 10 °C/hour; the maximum cool-down rate is 30 °C/hour.[9]

ECCS

The reactor is equipped with an emergency core cooling system (ECCS), consisting of dedicated water reserve tank, hydraulic accumulators, and pumps. ECCS piping is integrated with the normal reactor cooling system. In case of total loss of power, the ECCS pumps are supposed to be powered by the rotational momentum of the turbogenerator rotor for the time before the diesel generators come online. The ECCS has three systems, connected to the coolant system headers. In case of damage, the first ECCS subsystem provides cooling for up to 100 seconds to the damaged half of the coolant circuit (the other half is cooled by the main circulation pumps), and the other two subsystems then handle long-term cooling of the reactor.[10]

The short-term ECCS subsystem consists of two groups of six accumulator tanks, containing water blanketed with nitrogen under pressure of 10 MPa, connected by fast-acting valves to the reactor. Each group can supply 50% of the maximum coolant flow to the damaged half of the reactor. The third group is a set of electrical pumps drawing water from the deaerators. The short-term pumps can be powered by the spindown of the main turbogenerators.[10]

ECCS for long-term cooling of the damaged circuit consists of three pairs of electrical pumps, drawing water from the pressure suppression pools; the water is cooled by the plant service water by means of heat exchangers in the suction lines. Each pair is able to supply half of the maximum coolant flow. ECCS for long-term cooling of the intact circuit consists of three separate pumps drawing water from the condensate storage tanks, each able to supply half of the maximum flow. The ECCS pumps are powered from the essential internal 6 kV lines, backed up by diesel generators. Some valves that require uninterrupted power are also backed up by batteries.[10]

Reactor control/supervision systems

The distribution of power density in the reactor is measured by ionization chambers located inside and outside the core. The physical power density distribution control system (PPDDCS) has sensors inside the core; the reactor control and protection system (RCPS) uses sensors in the core and in the lateral biological shield tank. The external sensors in the tank are located around the reactor middle plane, therefore do not indicate axial power distribution nor information about the power in the central part of the core. There are over 100 radial and 12 axial power distribution monitors, employing self-powered detectors. Reactivity meters and removable startup chambers are used for monitoring of reactor startup. Total reactor power is recorded as the sum of the currents of the lateral ionization chambers. The moisture and temperature of the gas circulating in the channels is monitored by the pressure tube integrity monitoring system.

The PPDCSS and RCPS are supposed to complement each other. The RCPS system consists of 211 movable control rods. Both systems, however, have deficiencies, most noticeably at low reactor power levels. The PPDDCS is designed to maintain reactor power density distribution between 10 and 120% of nominal levels and to control the total reactor power between 5 and 120% of nominal levels. The LAC-LAP (local automatic control and local automatic protection) RPCS subsystems rely on ionization chambers inside the reactor and are active at power levels above 10%. Below those levels, the automatic systems are disabled and the in-core sensors are not accessible. Without the automatic systems and relying only on the lateral ionization chambers, control of the reactor becomes very difficult; the operators do not have sufficient data to control the reactor reliably and have to rely on their intuition. During startup of a reactor with a poison-free core this lack of information can be manageable because the reactor behaves predictably, but a non-uniformly poisoned core can cause large nonhomogenities of power distribution, with potentially catastrophic results.

The reactor emergency protection system (EPS) was designed to shut down the reactor when its operational parameters are exceeded. The design accounted for steam collapse in the core when the fuel element temperature falls below 265 °C, coolant vaporization in fuel channels in cold reactor state, and sticking of some emergency protection rods. However, the slow insertion speed of the control rods, together with their design causing localized positive reactivity as the displacer moves through the lower part of the core, created a number of possible situations where initiation of the EPS could itself cause or aggravate a reactor runaway.

The computer system for calculation of the reactivity margin was collecting data from about 4000 sources. Its purpose was to assist the operator with steady-state control of the reactor. 10–15 minutes were required to cycle through all the measurements and calculate the results.

The operators could disable some safety systems, reset or suppress some alarm signals, and bypass automatic scram, by attaching patch cables to accessible terminals. This practice was allowed under some circumstances.

The reactor is equipped with a fuel rod leak detector. A scintillation counter detector, sensitive to energies of short-lived fission products, is mounted on a special dolly and moved over the outlets of the fuel channels, issuing an alert if increased radioactivity is detected in the steam-water flow.

Containment

The bottom part of the reactor is enclosed in a leaktight compartment. There is a space between the reactor bottom and the floor. The reactor cavity overpressure protection system consists of steam relief assemblies embedded in the floor and leading to Steam Distributor Headers covered with rupture discs and opening into the Steam Distribution Corridor below the reactor, on level +6. The floor of the corridor contains entrances of a large number of vertical pipes, leading to to the bottoms of the Pressure Suppression Pools ("bubbler" pools) located on levels +3 and +0. In the event of an accident, which was predicted to be at most a rupture of one or two pressure channels, the steam was to be bubbled through the water and condensed there, reducing the overpressure in the leaktight compartment. The flow capacity of the pipes to the pools limited the protection capacity to simultaneous rupture of two pressure channels; a higher number of failures would cause pressure buildup sufficient to lift the cover plate ("Structure E," after the explosion nicknamed "Elena"), sever the rest of the fuel channels, destroy the control rod insertion system, and potentially also withdraw control rods from the core.[18] The containment was designed to handle failures of the downcomers, pumps, and distribution and inlet of the feedwater. The leaktight compartments around the pumps can withstand overpressure of 0.45 MPa. The distribution headers and inlets enclosures can handle 0.08 MPa and are vented via check valves to the leaktight compartment. The reactor cavity can handle overpressure of 0.18 MPa and is vented via check valves to the leaktight compartment. The pressure suppression system can handle a failure of one reactor channel, a pump pressure header, or a distribution header. Leaks in the steam piping and separators are not handled, except for maintaining slightly lower pressure in the riser pipe gallery and the steam drum compartment than in the reactor hall. These spaces are also not designed to withstand overpressure. The steam distribution corridor contains surface condensers. The sprinkler systems, operating during both accident and normal operation, are fed from the pressure suppression pools through heat exchangers cooled by the plant service water, and cool the air above the pools. Jet coolers are located in the topmost parts of the compartments; their role is to cool the air and remove the steam and radioactive aerosol particles.[10]

Hydrogen removal from the leaktight compartment is performed by removal of 800 m3/hour of air, its filtration, and discharge into the atmosphere. The air removal is stopped automatically in case of a coolant leak and has to be reinstated manually. Hydrogen is present during normal operation due to leaks of coolant (assumed to be up to 2 tons/hour).[10]

Electrical systems

The power plant is connected to the 330 kV and 750 kV electrical grid. The block has two electrical generators connected to the 750 kV grid by a single generator transformer. The generators are connected to their common transformer by two switches in series. Between them, the unit transformers are connected to supply power to the power plant's own systems; each generator can therefore be connected to the unit transformer to power the plant, or to the unit transformer and the generator transformer to also feed power to the grid. The 330 kV line is normally not used, and serves as an external power supply, connected by a station transformer to the power plant's electrical systems. The plant can be powered by its own generators, or get power from the 750 kV grid through the generator transformer, or from the 330 kV grid via the station transformer, or from the other power plant block via two reserve busbars. In case of total external power loss, the essential systems can be powered by diesel generators. Each unit transformer is connected to two 6 kV main power boards, A and B (e.g. 7A, 7B, 8A, 8B for generators 7 and 8), powering principal non-essential drivers and connected to transformers for the 4 kV main power and the 4 kV reserve busbar. The 7A, 7B, and 8B boards are also connected to the three essential power lines (namely for the coolant pumps), each also having its own diesel generator. In case of a coolant circuit failure with simultaneous loss of external power, the essential power can be supplied by the spinning down turbogenerators for about 45–50 seconds, during which time the diesel generators should start up. The generators are started automatically within 15 seconds at loss of off-site power.[10]

Turbogenerators

The electrical energy is generated by a pair of 500 MW hydrogen-cooled turbogenerators. These are located in the 600-meter-long machine hall, adjacent to the reactor building. The turbines, the venerable five-cylinder K-500-65/3000, are supplied by the Kharkiv turbine plant; the electrical generators are the TBB-500. The turbine and the generator rotors are mounted on the same shaft; the combined weight of the rotors is almost 200 t and their nominal rotational speed is 3000 rpm. The turbogenerator is 39 m long and its total weight is 1200 t. The coolant flow for each turbine is 82,880 tons/hour. The generator produces 20 kV 50 Hz AC power. The generator's stator is cooled by water while its rotor is cooled by hydrogen. The hydrogen for the generators is manufactured on-site by electrolysis.[8] The design and reliability of the turbines earned them the State Prize of Ukraine for 1979.

The Kharkiv turbine plant (now Turboatom) later developed a new version of the turbine, K-500-65/3000-2, in an attempt to reduce use of valuable metal. The Chernobyl plant was equipped with both types of turbines; Block 4 had the newer ones. The newer turbines, however, turned out to be more sensitive to their operating parameters, and their bearings had frequent problems with vibrations.[19]

Accident

On 26 April 1986 at 1:23 a.m., reactor 4 suffered a massive, catastrophic power excursion. This caused a steam explosion, followed by a second (chemical, not nuclear) explosion from the ignition of generated hydrogen mixed with air, which tore the top from the reactor and its building and exposed the reactor core. This dispersed large amounts of radioactive particulate and gaseous debris containing fission products including cesium-137, strontium-90, and other highly radioactive reactor waste products.[20] The open core also allowed atmospheric oxygen to contact the super-hot core containing 1,700 tonnes[21] of combustible graphite moderator. The burning graphite moderator increased the emission of radioactive particles, carried by the smoke. The reactor was not contained by any kind of hard containment vessel (unlike all Western plants, Soviet reactors often did not have them).[22] Radioactive particles were carried by wind across international borders.

Planning the test of a potential safety feature

A rotor of a modern day steam turbine.

During the daytime of 25 April 1986, reactor 4 was scheduled to be shut down for maintenance as it was near the end of its first fuel cycle. An experiment was scheduled to test a potential safety emergency core cooling feature during the shutdown procedure.

Following an emergency shutdown (scram), cooling is required to keep the temperature in the reactor core low enough to avoid fuel damage. The reactor consisted of about 1,600 individual fuel channels and each operational channel required a flow of 28 metric tons (28,000 litres (7,400 USgal)) of water per hour. There was concern that in case of an external power failure the Chernobyl power station would overload, leading to an automated safety shut down, in which case there would be no external power to run the plant's cooling water pumps. Chernobyl's reactors had three backup diesel generators. The generators required 15 seconds to start up but took 60–75 seconds to attain full speed and reach the capacity of 5.5 MW required to run one main cooling water pump.

Nuclear power reactors require cooling flow to remove decay heat, even when not actively generating power. In case of an external power failure, the reactor would automatically scram: control rods would be inserted and stop the nuclear fission process (and hence steam generation). However, in the spent fuel, the fission products themselves are radioactive and continue to produce heat as they decay. This could amount to 1-2 percent of the normal output of the plant. If not immediately removed by coolant systems, the heat could lead to core damage.

This one-minute power gap was considered unacceptable and it was suggested that the mechanical energy (rotational momentum) of the steam turbine could be used to generate electricity to run the main cooling water pumps while it was spinning down. In theory, analyses indicated that the residual momentum had the potential to provide power for 45 seconds, which would bridge the power gap between the onset of the external power failure and the full availability of electric power from the emergency diesel generators, but this capability needed to be confirmed experimentally. Previous tests had ended unsuccessfully. An initial test in 1982 showed that the excitation voltage of the turbine-generator was insufficient; it did not maintain the desired magnetic field during the generator spin-down. The system was modified, and in 1984 the test was repeated, but the retest proved unsuccessful. In 1985 the test was attempted a third time, but it also yielded negative results. This test procedure was to be repeated again in 1986.[23]

The test was focused on the switching sequences of the electrical supplies for the reactor. Since the test procedure was to begin when the reactor was scrammed automatically at the very beginning of the experiment, the experiment was not anticipated to have any detrimental effect on the safety of the reactor. Therefore, the test program was not formally coordinated with either the chief designer of the reactor (NIKIET) nor the scientific manager. Instead, it was approved only by the director of the plant (and even this approval was not consistent with established procedures). According to the test parameters, at the start of the experiment, the thermal output of the reactor should have been no lower than 700 MW. If conditions had been as planned, the test almost certainly would have proceeded safely; the eventual disaster resulted from attempts to boost the reactor output once the experiment had started, inconsistent with the approved procedure.[24]

The Chernobyl power plant had been in operation for two years without the capability to ride through the first 60–75 seconds of a total loss of electric power – an important safety feature. The station managers presumably wished to correct this at the first opportunity. This may explain why they continued the test even when serious problems arose, and why the requisite approval for the test was not sought from the Soviet nuclear oversight regulator (even though there was a representative at the complex of 4 reactors).[25]

The experimental procedure was intended to run as follows:

  • the reactor was to be running at a low power, but >700 MW
  • the steam turbine was to be run up to full speed
  • when these conditions were achieved, the steam supply was to be closed off
  • the turbines would be allowed to freewheel down
  • generator performance was to be recorded to determine whether it could provide the bridging power for coolant pumps

Turbogenerator vibrations measurement

Block 4 was equipped with the newer generation of the turbogenerators. These turned out to be prone to vibrations, and required periodic readjustment and balancing. For that purpose, the Kharkiv plant dispatched specialist technicians. In late 1985, the plant bought a mobile vibration analysis laboratory, a highly sophisticated, expensive, and unique electronics system mounted in a two-seat Mercedes-Benz van, from the Swiss company Vibro-meter. The laboratory was almost the only one in the entire Soviet Union. Its availability was an important reason against cancelling the test; it was not certain when it would be available again. So the testing had to proceed despite the known unfavorable conditions of the reactor, similar to the 1975 partial meltdown incident in the Leningrad plant.[26]

Parallel to the safety test, analysis of the turbogenerator vibrations was planned. The vibrolaboratory with a driver and three vibration specialists was dispatched from the Kharkiv plant, with Savenkov and Strelkov (the driver) going by car and Popov and Kabanov by train. On arrival at the plant, the laboratory was parked directly inside the machine hall, on Level 0; the normal procedure was to park outside and connect sensors by remote cables; however, that would have required making a hole in the wall.

Particular attention had to be paid to bearing number 12 of turbogenerator 8. The Leningrad-based supplier of the generators, Электросила, attempted to integrate an emergency lubricant reservoir into the bearing housing, but such bearings were found to produce high vibrations. Numerous attempts by the power plant and Львовэнергоремонт technicians to suppress the vibrations failed to get them below the limits allowed by GOST. Despite repeated urging, Elektrosila did not dispatch technicians to attend to the problem. Meanwhile, the vibrations resulted in a fatigue crack of the bearing oil line and leak of combustible oil. The problem was temporarily fixed by the turbine shop servicemen. Kharkiv Turbine Works specialists were willing to not only measure the vibration characteristics of the turbines, but also perform detailed investigation of the bearing. During the night of April 26, the vibrolaboratory was parked on Level 0 at the end of the machine hall, in the compartment of turbogenerator 8.[27]

At the moment of the explosion, Popov was in the control room, Savenkov and Kabanov were in the vibrolaboratory, and Strelkov, the driver, was in the Pripyat hotel. The specialists attempted to save the laboratory buried in debris, but did not succeed. The radiation at Level 0 was too high and they received a high dose that for Popov and Savenkov proved to be lethal.

At Popov's burial, the Kharkiv plant general designer promised to name the vibrolaboratory after the two fallen specialists. However that did not happen, as after the vehicle was recovered in 1987, its decontamination proved impossible.[19]

Conditions prior to the accident

The conditions to run the test were established prior to the day shift of 25 April 1986. The day shift workers had been instructed in advance about the test and were familiar with procedures. A special team of electrical engineers was present to test the new voltage regulating system.[28] As planned, on 25 April a gradual reduction in the output of the power unit was begun at 01:06 a.m., and by the beginning of the day shift the power level had reached 50%. Another regional power station unexpectedly went off-line, and the Kiev electrical grid controller requested that the further reduction of Chernobyl's output be postponed, as power was needed to satisfy the peak evening demand. The Chernobyl plant director agreed and postponed the test.

At 11:04 p.m., the Kiev grid controller allowed the reactor shut-down to resume. This delay had some serious consequences: the day shift had long since departed, the evening shift was also preparing to leave, and the night shift would not take over until midnight, well into the job. Further rapid reduction in the power level from 50% was actually executed during the shift change-over. According to plan, the test should have been finalized during the daytime and the night shift would only have had to maintain decay heat cooling systems in an otherwise shut-down plant; the night shift had very limited time to prepare for and carry out the experiment. Alexander Akimov was chief of the night shift, and Leonid Toptunov was the operator responsible for the reactor's operational regime, including the movement of the control rods. Toptunov was a young engineer who had worked independently as a senior engineer for approximately three months.[29]

The test plan called for the power output of reactor 4 to be reduced from its nominal 3200 MW thermal to 700–1000 MW thermal.[30] The power level established in the test program (700 MW) was achieved at 00:05 a.m. on 26 April; however, because of the natural production in the core of a neutron absorber, xenon-135, reactor power continued to decrease, even without operator action. As the power reached approximately 500 MW, Toptunov committed an error and inserted the control rods too far, bringing the reactor to a near-shutdown state. The exact circumstances will probably never be known, as both Akimov and Toptunov died from radiation sickness.

The reactor power dropped to 30 MW thermal (or less) - an almost completely shutdown power level that was approximately 5 percent of the minimum initial power level established as safe for the test.[31] Control-room personnel made a decision to restore the power and extracted the reactor control rods,[32] though several minutes elapsed after their extraction until the power output began to increase and subsequently stabilize at 160-200 MW (thermal). In this case the majority of control rods were withdrawn to their upper limits, but the low value of the operational reactivity margin restricted further rise of reactor power. Rapid reduction in the power and subsequent operation at the level of less than 200 MW led to increased poisoning of the reactor core by the accumulation of xenon-135, which made it necessary to extract additional control rods from the reactor core.

The operation of the reactor at the low power level with a small reactivity margin was accompanied by unstable temperature and flow and possibly by instability of neutron flux.[33] The control room received repeated emergency signals of the levels in the steam/water separator drums, of relief valves opened to relieve excess steam into a turbine condenser, of large excursions in the flow rate of feed water, and from the neutron power controller. In the period between 00:35 a.m and 00:45 a.m., apparently to preserve the reactor power level, emergency alarm signals concerning thermal-hydraulic parameters were ignored. Emergency signals from the Reactor Emergency Protection System (EPS-5) triggered a trip, turning off both turbine-generators.[34]

After a more or less stable state at a power level of 200 MW was achieved, preparation for the experiment continued. As part of the test plan, at 1:05 a.m. on 26 April extra water pumps were activated, increasing the water flow. The increased coolant flow rate through the reactor produced an increase in the inlet coolant temperature of the reactor core, which now more closely approached the nucleate boiling temperature of water, reducing the safety margin. The flow exceeded the allowed limit at 1:19 a.m. At the same time the extra water flow lowered the overall core temperature and reduced the existing steam voids in the core.[35] Since water also absorbs neutrons (and the higher density of liquid water makes it a better absorber than steam), turning on additional pumps decreased the reactor power. This prompted the operators to remove the manual control rods further to maintain power.[36]

All these actions led to an extremely unstable reactor configuration. Nearly all of the control rods were removed, which limited the value of the safety rods when initially inserted in a scram. Further, the reactor coolant had limited boiling, but had limited margin to boiling, so any power excursion would produce boiling, reducing neutron absorption by the water. This left the reactor in an unstable configuration that was clearly outside the safe operating envelope established by the designers.

Experiment and explosion

Aerial view of the damaged core. Roof of the turbine hall is damaged (image center). Roof of the adjacent reactor 3 (image lower left) shows minor fire damage.
Lumps of graphite moderator ejected from the core. The largest lump shows an intact control rod channel.

At 1:23:04 a.m. the experiment began. The steam to the turbines was shut off, and a run down of the turbine generator began, together with four (of the total eight) Main Circulating Pumps (MCP). The diesel generator started and sequentially picked up loads, which was complete by 01:23:43; during this period the power for these four MCPs was supplied by the coasting down turbine generator. As the momentum of the turbine generator that powered the water pumps decreased, the water flow rate decreased, leading to increased formation of steam voids in the core. Because of the positive void coefficient of the RBMK reactor at low reactor power levels, it was now primed to embark on a positive feedback loop, in which the formation of steam voids decreased the ability of the liquid water coolant to absorb neutrons, which increased the reactor's power output, causing yet more water to flash into steam, and yet a further power increase. However, during almost the entire period of the experiment the automatic control system successfully counteracted this positive feedback, continuously inserting control rods into the reactor core to limit the power rise.

At 1:23:40, as recorded by the SKALA centralized control system, the EPS-5 button (also known as the AZ-5 button) of the reactor emergency protection system was pressed, which initiated a scram — a shutdown of the reactor, fully inserting all control rods, including the manual control rods that had been incautiously withdrawn earlier. The reason the EPS-5 button was pressed is not known, whether it was done as an emergency measure or simply as a routine method of shutting down the reactor upon completion of the experiment. There is a view that the scram may have been ordered as a response to the unexpected rapid power increase, although there is no recorded data convincingly testifying to this.

Some have suggested that the button was not pressed but rather that the signal was automatically produced by the emergency protection system; however, the SKALA clearly registered a manual scram signal. In spite of this, the question as to when or even whether the EPS-5 button was pressed was the subject of debate. There are assertions that the pressure was caused by the rapid power acceleration at the start, and allegations that the button was not pressed until the reactor began to self-destruct.[37] Others assert that it happened earlier and in calm conditions. Dyatlov writes in his book:

Prior to 01:23:40, systems of centralized control … did not register any parameter changes that could justify the scram. The Commission … gathered and analyzed large amounts of material and, as stated in its report, failed to determine the reason why the scram was ordered. There was no need to look for the reason. The reactor was simply being shut down upon the completion of the experiment.[38]

For whatever reason the EPS-5 button was pressed, insertion of control rods into the reactor core began. The control rod insertion mechanism operated at a relatively slow speed (0.4 m/s) taking 18–20 seconds to travel the full approximately 7-meter core length (height). A bigger problem was a flawed graphite-tip control rod design, which initially displaced coolant before neutron-absorbing material was inserted and the reaction slowed. As a result, the scram actually increased the reaction rate in the lower half of the core. At this point a massive power spike occurred, and the core overheated. Some of the fuel rods fractured, blocking the control rod columns and causing the control rods to become stuck after being inserted only one-third of the way. Within three seconds the reactor output rose above 530 MW.[39] The subsequent course of events was not registered by instruments: it is known only as a result of mathematical simulation. According to some estimations, the reactor jumped to around 30 GW thermal, ten times the normal operational output, but not immediately. First a great rise in power caused an increase in fuel temperature and massive steam buildup with rapid increase in steam pressure. This destroyed fuel elements and ruptured the channels in which these elements were located.[40]

It was not possible to reconstruct the precise sequence of the processes that led to the destruction of the reactor and the power unit building. There is a general understanding that it was steam from the wrecked channels entering the reactor inner structure that caused the destruction of the reactor casing, tearing off and lifting by force the 2,000 ton upper plate (to which the entire reactor assembly is fastened). Apparently this was the first explosion that many heard.[41] This was a steam explosion like the explosion of a steam boiler from the excess pressure of vapor. This ruptured further fuel channels – as a result the remaining coolant flashed to steam and escaped the reactor core. The total water loss combined with a high positive void coefficient to increase the reactor power. A second, more powerful explosion occurred about two or three seconds after the first; evidence indicates that the second explosion resulted from a nuclear excursion.[42]

There were initially several hypotheses about the nature of the second explosion. One view was that "the second explosion was caused by the hydrogen which had been produced either by the overheated steam-zirconium reaction or by the reaction of red-hot graphite with steam that produce hydrogen and carbon monoxide." According to another hypothesis, this explosion was of a nuclear nature,[43] i.e., the thermal explosion of the reactor as a result of the uncontrollable escape of fast neutrons caused by the complete water loss in the reactor core. A third hypothesis was that the explosion was caused, exceptionally, by steam. According to this version, the flow of steam and the steam pressure caused all the destruction following the ejection from the shaft of a substantial part of the graphite and fuel.

According to observers outside Unit 4, burning lumps of material and sparks shot into the air above the reactor. Some of them fell onto the roof of the machine hall and started a fire. About 25 per cent of the red-hot graphite blocks and overheated material from the fuel channels was ejected. ... Parts of the graphite blocks and fuel channels were out of the reactor building. ... As a result of the damage to the building an airflow through the core was established by the high temperature of the core. The air ignited the hot graphite and started a graphite fire.[44]

However, the ratio of xenon radioisotopes released during the event provides compelling evidence that the second explosion was a nuclear power transient. This nuclear transient released ~0.01 kilotons of energy; the analysis indicates that the nuclear excursion was limited to a small portion of the core.[42]

The nuclear excursion dispersed the core and effectively terminated that phase of the event. However, the graphite fire continued, greatly contributing to the spread of radioactive material and the contamination of outlying areas.[45]

Contrary to safety regulations, a combustible material (bitumen) had been used in the construction of the roof of the reactor building and the turbine hall. Ejected material ignited at least five fires on the roof of the (still operating) adjacent reactor 3. It was imperative to put those fires out and protect the cooling systems of reactor 3.[46] Inside reactor 3, the chief of the night shift, Yuri Bagdasarov, wanted to shut down the reactor immediately, but chief engineer Nikolai Fomin would not allow this. The operators were given respirators and potassium iodide tablets and told to continue working. At 05:00, however, Bagdasarov made his own decision to shut down the reactor, leaving only those operators there who had to work the emergency cooling systems.[47]

Radiation levels

Approximate radiation levels at different locations shortly after the explosion:[48]

location radiation (roentgens/hour)
vicinity of the reactor core 30,000
fuel fragments 15,000-20,000
debris heap at the place of circulation pumps 10,000
debris near the electrolyzers 5,000-15,000
water in the Level +25 feedwater room 5,000
level 0 of the turbine hall 500-15,000
area of the affected unit 1,000-1,500
water in Room 712 1,000
control room, shortly after explosion 3-5
Gidroelektromontazh depot 30
nearby concrete mixing unit 10-15

Plant layout

based on the image of the plant[49]
level objects
49.6 roof of the reactor building, gallery of the refueling mechanism
39.9 roof of the deaerator gallery
35.5 floor of the main reactor hall
31.6 upper side of the upper biological shield, floor of the space for pipes to steam separators
28.3 lower side of the turbine hall roof
24.0 deaerator floor, measurement and control instruments room
16.4 floor of the pipe aisle in the deaerator gallery
12.0 main floor of the turbine hall, floor of the main circulation pump motor compartments
10.0 control room, floor under the reactor lower biological shield, main circulation pumps
6.0 steam distribution corridor
2.2 upper pressure suppression pool
0.0 ground level; house switchgear, turbine hall level
-0.5 lower pressure suppression pool
-5.2, -4.2 other turbine hall levels
-6.5 basement floor of the turbine hall

Individual involvement

Khodemchuk memorial, located outside the control room 4 where the observation gallery was
File:Chernobyl firemens memorial.jpg
Chernobyl firemen memorial
Model of the reactor and turbine hall
Most of the information here is based on Grigoriy Medvedev's work[48]

In the night from 25 to 26 April, in the two power plant complexes there were 160 people on duty, including technicians and maintenance personnel of the various departments. Three hundred more workers were present at the building site of the third complex of the blocks 5 and 6.

Nikolai Gorbachenko, a radiation monitoring technician, at the beginning of his shift checked Unit 3; he skipped the check of Unit 4 as it was being shut down, so at the moment of the accident he was located in the duty room. A flat and powerful thud shook the building; he and his assistant Pshenichnikov thought it was a water hammer occurring during a turbine shutdown. Another flat thud followed, accompanied by lights going out, the control panel of Unit 4 losing signal, latched double doors being blown apart by the blast, and black and red powder falling from the ventilation vent; emergency lights then switched on. Telephone connection with Unit 4 was cut. The corridor to the deaerator galleries was full of steam and white dust. The radiation counters went off-scale, and the high-range one burned out when switched on; the portable instruments were capable of showing at most 4 roentgens/hour, while the radiation on the roof ranged between 2000 and 15000 roentgens/hour. He went to the turbine hall to survey the damage, saw scattered pieces of concrete, and returned to the duty room. Meeting two men there, together with them he went to search for Shashenok, found him unconscious in a damaged instrument room, and carried him down. He returned to his post and changed clothes and shoes. He was then ordered to look for Khodemchuk, but the search was unsuccessful. He went to the control room and with Dyatlov went outside to survey the reactor building. At 5 am he began feeling weak and vomiting and was transported to hospital, from where he was released on October 27.

The night shift main circulating pump operator, Valery Khodemchuk, was likely killed immediately; he was located in the collapsed part of the building, in the far end of the southern main circulating pumps engine room at level +10. His body was never recovered and is entombed in the reactor debris.

Vladimir Sashenok, the automatic systems adjuster from Atomenergonaladka(the Chernobyl startup and adjustment enterprise), was supposed to be in Room 604, the location of the measurement and control instruments, on the upper landing across the turbine room, on level +24, under the reactor feedwater unit; he was reporting the states of the pressure gauges of the profile of the multiple forced circulation circuit to the computer room by telephone. The communication lines were cut during the explosion. Shashenok received deep thermal and radiation burns over his entire body when the overpressure spike destroyed the isolation membranes and the impulse pipes of the manometers in his instrument room just before the explosion, which then demolished the room itself. The landing was found damaged, covered with ankle-deep water, and there were leaks of boiling water and radioactive steam. Sashenok was found unconscious in Room 604, pinned under a fallen beam, with bloody foam coming out of his mouth. His body was severely contaminated by radioactive water. He was carried out by Gorbachenko and Palamarchuk and died at 6 am in the Pripyat hospital under care of the chief physician, Leonenko Vitaliy, without regaining consciousness. Gorbachenko suffered a radiation burn on his back where Sashenok's hand was located when he helped carry him out. Khodemchuk and Sashenok were the first two victims of the disaster.

Oleg Genrikh, an operator of the control room on Level +36, was taking a nap in a windowless room adjacent to the control room. The window in the control room was broken and the lights went out. His colleague, Anatoly Kurguz, was in the control room with three open doors between him and the reactor room; at the moment of the explosion, he suffered severe burns from steam entering the control room. Genrikh received less serious burns as he was protected by the windowless room. The stairs on the right side were damaged; he managed to escape by the stairs on the left.[50] On the way back they were joined by Simeonov and Simonenko, the gas loop operators, all four heading to the control room. Kurguz was shortly afterwards evacuated by an ambulance; aware of dangers of radiation contamination, Genrikh took a shower and changed his clothes.

Alexander Yuvchenko was located in his office between reactors 3 and 4, on Level 12.5; he described the event as a shock wave that buckled walls, blew doors in, and brought a cloud of milky grey radioactive dust and steam. The lights went out. He met a badly burned, drenched and shocked pump operator, who asked him to rescue Khodemchuk; that quickly proved impossible as that part of the building did not exist anymore. Yuvchenko, together with the foreman Yuri Tregub, ran out of the building and saw half of the building gone and the reactor emitting a blue glow of ionized air. They returned to the building and met Valeri Perevozchenko and two junior technicians, Kudryavtsev and Proskuryakov, ordered by Dyatlov to manually lower the presumably seized control rods. Tregub went to report the extent of damage to the control room. Despite Yuvchenko's explanation that there were no control rods left, the four climbed a stairwell to level 35 to survey the damage; Yuvchenko held open the massive door into the reactor room and the other three proceeded in to locate the control rod mechanism; after no more than a minute of surveying the reactor debris, enough for all three to sustain fatal doses of radiation, they returned, their skin darkened with "nuclear tan" in reaction to the high radiation dose. The three were the first to die in the Moscow hospital. Yuvchenko meanwhile suffered serious beta burns and gamma burns to his left shoulder, hip and calf as he kept the radioactive-dust-covered door open. It was later estimated he received a dose of 4.1 Sv. At 3 am he began vomiting, at 6 am he could not walk anymore; he later spent a year in the Moscow hospital receiving blood and plasma transfusions and received numerous skin grafts.[51][52]

Valeriy Ivanovich Perevozchenko, the reactor section foreman, was present on the open platform at level +50 shortly before the explosion. He witnessed the 350 kg blocks atop the fuel channels of the Upper Biological Shield jumping up and down and felt the shock waves through the building structure; the rupture of the pressure channels was in progress. He ran down the spiral staircase to Level +10, through the deaerator gallery and the corridor to the control room, to report his observations, arriving shortly after the explosions, then returned to search for his comrades. He witnessed the destruction of the reactor building from the broken windows of the deaerator gallery. With his face already tanned by the radiation, he went to the dosimetry room and asked Gorbachenko for radiation levels; Gorbachenko left with Palamarchuk to rescue Shashenok while Perevozchenko went through the graphite and fuel containing radioactive rubble on Level 10 to the remains of Room 306 in an unsuccessful attempt to locate Khodemchuk, close to debris emitting over 10,000 roentgens/hour. He then went to the control room of Genrikh and Kurguz and found it empty; vomiting and losing consciousness, he returned to the control room to report on the situation.

Vyacheslav Brazhnik, the senior turbine machinist operator, ran into the control room to report fire in the turbine hall. Pyotr Palamarchuk, the Chernobyl enterprise group supervisor, together with Razim Davletbayev, followed him back to the turbine room. They witnessed fires on levels 0 and +12, broken oil and water pipes, roof debris on top of turbine 7, and scattered pieces of reactor graphite and fuel, with the linoleum on the floor burning around them. Palamarchuk unsuccessfully attempted to contact Sashenok in Room 604, then ran around the turbogenerator 8, down to Level 0 and urged the two men from the Kharkov mobile laboratory, assigned to record the turbine 8 vibrations, to leave; they, however, had both already received a lethal radiation dose. Akimov asked Palamarchuk to look for Gorbachenko and then rescue Sashenok as the communication with the dosimetry room was cut. Palamarchuk met Gorbachenko by the staircase on Level +27, then they together found and recovered Shashenok's unconscious body.[48]

Aleksandr Kudryavtsev and Viktor Proskuryakov, the SIUR trainees from other shifts, were present to watch Toptunov and learn. After the explosion they were sent by Akimov to the central hall to turn the handles of the system for manual lowering of the presumably seized control rods. They ran through the deaerator gallery to the right to the VRSO unit elevator, found it destroyed, so climbed up the staircase instead, towards Level 36; they missed Kurguz and Genrikh, who used another stairwell. Level 36 was destroyed, covered with rubble. They went through a narrow corridor towards the central hall, entered the reactor hall, and found it blocked with rubble and fragments; dangling fire hoses were pouring water into the remains of the reactor core, the firemen not there anymore. The Upper Biological Shield was slanted, jammed into the reactor shaft; a blue and red fire raged in the hole. The minute the two stood above the reactor was enough to darken their bodies with "nuclear tan" and give them a fatal radiation dose. They returned back to Level 10 and to the control room, reporting the situation; Dyatlov insisted they were wrong, the explosion had been caused by hydrogen-oxygen mixture in the 110 m3 emergency tank and the reactor itself was intact.

Anatoliy Dyatlov, the deputy chief engineer, supervised the test. At the moment reactor power slipped to 30 MW thermal, he insisted the operators continue the test. He overrode Akimov's and Toptunov's objections, threatening to hand the shift to Tregub (the previous shift operator who had remained on-site), intimidating them into attempting to increase the reactor power. The power stabilized at 200 MWt at around 1:00 a.m. and did not rise further, due to continued xenon poisoning of the core. Later the test was commenced, then the reactor showed power excursion and was scrammed; the control rods seized and the explosion occurred shortly afterwards. Dyatlov ordered reactor cooling with emergency speed, assuming the reactor was intact and the explosion had been caused by hydrogen accumulating in the emergency tank of the safety control system. Other employees went to the control room, reporting damage. Dyatlov went to the backup control room, pressing the AZ-5 button there and disconnecting power to the control rod servodrives; despite seeing the graphite blocks scattered on the ground outside the plant, he still believed the reactor was intact. Kudryavtsev and Proskuryakov returned to report the reactor damage they had seen, but Dyatlov insisted what they had seen was the results of an explosion of the emergency tank, claiming the explosion of the 110 m3 tank at Level +71 was sufficient to destroy the central hall roof. Dyatlov reported his assumptions as reality to Bryukhanov and Fomin, the higher-level managers. In the corridor, he met Genrikh and Kurguz and sent them to the medical station. He ran to the control room of Block 3, ordered Bagdasarov to shut reactor 3 down, then returned to control room 4 and ordered Akimov to call the daytime shift and get people to the affected unit; namely Lelechenko, whose crew had to remove hydrogen from the Generator 8 electrolyzer. At 2:00, Dyatlov ordered Akimov to feed water to the reactor, and together with Gorbachenko went to survey the plant from the outside. Despite seeing the fuel and graphite scattered around, he still believed the reactor was intact. They then returned to the control room. At 5 am, he got sick and together with Gorbachenko went to the medical unit. Fomin replaced him on his post with Sitnikov.

Aleksandr Akimov, the unit shift chief, was in charge of the test itself. He took over the shift at midnight from Tregub, who stayed on-site. The drop in reactor power from 1500 MWt to 30 MWt was disconcerting; he wanted to abort the test. He supported Toptunov's decision to shut down the poisoned reactor, but was overriden by Dyatlov and forced to continue. At 1:23:04 the test began, and the main circulation pumps started cavitating due to the too high temperature of inlet water. The coolant started boiling in the reactor, and the reactor power slowly increased. Toptunov reported a power excursion to Akimov. At 1:23:40 Akimov pressed the AZ-5 button, class-5 emergency. The control rods, according to the synchro indicators, seized at a depth of between 2 and 2.5 meters instead of the entire core depth of 7 meters. Akimov disconnected the clutches of the control rod servos to let the rods descend into the core by their own weight, but the rods did not move. The reactor was now making rumbling noises. Akimov was confused. The reactor control panel indicated no water flow and failure of pumps. The explosion occurred, the air filled with dust, power went out, and only battery-powered emergency lights stayed in operation. Perevozchenko ran into the control room, reporting the collapse of the reactor top. Brazhnik ran in from the turbine hall, reporting fire there. Brazhki, Akimov, Davletbayev, and Palamarchuk ran into the turbine hall, having seen scattered debris and multiple fires on Levels 0 and +12. Akimov called the fire station and the chiefs of electrical and other departments, asking for electrical power for coolant pumps, removal of hydrogen from hydrogen generators, and other emergency procedures to stabilize the plant and contain the damage. Internal telephone lines were disabled; Akimov sent Palamarchuk to contact Gorbachenko. Assuming the reactor was intact, he sent Kudryavtsev and Proskuryakov to the central hall to lower the reactor control rods manually. Kudryavtsev and Proskuryakov returned from the reactor and reported its state to Akimov and Dyatlov. Insisting the reactor was intact, Akimov ordered Stolyarchuk and Busygin to turn on the emergency feedwater pumps. Davletbayev reported loss of electrical power, torn cables, and electric arcs. Akimov sent Metlenko to help in the turbine hall with manual opening of the cooling system valves, which was expected to take at least 4 hours per valve. Perevozchenko returned and reported that the reactor was destroyed, but Akimov insisted it was intact. At 3:30, Telyatnikov contacted Akimov, asking what was happening to his firemen; Akimov sent him a dosimetrist. Akimov, already nauseous, was replaced at 6:00 by the unit chief Vladimir Alekseyevich Babychev, but together with Toptunov stayed in the plant. Believing the water flow to the reactor to be blocked by a closed valve somewhere, they went to the half-destroyed feedwater room on Level +24. Together with Nekhayev, Orlov, and Uskov, they opened the valves on the two feedwater lines, then climbed over to Level +27 and almost knee-deep in a mixture of fuel and water, opened two valves on the 300 line; due to advancing radiation poisoning, they did not have the strength to open the valves on the sides. Akimov and Toptunov spent several hours turning valves; the radioactive water in Room 712 was half submerging the pipeline. Smagin went in to open the third valves, spent 20 minutes in the room, and received 280 rads. Akimov was evacuated to hospital. Until his death, he insisted he had done everything correctly.

Bryukhanov, the plant manager, arrived at 2:30. Akimov reported a serious radiation accident but intact reactor, fires in the process of being extinguished, and a second emergency water pump being readied to cool the reactor. Due to limitations of available instruments, they seriously underestimated the radiation level. At 3 am, Bryukhanov called Maryin, the deputy secretary for the nuclear power industry, reporting Akimov's version of the situation. Maryin sent the message further up the chain of command, to Frolyshev, who then called Dolgikh, who called Gorbachev and other members of the Politburo. At 4 am, Moscow ordered feeding of water to the reactor.

Chief engineer Fomin arrived in the Block 4 control room at 4:30. Akimov reported an intact reactor and explosion of the emergency water feed tank. Fomin ordered continuous feeding of water into the reactor, which was already in progress by emergency pump 2 from the deaerators. Fomin kept pressing the staff to feed water to the reactor and transferred more people to Unit 4 to replace those being disabled by radiation. After Dyatlov left, Fomin ordered Sitnikov, his replacement, to climb to the roof of Unit C and survey the reactor; Sitnikov obeyed and received a fatal radiation dose there; at 10 am he returned and reported to Fomin and Bryukhanov that the reactor was destroyed. The managers refused to believe him and ordered continued feeding of water into the reactor; the water, however, flowed through the severed pipes into the lower levels of the plant, carrying radioactive debris and causing short circuits in the cableways common to all four blocks.

Deaths and survivors

(survivors, unless date of death is specified)[19][27][51][53][54][55][56][57][58]

Name Cyrillic name Date of birth Date of death Cause of death/injury Role
Akimov, Aleksandr Fyodorovich Акимов, Александр (Саша) Фёдорович 1953-05-06 1986-05-11 radiation burns on 100% of body Unit #4 shift leader in the control room at the reactor control panel at the moment of explosion, with Toptunov; received fatal dose during attempts to restart feedwater flow into the reactor; posthumously awarded the Order "For Courage" of third degree[55]
Badaev, Yuri Yurievich Бадаев, Юрий Юрьевич SKALA computer operator, electromechanic (DES), block 4 at the moment of the explosion in the SKALA room[59]
Bagdasarov, Yuri Eduardovich Багдасаров, Юрий Эдуардович survivor shift leader, block 3
Baranov, Anatoly Ivanovich Баранов, Анатолий Иванович 1953-06-13 1986-05-20 electrical engineer, senior electrician posthumously awarded the Order "For Courage" of third degree[55]
Bondarenko, Nikolai Sergeevich Бондаренко, Николай Сергеевич oxygen-nitrogen station, operator at the moment of the explosion stationed in the nitrogen-oxygen station, 200 meters from the Block 4 [59]
Borec, V.I.  ? former Leningrad power plant block shift leader; in charge of preparation of the test, would supervise it according to the original schedule, asked Dyatlov to cancel it due to the state of the reactor. Went home for the night, was called on-site to assist with post-accident situation.[26]
Brazhnik, Vyacheslav (Slava) Stefanovych Бражник, Вячеслав Степанович 1957-05-03 1986-05-14 turbine operator, senior turbine machinist operator in the turbine hall at the moment of explosion; received fatal dose (over 1000 rad) during firefighting and stabilizing the turbine hall, died in Moscow hospital; posthumously awarded the Order "For Courage" of third degree[55]; irradiated by a piece of fuel lodged on a nearby transformer of turbogenerator 7 during manual opening of the turbine emergency oil drain valves
Bryukhanov, Viktor Брюханов, Виктор 1936? plant director former director of the Balakovo Nuclear Power Plant; after the disaster stripped of Communist party membership, arrested in August 1986, spent a year in Kiev prison awaiting trial[60]; found guilty of gross violation of safety regulations, sentenced to 10 years of labor camp plus concurrent 5 years for abuse of power[61]
Busygin, Herman Viktorovich Бусыгин, Герман Викторович 1993 survivor turbine shop shift leader received about 350 roentgens during firefighting and stabilizing the turbine hall
Chugunov, Vladimir Aleksandrovich Чугунов, Владимир Александрович reactor shop 1 deputy director radiation burn on right side, right hand, received sublethal radiation dose during post-accident site survey[26]
Davletbayev, Razim I. Давлетбаев, Разим survivor turbine shop deputy chief in control room at desk T at the moment of explosion; received about 350 roentgens during firefighting and stabilizing the turbine hall
Degtyarenko, Viktor Mykhaylovych Дегтяренко, Виктор Михайлович 1954-08-10 1986-05-19 reactor operator at the moment of explosion close to the pumps; posthumously awarded the Order "For Courage" of third degree[55][62], face scalded by steam or hot water[63]
Dik, G.A. Дик, Г.А. plant employee morning shift[63]
Dyatlov, Anatoly Stepanovich Дятлов, Анатолий Степанович 1931-03-03 1995-12-13 survivor; heart failure due to 390 rem dose plant vice chief engineer Fomin's assistant; supervised the test, present in the control room at the moment of explosion; received about 400 rads when surveying the reactor damage from the outside with Gorbachenko; radiation burns on face, right hand, legs; after the disaster stripped of Communist party membership, arrested in August 1986, spent a year in Kiev prison awaiting trial[60]; found guilty of gross violation of safety regulations, sentenced to 10 years of labor camp[61]
Dzyubak, Aleksei Дзюбак, Алексей survivor, radiation exposure est. 300 rad construction worker, Block 5 exposed to fallout about 300 meters from Block 4 during return from night shift; spent half year in the Moscow clinic[64]
Elshin, M.A. Ельшин, М.А. thermal plant automation and measurement, shift leader present in the control room when the reactor power dropped; returned to his office when power was stabilized, where he was in the moment of explosion[59]
Fomin, Nikolai Maksimovich Фомин, Николай Максимович 1937? chief engineer arrived at 4:30; spent a month in the Moscow clinic; after the disaster stripped of Communist party membership, arrested in August 1986, spent a year in Kiev prison awaiting trial[60]; cleared of charges of abuse of power, found guilty of gross violation of safety regulations, sentenced to 10 years of labor camp[61], released soon afterwards because of a nervous breakdown
Gazin, Sergei Nikolaevich Газин, Сергей Николаевич turbogenerator chief engineer from shift 16:00-24:00, stayed to watch the test, in control room at desk T with Kirchenbaum at the moment of explosion
Genrykh, Oleg Генрих, Олег survivor operator, central hall scalded by radioactive steam entering his control room; his colleague, Anatoly Kurguz, did not survive
Golovnenko, Mikhail Головненко, Миша firefighter, driver
Gorbachenko, Nikolai Feodosyevkh Горбаченко, Николай Феодосьевич 1954? survivor dosimetrist received about 300 or 400 rads when surveying the reactor damage from the outside with Dyatlov; received radiation burns during recovery of Shashenok; released from hospital on 27 October
Hanzhuk, Mykola Oleksandrovych Ганжук, Николай Александрович 1960-06-26 1986-10-02 helicopter crash helicopter pilot died in a helicopter accident
Ignatenko, Vasyli Ivanovych Игнатенко, Василий Иванович 1961-03-13 1986-05-13 fireman senior sergeant, first crew on the reactor roof, received fatal dose during attempt to extinguish the roof and the reactor core, died two weeks later in Moscow Hospital 6[65]
Ivanenko, Yakaterina Alexandrovna Иваненко, Екатерина Александровна 1932-09-11 1986-05-26 Pripyat city police guard guarded a gate opposite to the Block 4, stayed on duty for the entire night until morning[64]
Kabanov, Aleksander F. Кабанов, Александр Ф. acute radiation syndrome, survivor Kharkov turbine plant vibration specialist, mobile laboratory in the car at Turbine 8; treated in Moscow hospital, survived with 2nd degree of disability[19]
Kavuntz, Aleksander Adamovich Кавунец, Александр Адамович turbine repair department chief
Khmel, Grigori Matvyevich Хмель, Григорий Матвеевич fireman firefighting car driver, Chernobyl region firefighting area
Khodemchuk, Valery Ilyich Ходемчук, Валерий Ильич 1951-03-24 1986-04-26 initial explosion main circulating pumps, senior operator stationed in the southern main circulating pumps engine room, likely killed immediately; body never found, likely buried under the wreckage of the steam separator drums; has a memorial sign in the Reactor 4 building; posthumously awarded the Order "For Courage" of third degree[55]
Khrystych, Leonid Ivanovych Христич, Леонид Иванович 1953-02-28 1986-10-02 helicopter crash helicopter pilot died in a helicopter accident
Kibenok, Viktor Mykolayovych Кибенок, Виктор Николаевич 1963-02-17 1986-05-11 fireman lieutnant, leader of the second unit, fighting fires in the reactor department, separator room, and the central hall; in 1987 posthumously named a Hero of the Soviet Union
Kirshenbaum, Igor Киршенбаум, Игорь turbine control senior engineer (SIUT), deputy head of unit 4 turbine section present in the control room, desk T, at the moment of explosion; in charge of switching off the Turbogenerator 8 and starting its spindown
Konoval, Yuriy Ivanovych Коновал, Юрий Иванович 1942-01-01 1986-05-28 electrician posthumously awarded the Order "For Courage" of third degree[55]
Korneyev, , Yuri Корнеев, Юрий Владимирович 1957? survivor turbine operator, turbine 8 engineer received about 350 (or 710[66]) roentgens during firefighting and stabilizing the turbine hall
Kovalenko, A.P. Коваленко, А.П. 1942?  ? fatal? radiation dose reactor shop 2, chief // reactor 4 supervisor former Tomsk-7 worker; received radiation dose during the post-accident site survey the next day[26]; after the disaster demoted, allowed to continue working in the plant while awaiting trial[60]; found guilty of violating safety regulations, sentenced to 3 years of labor camp[61]
Kudryavtsev, Aleksandr Hennadiyovych Кудрявцев, Александр (Саша) Геннадиевич 1957-12-11 1986-05-14 SIUR trainee present in the control room at the moment of explosion; received fatal dose of radiation during attempt to manually lower the control rods as he looked directly to the open reactor core; posthumously awarded the Order "For Courage" of third degree[55]
Kukhar, A.A. Кухар, А.А. electrical laboratory, chief at the central control room with Lelechenko; at the moment of explosion just arrived to the block 4 control room[59]
Kurguz, Anatoly Kharlampiyovych Кургуз, Анатолий Харлампиевич 1957-06-12 1986-05-12 operator, central hall scalded by radioactive steam entering his control room; his colleague, Oleg Genrikh, was spared the worst and survived
Kuryavchenko, Nikolai Gordeevich Курявченко, Николай Гордеевич SKALA computer operator, electromechanic (DES), block 3 in block 3[59]
Lelechenko, Aleksandr Grigoryevich Лелеченко, Александр Григорьевич 1938-07-26 1986-05-07 fatal radiation exposure, 2500 rads plant worker, deputy chief of the electrical shop former Leningrad power plant electrical shop shift leader[26]; at the central control room with Kukhar; at the moment of explosion just arrived to the block 4 control room[59]; in order to spare his younger colleagues a radiation exposition he himself went through radioactive water and debris three times to switch off the electrolyzers and the feed of hydrogen to the generators, then tried to supply voltage to feedwater pumps; after receiving first aid, returned to the plant and worked for several more hours. Died in Kiev hospital.
Lopatyuk, Viktor Ivanovich Лопатюк, Виктор Иванович 1960-08-22 1986-05-17 electrician received fatal dose during switching off the electrolyzer[67]
Luzganova, Klavdia Ivanovna Лузганова, Клавдия Ивановна 1927-05-09 1986-07-31 radiation exposure, est. 600 rad Pripyat city police guard[57] guarded the construction site of the spent fuel storage building about 200 meters from Block 4[64]
Lysyuk, G.V. Лысюк, Г.В. electrician, shop chief at the moment of the explosion in the control room; in charge of issuing the simulated Maximum Projected Accident signal on Metlenko's command[59]
Metlenko, Gennady Petrovich Метленко, Геннадий Петрович Dontechenergo, senior brigade electroengineer at the moment of explosion present with two assistants in the N area of the control room, at the oscillographs; supposed to monitor the slowdown rate of the spinning down turbogenerator, and its electrical characteristics, worked together with Kirchenbaum; after the explosion sent to help in the turbine hall but sent back from there[59]
Miruzhenko, Daniel Terentyevich Мируженко, Данила Терентьевич survivor, radiation exposure security guard Gidroelektromontazh construction site about 300 meters from Block 4[64]
Nekhaev, Aleksandr A. Нехаев, Александр А. morning shift, helped Akimov and Toptunov opening the valves to feed water to the reactor through steam separator drums and main circulation pumps[68]
Novyk, Oleksandr Vasylyovych Новик, Александр Васильевич 1961-08-11 1986-07-26 turbine equipment machinist-inspector received fatal dose (over 1000 rad) during firefighting and stabilizing the turbine hall, died in Moscow hospital; posthumously awarded the Order "For Courage" of third degree[55]; irradiated by a piece of fuel lodged on a nearby transformer of the turbogenerator 7 during attempts to call the control room
Orlov, Vyacheslav/Vladimir (Slava) Alekseyevich Орлов, Вячеслав/Владимир (Слава) Алексеевич radiation sickness reactor department deputy chief got non-lethal dose of radiation during post-accident site survey the next day, became disabled[26][69]
Orlov, Ivan Lukych Орлов, Иван Лукич 1945-01-10 1986-05-13 physicist received fatal dose during attempts to restart feedwater flow into the reactor
Palamarchuk, Pyotr (Petya) Паламарчук, (Петя) 1951? survivor[70] survived dose of 800 rad Atomenergonaladka, group supervisor, laboratory director (Chernobyl startup and adjustment enterprise)
Perchuk, Kostyantyn Hryhorovich Перчук, Константин Григорьевич 1952-11-23 1986-05-20 turbine operator, senior engineer in the turbine hall at the moment of explosion; received fatal dose (over 1000 rad) during firefighting and stabilizing the turbine hall, died in Moscow hospital; posthumously awarded the Order "For Courage" of third degree[55]; irradiated by a piece of fuel lodged on a nearby transformer of the turbogenerator 7 during manual opening of the turbine emergency oil drain valves
Perevozchenko, Valery Ivanovich (Valera) Перевозченко, Валерий Иванович 1947-05-06 1986-06-13 foreman, reactor section received fatal dose of radiation during attempt to locate and rescue Khodemchuk and others, and manually lower the control rods; together with Kudryavtsev and Proskuryakov he looked directly to the open reactor core; posthumously awarded the Order "For Courage" of third degree[55]; radiation burns on side and back
Petrovskiy fireman watched the fire spread from the roof of Unit C until 6 am as ordered by Teliatnikov
Popov, Georgi Illiaronovich Попов, Георгий Илларионович 1940-02-21 1986-06-13 acute radiation sickness Kharkov turbine plant vibration specialist, mobile laboratory in the car at Turbine 8; buried in Mitinskoe Cemetery[19]
Pravik, Vladimir Pavlovych Правик, Владимир (Володя) Павлович 1962-06-13 1986-05-11 radiation burns fireman lieutenant, first crew on the reactor roof, repeatedly visited the reactor and the roof of Unit C at Level 71 to supervise the firefighting; received fatal dose during attempt to extinguish the roof and the reactor core, died two weeks later in Moscow Hospital 6; his eyes are said to have been turned from brown to blue by the intensity of the radiation[51]; in 1987 posthumously named a Hero of the Soviet Union
Prishchepa, V.A. Прищепа, В.А. fireman Pravik's unit, watched the fire spread from the roof of Unit C until 6 am as ordered by Teliatnikov
Proskuryakov, Viktor Vasilyevich Проскуряков, Виктор (Витя) Васильович 1955-04-09 1986-05-17 SIUR trainee present in the control room at the moment of explosion; received fatal dose of radiation during attempt to manually lower the control rods as he looked directly to the open reactor core; posthumously awarded the Order "For Courage" of third degree[55]; 100% radiation burns
Rogozhkin, Boris V. Рогожкин 1935? block shift leader supervisor of the 0:00-8:00 shift; after the disaster demoted, allowed to continue working in the plant while awaiting trial[60]; found guilty of gross violation of safety regulations, sentenced to 5 years of labor camp plus two years concurrently for negligence and unfaithful execution of duty[61]
Rysin, Aleksei Vladimirovich Рысин, Алексей Владимирович turbine operation senior engineer
Savenkov, Volodomyr Ivanovych Савенков, Владимир Иванович 1958-02-15 1986-05-21 acute radiation sickness Kharkov turbine plant vibration specialist, mobile laboratory in the car at Turbine 8; first one to become sick; buried in Kharkov in a lead coffin[19]
Shapovalov, Anatoliy Ivanovych Шаповалов, Анатолий Иванович 1941-04-06 1986-05-19 electrician posthumously awarded the Order "For Courage" of third degree[55]
Shashenok, Vladimir (Volodya) Nikolaevich Шашенок, Владимир Николаевич 1951-04-21 1986-04-26 thermal and radiation burns, trauma Atomenergonaladka, adjuster of automatic systems (Chernobyl startup and adjustment enterprise) stationed in Room 604, found pinned down under a fallen beam, with broken spine, broken ribs, deep thermal and radiation burns, and unconscious; died in hospital without regaining consciousness
Shavrey, Leonid Mikhailovich Шаврей, Леонид Михайлович 1952? survivor fireman, squad commander Pravik's unit, watched the fire spread from the roof of Unit C until 6 am as ordered by Teliatnikov; he received about 600 roentgens; checked in hospital on April 29, received bone marrow transplant, released on June 11; served as a fireman in Vyzhgorod until 1994[66]
Shlelyayn, Anatoly Vladislavovich Шлеляйн, Анатолий Владиславович SKALA computer operator, senior officer (SDIVT), block 3 in block 3[59]
Sitnikov, Anatoly Andreyevich (Tolya) Ситников, Анатолий Андреевич 1940-01-20 1986-05-30 deputy chief operational engineer, physicist received fatal dose (about 1500 roentgens), mostly to head, after being sent by Fomin to survey the reactor hall and look at the reactor from the roof of Unit C
Smagin, Viktor Grigoryevich Смагин, Виктор shift foreman, reactor 4
Strelkov, V.D. Стрелков, В.Д. radiation exposition, survivor Kharkov turbine plant vibration mobile laboratory driver, in Pripyat hotel at the time of the explosion; low radiation exposition resulting in later 3rd degree disability[19]
Stolyarchuk, Boris Столярчук senior unit 4 control engineer present in the control room, desk P, at the moment of the explosion, controlling the feedwater and deaerator mechanisms
Telyatnikov, Leonid Petrovich Телятников, Леонид Петрович 1951-01-25 2004-12-02 survivor, received est. 4 Gy firefighter head of the plant fire department; in 1987 named a Hero of the Soviet Union; according to Shavrey, arrived on the scene drunk[66], as he was called from a birthday celebration for his brother
Tishchura, Volodymyr Ivanovych Тищура, Владимир Иванович 1959-12-15 1986-05-10 radiation burns fireman sergeant, Kibenok's unit, fighting fires in the reactor department, separator room, and the central hall
Titenok, Nikolai Ivanovych Титенок, Николай Иванович 1962-12-05 1986-05-16 radiation burns external and internal, incl. blistered heart fireman senior sergeant, Kibenok's unit, fighting fires in the reactor department, separator room, and the central hall; received fatal dose during attempt to extinguish the roof and the reactor core, died two weeks later in Moscow Hospital 6
Tolstiakov, Petr was fishing at the shore of the cooling water channel, witnessed the explosion
Toptunov, Leonid (Lenya) Fedorovych Топтунов, Леонид (Леня) Федорович 1960-08-16 1986-05-14 SIUR, senior engineer for management of the reactor (reactor operator) in the control room at the reactor control panel at the moment of explosion, with Akimov; received fatal dose during attempts to restart feedwater flow into the reactor; posthumously awarded the Order "For Courage" of third degree[55]
Tormozin, Andrei Тормозин, Андрей survivor turbine equipment machinist-inspector in the turbine hall at the moment of explosion; received about 350 (or 860[66]) roentgens during firefighting and stabilizing the turbine hall; received contact burn on his buttocks from sitting on a hot oil line
Tregub, Yuri Yurievich Трегуб, Юрий Юрьевич survivor shift leader, previous shift present in the control room at the moment of explosion[71], received non-lethal dose of radiation when manually opening cooling system valves[63]
Uskov, Arkadiy Gennadievich Усков, Аркадий Геннадиевич reactor operator, senior engineer, block 1 received non-fatal radiation dose when helping Orlov, Akimov and Toptunov to manually open cooling system valves[63][69]
Vashchuk, Mykola Vasylyovych Ващук, Николай Васильевич 1959-06-05 1986-05-14 fireman sergeant, Kibenok's unit, fighting fires in the reactor department, separator room, and the central hall
Verkhovod, V.F. Верховод, В.Ф. SKALA computer operator, senior officer (SDIVT), block 4 at the moment of the explosion in the SKALA room[59]
Vershynin, Yuriy Anatoliyovych Вершинин, Юрий Анатольевич 1959-05-22 1986-07-21 turbine equipment machinist-inspector in the turbine hall at the moment of explosion; received fatal dose (over 1000 rad) during firefighting and stabilizing the turbine hall, died in Moscow hospital; posthumously awarded the Order "For Courage" of third degree[55]; irradiated by a piece of fuel lodged on a nearby transformer of the turbogenerator 7 during attempts to call the control room
Vorobyov, Volodymyr Kostyantynovych Воробьев, Владимир Константинович 1956-03-21 1986-10-02 helicopter crash helicopter pilot died in a helicopter accident
Yunhkind, Oleksandr Yevhenovych Юнгкинд, Александр Евгеньевич 1958-04-15 1986-10-02 helicopter crash helicopter pilot died in a helicopter accident
Yuvchenko, Aleksander Юрченко, Александр 1962? 2009?[72] beta and gamma radiation burns, about 410 rem maintenance department at the moment of the explosion in his office; received burns from radioactive dust on reactor room door he held open for Kudryavtsev and Proskuryakov, started feeling sick at about 3 am, at 6 am too weak to walk, taken by an ambulance to the hospital[51][73]
Zakharov, Anatoliy 1953? survivor firefighter, brigade commander one of the first on the scene, remained until 2pm, cycled home; assumed to receive 300 rem dose, spent 2 months in Kiev hospital; awarded Order of the Red Star for bravery in 1986, declared total invalid in 1992[51][74]
Zapyoklij Запёклый survivor, radiation exposure est. 300 rad construction worker, Block 5, foreman exposed to fallout about 300 meters from Block 4 during return from night shift; spent half year in the Moscow clinic[64]

Immediate crisis management

Radiation levels

The radiation levels in the worst-hit areas of the reactor building have been estimated to be 5.6 röntgen per second (R/s) (0.056 Grays per second, or Gy/s), which is equivalent to 20,000 röntgen per hour (R/hr) (200 Gy per hour, or Gy/hr). A lethal dose is around 500 röntgen (5 Gy) over 5 hours, so in some areas, unprotected workers received fatal doses within several minutes. However, a dosimeter capable of measuring up to 1,000 R/s (10 Gy/s) was inaccessible because of the explosion, and another one failed when turned on. All remaining dosimeters had limits of 0.001 R/s (0.00001 Gy/s) and therefore read "off scale." Thus, the reactor crew could ascertain only that the radiation levels were somewhere above 0.001 R/s (3.6 R/hr, or 0.036 Gy/hr), while the true levels were much higher in some areas.[75]

Because of the inaccurate low readings, the reactor crew chief Alexander Akimov assumed that the reactor was intact. The evidence of pieces of graphite and reactor fuel lying around the building was ignored, and the readings of another dosimeter brought in by 4:30 a.m. were dismissed under the assumption that the new dosimeter must have been defective.[75] Akimov stayed with his crew in the reactor building until morning, trying to pump water into the reactor. None of them wore any protective gear. Most of them, including Akimov, died from radiation exposure within three weeks.[76]

Fire containment

Firefighter Leonid Telyatnikov, being decorated for bravery.

Shortly after the accident, firefighters arrived to try to extinguish the fires. First on the scene was a Chernobyl Power Station firefighter brigade under the command of Lieutenant Volodymyr Pravik, who died on 9 May 1986 of acute radiation sickness. They were not told how dangerously radioactive the smoke and the debris were, and may not even have known that the accident was anything more than a regular electrical fire: "We didn't know it was the reactor. No one had told us."[77]

Grigorii Khmel, the driver of one of the fire-engines, later described what happened:

We arrived there at 10 or 15 minutes to two in the morning ... We saw graphite scattered about. Misha asked: "What is graphite?" I kicked it away. But one of the fighters on the other truck picked it up. "It's hot," he said. The pieces of graphite were of different sizes, some big, some small enough to pick up ...
We didn't know much about radiation. Even those who worked there had no idea. There was no water left in the trucks. Misha filled the cistern and we aimed the water at the top. Then those boys who died went up to the roof - Vashchik Kolya and others, and Volodya Pravik ... They went up the ladder ... and I never saw them again.[78]

However, Anatoli Zakharov, a fireman stationed in Chernobyl since 1980, offers a different description:

I remember joking to the others, "There must be an incredible amount of radiation here. We'll be lucky if we're all still alive in the morning."

20 years after the disaster, he claimed the firefighters from the Fire Station No 2 were aware of the risks.

Of course we knew! If we'd followed regulations, we would never have gone near the reactor. But it was a moral obligation - our duty. We were like kamikaze.[51]

The immediate priority was to extinguish fires on the roof of the station and the area around the building containing Reactor No. 4 to protect No. 3 and keep its core cooling systems intact. The fires were extinguished by 5 a.m., but many firefighters received high doses of radiation. The fire inside Reactor No. 4 continued to burn until 10 May 1986; it is possible that well over half of the graphite burned out.[21] The fire was extinguished by a combined effort of helicopters dropping over 5,000 tonnes of materials like sand, lead, clay, and boron onto the burning reactor and injection of liquid nitrogen. Ukrainian filmmaker Vladimir Shevchenko captured film footage of a Mi-8 helicopter as it collided with a nearby construction crane, causing the helicopter to fall near the damaged reactor building and kill its four-man crew.[79]

From eyewitness accounts of the firefighters involved before they died (as reported on the CBC television series Witness), one described his experience of the radiation as "tasting like metal," and feeling a sensation similar to that of pins and needles all over his face. (This is similar to the description given by Louis Slotin, a Manhattan Project physicist who died days after a fatal radiation overdose from a criticality accident.)[80]

The explosion and fire threw hot particles of the nuclear fuel and also far more dangerous fission products, radioactive elements like caesium-137, iodine-131, strontium-90 and other radionuclides, into the air: the residents of the surrounding area observed the radioactive cloud on the night of the explosion.

Timeline
  • 1:26:03 - fire alarm activated
  • 1:28 - arrival of local firefighters, Pravik's guard
  • 1:35 - arrival of firefighters from Pripyat, Kibenok's guard
  • 1:40 - arrival of Telyatnikov
  • 2:10 - turbine hall roof fire extinguished
  • 2:30 - main reactor hall roof fires suppressed
  • 3:30 - arrival of Kiev firefighters[81]
  • 4:50 - fires mostly localized
  • 6:35 - all fires extinguished[82]

Evacuation of Pripyat

The nearby city of Pripyat was not immediately evacuated.

Evacuation of Pripyat.

Only after radiation levels set off alarms at the Forsmark Nuclear Power Plant in Sweden[83] did the Soviet Union admit that an accident had occurred, but authorities attempted to conceal the scale of the disaster. To evacuate the city of Pripyat, the following warning message was reported on local radio: "An accident has occurred at the Chernobyl Nuclear Power Plant. One of the atomic reactors has been damaged. Aid will be given to those affected and a committee of government inquiry has been set up." This message gave the false impression that any damage or radiation was localized.

The government committee formed to investigate the accident, led by Valeri Legasov, arrived at Chernobyl in the evening of 26 April. By that time two people were dead and 52 were in the hospital. During the night of 26–27 April - more than 24 hours after the explosion - the committee, faced with ample evidence of extremely high levels of radiation and a number of cases of radiation exposure, had to acknowledge the destruction of the reactor and order the evacuation of Pripyat.

The evacuation began at 2 p.m. on 27 April. To reduce baggage, the residents were told the evacuation would be temporary, lasting approximately three days. As a result, Pripyat still contains personal belongings. An exclusion zone of 30 km/19 mi remains in place today.

Steam explosion risk

Chernobyl Corium lava flows formed by fuel-containing mass in the basement of the plant. Lava flow (1). Concrete (2). Steam pipe (3). Electrical equipment (4).[84]

Two floors of bubbler pools beneath the reactor served as a large water reservoir from the emergency cooling pumps and as a pressure suppression system capable of condensing steam from a (small) broken steam pipe; the third floor above them, below the reactor, served as a steam tunnel. The steam released from a broken pipe was supposed to enter the steam tunnel and be led into the pools to bubble through a layer of water. The pools and the basement were flooded because of ruptured cooling water pipes and accumulated fire water. They now constituted a serious steam explosion risk. The smoldering graphite, fuel and other material above, at more than 1200°C,[85] started to burn through the reactor floor and mixed with molten concrete that had lined the reactor, creating corium, a radioactive semi-liquid material comparable to lava.[84][86] If this mixture had melted through the floor into the pool of water, it would have created a massive steam explosion that would have ejected more radioactive material from the reactor. It became an immediate priority to drain the pool.[87]

The bubbler pool could be drained by opening its sluice gates. Heroic volunteers in diving suits entered the radioactive water and managed to open the gates. These were engineers Alexei Ananenko (who knew where the valves were) and Valeri Bezpalov, accompanied by a third man, Boris Baranov, who provided them with light from a lamp, though this lamp failed, leaving them to find the valves by feeling their way along a pipe. All of them returned to the surface and according to Ananenko, their colleagues jumped for joy when they heard they had managed to open the valves. Despite their good condition after completion of the task, all of them suffered from radiation sickness, and at least two - Ananenko and Bezpalov - later died.[citation needed] Some sources claim incorrectly that they died in the plant.[88] It is likely that intense alpha radiation hydrolyzed the water, generating a low-pH hydrogen peroxide (H2O2) solution akin to an oxidizing acid.[89] Conversion of bubbler pool water to H2O2 is confirmed by the presence in the Chernobyl lavas of studtite and metastudtite,[90][91] the only minerals that contain peroxide.[92]

Fire brigade pumps were then used to drain the basement. The operation was not completed until 8 May, after 20,000 tonnes of highly radioactive water were pumped out.

With the bubbler pool gone, a meltdown was less likely to produce a powerful steam explosion. To do so, the molten core would now have to reach the water table below the reactor. To reduce the likelihood of this, it was decided to freeze the earth beneath the reactor, which would also stabilize the foundations. Using oil drilling equipment, injection of liquid nitrogen began on 4 May. It was estimated that 25 tonnes of liquid nitrogen per day would be required to keep the soil frozen at -100°C.[93] This idea was soon scrapped and the bottom room where the cooling system would have been installed was filled with cement.

Debris removal

The worst of the radioactive debris was collected inside what was left of the reactor, much of it shoveled in by liquidators wearing heavy protective gear (dubbed "bio-robots" by the military); these workers could only spend a maximum of 40 seconds at a time working on the rooftops of the surrounding buildings because of the extremely high doses of radiation given off by the blocks of graphite and other debris. The reactor itself was covered with bags containing sand, lead, and boric acid dropped from helicopters (some 5,000 metric tonnes during the week following the accident). By December 1986 a large concrete sarcophagus had been erected, to seal off the reactor and its contents.[94]

Many of the vehicles used by the "liquidators" remain parked in a field in the Chernobyl area to this day, most giving off doses of 10-30 R/hr (0.1-0.3 Gy/hr) over 20 years after the disaster.[95]

Causes

There were two official explanations of the accident: the first, subsequently acknowledged as erroneous, was published in August 1986 and effectively placed the blame on the power plant operators. To investigate the causes of the accident the IAEA created a group known as the International Nuclear Safety Advisory Group (INSAG), which in its report of 1986, INSAG-1, on the whole also supported this view, based on the data provided by the Soviets and the oral statements of specialists.[96] In this view, the catastrophic accident was caused by gross violations of operating rules and regulations. "During preparation and testing of the turbine generator under run-down conditions using the auxiliary load, personnel disconnected a series of technical protection systems and breached the most important operational safety provisions for conducting a technical exercise."[97] This was probably due to their lack of knowledge of nuclear reactor physics and engineering, as well as lack of experience and training. According to these allegations, at the time of the accident the reactor was being operated with many key safety systems shut off, most notably the Emergency Core Cooling System (ECCS). Personnel had an insufficiently detailed understanding of technical procedures involved with the nuclear reactor, and knowingly ignored regulations to speed test completion.[97]

The developers of the reactor plant considered this combination of events to be impossible and therefore did not allow for the creation of emergency protection systems capable of preventing the combination of events that led to the crisis, namely the intentional disabling of emergency protection equipment plus the violation of operating procedures. Thus the primary cause of the accident was the extremely improbable combination of rule infringement plus the operational routine allowed by the power station staff.[98]

In this analysis of the causes of the accident, deficiencies in the reactor design and in the operating regulations that made the accident possible were set aside and mentioned only casually. Serious critical observations covered only general questions and did not address the specific reasons for the accident. The following general picture arose from these observations. Several procedural irregularities also helped to make the accident possible. One was insufficient communication between the safety officers and the operators in charge of the experiment being run that night. The reactor operators disabled safety systems down to the generators, which the test was really about. The main process computer, SKALA, was running in such a way that the main control computer could not shut down the reactor or even reduce power. Normally the reactor would have started to insert all of the control rods. The computer would have also started the "Emergency Core Protection System" that introduces 24 control rods into the active zone within 2.5 seconds, which is still slow by 1986 standards. All control was transferred from the process computer to the human operators.

This view is reflected in numerous publications and also artistic works on the theme of the Chernobyl accident that appeared immediately after the accident,[99], and for a long time remained dominant in the public consciousness and in popular publications.

However, in 1993 the IAEA Nuclear Safety Advisory Group (INSAG) published an additional report, INSAG-7,[24] which reviewed "that part of the INSAG-1 report in which primary attention is given to the reasons for the accident." In this later report, most of the accusations against staff for breach of regulations were acknowledged to be erroneous, based on incorrect information obtained in August 1986. This report reflected another view of the reasons for the accident, presented in appendix I.
According to this account, turning off the ECCS, and also interfering with the settings on the protection equipment and blocking the level and pressure in the separator drum, did not contribute to the original cause of the accident and its magnitude, though they were possibly a breach of regulations. Turning off the emergency system designed to protect against the stopping of the two turbine generators was not a breach of regulations.

Human factors contributed to the conditions that led to the disaster, namely working with a small operational reactivity margin (ORM) and working at a low level of power in the reactor, less than 700 MW - the level documented in the run-down test program. Nevertheless, working at this low level of power was not forbidden in the regulations, despite what Soviet experts asserted in 1986.[100]
Regulations forbade work with a small margin of reactivity. However, "... post-accident studies have shown that the way in which the real role of the ORM is reflected in the Operating Procedures and design documentation for the RBMK-1000 is extremely contradictory," and furthermore, "ORM was not treated as an operational safety limit, violation of which could lead to an accident."[101],(see also [102]).

According to this report, the chief reasons for the accident lie in the peculiarities of physics and in the construction of the reactor. There are two such reasons:

  • The reactor had a dangerously large positive void coefficient. The void coefficient is a measurement of how a reactor responds to increased steam formation in the water coolant. Most other reactor designs have a negative coefficient, i.e. they attempt to decrease heat output when the vapor phase in the reactor increases, because if the coolant contains steam bubbles, fewer neutrons are slowed down. Faster neutrons are less likely to split uranium atoms, so the reactor produces less power (a negative feed-back). Chernobyl's RBMK reactor, however, used solid graphite as a neutron moderator to slow down the neutrons, and the water in it, on the contrary, acts like a harmful neutron absorber. Thus neutrons are slowed down even if steam bubbles form in the water. Furthermore, because steam absorbs neutrons much less readily than water, increasing the intensity of vaporization means that more neutrons are able to split uranium atoms, increasing the reactor's power output. This makes the RBMK design very unstable at low power levels, and prone to suddenly increasing energy production to a dangerous level. This behavior is counter-intuitive, and this property of the reactor was unknown to the crew.
  • A more significant flaw was in the design of the control rods that are inserted into the reactor to slow down the reaction. In the RBMK reactor design, the lower part of each control rod was made of graphite and was 1.3 meters shorter than necessary, and in the space beneath the rods were hollow channels filled with water. The upper part of the rod - the truly functional part that absorbs the neutrons and thereby halts the reaction - was made of boron carbide. With this design, when the rods are inserted into the reactor from the uppermost position, the graphite parts initially displace some coolant. This greatly increases the rate of the fission reaction, since graphite (in the RBMK) is a more potent neutron moderator (absorbs far fewer neutrons than the boiling light water). Thus for the first few seconds of control rod activation, reactor power output is increased, rather than reduced as desired. This behavior is counter-intuitive and was not known to the reactor operators.
  • Other deficiencies besides these were noted in the RBMK-1000 reactor design, as were its non-compliance with accepted standards and with the requirements of nuclear reactor safety.

Both views were heavily lobbied by different groups, including the reactor's designers, power plant personnel, and the Soviet and Ukrainian governments. According to the IAEA's 1986 analysis, the main cause of the accident was the operators' actions. But according to the IAEA's 1993 revised analysis the main cause was the reactor's design.[103] One reason there were such contradictory viewpoints and so much debate about the causes of the Chernobyl accident was that the primary data covering the disaster, as registered by the instruments and sensors, were not completely published in the official sources.

Once again, the human factor had to be considered as a major element in causing the accident. INSAG notes that both the operating regulations and staff handled the disabling of the reactor protection easily enough: witness the length of time for which the ECCS was out of service while the reactor was operated at half power. INSAG’s view is that it was the operating crew's deviation from the test program that was mostly to blame. “Most reprehensibly, unapproved changes in the test procedure were deliberately made on the spot, although the plant was known to be in a very different condition from that intended for the test.” [104]

As in the previously released report INSAG-1, close attention is paid in report INSAG-7 to the inadequate (at the moment of the accident) “culture of safety” at all levels. Deficiency in the safety culture was inherent not only at the operational stage but also, and to no lesser extent, during activities at other stages in the lifetime of nuclear power plants (including design, engineering, construction, manufacture and regulation). The poor quality of operating procedures and instructions, and their conflicting character, put a heavy burden on the operating crew, including the Chief Engineer. “The accident can be said to have flowed from a deficient safety culture, not only at the Chernobyl plant, but throughout the Soviet design, operating and regulatory organizations for nuclear power that existed at that time.” [104]

Effects

International spread of radioactivity

The nuclear meltdown produced a radioactive cloud that was detected over all of Europe except for the Iberian Peninsula.[105][106][107]

The initial evidence that a major release of radioactive material was affecting other countries came not from Soviet sources, but from Sweden, where on the morning of April 28[108] workers at the Forsmark Nuclear Power Plant (approximately 1,100 km (680 mi) from the Chernobyl site) were found to have radioactive particles on their clothes.[109] It was Sweden's search for the source of radioactivity, after they had determined there was no leak at the Swedish plant, that at noon on April 28 led to the first hint of a serious nuclear problem in the western Soviet Union. Hence the evacuation of Pripyat on April 27, 36 hours after the initial explosions, was silently completed before the disaster became known outside the Soviet Union. The rise in radiation levels had at that time already been measured in Finland, but a civil service strike delayed the response and publication.[110]

Contamination from the Chernobyl accident was scattered irregularly depending on weather conditions. Reports from Soviet and Western scientists indicate that Belarus received about 60% of the contamination that fell on the former Soviet Union. However, the 2006 TORCH report stated that half of the volatile particles had landed outside Ukraine, Belarus, and Russia. A large area in Russia south of Bryansk was also contaminated, as were parts of northwestern Ukraine. Studies in surrounding countries indicate that over one million people could have been affected by radiation.[111]

Recently published data from a long-term monitoring program (The Korma-Report)[112] show a decrease in internal radiation exposure of the inhabitants of a region in Belarus close to Gomel. Resettlement may even be possible in prohibited areas provided that people comply with appropriate dietary rules.

In Western Europe, precautionary measures taken in response to the radiation included seemingly arbitrary regulations banning the importation of certain foods but not others. In France some officials stated that the Chernobyl accident had no adverse effects.[citation needed]

Radioactive release (source term)

The external gamma dose for a person in the open near the Chernobyl site.
Contributions of the various isotopes to the (atmospheric) dose in the contaminated area soon after the accident.

Like many other releases of radioactivity into the environment, the Chernobyl release was controlled by the physical and chemical properties of the radioactive elements in the core. While the general population often perceives plutonium as a particularly dangerous nuclear fuel, its effects are almost eclipsed by those of its fission products. Particularly dangerous are highly radioactive compounds that accumulate in the food chain, such as some isotopes of iodine and strontium.

Two reports on the release of radioisotopes from the site were made available, one by the OSTI and a more detailed report by the OECD, both in 1998.[113][114] At different times after the accident, different isotopes were responsible for the majority of the external dose. The dose that was calculated is that received from external gamma irradiation for a person standing in the open. The dose to a person in a shelter or the internal dose is harder to estimate.

The release of radioisotopes from the nuclear fuel was largely controlled by their boiling points, and the majority of the radioactivity present in the core was retained in the reactor.

Two sizes of particles were released: small particles of 0.3 to 1.5 micrometers (aerodynamic diameter) and large particles of 10 micrometers. The large particles contained about 80% to 90% of the released nonvolatile radioisotopes zirconium-95, niobium-95, lanthanum-140, cerium-144 and the transuranic elements, including neptunium, plutonium and the minor actinides, embedded in a uranium oxide matrix.

Health of plant workers and local people

In the aftermath of the accident, 237 people suffered from acute radiation sickness, of whom 31 died within the first three months.[115][116] Most of these were fire and rescue workers trying to bring the accident under control, who were not fully aware of how dangerous exposure to the radiation in the smoke was. Some 135,000 people were evacuated from the area, including 50,000 from Pripyat.

Residual radioactivity in the environment

Rivers, lakes and reservoirs

Earth Observing-1 image of the reactor and surrounding area in April of 2009.

The Chernobyl nuclear power plant is located next to the Pripyat River, which feeds into the Dnipro River reservoir system, one of the largest surface water systems in Europe. The radioactive contamination of aquatic systems therefore became a major issue in the immediate aftermath of the accident.[117] In the most affected areas of Ukraine, levels of radioactivity (particularly radioiodine: I-131, radiocaesium: Cs-137 and radiostrontium: Sr-90) in drinking water caused concern during the weeks and months after the accident. After this initial period, however, radioactivity in rivers and reservoirs was generally below guideline limits for safe drinking water.[117]

Bio-accumulation of radioactivity in fish[118] resulted in concentrations (both in western Europe and in the former Soviet Union) that in many cases were significantly above guideline maximum levels for consumption.[117] Guideline maximum levels for radiocaesium in fish vary from country to country but are approximately 1,000 Bq/kg in the European Union.[119] In the Kiev Reservoir in Ukraine, concentrations in fish were several thousand Bq/kg during the years after the accident.[118] In small "closed" lakes in Belarus and the Bryansk region of Russia, concentrations in a number of fish species varied from 0.1 to 60 kBq/kg during the period 1990–92.[120] The contamination of fish caused short-term concern in parts of the UK and Germany and in the long term (years rather than months) in the affected areas of Ukraine, Belarus, and Russia as well as in parts of Scandinavia.[117]

Groundwater

Map of radiation levels in 1996 around Chernobyl.

Groundwater was not badly affected by the Chernobyl accident since radionuclides with short half-lives decayed away long before they could affect groundwater supplies, and longer-lived radionuclides such as radiocaesium and radiostrontium were adsorbed to surface soils before they could transfer to groundwater.[121] However, significant transfers of radionuclides to groundwater have occurred from waste disposal sites in the 30 km (19 mi) exclusion zone around Chernobyl. Although there is a potential for transfer of radionuclides from these disposal sites off-site (i.e. out of the 30 km (19 mi) exclusion zone), the IAEA Chernobyl Report[121] argues that this is not significant in comparison to current levels of washout of surface-deposited radioactivity.

Flora and fauna

After the disaster, four square kilometres of pine forest in the immediate vicinity of the reactor turned reddish-brown and died, earning the name of the "Red Forest".[122] Some animals in the worst-hit areas also died or stopped reproducing. Most domestic animals were evacuated from the exclusion zone, but horses left on an island in the Pripyat River 6 km (4 mi) from the power plant died when their thyroid glands were destroyed by radiation doses of 150–200 Sv.[123] Some cattle on the same island died and those that survived were stunted because of thyroid damage. The next generation appeared to be normal.[123]

A robot sent into the reactor itself has returned with samples of black, melanin-rich radiotrophic fungi that are growing on the reactor's walls.[124]

Chernobyl after the disaster

The Pripyat Ferris wheel as seen from inside the town's Palace of Culture.

Following the accident, questions arose about the future of the plant and its eventual fate. All work on the unfinished reactors 5 and 6 was halted three years later. However, the trouble at the Chernobyl plant did not end with the disaster in reactor 4. The damaged reactor was sealed off and 200 metres (660 ft) of concrete was placed between the disaster site and the operational buildings. The Ukrainian government continued to let the three remaining reactors operate because of an energy shortage in the country. In 1991, a fire broke out in the turbine building of reactor 2;[125] the authorities subsequently declared the reactor damaged beyond repair and had it taken offline. Reactor 1 was decommissioned in November 1996 as part of a deal between the Ukrainian government and international organizations such as the IAEA to end operations at the plant. On 15 December 2000, then-President Leonid Kuchma personally turned off Reactor 3 in an official ceremony, shutting down the entire site.[126]

Chernobyl's Exclusion Zone

In his book Disasters: Wasted Lives, Valuable Lessons, economist and crisis consultant Randall Bell writes after his research at Chernobyl:

There is a 17-mile (sic) Exclusion Zone around Chernobyl where officially nobody is allowed to live, but people do. These "resettlers" are elderly people who lived in the region prior to the disaster. Today there are approximately 10,000 people between the ages of 60 and 90 living within the Zone around Chernobyl. Younger families are allowed to visit, but only for brief periods of time.

Eventually the land could be utilized for some sort of industrial purpose that would involve concrete sites. But estimates range from 60 – 200 years before this would be allowed. Farming or any other type of agricultural industry would be dangerous and completely inappropriate for at least 200 years. It will be at least two centuries before there is any chance the situation can change within the 1.5-mile Exclusion Zone. As for the #4 reactor where the meltdown occurred, we estimate it will be 20,000 years before the real estate will be fully safe.[127]

Controversy over "Wildlife Haven" claim

The Exclusion Zone around the Chernobyl nuclear power station is reportedly a haven for wildlife.[128][129] As humans were evacuated from the area just over 23 years ago, existing animal populations multiplied and rare species not seen for centuries have returned or have been reintroduced, for example lynx, wild boar, wolf, Eurasian brown bear, European bison, Przewalski's horse, and eagle owl.[128][129] Birds even nest inside the cracked concrete sarcophagus shielding in the shattered remains of reactor number 4.[130] The Exclusion Zone is so lush with wildlife and greenery that in 2007 the Ukrainian government designated it a wildlife sanctuary, "Chernobyl Special";[131] and at 488.7 km2 it is one of the largest wildlife sanctuaries in Europe.[129]

According to a 2005 U.N. report, wildlife has returned despite radiation levels that are presently 10 to 100 times higher than normal background radiation. Although they were significantly higher soon after the accident, the levels have fallen because of radioactive decay.[130]

Some researchers claim that by halting the destruction of habitat, the Chernobyl disaster helped wildlife flourish. Biologist Robert J. Baker of Texas Tech University was one of the first to report that Chernobyl had become a wildlife haven and that many rodents he has studied at Chernobyl since the early 1990s have shown remarkable tolerance for elevated radiation levels.[130]

However Møller et al. (2005) suggested that reproductive success and annual survival rates of barn swallows are much lower in the Chernobyl exclusion zone; 28% of barn swallows inhabiting Chernobyl return each year, while at a control area at Kanev 250 km to the southeast, the return rate is around 40%.[132][133] A later study by Møller et al. (2007) furthermore claimed an elevated frequency of 11 categories of subtle physical abnormalities in barn swallows, such as bent tail feathers, deformed air sacs, deformed beaks, and isolated albinistic feathers.[134]

However, another researcher criticized these findings and instead proposed that a lack of human influence in the exclusion zone locally reduced the swallows' insect prey and that radiation levels across the vast majority of the exclusion zone are now too low to have an observable negative effect.[135] But the criticisms raised were responded to in Møller et al. (2008).[136] It is possible that barn swallows are particularly vulnerable to elevated levels of ionizing radiation because they are migratory; they arrive in the exclusion area exhausted and with depleted reserves of radio-protective antioxidants after an arduous journey.[132]

Several research groups have suggested that plants in the area have adapted to cope with the high radiation levels, for example by increasing the activity of DNA cellular repair machinery and by hypermethylation.[137][138][138][139] (see Radiation Hormesis). Given the uncertainties, further research is needed to assess the long-term health effects of elevated ionizing radiation from Chernobyl on flora and fauna.[130]

Chernobyl today

Monument in Rivne, Ukraine.

The Chernobyl reactor is now enclosed in a large concrete sarcophagus, which was built quickly to allow continuing operation of the other reactors at the plant.[140]

A New Safe Confinement was to have been built by the end of 2005; however, it has suffered ongoing delays and is currently expected to be completed in 2012. The structure will be built adjacent to the existing shelter and then will be slid into place on rails. It is to be a metal arch 105 meters (344.4 feet) high and spanning 257 meters (842.9 feet), to cover both unit 4 and the hastily built 1986 structure. The Chernobyl Shelter Fund, set up in 1997, has received 810 million from international donors and projects to cover this project and previous work. It and the Nuclear Safety Account, also applied to Chernobyl decommissioning, are managed by the European Bank for Reconstruction and Development (EBRD).[citation needed]

As of 2006, some fuel remained in the reactors at units 1 through 3, most of it in each unit's cooling pond, as well as some material in a small spent fuel interim storage facility pond (ISF-1).

In 1999 a contract was signed for construction of a radioactive waste management facility to store 25,000 used fuel assemblies from units 1–3 and other operational wastes, as well as material from decommissioning units 1–3 (which will be the first RBMK units decommissioned anywhere). The contract included a processing facility able to cut the RBMK fuel assemblies and to put the material in canisters, which were to be filled with inert gas and welded shut. The canisters were to be transported to dry storage vaults, where the fuel containers would be enclosed for up to 100 years. This facility, treating 2500 fuel assemblies per year, would be the first of its kind for RBMK fuel. However, after a significant part of the storage structures had been built, technical deficiencies in the concept emerged, and the contract was terminated in 2007. The interim spent fuel storage facility (ISF-2) will now be completed by others by mid-2013.[citation needed]

Another contract has been let for a liquid radioactive waste treatment plant, to handle some 35,000 cubic meters of low- and intermediate-level liquid wastes at the site. This will need to be solidified and eventually buried along with solid wastes on site.[citation needed]

In January 2008, the Ukrainian government announced a 4-stage decommissioning plan that incorporates the above waste activities and progresses towards a cleared site.[111]

Lava-like Fuel-Containing Materials (FCMs)

The radioactivity levels of different isotopes in the FCM, as back-calculated by Russian workers to April 1986.

According to official estimates, about 95% of the fuel in the reactor at the time of the accident (about 180 tonnes) remains inside the shelter, with a total radioactivity of nearly 18 million curies (670 PBq). The radioactive material consists of core fragments, dust, and lava-like "fuel-containing materials" (FCM, also called "corium") that flowed through the wrecked reactor building before hardening into a ceramic form.

Three different lavas are present in the basement of the reactor building: black, brown, and a porous ceramic. They are silicate glasses with inclusions of other materials within them. The porous lava is brown lava that dropped into water and thus cooled rapidly.

Degradation of the lava

It is unclear how long the ceramic form will retard the release of radioactivity. From 1997 to 2002 a series of papers were published that suggested that the self-irradiation of the lava would convert all 1,200 tons into a submicrometre and mobile powder within a few weeks.[141] But it has been reported that the degradation of the lava is likely to be a slow and gradual process rather than sudden and rapid.[142] The same paper states that the loss of uranium from the wrecked reactor is only 10 kg (22 lb) per year. This low rate of uranium leaching suggests that the lava is resisting its environment. The paper also states that when the shelter is improved, the leaching rate of the lava will decrease.

Some of the surfaces of the lava flows have started to show new uranium minerals such as Na4(UO2)(CO3)3 and uranyl carbonate. However, the level of radioactivity is such that during one hundred years the self irradiation of the lava (2 × 1016 α decays per gram and 2 to 5 × 105 Gy of β or γ) will fall short of the level of self irradiation required to greatly change the properties of glass (1018 α decays per gram and 108 to 109 Gy of β or γ). Also the rate of dissolution of the lava in water is very low (10−7 g-cm−2 day−1), suggesting that the lava is unlikely to dissolve in water.[142]

Possible consequences of further collapse of the Sarcophagus

The Sarcophagus, the concrete block surrounding reactor #4

The protective box that was placed over the wrecked reactor was named object "Shelter" by the Soviet government, but the media and the public know it as the "sarcophagus."

The present shelter is constructed over the ruins of the reactor building. The two "Mammoth Beams" that support the roof of the shelter rest partly on the structurally unsound west wall of the reactor building that was damaged by the accident.[143] The western end of the shelter roof is supported by a wall at a point designated axis 50. This wall is reinforced concrete, and was cracked by the accident. In December 2006 the "Designed Stabilisation Steel Structure" (DSSS) was extended until 50% of the roof load (about 400 tons) was transferred from the axis 50 wall to the DSSS.[citation needed] The DSSS is a yellow steel object that has been placed next to the wrecked reactor; it is 63 metres (207 ft) tall and has a series of cantilevers that extend through the western buttress wall, and is intended to stabilize the sarcophagus.[144] This was done because if the wall of the reactor building or the roof of the shelter were to collapse, then large amounts of radioactive dust and particles would be released directly into the atmosphere, resulting in a large new release of radioactivity into the environment.

A further threat to the shelter is the concrete slab that formed the "Upper Biological Shield" (UBS), situated above the reactor prior to the accident.[citation needed] This concrete slab was thrown upwards by the explosion in the reactor core and now rests at approximately 15° from vertical. The position of the upper bioshield is considered inherently unsafe, as only debris supports it in its nearly upright position. A collapse of the bioshield would further exacerbate the dust conditions in the shelter, possibly spreading some quantity of radioactive materials out of the shelter, and could damage the shelter itself. The UBS is a circle 15 meters in diameter, weighing 1000 tons and consisting of 2000 cubes, each located above a fuel channel. The shield, called Pyatachok ("five kopek coin") before the disaster, was afterwards named Component "E" and nicknamed "Elena"; the twisted fuel bundles still attached to it are called "Elena's hair."[145][146][147]

Grass and forest fires

It is known that fires can make radioactivity mobile again.[148][149][150][151] In particular V.I. Yoschenko et al. reported on the possibility of increased mobility of caesium, strontium, and plutonium due to grass and forest fires.[152] As an experiment, fires were set and the levels of the radioactivity in the air downwind of these fires was measured.

Grass and forest fires have happened inside the contaminated zone, releasing radioactive fallout into the atmosphere. In 1986 a series of fires destroyed 23.36 km2 (5,772 acres) of forest, and several other fires have since burned within the 30 km (19 mi) zone. A serious fire in early May 1992 affected 5 km2 (1,240 acres) of land including 2.7 km2 (670 acres) of forest. This resulted in a great increase in the levels of caesium-137 in airborne dust.[148][153][154][155]

Recovery process

Recovery projects

The Chernobyl Shelter Fund

The Chernobyl Shelter Fund was established in 1997 at the Denver 23rd G8 summit to finance the Shelter Implementation Plan (SIP). The plan calls for transforming the site into an ecologically safe condition by means of stabilization of the Sarcophagus followed by construction of a New Safe Confinement (NSC). While the original cost estimate for the SIP was US$768 million, the 2006 estimate was $1.2 billion. The SIP is being managed by a consortium of Bechtel, Battelle, and Electricité de France, and conceptual design for the NSC consists of a movable arch, constructed away from the shelter to avoid high radiation, to be slid over the sarcophagus. The NSC is expected to be completed in 2012, and will be the largest movable structure ever built.

Dimensions:

  • Span: 270 m (886 ft)
  • Height: 100 m (330 ft)
  • Length: 150 m (492 ft)

The United Nations Development Programme

The United Nations Development Programme has launched in 2003 a specific project called the Chernobyl Recovery and Development Programme (CRDP) for the recovery of the affected areas.[156] The programme was initiated in February 2002 based on the recommendations in the report on Human Consequences of the Chernobyl Nuclear Accident. The main goal of the CRDP’s activities is supporting the Government of Ukraine in mitigating long-term social, economic, and ecological consequences of the Chernobyl catastrophe. CRDP works in the four most Chernobyl-affected areas in Ukraine: Kyivska, Zhytomyrska, Chernihivska and Rivnenska.

The International Project on the Health Effects of the Chernobyl Accident

The International Project on the Health Effects of the Chernobyl Accident (IPEHCA) was created and received US $20 million, mainly from Japan, in hopes of discovering the main cause of health problems due to 131I radiation. These funds were divided between Ukraine, Belarus, and Russia, the three main affected countries, for further investigation of health effects. As there was significant corruption in former Soviet countries, most of the foreign aid was given to Russia, and no positive outcome from this money has been demonstrated.

Assessing the disaster's effects on human health

Mental Health Effects

The anxiety caused by the accident, which appears to show no sign of diminishing, and its negative impact on the living conditions in the affected areas, may be the principal reason for the increase in poor reported health.[citation needed] Beyond this, it has been argued that a culture has developed in which people perceive themselves to be victims, where there is a lack of trust, where ill-health is expected, where there are general feelings of anxiety, instability, helplessness, and a generalized fear about the future; all of which have resulted in an increased inability to adjust to changed circumstances. The negative impact of the accident has been compounded by a breakdown in the infrastructure of community life, increased poverty, poor diet and generally poor living conditions, which have further deteriorated following the break-up of the USSR in 1991.[citation needed]

Physical Health Effects

  • Down's syndrome (trisomy 21). In West Berlin, Germany, prevalence of Down's syndrome (trisomy 21) peaked 9 months following the main fallout.[ 11, 12] Between 1980 and 1986, the birth prevalence of Down's syndrome was quite stable (i.e., 1.35–1.59 per 1,000 live births [27–31 cases]). In 1987, 46 cases were diagnosed (prevalence = 2.11 per 1,000 live births). Most of the excess resulted from a cluster of 12 cases among children born in January 1987. The prevalence of Down's syndrome in 1988 was 1.77, and in 1989, it reached pre-Chernobyl values. The authors noted that the isolated geographical position of West Berlin prior to reunification, the free genetic counseling, and complete coverage of the population through one central cytogenetic laboratory support completeness of case ascertainment; in addition, constant culture preparation and analysis protocols ensure a high quality of data.
  • Chromosomal aberrations. Reports of structural chromosome aberrations in people exposed to fallout in Belarus and other parts of the former Soviet Union, Austria, and Germany argue against a simple dose-response relationship between degree of exposure and incidence of aberrations. These findings are relevant because a close relationship exists between chromosome changes and congenital malformations. Inasmuch as some types of aberrations are almost specific for ionizing radiation, researchers use aberrations to assess exposure dose. On the basis of current coefficients, however, one cannot assume that calculation of individual exposure doses resulting from fallout would not induce measurable rates of chromosome aberrations.
  • Neural tube defects (NTDs) in Turkey. During the embryonic phase of fetal development, the neural tube differentiates into the brain and spinal cord (i.e., collectively forming the central nervous system). Chemical or physical interactions with this process can cause NTDs. Common features of this class of malformations are more or less extended fissures, often accompanied by consecutive dislocation of central nervous system (CNS) tissue. NTDs include spina bifida occulta and aperta, encephalocele, and - in the extreme case - anencephaly. The first evidence in support of a possible association between CNS malformations and fallout from Chernobyl was published by Akar et al. in 1988. The Mustafakemalpasa State Hospital, Bursa region, covers a population of approximately 90,000. Investigators have documented the prevalence of malformations since 1983. The prevalence of NTDs was 1.7 to 9.2 per 1,000 births, but during the first 6 months of 1987 increased to 20 per 1,000 (12 cases). The excess was most pronounced for the subgroup of anencephalics, in which prevalence increased 5-fold (i.e., 10 per 1,000 [6 cases]). In the consecutive months that followed (i.e., July-December 1987), the prevalence decreased again (1.3 per 1,000 for all NTDs, 0.6 per 1,000 for anencephaly), and it reached pre-Chernobyl levels during the first half of 1988 (all NTDs: 0.6 per 1,000; anencephaly: 0.2 per 1,000). This initial report was supported by several similar findings in observational studies from different regions of Turkey.[citation needed]
Demonstration on Chernobyl day near WHO in Geneva

An international assessment of the health effects of the Chernobyl accident is contained in a series of reports by the United Nations Scientific Committee of the Effects of Atomic Radiation (UNSCEAR).[157] UNSCEAR was set up as a collaboration between various UN bodies, including the World Health Organisation, after the atomic bomb attacks on Hiroshima and Nagasaki, to assess the long-term effects of radiation on human health.

UNSCEAR has conducted 20 years of detailed scientific and epidemiological research on the effects of the Chernobyl accident. Apart from the 57 direct deaths in the accident itself, UNSCEAR originally predicted up to 4,000 additional cancer cases due to the accident.[158] However, the latest UNSCEAR reports suggest that these estimates were overstated.[159] In addition, the IAEA states that there has been no increase in the rate of birth defects or abnormalities, or solid cancers (such as lung cancer) corroborating UNSCEAR's assessments.[160]

Precisely, UNSCEAR states:

Among the residents of Belaruss 09, the Russian Federation and Ukraine there had been, up to 2002, about 4,000 cases of thyroid cancer reported in children and adolescents who were exposed at the time of the accident, and more cases are to be expected during the next decades. Notwithstanding problems associated with screening, many of those cancers were most likely caused by radiation exposures shortly after the accident. Apart from this increase, there is no evidence of a major public health impact attributable to radiation exposure 20 years after the accident. There is no scientific evidence of increases in overall cancer incidence or mortality rates or in rates of non-malignant disorders that could be related to radiation exposure. The risk of leukaemia in the general population, one of the main concerns owing to its short latency time, does not appear to be elevated. Although those most highly exposed individuals are at an increased risk of radiation-associated effects, the great majority of the population is not likely to experience serious health consequences as a result of radiation from the Chernobyl accident. Many other health problems have been noted in the populations that are not related to radiation exposure.[159]

Thyroid cancer is generally treatable.[161] With proper treatment, the five-year survival rate of thyroid cancer is 96%, and 92% after 30 years.[162]

The Chernobyl Forum is a regular meeting of IAEA, other United Nations organizations (FAO, UN-OCHA, UNDP, UNEP, UNSCEAR, WHO, and the World Bank), and the governments of Belarus, Russia, and Ukraine that issues regular scientific assessments of the evidence for health effects of the Chernobyl accident.[163] The Chernobyl Forum concluded that twenty-eight emergency workers died from acute radiation syndrome including beta burns and 15 patients died from thyroid cancer, and it roughly estimated that cancer deaths caused by Chernobyl may reach a total of about 4,000 among the 600,000 people having received the greatest exposures. It also concluded that a greater risk than the long-term effects of radiation exposure is the risk to mental health of exaggerated fears about the effects of radiation:[164]

The designation of the affected population as “victims” rather than “survivors” has led them to perceive themselves as helpless, weak and lacking control over their future. This, in turn, has led either to over cautious behavior and exaggerated health concerns, or to reckless conduct, such as consumption of mushrooms, berries and game from areas still designated as highly contaminated, overuse of alcohol and tobacco, and unprotected promiscuous sexual activity.[165]

Fred Mettler commented that 20 years later:[166]

The population remains largely unsure of what the effects of radiation actually are and retain a sense of foreboding. A number of adolescents and young adults who have been exposed to modest or small amounts of radiation feel that they are somehow fatally flawed and there is no downside to using illicit drugs or having unprotected sex. To reverse such attitudes and behaviors will likely take years although some youth groups have begun programs that have promise.

In addition, disadvantaged children around Chernobyl suffer from health problems that are attributable not only to the Chernobyl accident, but also to the poor state of post-Soviet health systems.[167]

Another study critical of the Chernobyl Forum report was commissioned by Greenpeace, which is well known for its anti-nuclear positions. In its report, Greenpeace alleges that: "the most recently published figures indicate that in Belarus, Russia and Ukraine alone the accident could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004." However, the Greenpeace report failed to discriminate between the general increase in cancer rates that followed the dissolution of the USSR's health care system and any separate effects of the Chernobyl accident.[168]

Lastly, in its report Health Effects of Chernobyl, the German affiliate of the International Physicians for the Prevention of Nuclear War (IPPNW) argued that more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected in the future.[169] According to some commentators, both the Greenpeace and IPPNW reports suffer from a lack of any genuine or original research and failure to understand epidemiologic data.[159] This said, it is important to bear in mind that many of the conclusions from reports such as UNSCEAR remain disputed by anti-nuclear groups.[170]

In popular culture

The Chernobyl accident attracted a great deal of interest. Because of the distrust that many people (both within and outside the USSR) had in the Soviet authorities, a great deal of debate about the situation at the site occurred in the first world during the early days of the event. Because of defective intelligence based on photographs taken from space, it was thought that unit number three had also suffered a dire accident.

A few authors claim that the official reports underestimate the scale of the Chernobyl tragedy, counting only 30 victims;[171] some estimate the Chernobyl radioactive fallout as hundreds of times that of the atomic bomb dropped on Hiroshima, Japan,[172][173] counting millions of exposed.

In general the public knew little about radioactivity and radiation and as a result their degree of fear was increased. Journalists mistrusted many professionals (such as the spokesman from the UK NRPB), and in turn encouraged the public to mistrust them.[174]

It was noted[175] that some governments tried to set stricter contamination level limits than their neighbors.

In Italy, the fear of nuclear accidents was dramatically increased by the Chernobyl accident: this was reflected in the outcome of the 1987 referendum about the construction of new nuclear plants in Italy. As a result of that referendum, Italy began phasing out its nuclear power plants in 1988.

The disaster features in the popular video game Call of Duty 4: Modern Warfare. In the game a fictional event set in Pripyat involves the player playing the role of Captain Price being sent to assassinate a buyer of the nuclear waste, which is to be used in a nuclear bomb.

Commemoration of the disaster

The Front Veranda (1986), a lithograph by Susan Dorothea White in the National Gallery of Australia, exemplifies worldwide awareness of the event. Heavy Water: A film for Chernobyl was released by Seventh Art in 2006 to commemorate the disaster through poetry and first-hand accounts.[176] The film secured the Cinequest Award as well as the Rhode Island "best score" award [2] along with a screening at Tate Modern.[177]

Chernobyl 20

This exhibit presents the stories of 20 people who have each been affected by the disaster, and each person's account is written on a panel. The 20 individuals whose stories are related in the exhibition are from Belarus, France, Latvia, Russia, Sweden, Ukraine, and the United Kingdom.

Developed by Danish photo-journalist Mads Eskesen, the exhibition is prepared in multiple languages including German, English, Danish, Dutch, Russian, and Ukrainian.

In Kiev, Ukraine, the exhibition was launched at the "Chernobyl 20 Remembrance for the Future" conference on April 23, 2006. It was then exhibited during 2006 in Australia, Denmark, the Netherlands, Switzerland, Ukraine, the United Kingdom, and the United States.

See also

Other

Further reading

Documents

The source documents, which relate to the emergency, published in the unofficial sources:

References

  1. ^ a b "IAEA Report". In Focus: Chernobyl. http://www.iaea.org/NewsCenter/Focus/Chernobyl/. Retrieved 2008-05-31. 
  2. ^ "Inside Chernobyl" National Geographic, April 2006
  3. ^ "Geographical location and extent of radioactive contamination". Swiss Agency for Development and Cooperation. http://www.chernobyl.info/index.php?navID=2.  (quoting the "Committee on the Problems of the Consequences of the Catastrophe at the Chernobyl NPP: 15 Years after Chernobyl Disaster", Minsk, 2001, p. 5/6 ff., and the "Chernobyl Interinform Agency, Kiev und", and "Chernobyl Committee: MailTable of official data on the reactor accident")
  4. ^ Kagarlitsky, Boris (1989). "Perestroika: The Dialectic of Change". in Mary Kaldor, Gerald Holden, Richard A. Falk. The New Detente: Rethinking East-West Relations. United Nations University Press. pp. 333–334. ISBN 0860919625.  "No one believed the first newspaper reports, which patently understated the scale of the catastrophe and often contradicted one another. The confidence of readers was re-established only after the press was allowed to examine the events in detail and without the existing censorship restrictions. The policy of openness (glasnost) and 'uncompromising criticism' of outmoded arrangements had been proclaimed back at the 27th Congress, but it was only in the tragic days of the Chernobyl disaster that glasnost began to change from an official slogan into an everyday practice. The truth about Chernobyl which eventually hit the newspapers opened the way to a more truthful examination of other social problems. More and more articles were written about drug abuse, crime, corruption and the mistakes of leaders of various ranks. A wave of 'bad news' swept over the readers in 1986-87, shaking the consciousness of society. Many were horrified to find out about the numerous calamities of which they had previously had no idea. It often seemed to people that there were many more outrages in the epoch of perestroika than before although, in fact, they had simply not been informed about them previously."
  5. ^ The Chernobyl Forum: 2003-2005. Chernobyl's Legacy: Health, Environmental, and Socio-Economic Impacts and Recommendations to the Governments of Belarus, the Russian Federation and UkrainePDF. IAEA. 2nd revised version. pg. 6
  6. ^ library.thinkquest.org – All four of the reactors at the Chernobyl nuclear power station were of the RBMK-type
  7. ^ http://www.laes.ru/new_lnpp/eng-htm/15.shtml
  8. ^ a b c d http://snpp.rosenergoatom.ru/eng/about/production/
  9. ^ a b c d e http://www-pub.iaea.org/MTCD/publications/PDF/Pub1211_web.pdf
  10. ^ a b c d e f g h i http://books.google.cz/books?id=oEqd0IeAhccC&pg=PA11&lpg=PA11&dq=chernobyl+deaerator&source=bl&ots=K55s8gNxqF&sig=USCHZjlALOA0rpIPnU6joRqRK84&hl=en&ei=M3aRS8OOJ5OEmgP3jM2XCw&sa=X&oi=book_result&ct=result&resnum=28&ved=0CFkQ6AEwGw#v=onepage&q=&f=false
  11. ^ a b c d http://www.insc.anl.gov/rbmk/reactor/channel.html
  12. ^ http://www.elemash.ru/en/production/Products/NFCP/RBMK/
  13. ^ a b http://www.osti.gov/bridge/servlets/purl/10194721-aGK72B/webviewable/10194721.pdf
  14. ^ http://www.insc.anl.gov/rbmk/reactor/assembly.html
  15. ^ http://whqlibdoc.who.int/euro/-1993/ICP_CEH_129.pdf
  16. ^ http://www.lei.lt/insc/handbook/hab1/hab12.html
  17. ^ http://www.pavrda.cz/cernobyl/rbmk/40.html
  18. ^ http://www-pub.iaea.org/MTCD/publications/PDF/Pub913e_web.pdf
  19. ^ a b c d e f g http://forum.pripyat.com/archive/index.php/t-2030.html
  20. ^ The handy Science answer book, compiled by the Science and Technology Department and the Carnegie Library of Pittsburgh.
  21. ^ a b Medvedev Z. (1990):73
  22. ^ Early Soviet Reactors and EU Accession
  23. ^ N.V.Karpan : 312-313
  24. ^ a b IAEA Report INSAG-7 Chernobyl Accident: Updating of INSAG-1 Safety Series, No.75-INSAG-7, IAEA, Vienna, (1991).
  25. ^ Medvedev Z. (1990):18-20. Medvedev writes: "The mere fact that the operators were carrying out an experiment that had not been approved by higher officials indicates that something was wrong with the chain of command. The State Committee on Safety in the Atomic Power Industry is permanently represented at the Chernobyl station. Yet the engineers and experts in that office were not informed about the program. In part, the tragedy was the product of administrative anarchy or the attempt to keep everything secret."
  26. ^ a b c d e f http://pripyat.com/ru/publications/version/2005/06/23/202.html
  27. ^ a b http://www.voropay.net/pages/pripyat/texts/davletbaev.html
  28. ^ A.S.Djatlov:30
  29. ^ Medvedev Z. (1990):36-38
  30. ^ (Russian) The official program of the test.
  31. ^ IAEA Report INSAG-7. Chernobyl Accident: Updating of INSAG-1 Safety Series, No.75-INSAG-7, IAEA, Vienna, (1991).:73
  32. ^ A.S.Djatlov:31
  33. ^ The accumulation of Xenon-135 in the core is burned out by neutrons. Higher power locations burn the Xenon out more quickly. This results in shifting neutron flux/power within a graphite-moderated reactor such as the RBMK.
  34. ^ The information on accident at the Chernobyl NPP and its consequences, prepared for IAEA, Atomic Energy, v. 61, 1986, p. 308-320.
  35. ^ The RBMK is a boiling water reactor, so in-core boiling is normal at higher power levels. The RBMK design has a negative void coefficient above 700 MW.
  36. ^ N.V.Karpan:349
  37. ^ (Russian) E.O.Adamov, Yu.M.Cherkashov, et al. «Channel Nuclear Power Reactor RBMK», Moscow, GUP NIKIET, 2006 (Chapter 13:578). ISBN 5-98706-018-4 (Hardcover).
  38. ^ (Russian) Anatoly Dyatlov, Chernobyl. How did it happen? Chapter 4.
  39. ^ Medvedev Z. (1990):31
  40. ^ (Russian) Фатахов Алексей Чернобыль как это было - 2
  41. ^ (Russian) R.I.Davletbaev «Last shift.» /«Chernobyl. Ten years later. Inevitability or chance?», Moscow, Energoatomizdat, 1995. -ISBN 5-283-03618-9. , p. 366
  42. ^ a b Pakhomov, Sergey A.; Yuri V. Dubasov (16 December 2009). "Estimation of Explosion Energy Yield at Chernobyl NPP Accident". Pure and Applied Geophysics (open access on Springerlink.com - © retained by authors). doi:10.1007/s00024-009-0029-9. 
  43. ^ (Russian)Checherov K.P. «Development of ideas about reasons and processes of emergency on the 4-th unit of Chernobyl NPP 26.04.1986», International conference "Shelter-98", Slavutich, Ukraine, 25. – 27. November 1998
  44. ^ Medvedev Z. (1990):32
  45. ^ Chernobyl: Assessment of Radiological and Health Impact (Chapter 1). Nuclear Energy Agency. 2002
  46. ^ Medvedev Z. (1990):42
  47. ^ Medvedev Z. (1990):44
  48. ^ a b c http://handle.dtic.mil/100.2/ADA335076
  49. ^ http://www.neimagazine.com/journals/Power/NEI/March_2006/attachments/RBMK1000Key.jpg
  50. ^ http://books.google.cz/books?id=O36UC03ODtcC&pg=PA30&lpg=PA30&ots=K9zDWI0dml&dq=%22oleg+heinrich%22&hl=en
  51. ^ a b c d e f http://www.guardian.co.uk/world/2006/mar/26/nuclear.russia
  52. ^ http://www.flatrock.org.nz/topics/money_politics_law/cheating_chernobyl.htm
  53. ^ http://www.infoukes.com/history/chornobyl/zuzak/page-08.html
  54. ^ http://www.chernobyl.info/index.php?userhash=&navID=240&lID=2&threadID=26
  55. ^ a b c d e f g h i j k l m n o http://pripyat.com/en/publications/2008/12/29/1979.html
  56. ^ http://www.kuto4ok.info/chernobyl.php
  57. ^ a b http://www.pomnimih.ru/info.php?categ=8&subcateg=76&id=27
  58. ^ http://www.krasnogorsk.ru/index.php?do=static&page=patriot.kp.chaes
  59. ^ a b c d e f g h i j http://chernobil.info/?p=2112
  60. ^ a b c d e http://www.time.com/time/daily/chernobyl/870720.court.html
  61. ^ a b c d e http://www.nytimes.com/1987/07/30/world/chernobyl-officials-are-sentenced-to-labor-camp.html?pagewanted=1
  62. ^ http://leopolis.blogspot.com/2006_04_01_archive.html
  63. ^ a b c d http://bluesbag6.narod.ru/index21.html
  64. ^ a b c d e http://library.narod.ru/tetr/tetr3.htm
  65. ^ http://www.chernobylinfo.com/voice-chernobyl-1.php
  66. ^ a b c d http://books.google.com/books?id=xAwAAAAAMBAJ&pg=PA45&lpg=PA45&dq=%22nikolai+gorbachenko%22&source=bl&ots=vtjRc_Hwsx&sig=njKtIE0YXG5a5afFUVVJM0AXSO0&hl=en&ei=GVKQS-jLEZWanwO36fSICw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CBAQ6AEwBA#v=onepage&q=%22nikolai%20gorbachenko%22&f=false
  67. ^ http://community.seattletimes.nwsource.com/archive/?date=20060425&slug=webchernobylwidows25
  68. ^ http://www.x-libri.ru/elib/sherb000/00000036.htm
  69. ^ a b http://www.x-libri.ru/elib/sherb000/00000034.htm
  70. ^ http://www.usnews.com/news/world/articles/2008/04/24/chernobyl-victims-struggle-with-consequences-of-radiation-exposure.html
  71. ^ http://chernobil.info/?p=105
  72. ^ http://forum.pripyat.com/archive/index.php/t-882.html
  73. ^ http://blog.vantende.net/articles/cheating_chernobyl/
  74. ^ http://www.wwenglish.com/en/voa/stan/2006/04/2006042511335.htm
  75. ^ a b Medvedev Z. (1990):42-50
  76. ^ Medvedev G. (1991):247-48
  77. ^ National Geographic. Meltdown in Chernobyl [Video].
  78. ^ Shcherbak, Y. (1987). Chernobyl. 6, p54. Yunost.  (Quoted in Medvedev Z. (1990):44)
  79. ^ Mil Mi-8 crash near Chernobyl http://www.youtube.com/watch?v=aw-ik1U4Uvk [Video].
  80. ^ Zeilig, Martin (August/September 1995). "Louis Slotin And 'The Invisible Killer'". The Beaver 75 (4): 20–27. http://www.mphpa.org/classic/FH/LA/Louis_Slotin_1.htm. Retrieved 2008-04-28. 
  81. ^ http://www.swrailway.gov.ua/rabslovo/?aid=62
  82. ^ http://surkino.edurm.ru/p4aa1.html
  83. ^ "Chernobyl haunts engineer who alerted world". CNN Interactive World News (Cable News Network, Inc.). 1996-04-26. http://www.cnn.com/WORLD/9604/26/chernobyl/230pm/index2.html. Retrieved 2008-04-28. 
  84. ^ a b Bogatov, S.; A. Borovoi, A. Lagunenko, E. Pazukhin, V. Strizhov, V. Khvoshchinskii (2008-12-01). "Formation and spread of Chernobyl lavas". Radiochemistry 50 (6): 650–654. doi:10.1134/S1066362208050131. 
  85. ^ Petrov, Yu.; Yu. Udalov, J. Subrt, S. Bakardjieva, P. Sazavsky, M. Kiselova, P. Selucky, P. Bezdicka, C. Jorneau, P. Piluso (2009-04-01). "Behavior of melts in the UO2-SiO2 system in the liquid-liquid phase separation region". Glass Physics and Chemistry 35 (2): 199–204. doi:10.1134/S1087659609020126. 
  86. ^ Journeau, C.; E. Boccaccio, C. Jégou, P. Piluso, G. Cognet (2001). Flow and Solidification of Corium in the VULCANO facility. http://www.plinius.eu/home/liblocal/docs/Flow_Solidification_VULCANO.pdf. 
  87. ^ Mevedev Z. (1990):58-59
  88. ^ Chernobyl: The End of the Nuclear Dream, 1986, p.178, by Nigel Hawkes et al., ISBN 0330297430
  89. ^ Sattonnay, G.; C. Ardois, C. Corbel, J. F. Lucchini, M. -F. Barthe, F. Garrido, D. Gosset (2001-01). "Alpha-radiolysis effects on UO2 alteration in water". Journal of Nuclear Materials 288 (1): 11–19. doi:10.1016/S0022-3115(00)00714-5. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXN-42993M3-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=987276167&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=176c731b3153a03f1c27bc6f948bd647. Retrieved 2009-08-21. 
  90. ^ Clarens, F.; J. de Pablo, I. Diez-Perez, I. Casas, J. Gimenez, M. Rovira (2004-12-01). "Formation of Studtite during the Oxidative Dissolution of UO2 by Hydrogen Peroxide: A SFM Study". Environmental Science & Technology 38 (24): 6656–6661. doi:10.1021/es0492891. 
  91. ^ Burakov, B. E.; E. E. Strykanova, E. B. Anderson (1997). "Secondary Uranium Minerals on the Surface of Chernobyl" Lava"". Materials Research Society Symposium Proceedings. 465. pp. 1309–1312. 
  92. ^ Burns, P. C; K. A Hughes (2003). "Studtite, (UO2)(O2)(H2O)2(H2O)2: The first structure of a peroxide mineral". American Mineralogist 88: 1165–1168. http://www.kubatko.com/studtitestructure.pdf. 
  93. ^ Medvedev Z. (1990):59
  94. ^ The Social Impact of the Chernobyl Disaster, 1988, p166, by David R. Marples ISBN 0-333-48198-4
  95. ^ "Chernobyl's silent graveyards". BBC News Online. 2006-04-20. http://news.bbc.co.uk/2/shared/spl/hi/pop_ups/06/in_pictures_chernobyl0s_silent_graveyards_/html/1.stm. 
  96. ^ IAEA Report INSAG-1 (International Nuclear Safety Advisory Group). Summary Report on the Post-Accident Review on the Chernobyl Accident. Safety Series No. 75-INSAG-1. IAEA, Vienna, 1986.
  97. ^ a b The information on accident at the Chernobyl NPP and its consequences, prepared for IAEA, Atomic Energy, v. 61, 1986, p. 311
  98. ^ The information on accident at the Chernobyl NPP and its consequences, prepared for IAEA, Atomic Energy, v. 61, 1986, p. 312
  99. ^ Medvedev, G. (1991)
  100. ^ IAEA Report INSAG-7. Chernobyl Accident: Updating of INSAG-1 Safety Series, No.75-INSAG-7, IAEA, Vienna, (1991).:18
  101. ^ IAEA Report INSAG-7. Chernobyl Accident: Updating of INSAG-1 Safety Series, No.75-INSAG-7, IAEA, Vienna, (1991).:79-83
  102. ^ (Russian) N.A.Dollezhal, I.Ya.Emelyanov «Channel Nuclear Power Reactor», Moscow, Atomizdat, (1980):34-35 (Hardcover)
  103. ^ NEI Source Book: Fourth Edition (NEISB_3.3.A1)
  104. ^ a b IAEA Report INSAG-7. Chernobyl Accident: Updating of INSAG-1 Safety Series, No.75-INSAG-7, IAEA, Vienna, (1991).:24
  105. ^ (French) "Tchernobyl, 20 ans après". RFI. 2006-04-24. http://www.rfi.fr/actufr/articles/076/article_43250.asp. Retrieved 2006-04-24. 
  106. ^ "TORCH report executive summary" (PDF). European Greens and UK scientists Ian Fairlie PhD and David Sumner. April 2006. http://www.greens-efa.org/cms/topics/dokbin/118/118559.torch_executive_summary@en.pdf. Retrieved 2006-04-21.  (page 3)
  107. ^ (French) "Path and extension of the radioactive cloudl". IRSN. http://www.irsn.fr/FR/popup/Pages/tchernobyl_animation_nuage.aspx. Retrieved 2006-12-16. 
  108. ^ IAEA Bulletin Autumn 1986PDF (0.38 MB)
  109. ^ Mould, Richard Francis (2000). Chernobyl Record: The Definitive History of the Chernobyl Catastrophe. CRC Press. p. 48. ISBN 0-750-306-70X. 
  110. ^ Ympäristön Radioaktiivisuus Suomessa — 20 Vuotta TshernobylistaPDF (7.99 MB)
  111. ^ a b "Chernobyl Accident". World Nuclear Association. May 2008. http://world-nuclear.org/info/chernobyl/inf07.html. Retrieved 2008-06-18. 
  112. ^ Dederichs, H.; Pillath, J.; Heuel-Fabianek, B.; Hill, P.; Lennartz, R. (2009): Langzeitbeobachtung der Dosisbelastung der Bevölkerung in radioaktiv kontaminierten Gebieten Weißrusslands - Korma-Studie. Vol. 31, series "Energy & Environment" by Forschungszentrum Jülich
  113. ^ Chernobyl source term, atmospheric dispersion, and dose estimation, EnergyCitationsDatabase, 1 November 1989
  114. ^ OECD Papers Volume 3 Issue 1, OECD, 2003
  115. ^ Hallenbeck, William H (1994). Radiation Protection. CRC Press. p. 15. ISBN 0-873-719-964. "Reported thus far are 237 cases of acute radiation sickness and 31 deaths." 
  116. ^ Mould 2000, p. 29. "The number of deaths in the first three months were 31[.]"
  117. ^ a b c d Chernobyl: Catastrophe and Consequences, Springer, Berlin ISBN 3-540-23866-2
  118. ^ a b Kryshev, I.I., Radioactive contamination of aquatic ecosystems following the Chernobyl accident. Journal of Environmental Radioactivity, 1995. 27: p. 207-219
  119. ^ EURATOM Council Regulations No. 3958/87, No. 994/89, No. 2218/89, No. 770/90
  120. ^ Fleishman, D.G., et al., Cs-137 in fish of some lakes and rivers of the Bryansk region and North-West Russia in 1990–1992. Journal of Environmental Radioactivity, 1994. 24: p. 145-158
  121. ^ a b "Environmental consequences of the Chernobyl accident and their remediation"PDF IAEA, Vienna
  122. ^ Wildlife defies Chernobyl radiation, by Stefen Mulvey, BBC News
  123. ^ a b The International Chernobyl Project Technical Report, IAEA, Vienna, 1991
  124. ^ "Black Fungus Found in Chernobyl Eats Harmful Radiation".
  125. ^ Information Notice No. 93-71
  126. ^ IAEA's Power Reactor Information System polled in May 2008 reports shut down for units 1, 2, 3 and 4 respectively at 1996/11/30, 1991/10/11, 2000/12/15 and 1986/04/26.
  127. ^ Bell, Randall. Disasters: Wasted Lives, Valuable Lessons. http://www.Strategy360.com. 
  128. ^ a b BBC, 20 April 2006, Wildlife defies Chernobyl radiation
  129. ^ a b c Mycio, Mary (2005-09-09). Wormwood Forest: A Natural History of Chernobyl. Joseph Henry Press. ISBN 0309094305. http://books.google.ie/books?id=pJ7X3Vft5BQC&printsec=frontcover&dq=Wormwood+Forest:+A+Natural+History+of+Chernobyl&ei=eQC8SsmMPIKuzQS8zYXdDw&client=firefox-a#v=onepage&q=&f=false. Retrieved 2009-09-25. 
  130. ^ a b c d Washington Post, 7 June 2007, Chernobyl Area Becomes Wildlife Haven
  131. ^ Mother Nature Network, 7 May 2009, Scientists disagree over radiation effects
  132. ^ a b Ravilious, Kate (2009-06-29). "Despite Mutations, Chernobyl Wildlife Is Thriving". National Geographic Magazine. ISSN 0027-9358. http://news.nationalgeographic.com/news/2006/04/0426_060426_chernobyl_2.html. Retrieved 2009-09-23. 
  133. ^ Møller, A. P.; T. A. Mousseau, G. Milinevsky, A. Peklo, E. Pysanets, T. Szép (2005). "Condition, reproduction and survival of barn swallows from Chernobyl". Journal of Animal Ecology 74 (6): 1102–1111. doi:10.1111/j.1365-2656.2005.01009.x. 
  134. ^ Møller, A.P; T.A Mousseau, F de Lope, N Saino (2007). "Elevated frequency of abnormalities in barn swallows from Chernobyl". Biology Letters 3 (4): 414–417. doi:10.1098/rsbl.2007.0136. PMID 17439847. PMC 1994720. http://rsbl.royalsocietypublishing.org/content/3/4/414.abstract. Retrieved 2009-09-23. 
  135. ^ Smith, J.T (2008-02-23). "Is Chernobyl radiation really causing negative individual and population-level effects on barn swallows?". Biology Letters 4 (1): 63–64. doi:10.1098/rsbl.2007.0430. PMID 18042513. PMC 2412919. http://rsbl.royalsocietypublishing.org/content/4/1/63.full.pdf+html. Retrieved 2009-09-23. 
  136. ^ Møller, A. P.; T. A. Mousseau, F. de Lope, N. Saino (2008). "Anecdotes and empirical research in Chernobyl". Biology Letters 4 (1): 65. doi:10.1098/rsbl.2007.0528. 
  137. ^ Danchenko, Maksym; Ludovit Skultety, Namik M. Rashydov, Valentyna V. Berezhna, L’ubomír Mátel, Terézia Salaj, Anna Pret’ová, Martin Hajduch (2009-06-05). "Proteomic Analysis of Mature Soybean Seeds from the Chernobyl Area Suggests Plant Adaptation to the Contaminated Environment". Journal of Proteome Research 8 (6): 2915–2922. doi:10.1021/pr900034u. PMID 19320472. 
  138. ^ a b Kovalchuk, Igor; Vladimir Abramov, Igor Pogribny, Olga Kovalchuk (2004-05-01). "Molecular Aspects of Plant Adaptation to Life in the Chernobyl Zone". Plant Physiol. 135 (1): 357–363. doi:10.1104/pp.104.040477. PMID 15133154. PMC 429389. http://www.plantphysiol.org/cgi/content/abstract/135/1/357. Retrieved 2009-09-24. 
  139. ^ Boubriak, I. I.; D. M. Grodzinsky, V. P. Polischuk, V. D. Naumenko, N. P. Gushcha, A. N. Micheev, S. J. McCready, D. J. Osborne (2008-01-01). "Adaptation and Impairment of DNA Repair Function in Pollen of Betula verrucosa and Seeds of Oenothera biennis from Differently Radionuclide-contaminated Sites of Chernobyl". Ann Bot 101 (2): 267–276. doi:10.1093/aob/mcm276. PMID 17981881. PMC 2711018. http://aob.oxfordjournals.org/cgi/content/abstract/101/2/267. Retrieved 2009-09-24. 
  140. ^ "Shelter" object description
  141. ^ V. Baryakhtar, V. Gonchar, A. Zhidkov and V. Zhidkov, Radiation damages and self-spluttering of high radioactive dielectrics: Spontaneous emission of submicrometre dust particles, Condensed Matter Physics, 2002, 5(3{31}), 449–471.
  142. ^ a b Borovoi, A. A. (2006). "Nuclear fuel in the shelter". Atomic Energy 100 (4): 249–256. doi:10.1007/s10512-006-0079-3. 
  143. ^ See BBC documentary
  144. ^ Nuclear Engineering International, July 2007, page 12.
  145. ^ http://www.angelfire.com/extreme4/kiddofspeed/journal/glossary.html
  146. ^ http://books.google.com/books?id=g-D869NdXYwC&pg=PA50&dq=corium+silicate&lr=&num=50&as_brr=3&cd=16#v=onepage&q=corium%20silicate&f=false
  147. ^ http://www.epa.gov/rpdweb00/rert/chernobyltour/blast_02.html
  148. ^ a b Dusha-Gudym, Sergei I. (August 1992). "Forest Fires on the Areas Contaminated by Radionuclides from the Chernobyl Nuclear Power Plant Accident". IFFN. Global Fire Monitoring Center (GFMC). pp. No. 7, p. 4–6. http://www.fire.uni-freiburg.de/iffn/country/rus/rus_7.htm. Retrieved 2008-06-18. 
  149. ^ http://www.maik.ru/abstract/radchem/4/radchem0102_abstract.pdfPDF (5.07 KB)
  150. ^ Davidenko, Eduard P.; Johann Georg Goldammer (January 1994). "News from the Forest Fire Situation in the Radioactively Contaminated Regions". http://www.fire.uni-freiburg.de/iffn/country/rus/rus_16.htm. 
  151. ^ Antonov, Mikhail; Maria Gousseva (2002-09-18). "Radioactive fires threaten Russia and Europe". Pravda.ru. http://newsfromrussia.com/main/2002/09/18/36851.html. 
  152. ^ Yoschenko et al., Journal of Environmental Radioactivity, 2006, 86, 143–163.
  153. ^ Transport of Radioactive Materials by Wildland fires in the Chernobyl Accident Zone: How to Address the ProblemPDF (416 KB)
  154. ^ Chernobyl Forests. Two Decades After the ContaminationPDF (139 KB)
  155. ^ Allard, Gillian. "Fire prevention in radiation contaminated forests". Forestry Department, FAO. http://www.fao.org/docrep/004/y2795e/y2795e08a.htm. Retrieved 2008-06-18. 
  156. ^ CRDP: Chernobyl Recovery and Development Programme (United Nations Development Programme)
  157. ^ "UNSCEAR assessment of the Chernobyl accident"
  158. ^ "IAEA Report". In Focus: Chernobyl. Archived from the original on 2007-12-17. http://web.archive.org/web/20071217112720/http://www.iaea.org/NewsCenter/Focus/Chernobyl/index.shtml. Retrieved 2006-03-29. 
  159. ^ a b c "UNSCEAR — Chernobyl health effects"
  160. ^ "IAEA — Chernobyl's Legacy"
  161. ^ Rosenthal, Elisabeth. (6 September 2005) Experts find reduced effects of Chernobyl. nytimes.com. Retrieved 14-02-08.
  162. ^ Thyroid Cancer
  163. ^ "Chernobyl Forum summaries"
  164. ^ Chernobyl Forum booklets by IAEA
  165. ^ International Atomic Energy Agency. What's the situation at Chernobyl? iaea.org Retrieved 2008-02-14.
  166. ^ International Atomic Energy Agency.Chernobyl's living legacy iaee.org Retrieved 14-02-08.
  167. ^ [1] "Chernobyl Forum booklets"
  168. ^ "Chernobyl death toll grossly underestimated". Greenpeace. 18 April 2006. http://www.greenpeace.org/international/news/chernobyl-deaths-180406. Retrieved 15 December 2008. 
  169. ^ "20 years after Chernobyl — The ongoing health effects". IPPNW. April , 2006. http://www.ippnw-students.org/chernobyl/research.html. Retrieved 2006-04-24. 
  170. ^ Greenpeace (2006-04). "The Chernobyl Catastrophe: Consequences on Human Health". http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/18_04_06_chernobyl.pdf. Retrieved 2010-02-16. 
  171. ^ Rotkiewicz, Marcin; Henryk Suchar and Ryszard Kamiñski (14 January 2001). ""Chernobyl: the Biggest BLUFF of the 20th Century"". Polish weekly Wprost. pp. no 2. http://www.wonuc.org/xfiles/chern_02.html. Retrieved 2008-06-18. 
  172. ^ Vidal, John (26 April 2006). ""Hell on Earth"". Guardian. http://www.guardian.co.uk/society/2006/apr/26/guardiansocietysupplement7. Retrieved 2008-06-18. 
  173. ^ "Global Radiation Exposures: Comparison of Damage among Hiroshima/Nagasaki, Chernobyl, and Semipalatinsk". Hiroshima International Council for Health Care of the Radiation-exposed (HICARE). Archived from the original on 2008-01-16. http://web.archive.org/web/20080116052646/http://www.hiroshima-cdas.or.jp/HICARE/en/10/hi04.html. Retrieved 2008-06-18. 
  174. ^ Kasperson, Roger E.; Stallen, Pieter Jan M. (1991). Communicating Risks to the Public: International Perspectives. Berlin: Springer Science and Media. pp. 160–162. ISBN 0792306015. 
  175. ^ Chernobyl ten years on OECD Nuclear Energy Agency report, November 1995PDF (2.75 MB)
  176. ^ Processing the Dark: Heavy Water – A Film for Chernobyl | Movie Mail UK
  177. ^ Heavy Water: a film for Chernobyl

External links

Coordinates: 51°23′22″N 30°05′56″E / 51.38944°N 30.09889°E / 51.38944; 30.09889 (Chernobyl disaster)








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