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The Toshiba 4S (Super Safe, Small and Simple) is a “nuclear battery” reactor design. It requires only minimal staffing.


General description

Vector image of the 4S design

The plant design is offered by a partnership that includes Toshiba and the Central Research Institute of Electric Power Industry (CRIEPI) of Japan. [1]

The technical specifications of the 4S reactor are unique in the nuclear industry. The actual reactor would be located in a sealed, cylindrical vault 30 m (98 ft) underground, while the building above ground would be 22 x 16 x 11 m (72 × 52.5 x 36 ft) in size. This power plant is designed to provide 10 megawatts of electrical power.

The 4S is a fast neutron reactor. It uses neutron reflector panels around the perimeter to maintain neutron density. These reflector panels replace complicated control rods, yet keep the ability to shut down the nuclear reaction in case of an emergency. Additionally, the Toshiba 4S utilizes liquid sodium as a coolant, allowing the reactor to operate 200 degrees hotter than if it used water. Using sodium allows the reactor to be unpressurized, even though water at this temperature would run at thousands of pounds per square inch.

The reactor is expected to provide electric energy for between 5 and 13 cents/kWh, factoring in only operating costs, to which unknown decommissioning and atomic waste processing and safe disposal costs need to be added. On paper, it has been determined that the reactor could run for 30 years without being refueled.

The Toshiba 4S Nuclear Battery is being proposed as the power source for the Galena Nuclear Power Plant in Galena, Alaska.

Current developments

Currently Toshiba, together with its Westinghouse subsidiary, is in the preliminary design review stage of the Design Certification process before the USNRC. [2] Application for certification of the design is currently planned for 2010 when the standardized Design Certification application will be filed for the 4S. The most recent meeting with the NRC took place on August 8, 2008, at which time the NRC's staff met with representatives of Toshiba and Westinghouse for a pre-application presentation of a Phenomena Identification and Ranking Table (PIRT) for the Toshiba 4S (Super-Safe, Small and Simple) reactor. Lawrence Livermore National Laboratory recently released an interesting study on the Toshiba 4S design, which provides an overview of the 4S design and suggests that certain goals may be easier to meet if lead is used as the coolant rather than sodium, due to lead's high transparency to neutrons and low transparency to γ radiation, though lead has a higher melting point than sodium does.[3]

The NRC received the latest version of the letter of intent from the designers of the reactor as of March 13, 2009. The approval process in on track for official submission to the USNRC in October 2010 of a standard application for Design Certification. During the week of October 16th, 2009, persons or organizations unknown submitted a Freedom of Information Act request to the USNRC requesting that "documents related to the Super-Safe, Small and Simple (4s) Nuclear Reactor from Toshiba Corporation particularly related to possible placement in Galena, Arkansas (sic), including tech info on reactor, safety assessments, nuclear material security, etc." be released to the requestors.[4]

External links

See also


  1. ^ Central Research Institute of Electric Power Industry
  2. ^ US NRC Backgrounder on New Nuclear Plant Designs
  3. ^ Minato, A.; Ueda, N.; Wade, D.; Greenspan, E.; Brown, N. (2005-11-02). "Small Liquid Metal Cooled Reactor Safety Study" (in Technical English). Technical Reports. Livermore, CA, USA: Lawrence Livermore National Laboratory. Retrieved 2010-01-02.  
  4. ^ Information Report to the Secretariat of the U.S. Nuclear Regulatory Commission for the Week Ending October 16th, 2009

Please see



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