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Samarium-151: Wikis

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Medium-lived
fission products
Prop:
Unit:
t½
a
Yield
%
Q *
KeV
βγ
*
155Eu 4.76 .0803 252 βγ
85Kr 10.76 .2180 687 βγ
113mCd 14.1 .0008 316 β
90Sr 28.9 4.505 2826 β
137Cs 30.23 6.337 1176 βγ
121mSn 43.9 .00005 390 βγ
151Sm 90 .5314 77 β
Long-lived
fission products
Prop:
Unit:
t½
Ma
Yield
%
Q *
KeV
βγ
*
99Tc 0.211 6.1385 294 β
126Sn 0.230 0.1084 4050 βγ
79Se 0.295 0.0447 151 β
93Zr 1.53 5.4575 91 βγ
135Cs 2.3  6.9110 269 β
107Pd 6.5  1.2499 33 β
129I 15.7  0.8410 194 βγ
Chain yield, % per fission[1]
Thermal Fast 14 MeV
232Th not fissile 0.399 ± 0.065 0.165 ± 0.035
233U 0.333 ± 0.017 0.312 ± 0.014 0.49 ± 0.11
235U 0.4204 ± 0.0071 0.431 ± 0.015 0.388 ± 0.061
238U not fissile 0.810 ± 0.012 0.800 ± 0.057
239Pu 0.776 ± 0.018 0.797 ± 0.037 secret
241Pu 0.86 ± 0.24 0.910 ± 0.025 secret

151Sm is a radioisotope of samarium with a half-life of 90 years, undergoing low-energy beta decay, and has a fission product yield of 0.4203% for thermal neutrons and U-235, about 39% of Sm-149's yield. The yield is somewhat higher for Pu-239.

Its neutron absorption cross section for thermal neutrons is high at 15200 barns, about 38% of samarium-149's absorption cross section, or about 20 times that of U-235. Since the ratios between the production and absorption rates of Sm-151 and Sm-149 are almost equal, the two isotopes should reach similar equilibrium concentrations. Since 149Sm reaches equilibrium in about 500 hours (20 days), 151Sm should reach equilibrium in about 50 days.

Since nuclear fuel is used for several years (burnup) in a nuclear power plant, the final amount of 151Sm in the spent nuclear fuel at discharge is only a small fraction of the total 151Sm produced during the use of the fuel. The low yield, low survival rate, and low decay energy mean that Sm-151 has insignificant nuclear waste impact compared to the two main medium-lived fission products Cs-137 and Sr-90.

See also

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