Samarium-151

SimpleNuclide|Samarium|151 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.

ee also

*Isotopes of samarium
* [http://www.ead.anl.gov/pub/doc/samarium.pdf ANL factsheet]