Samarium-151
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| Medium-lived fission products |
||||
|---|---|---|---|---|
| Property: t½ Unit: (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 |
||||
|---|---|---|---|---|
| Property: t½ Unit: (Ma) |
Yield (%) |
Q * (KeV) |
βγ * |
|
| 99Tc | .211 | 6.1385 | 294 | β |
| 126Sn | .230 | .1084 | 4050 | βγ |
| 79Se | .295 | .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 | .8410 | 194 | βγ |
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.
