Palladium-107
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| 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 |
Palladium-107 is the second longest lived (halflife of 6.5 million years) and least radioactive (decay energy only 33 KeV, specific activity 5×10-5 Ci/g) of the 7 long-lived fission products. It undergoes pure beta decay (no gamma radiation) to silver-107.
Its yield from thermal neutron fission of uranium-235 is 0.1629% per fission, only 1/4 that of iodine-129, and only 1/40 those of Tc-99, Zr-93, and Cs-135. Yield from U-233 is slightly lower, but yield from Pu-239 is much higher, 3.3%. Yields are higher in fast fission or in fission of heavier nuclei.
According to [1] fission palladium contains the isotopes 104Pd (16.9%), 105Pd (29.3%), 106Pd (21.3%), 107Pd (17%), 108Pd (11.7%) and 110Pd (3.8%). According to another source, the proportion of 107Pd is 9.2% for palladium from thermal neutron fission of U-235, 11.8% for U-233, and 20.4% for Pu-239. (and the Pu-239 yield of palladium is about 10 times that of U-235.)
Because of this dilution and because 105Pd has 11 times the neutron absorption cross section, 107Pd is not amenable to disposal by nuclear transmutation. However, as a noble metal, palladium is not as mobile in the environment as iodine or technetium.
