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Samarium-149 is an observationally stable isotope of samarium (predicted to decay, but no decays have ever been observed, giving it a half-life at least several orders of magnitude longer than the age of the universe), and a product of the decay chain from the fission product 149 Nd (yield 1.0888%).
Samarium-149 (149 Sm) is an observationally stable isotope of samarium (predicted to decay, but no decays have ever been observed, giving it a half-life at least several orders of magnitude longer than the age of the universe), and a product of the decay chain from the fission product 149 Nd (yield 1.0888%).
Samarium-149 is the second most important neutron poison in nuclear reactor physics. Samarium-151, produced at lower yields, is the third most abundant medium-lived fission product but emits only weak beta radiation. Both have high neutron absorption cross sections, so that much of them produced in a reactor are later destroyed there by neutron ...
Because samarium-149 is not radioactive and is not removed by decay, it presents problems somewhat different from those encountered with xenon-135. The equilibrium concentration (and thus the poisoning effect) builds to an equilibrium value during reactor operation in about 500 hours (about three weeks), and since samarium-149 is stable, the ...
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beta decays to very long lived Samarium-147 (half life>age of the universe); has seen some use in radioisotope thermoelectric generators: 1.0888%: Samarium: 149 Sm: Observationally stable: 2nd most significant neutron poison. 0.9% [3] Iodine: 129 I: 15.7 My: Long-lived fission product. Candidate for disposal by nuclear transmutation. 0.4203% ...
Other fission products, such as xenon-135 and samarium-149, have a high neutron absorption cross section. Since a nuclear reactor must balance neutron production and absorption rates, fission products that absorb neutrons tend to "poison" or shut the reactor down; this is controlled with burnable poisons and control rods.
Samarium has seven naturally occurring isotopes, and neodymium has seven. The two elements are joined in a parent–daughter relationship by the alpha decay of parent 147 Sm to radiogenic daughter 143 Nd with a half-life of 1.066(5) × 10 11 years and by the alpha decay of 146 Sm (an almost-extinct radionuclide with a half-life of 9.20(26) × 10 7 years [2] [a]) to produce 142 Nd.