Question

The plutonium isotope ${}^{239}Pu$ is produced as a by-product in nuclear reactors and hence is accumulating in our environment. It is radioactive,decaying with a half-life of $2.41\times {10}^{4}y$ . (a) How many nuclei of Pu constitute a chemically lethal dose of 2.00 mg? (b) What is the decay rate of this amount?

Answer 1

The nuclei of 238U can capture neutrons and beta-decay. With a large amount of neutrons available due to the fission of ${}^{235}U$, the probability for this process is substantially increased, resulting in a much higher decay rate for ${}^{238}U$ and causing the depletion of ${}^{238}U$ (and relative enrichment of ${}^{235}U)$.