Plutonium-241

[1] The longer spent nuclear fuel waits before reprocessing, the more 241Pu decays to americium-241, which is nonfissile (although fissionable by fast neutrons) and an alpha emitter with a half-life of 432 years; 241Am is a major contributor to the radioactivity of nuclear waste on a scale of hundreds or thousands of years.

[citation needed] In its fully ionized state, the beta-decay half-life of 241Pu94+ decreases to 4.2 days, and only bound-state beta decay is possible.

With a Q-value of 5.055±0.005 MeV, it can emit Auger electrons and associated X-rays, unlike the beta-decay process.

[1] Americium has lower valence and lower electronegativity than plutonium, neptunium or uranium, so in most nuclear reprocessing, americium tends to fractionate with the alkaline fission products – lanthanides, strontium, caesium, barium, yttrium – rather than with other actinides.

In a thermal reactor, 241Am captures a neutron to become americium-242, which quickly becomes curium-242 (or, 17.3% of the time, 242Pu) via beta decay.