Minor actinide

[2] The most important isotopes of these elements in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.

Plutonium and the minor actinides will be responsible for the bulk of the radiotoxicity and heat generation of spent nuclear fuel in the long term (300 to 20,000 years in the future).

The ingrowth of americium in plutonium is one of the methods for identifying the origin of an unknown sample of plutonium and the time since it was last separated chemically from the americium.

[4] In general, as the energy of the neutrons increases, the ratio of the fission cross section to the neutron capture cross section changes in favour of fission.

[5] Some of the minor actinides have been found in fallout from bomb tests.

Transmutation flow between 238 Pu and 244 Cm in LWR. [ 1 ]
Fission percentage is 100 minus shown percentages.
Total rate of transmutation varies greatly by nuclide.
245 Cm– 248 Cm are long-lived with negligible decay.