This article needs additional citations for . verification (April 2009)
Transmutation ﬂow between
Cm in LWR.
Fission percentage is 100 minus shown percentages.
Total rate of transmutation varies greatly by nuclide.
Cm are long-lived with negligible decay.
Minor actinides in the periodic table
Major actinides in the periodic table
minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium. The most important isotopes 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 used nuclear fuel in the medium term (300 to 20,000 years in the future). 
The plutonium from a power reactor tends to have a greater amount of
Pu-241 than the plutonium generated by the lower burnup operations designed to create weapons-grade plutonium. Because the reactor-grade plutonium contains so much Pu-241 the presence of americium-241 makes the plutonium less suitable for making a nuclear weapon. 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.
Americium is commonly used in industry as both an
alpha particle and low photon energy gamma radiation source. For instance it is used in many smoke detectors. Americium can be formed by neutron capture of Pu-239 and Pu-240 forming Pu-241 which then decays by beta decay to Am-241. 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. Hence if MOX is used in a thermal reactor such as a boiling water reactor (BWR) or pressurized water reactor (PWR) then more americium can be expected in the used fuel than that from a fast neutron reactor. 
Some of them have been found in
fallout from bomb tests. See Actinides in the environment for details of the actinides in the environment.
Transuranics in LWR spent fuel ( burnup 55 GWd th/T) and mean neutron consumption to fission 
Negative numbers mean net neutron producer
References [ edit ]
^ Sasahara, Akihiro; Matsumura, Tetsuo; Nicolaou, Giorgos; Papaioannou, Dimitri (April 2004). "Neutron and Gamma Ray Source Evaluation of LWR High Burn-up UO2 and MOX Spent Fuels". Journal of Nuclear Science and Technology. 41 (4): 448–456. doi: 10.3327/jnst.41.448.
^ Moyer, Bruce A. (2009). . CRC Press. p. 120. Ion Exchange and Solvent Extraction: A Series of Advances, Volume 19 ISBN 9781420059700.
^ Stacey, Weston M. (2007). . John Wiley & Sons. p. 240. Nuclear Reactor Physics ISBN 9783527406791.
^ Raj, Gurdeep (2008). Krishna Prakashan Media. p. 356. Advanced Inorganic Chemistry Vol-1, 31st ed. ISBN 9788187224037.
^ Berthou, V.; et al. (2003). "Transmutation characteristics in thermal and fast neutron spectra: application to americium" (PDF). Journal of Nuclear Materials. 320: 156–162. doi: 10.1016/S0022-3115(03)00183-1.
^ Etienne Parent (2003). "Nuclear Fuel Cycles for Mid-Century Deployment" (PDF). MIT. p. 104.