Transmutation of transuranium elements (i.e. actinides minus actinium to uranium) such as the isotopes of plutonium (about 1wt% in the light water reactors used nuclear fuel or the minor actinides (MAs, i.e. neptunium, americium, and curium), about 0.1wt% each in light water reactors used nuclear fuel) has the potential to help solve some problems posed by the management of radioactive waste by reducing the proportion of long-lived isotopes it contains. (This does not rule out the need for a deep geological repository for high level radioactive waste.) When irradiated with fast neutrons in a nuclear reactor, these isotopes can  undergo nuclear fission, destroying the original actinide isotope and producing a spectrum of radioactive and nonradioactive fission products.
Ceramic targets containing actinides can be bombarded with neutrons to induce transmutation reactions to remove the most difficult long-lived species. These can consist of actinide-containing solid solutions such as , , , ,  or just actinide phases such as , , ,  mixed with some inert phases such as , , ,  and . The role of non-radioactive inert phases is mainly to provide stable mechanical behaviour to the target under neutron irradiation.
There are issues with this P&T (partitioning and transmutation) strategy however:
* it is limited by the costly and cumbersome need to separate long-lived fission product isotopes before they can undergo transmutation. 
* some long-lived fission products, including the nuclear waste product caesium-137, are unable to capture enough neutrons for effective transmutation to occur due to their small neutron cross-section and resultingly low capture rate. 
The new study led by Satoshi Chiba at Tokyo Tech (called "Method to Reduce Long-lived Fission Products by Nuclear Transmutations with Fast Spectrum Reactors") shows that effective transmutation of long-lived fission products can be achieved in fast spectrum reactors without the need for isotope separation. This can be achieved by adding a yttrium deuteride moderator.