I n this section, we will first give a summary of some fundamental features of transmutation. We will use very basic physics concepts in order to characterize the TRU properties that play a key role in the definition of any transmutation strategy. In the next section we will indicate how the application of these fundamental features leads to the selection of the most appropriate reactor concepts for transmutation and indicates the major issues and consequences for the fuel cycle.

As indicated above, to achieve transmutation, TRU-loaded fuel is irradiated in a neutron field. Several features characterize the transmutation potential of a specific neutron field for each TRU isotope:

Fission of isotope A should be favored against (n, y) and (n, xn) reactions.

Starting from isotope A, reactions giving rise to A+1, A+2, etc., should be minimized. In any event, the radioactive properties of isotopes A+1, A+2, etc., should be carefully investigated in terms of decay heat, neutron production, etc., in order to evaluate all consequences of transmutation.

The isotopes that successively lead towards full fission should, as much as possible, be ‘neutron producers’ rather than ‘neutron consumers’, in order to allow a viable core neutron balance.4