Seven key technical domains have been identified,54 where important choices, feasibility assessments and new specific developments are needed: 1) choice of FR core conversion ratio, 2) reactor type, 3) heterogeneous versus homogeneous recycling, 4) transmutation fuels and targets, 5) MA content in the fuel, 6) recovery of grouped TRU versus MA/Pu separation and, possibly, selective MA separation, 7) aqueous versus pyrometallurgical reprocessing for transmutation fuels.

The corresponding ‘option tree’,54 is shown in Fig. 17.9.

In the following the options within the seven technical domains and associated challenges are briefly described.