In this case the multi-recycling of TRUs in FRs is considered as the most appropriate strategy, due to the possibility of increasing U utilization by a factor of >50 and of using a large variety of fuels loaded with TRUs. The scheme in Fig. 17.4 summarizes the features of this scenario and indicates some of the most outstanding issues at each step of the fuel cycling. As indicated, both homogeneous and heterogeneous recycling options can be implemented in this scenario. For homogeneous recycling, it would be sufficient to chemically recover TRUs without separating out the MAs. For heterogeneous recycling, however, it would be necessary to separate Pu (or Pu+Np) from MAs. In this case the MAs could be kept together or separated into Cm and Am to allow Cm to decay in a dedicated facility.

Homogeneous recycling requires the TRU-bearing fuel to be fabricated at an industrial scale, as required by a fast reactor fleet deployment, albeit at a low MA content (< 5%). The alternative, heterogeneous recycling, concentrates the MA/ TRU-bearing fuel in a separate and, in principle, smaller fuel cycle, although with higher MA content and, consequently, higher post-irradiation neutron emission and decay heat (see Section 17.3.3).

It has been shown that this scenario (whatever the recycling mode) would allow the waste radiotoxicity in the repository to decrease to the level of the original uranium ore after 200-300 years.2’ 25