As indicated in Section 17.3, two modes are possible: a) homogeneous recycling of all the TRU elements without further separation or b) heterogeneous recycling of separated MAs (possibly recombined with some TRUs) as targets in specific assemblies, e. g. at the periphery of a fast reactor core. As indicated in 17.3.3, one significant consequence of TRU or MA recycling is an increase (compared to

Pu-only multi-recycling) in spontaneous neutron production after irradiation, which causes difficulties in subsequent fuel fabrication. Homogeneous and heterogeneous recycling should be compared in terms of their respective impact on the fuel cycle.