A comparative analysis of fuel cycles using accelerator-driven subcritical reactors

We have performed detailed Monte Carlo simulations of different sub-critical fast reactor fuel configurations leading to the possible use of these devices as energy generators. The method is based on the coupling between a validated neutron transport code and a mathematical solution of the equations describing the time evolution of the neutron spectrum and mean cross sections during the reactor operation. We present results which indicate the need of such a detailed treatment in specific situations where the time evolution of the hybrid reactor physical parameters is significant over the duration of one 5-year fuel cycle. We have optimized the geometrical and operational characteristics of reactors based on ²³²Th/²³³U and U/Pu oxide fuels, studied the evolution of their reactivities, and simulated their operation over 20 fuel cycles. Quantitative results are presented for their inventories, waste production and induced radiotoxicities under alternative scenarios of fuel reprocessing. An our calculations indicate advantages for fuels having thorium as their fertile element. Possible paths to start a thorium-based fuel cycle are presented