Evaluation of criticality and depletion for different reactivity insertions in fusion-fission hybrid systems - 5418

Fusion-Fission Hybrid Systems were studied to fuel regeneration, partitioning and transmutation using fuel removed from PWR-spent fuel, then reprocessed by Urex+ and spiked with thorium. Monteburns 2.0 (MCNP5/ORIGEN 2.1) code was used to simulate burn-up and neutronic parameters of the fuel. These systems might be interrupted for some technical problems during few days or longer periods to perform maintenance to fusion source without shutting down the fission system. Therefore, in this work, the aim was to investigate the nuclear fuel evolution in three different cases in which the fission system continues working at full power for both hybrid systems. The first case has external irradiation during 360 days and 5 days without it (a temporary shutdown of the external source). In the second case, 5 sub-cases in which three of them present variations in the burnup are presented. One of them uses one year of external source and the next year the fission chain; other one uses one year external source and the next year decay; and the last uses one year just using the fission chain and the next year the decay. These three cases are compared with the burnup using the external source and just the fission chain continuously during 10 years. The third case performs a comparison between two situations: maintaining constant the fusion power which induces variations on the fission power; and maintaining the fission power constant which induces variation in the fusion power. The multiplication factor and nuclear fuel evolution were analyzed during 10 years of burn-up. The results indicated the variations on the multiplication factor as well as the effects in the portioning and transmutation of the different elements. (authors)