Preliminary Study on Transition to Thorium Fuel Cycle in SD-TMSR
—Molten salt reactors (MSRs) represent advances in safety, sustainability, proliferation resistance, and economics. Therefore, an MSR has been chosen as one of the promising reactors for next generation by the Generation IV International Forum. The MSR has been designed to operate on the basis of the Th/<sup>233</sup>U fuel cycle. Hence, <sup>233</sup>U does not exist in nature; it is required to investigate commercially available fuel materials to replace <sup>233</sup>U in starting fuel. We have analyzed the fuel cycle and neutron performance of the SD-TMSR with three different fissile materials loading at startup: low-enriched uranium (LEU) (19.79%), reactor-grade Pu, and <sup>233</sup>U. Two different feed mechanisms have been applied. Moreover, the MSR burnup routine within SERPENT-2 has been utilized to simulate the online reprocessing and refueling in the SD-TMSR. In conclusion, the continuous flow of Pu reactor-grade offers the transition to a thorium fuel cycle within a relatively short time (≈4.5 yr) compared to 26 yr for <sup>233</sup>U startup fuel.