Transmutation of americium and neptunium in the single-fluid double-zone thorium-based molten salt reactor

•A new approach compared to solid-fuel reactors for MAs loading was introduced.•The transmutation performance of 241Am and 237Np in the critical SD-TMSR was investigated.•The transmutation ratio was calculated using the SERPENT-2 Monte-Carlo code.•The on-line reprocessing and refueling was applied during burnup. In the current work, we introduce a new approach compared to solid-fuel reactors to load the minor actinides (MAs) into the Single-fluid Double-zone Thorium-based Molten Salt Reactor (SD-TMSR). The proposed approach merges the advantages of both homogeneous and heterogeneous approaches. Among MAs nuclides, 241Am and 237Np are selected for transmutation due to their long half-life. We simulate two separate tanks; Pu + U tank and FPs tank. In this study, a tank is a right cylinder with a volume of 1.0 m3. The Pu + U tank is used to store Pu and U isotopes extracted from the central channel of the SD-TMSR. However, the FPs tank is used to store all fission products (FPs) produced from the transmutation process in the central channel. The overall change in the actinides and FPs mass during the irradiation has been calculated using direct SERPENT-2 calculations. The results show that the transmutation ratio of 241Am and 237Np reaches 98.5% and 93.2%, respectively after 1500 days of irradiation. We notice that the major isotope in the Pu + U tank is 238Pu. Under 241Am irradiation, our proposed approach offers ≈0.3kg of 238Pu after 1 year of operation. However, under 237Np irradiation, 2.5 times more 238Pu can be extracted after the same period of operation. The produced 238Pu can be used in the radioisotope thermoelectric generators (RTG, RITEG) and radioisotope heater units.