Transition toward thorium fuel cycle in a molten salt reactor by using plutonium

The molten salt reactor （MSR）, as one of the Generation IV advanced nuclear systems, has attracted a worldwide interest due to its excellent performances in safety, economics, sustainability, and proliferation resistance. The aim of this work is to provide and evaluate possible solutions to fissile 233U production and further the fuel transition to thorium fuel cycle in a thermal MSR by using plutonium partitioned from light water reactors spent fuel. By using an in-house developed tool, a breeding and burning （B＆B） scenario is first introduced and analyzed from the aspects of the evolution of main nuclides, net 233U production, spectrum shift, and temperature feedback coefficient. It can be concluded that such a Th/Pu to Th/233U transition can be accomplished by employing a relatively fast fuel reprocessing with a cycle time less than 60 days. At the equilibrium state, the reactor can achieve a conversion ratio of about 0.996 for the 60-day reprocessing period （RP） case and about 1.047 for the 10-day RP case. The results also show that it is difficult to accomplish such a fuel transition with limited reprocessing （RP is 180 days）, and the reactor operates as a converter and burns the plu- tonium with the help of thorium. Meanwhile, a pre- breeding and burning （PB＆B） scenario is also analyzed briefly with respect to the net 233U production and evolu- tion of main nuclides. One can find that it is more efficient to produce 233U under this scenario, resulting in a double time varying from about 1.96 years for the 10-day RP case to about 6.15 years for the 180-day RP case.