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

Abstract

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 $$^{233} \hbox {U}$$ 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 $$^{233} \hbox {U}$$ production, spectrum shift, and temperature feedback coefficient. It can be concluded that such a Th/Pu to $$\hbox {Th}/^{233} \hbox {U}$$ 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 plutonium with the help of thorium. Meanwhile, a pre-breeding and burning (PB&B) scenario is also analyzed briefly with respect to the net $$^{233} \hbox {U}$$ production and evolution of main nuclides. One can find that it is more efficient to produce $$^{233} \hbox {U}$$ 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.