Abstract
Molten salt reactor (MSR) is one of the generation IV reactor which fuel is liquid phase state of molten salt fluorides. MSRs are distinguished by the circulation of fluid fuel in and out of reactor cores, which provides unique advantages for innovative applications, such as fuel addition, fission products removal. However, these features complicate neutronics analyses because of online reprocessing and fuel mixing. The goal of this research is to establish the Neutronics and Thermal-Hydraulics coupled calculation procedures, and to take fuel depletion, circulation and reprocessing into consideration in stepwise neutronics simulations. The properties of system will converge in the steady state after a long-timed operation. With iterated neutronics and CFD simulations, the behavior of fluid dynamics, including velocity, power and temperature distributions for full core were known. The power and temperature distributions of the system eventually converged as iterations proceed. The circulation of molten salt is driven by buoyancy and gravity forces due to the change of fluid density at different temperatures. Under the prescribed condition, the feasibility of natural circulation in fuel cycle is supported An automatic calculation procedure was developed to analyze MSR operations with online reprocessing. Because of significant variations in temperature and energy distributions over the system, the whole molten loop was divided into several zones. The fuel composition of every zones should be mixed after depletion. After mixing the fuel, the fuel composition was adjusted by online reprocessing so that the k-effective in stepwise calculation was limited in control. Based on the converged temperature distribution of fuel in equilibrium, a fuel depletion analysis considering fuel circulation and reprocessing was performed to simulate a scenario of five years continuous operation of system.