Development of the neutron kinetics code for thermal molten salt reactor

In the molten salt reactor, the delayed neutron precursors continuously change their position both in the core and in the external loop due to the flow of fuel, which lead to the loss of reactivity and decrease of effective delayed neutron fraction. Therefore, the neutron kinetics of molten salt reactor is significantly different from that of conventional reactors using solid fuels. In this study, a 3D neutron kinetics model of molten salt reactor considering the flow effects of delayed neutron precursors was established. The analytic basis functions expansion nodal method for arbitrary triangular-z node was performed to solve the three dimensional neutron diffusion equations and the method of characteristics was used to find the solution of delayed neutron precursor equations within the whole primary circuit. To verify the code, calculations were preformed on a homogeneous reactor model. The results were in good agreement with the reference results. Besides, the influence of fuel circulation on the kinetic characteristic of reactor was investigated. The results showed some special phenomenon in the molten salt reactor.