Study on the characteristics of the sodium heat pipe in passive residual heat removal system of molten salt reactor

High temperature heat pipes have been widely used in the heat transfer field due to the high conductivity, good isothermality and self-actuating. Using heat pipe might help to improve the heat dissipation performance of passive residual heat removal system (PRHRS) of molten salt reactor (MSR). In this paper, a preliminary concept PRHRS of MSR using sodium heat pipes is proposed detailedly, and then the transient performance of high temperature sodium heat pipe is numerically simulated in the case of MSR accident. The model of the heat pipe is composed of three conjugate heat transfers, i.e. the vapor space, wick structure and wall. Based on finite element method, the governing equations coupled with boundary conditions are solved using FORTRAN code to acquire the profiles of the temperature, velocity and pressure during the heat pipe startup. Numerical results indicated that high temperature sodium heat pipe had a successful startup and can remove the residual heat of fuel salt rapidly at the steady state for the accident of MSR.