Numerical analysis on flow distribution of nuclear reactor core inlet under ocean conditions

Abstract

The high consumption of traditional energy is difficult to support the development of marine resources. Floating Nuclear Power Plant (FNPP) can be used for energy supply due to their advantages such as high power and low cost. Considering that ocean conditions can seriously cause flow fluctuations at the core inlet, this paper establishes a Reactor Pressure Vessel (RPV) model that includes a porous medium core model for numerical analysis. The momentum source is added to the control equation to achieve introduction of ocean conditions, which solves the problem of plane data errors in dynamic mesh method. Therefore, the flow distribution at the core inlet can be obtained under ocean conditions and the local flow characteristics in the lower chamber can be comprehensively observed. The results shown that nonlinear motion can promote more uniform flow distribution at the core inlet, enhancement of the additional force in motion can effectively suppress vortices. In the early stages of motion, rolling motion will cause inlet flow of most fuel assemblies to be too high or too low, it is necessary to adjust the reactor power output accordingly. In linear motion, surging motion does not improve the non-uniformity of flow distribution at the core inlet, but it can increase the stability of coolant flow in the lower chamber and reduces the number of vortices. Heaving motion has very little impact on flow distribution at the core inlet due to it is consistent with the mainstream direction. Coupled motion can enhance the uniformity of core inlet flow compared to single degree of freedom motion and more attention should be paid to adjusting initial reactor power output.