CFD simulation of a full-scale three-dimensional flow and temperature distribution inside a reactor under ocean conditions

A series of three-dimensional full-scale fluid flow simulations are performed based on an integrated thermal marine reactor under ocean conditions. The aim is to understand the effects of ship motions including rolling, heaving, and inclination on flow field and thermal–hydraulic performance. Both forced circulation and natural circulation are taken into account since the abilities of coolant to maintain its original motion under ocean conditions are different. The temperature distribution, velocity field, and flow rate distribution of a static reactor are presented first for comparison. After additional forces or accelerations are introduced, the flow field in the marine reactors subjected to different types of ocean motions is explored. Results show that the rolling motion would have more significant impacts on marine reactors in natural circulation concerning temperature and SG (steam generator) flow rate. In natural circulation, the SG flow rate fluctuation can reach 35 kg/s when the rolling angle increases to 45°, compared to the maximum fluctuation of 8 kg/s under forced circulation. The rolling motion also greatly affects the flow field and flow rate distribution at the core inlet. Obvious vortex flows can be observed in the annulus both for forced circulation and natural circulation. The core channel with the minimum flow rate appears to be randomly located for the reactor subjected to rolling motion. For reactors in heaving motion, the fluid velocity changes periodically, and the flow rate in the SG and core regions increases significantly with the increase of the heaving period and acceleration. As for inclined reactors, the average velocity in the core becomes smaller while the temperature increases as the inclination angle of the reactor increases.