Calculation and Analysis of Rod Dropping Process of Improved Control Rod Assembly for Supercritical Pressurized Water Reactor

In order to verify whether the improved control rod assembly of supercritical pressurized water reactor (SCWR) can achieve the expected hydraulic buffering function, the rod dropping process is analyzed by using Fluent based on 6 degree of freedom model, which is an option of the layering dynamic mesh method. The control rod assembly dropping time and rod dropping final velocity are analyzed. The results show that compared with the design before the improvement, the dropping time of the improved control rod assembly is increased, but it can still meet the safety requirements; Compared with that before the improvement, the rod dropping final velocity is significantly reduced, and the impact force of rod dropping is thus reduced, so as to ensure the structural integrity of control rod assembly and fuel assembly. The design of the improved control rod assembly can achieve the expected hydraulic buffering function and can be used in the core design of supercritical pressurized water reactor.