Research And Application Of A Multi-Scale Coupled Model For The Reactor Cavity Cooling System Of High Temperature Gas-cooled Reactor

The reactor cavity cooling system(RCCS)of modular high temperature gas-cooled reactor(MHTGR)is used to remove the heat in the reactor cavity and the reactor core,which plays a very important role in guaranteeing the reactor safety.During operation of the RCCS,heat transfer process in the reactor cavity is a very key segment,and there is an interaction relationship between the global heat removal characteristic of the system and the local heat transfer process in the reactor cavity.Therefore,it is very important to simultaneously investigate the global heat removal characteristic of the system and the local heat transfer process in the reactor cavity.In this dissertation,a three-dimensional numerical model used to simulate the local heat transfer process in the reactor cavity was developed.With this model,the local heat transfer processes in the reactor cavity under five experimental conditions were simulated.The computational results are in good agreement with the experimental results,which demonstrates the accuracy of the three-dimensional numerical model.Moreover,a onedimensional transient analysis model used to calculate the global heat removal characteristic of the RCCS was developed,and the code about the model was also developed.Transient characteristics of the RCCS under the startup condition of HTR-10 was calculated with this code.The computational results also agree well with the experimental results,which demonstrates the accuracy of the one-dimensional transient analysis model and the feasibility of the method to develop the code.By coupling the three-dimensional numerical model and the one-dimensional transient analysis model,a multi-scale coupled transient analysis model which could simultaneously calculate the global heat removal characteristic of the RCCS and the local heat transfer process in the reactor cavity was developed,and the corresponding coupled code was also developed.In order to diminish the computational error caused by the bad continuity,the domain overlapping subroutine iteration method(DOSIM)was proposed.This method can effectively diminish the computational error,and it is especially used for developing the coupled model and code which includes closed natural circulation loop.Based on the coupled model,the variations of the global heat removal characteristic of the RCCS and the local heat transfer process in the reactor cavity under the normal operation conditions and accident conditions of HTR-10 were respectively calculated and analyzed.The computational results are in good agreement with the experimental results,which demonstrates the accuracy of the coupled model and the feasibility of the DOSIM.The results show that the RCCS can effectively remove the heat in the reactor core,demonstrating the rationality of the two redundantly designed subsystems and the reliability of the heat removal capacity of the RCCS under accident conditions.What's more,the effects of water cooled panel structure and air cooled tower height on heat removal capacity of the RCCS were calculated,and the design of interval water cooled panel was proposed.The results show that this design can optimize the heat transfer process in the water cooled panel and enhance the heat removal capacity of the RCCS.The researches in this dissertation provide new tools and methods for the theoretical research and engineering application of the RCCS of MHTGR,which has important significance for the engineering design,optimization,operation and theoretical analysis of the RCCS.