Investigation On The Operation Characterustics Of 100kWe Brayton Cycle System Coupled With Lithium Cooled Space Fast Reactor

Space nuclear reactor power has become an important choice of space power because of its advantages of high power density,long service life and not affected by the external conditions of space application,and is gradually being widely concerned.In this thesis,a system simulation platform has been established which can simulate a lithium-cooled fast reactor coupled with a Brayton cycle system.The process of the platform building is divided into two stages,namely physical calculation;system thermal-hydraulic calculation as well as operation simulation.Using the MCNP program such key parameters as fuel temperature feedback coefficient,Doppler reactivity coefficient and average fission energy etc.are calculated,which act as input for the reactor kinetics module of RELAP5 code.The RELAP5 program is modified and further used as the tool of system simulation.By modifying the query function in RELAP5 program,the physical property model of lithium and helium-xenon gas mixture,and liquid metal heat transfer correlation are added,so that the program can identify and correctly calculate the primary and secondary system performances.Through the establishment of control system and protection system,simulation of system transient are conducted.Moreover,such accident scenarios as loss of flow,reactivity insertion,loss of heat sink are calculated and safety performance of the system are studied.For example,in the event of loss of flow accident,the lithium-cooled fast reactor can shut down by its own reactive feedback and shutdown protection system,and the fuel temperature is kept within the safety limit.The simulation practice within the thesis primarily proves that simulation of space nuclear reactor system based on the platform developed by MCNP and RELAP5 is feasible,and it might provide reference for further research of space reactor system.