Thermal Hydraulic Analysis Of CFETR Water Cooled Blanket Under Transient Condition And Typical Accident

Nuclear fusion is known as the most effective way in the future to solve energy problems.And blanket is the key component to achieve the function of energy transfer.In a fusion reactor,the fusion reaction produces high energy neutrons,and the blanket is designed to slow and absorb neutrons in a reliable and efficient manner.Energy absorbed from the fast neutrons is extracted and passed into the primary coolant in the blanket.Hence,the design of the blanket will strongly affect the operating power and the safety of fusion reactors.It is significant to analyze the hydraulic properties and heat transfer properties of the blanket,and design control systems to maintain the stability of important parameter.A Water Cooled Ceramic Breeder blanket(WCCB)sector blanket of Chinese Fusion Engineering Test Reactor(CFETR)is the object of this thesis.In the first place,the original complicated design of the blanket is simplified reasonably.Then,a RELAP 5 model is adopted,including WCCB sector blanket,pressurizer,steam generator and main pump.The thermal hydraulic properties in steady state,loss of flow accident,loss of heat sink and station blackout accident is analyzed.The calculation of the loss accident shows that if the fusion reaction stops immediately after the accident,the blanket can establish a natural circulation under the effect of the decay heat and the heat sink of the secondary loop to provide effective long-term cooling.If no mitigation measures are taken during the accident,the RAFM steel and tungsten armor of first wall will soon fail and a vacuum vessel break will occur.The calculation of the heat sink loss accident shows that the temperature and pressure of the primary loop increase during the accident,the flow rate drops,and the temperature of blanket material rises.The RAFM steel of the first wall and the cooling plate successively exceeds the limit,eventually causing a loss of coolant accident inside the blanket.As a mitigation measure,the fusion reaction is immediately stopped,and the emergency system is put into service in 14 minutes after the accident to resume the flow of the second loop.This ensures that the loop pressure does not trigger the pressurizer safety valve and the fluid inside the blanket does not reach the saturation temperature.In the station blackout accident,the fusion reaction was stopped due to loss of control of the plasma,the flow of coolant in the first and second loops was lost.The decay heat became the only heat source.The blanket did not fail after 15 hours.Recovering the flow of the second circuit after the accident can build a natural circulation in the first loop and remove the decay heat.In order to maintain the stability of the main thermal parameters in the operation of the blanket sector,the pressure,power,and temperature control systems are set for the blanket.The pressure is regulated by the pressurizer,which can effectively maintain the loop pressure stability under the expected operating conditions of increasing power.The power control is designed to match the primary loop power and the secondary load of the steam generator.Based on this,the temperature is added as input of power control to maintain the stability of the inlet temperature.