Thermal-hydraulic Design And Safety Study Of Water Cooled Ceramic Breeder Blanket Primary Heat Transfer System For CFETR

Chinese Fusion Engineeing Testing Reactor(CFETR)is the next device in the roadmap to realize fusion energy in China,which aims to bridge the gap between International Thermonuclear Experimental Reactor(ITER)and future fusion DEMOnstration reactor.The primary objectives of CFETR are demonstrating fusion energy production,tritium self-sufficiency long pulse or steady-state operaion with duty cycle about 0.3-0.5.It will operate in two phases:Phase I focuses on a modest fusion power of up to 200 MW,while Phase ? aims for DEMO validation with a fusion power of 1.5 GW.The Water-Cooled Ceramic Breeder(WCCB)Blanket is one of the candidate concepts for CFETR,and it shoulders the responsibility of tritium production and energy conversion.The primary heat transfer system(PHTS)is responsible for removing the nuclear heat deposited inside blanket modules and delivering it to the turbines to generate electricity.Concering the PHTS based on WCCB,when the system is in steady state operation at each phase,it is necessary to ensure that the thermal-hydrulics parameters of the system operate within a reasonable range,so that the heat of the blanket is used for power generation.In the case of an accident,the system needs to take away the decay heat of the blanket to prevent the related structure from over-temprature and over-pressure,ensure structural integrity,and confine radioactive materials.The research on thermal hydraulics design and safety of PHTS of WCCB blanket is of great significance for the efficient power generation and the safe operation of CFETR.Firstly,for the typical WCCB module,the preliminary themal hydraulics safety analysis of steady state and accident conditions was carried out using the RELAP5 program.Steady-state analysis results showed that the blanket meets the design requirements for steady-state operation.Preliminary safety analysis was carried out for three accidents:in-vessel LOCA,in-box LOCA and ex-vessel LOCA.The analysis showed that in the case of safety measures taken,no overpressure occurred in each equipment during the accident,and the FW temperature did not exceed the temperature limit.Targeting the two phases' operation of CFETR,the thermal hydraulics design principle and operation scheme of the WCCB PHTS were proposed.The design principle is using one set of system to operate at two different fusion powers.The operating scheme is to keep the average temperature of the primary coolant constant.The thermal parameters of the two operating phases were designed according to the design principles and operating scheme.Based on the larger power of 1.5GW fusion power,the preliminary design of the PHTS spatial layout,main pipeline,steam generator,main pump and pressurizer was carried out.Based on the designed WCCB PHTS,a RELAP5 model was established.Then the steady-state analyses of the system in Phase ? and Phase ? were carried out.The steady-state results showed that the WCCB PHTS can operate stably under two phases.Based on the steady-state results,the calculation and analysis of the loss of coolant accident(LOFA)and the loss of heat sink(LOHS)accident were carried out for the PHTS under each phase.Firstly,the process and consequences of the accident without intervention were analyzed.Then,according to the consequences of the accident,the mitigation measures such as shutting down the plasma reaction and restoring the water supply were proposed.As for the active plasma shutdown,two scenarios were taken into consideration,those are fast plasma termination in Is and a normal soft plasma shutdown in 60s.Finally,the responses of the system after the accident mitigation measures were analyzed,the results showed that the mitigation measures taken are effective and the reactor can be safely shut down.Based on the previous design of the PHTS,an alternative PHTS layout was proposed.Then the RELAP5 model of the alternative system was established.The steady-state analysis of the system was carried out under Phase ? and Phase ?.The analysis results were basically consistent with the design values.Based on the steady-state results,the PHTS under Phase ? were analyzed for the accidents of LOFA and LOHS.The results showed that for the case of LOFA,the alternative design is safer;for the LOHS,the alternative design showed no obvious advantage.In this thesis,the thermal hydraulic design of the WCCB PHTS and the safety study under typical accidents were carried out for the two-phase operation of CFETR.The relevant research results will help to understand the design and safety characteristics of the CFETR PHTS under multi-power operation.