Extension,Verification And Application Of The Flowing Molten Salt Contact With Non-Condensable Gas Problem On RELAP5 Code

As one of the generation IV reactors,molten salt reactor(MSR)has been widely concerned and studied by the international nuclear power industry in recent years because of its superior performance.At present,the design and development of molten salt reactor systems are actively carried out worldwide.The system safety analysis code is an important tool for molten salt reactor safety analysis.It plays an important role in the simulation analysis of the reactor startup,shutdown,normal operation,design basis accidents,and beyond design basis accident.However,there are few system safety analysis codes can be applied for MSR analysis.Therefore,many organizations both at home and abroad try to extend the LWR system safety analysis codes and make them possible to be used for molten salt reactor systems.Based on the RELAP/SCDAPSIM/MOD4.0 code,Shanghai Institute of Applied Physics,the Chinese Academy of Sciences,developed a safety analysis code called RELAP5-MSR for molten salt reactor system.However,this version of the code cannot model the coexistence of flowing molten salt and non-condensable gas.In the paper,one first identifies the reason for the problem of molten salt contacting with non-condensable gas.Then,a solution for the problem by adding molten salt vapor phase properties and modifying the calculation process of fluid properties in RELAP5-MSR is proposed.Next,several typical case analyses,code-to-code comparison and experimental data comparison are performed and used to initially validate the applicability and validity of the extended RELAP5-MSR code.Finally,the new version of RELAP5-MSR code is used to conduct a safety analysis of a 10 MWth TMSR-SF1 system.The results show that the simulation results and the design value are in good agreement,and the extended RELAP5-MSR is applicable to the TMSR-SF1 system.In addition,the Station Blackout transient calculation is performed and the results show that,after the accident,the maximum temperatures of the fuel and the coolant were both less than their safety limits.Therefore,the passive residual heat removal system can ensure TMSR-SF1 system safety in a short time.The pressure response curve indicates that the system pressure continues rising after the accident.The results suggest adopting the corresponding pressure control strategy can protect reactor system's safety.The original RELAP5-MSR code is incapable to model the coexistence of molten salts with non-condensable gases.Work done in the paper extends RELAP5-MSR code and initially validates that the code is appropriate to analyze molten salt reactors.The modified code provides a powerful tool for molten salt reactor system design and safety license applications.The transient analyses and safety assessments for TMSR-SF1 with the extended RELAP5-MSR provide an important reference and has a guiding significance to attain a optimal design of TMSR-SF1 system.