Research On The Effect Of PCS Heat Exchanger On Hydrogen Behavior In Containment Under Severe Accidents

Hualong Advanced pressurized water reactor adopts the design concept of combining passive and active safety systems,and adopts a large number of passive safety technologies to deal with accident conditions.The passive containment cooling system(PCS)uses built-in heat exchangers to cool the containment atmosphere under severe accidents,which is different from the current mainstream second-generation nuclear power plant(M310),The third generation nuclear power plant(AP type)Hualong PCS heat exchangers has many unique thermal hydraulic physical phenomena during operation.How to accurately analyze the main thermal hydraulic phenomena inside the containment of PCS heat exchangers under severe accidents and propose a systematic and scientific modeling analysis method for scaling test equipment is a problem that needs to be solved.This article conducts simulation calculations and experimental research on the main thermal hydraulic phenomena unique to the Hualong PCS heat exchangers.First,select the existing relevant closed space heat exchanger test with non condensable gas steam condensation,carry out the research on equivalent modeling technology,select the appropriate geometric modeling and physical model,and use the CFD software STAR-CCM+ for numerical calculation,to compare and analyze the test results.Verify the reliability of the calculation method,geometric modeling and physical model,and master the main thermal hydraulic phenomena such as multi-component gas distribution and flow in the pressure vessel under the action of the heat exchanger.Secondly,using the comprehensive containment thermal hydraulic testing device as the model,based on the Hierarchical,Two-Tiered Scaling analysis(H2TS)method and combined with the volume power method,scaling analysis research is carried out.A scaling scheme with multiple subsystems and multiple physical process coupling is proposed for numerical calculation.Based on the characteristics of the PCS system and severe accident process,numerical calculation research is conducted on the influence of the PCS heat exchangers on the gas distribution inside the containment,Analyze the helium distribution inside the containment under different conditions and obtain the influence of PCS heat exchangers on the hydrogen behavior inside the containment.The calculation results indicate that the gas distribution inside the containment is related to the pressure response inside the containment.Under other conditions being the same,as the pressure inside the containment gradually decreases,the helium concentration in the lower space of the PCS heat exchangers inside the containment gradually increases.Finally,based on the gas distribution pattern obtained from the previous analysis,the space inside the containment is divided.Based on the quality control equation inside the containment,the dimensionless number of helium gas distribution inside the containment is derived,and different scaling schemes are designed to verify this dimensionless number.The prototype and experimental devices are used as research objects to explore the impact of PCS heat exchangers on the distribution of hydrogen gas inside the containment under different size ratios,Analyze the possible scale effects caused by the difference in size between the prototype device and the modeled device.The rationality of dimensionless numbers was verified through numerical calculations,and the differences in size were approximately unaffected in the study of the influence of PCS heat exchangers on gas distribution inside the containment when designing a reasonable scaling scheme.