球床模块式高温气冷堆稳态与瞬态热工水力分析OA

The pebble-bed modular high-temperature gas-cooled reactor(HTGR)is one of the most promis-ing technologies for meeting the requirements of fourth-generation nuclear energy systems.The high tempera-ture reactor-pebble bed module(HTR-PM)demonstration plant,located in Shidao Bay,Shandong Prov-ince,is the world's first modular high-temperature gas-cooled reactor nuclear power plant.In this paper,a RELAP5-based simulation and analysis method for pebble-bed HTGRs is investigated.A plant-level system model based on the system characteristics of HTR-PM is established,which includes the reactor core flow paths,the fuel thermal components,the transverse heat-conducting components and the steam generator.Us-ing this model,steady-state thermal-hydraulic analysis was carried out,and the impact of bypass flow frac-tions on core thermal performance was conducted.The steady-state thermal-hydraulic analyses of 100%full power(100%FP)and 50%full power(50%FP)conditions demonstrate strong agreement between RELAP5 and THERMIX.The impact of bypass flow fractions on the core thermal effect showed that a 10%increase in bypass flow fraction elevates the average core temperature by approximately 40～60℃,with local hot spot temperature rises above 90℃,indicating that the bypass fraction plays an important role in the core thermal effect.Optimizing structural design to reduce the bypass flow fraction is of great significance for core thermal-hydraulic safety.Based on the steady-state results,conservative assumptions were adopted to simu-late the plant outage Anticipated Transient without Scram(ATWS)accident under rated power equilibrium core conditions.The strong negative temperature feedback coefficient of the HTR-PM was validated,demon-strating that peak fuel temperatures remained below the design limit of 1620℃during ATWS scenarios,once again confirming the inherent safety of pebble-bed modular HTGR.This study is based on an independent sys-tematic analysis program,which is a supplement and extension of the existing analysis tools for pebble-bed modular HTGRs;the study provides detailed modelling and analysis methodology with rich data,which can be used as a reference for further and comprehensive application of RELAP5 to the complex thermal-hydraulic and accident analysis of pebble-bed modular HTGRs.