Thermal-hydraulicanalysisontheeffectofoperatoractioninthelossofshutdowncoolingsystemaccidentinaPWROriginalResearchArticle

ItisnecessarytodevelopPSAmethodologyandintegratedaccidentmanagementtechnologyduringlowpower/shutdownoperations.Todevelopthistechnology,thermal-hydraulicanalysisisnecessarilyrequiredtoaccessthetrendofplantprocessparametersandoperatorʹsgracetimeafterinitiationoftheaccident.Inthisstudy,thethermal-hydraulicbehaviorinthelossofshutdowncoolingsystemaccidentduringlowpower/shutdownoperationsattheKoreanstandardnuclearpowerplantwasanalyzedusingthebest-estimatethermal-hydraulicanalysiscode,MARS2.1.Theeffectsofoperatorʹsactionandinitiationofaccidentmitigationsystem,suchassafetyinjectionandgravityfeedonmitigationoftheaccidentduringshutdownoperationsarealsoanalyzed. Whensteamgeneratorsareunavailableorventpathswithlargecross-sectionalareaareopenintheaccident,thecoredamageoccursearlierthanthecasesofsteamgeneratorsavailableorventpathswithsmallcross-sectionalarea.Ifanoperatortakesanactiontomitigatetheaccident,theaccidentcanbemitigatedconsiderably.Tomitigatetheaccident,high-pressuresafetyinjectionismoreeffectiveinPOS4BandgravityfeedismoreeffectiveinPOS5.Theresultsofthisstudycancontributetotheplantsafetyimprovementbecausethosecanprovidethetimeforanoperatortotakeanactiontomitigatetheaccidentbyprovidingquantitativetimeofcoredamage.Theresultsofthisstudycanalsoprovideinformationindevelopingoperatingprocedureandaccidentmanagementtechnology.