EffectsofnuclearislandconnectedbuildingsonseismicbehaviourofreactorinternalsinapooltypefastbreederreactorOriginalResearchArticle

Theseismicanalysisofreactorassemblyhousingtheprimarycircuitofatypical500MWecapacitypooltypefastbreederreactor(PFBR)isreported.Thereactorassemblyissupportedonthereactorvaultwithinthenuclearislandconnectedbuildings(NICB).Theseismicresponses,viz.criticaldisplacements,sloshingheights,stressesandstrainenergyvaluesinthevesselsaredeterminedforthereactorassemblybydetailedfiniteelementanalysisincludingthefluid–structureinteractionandsloshingeffects.Analysisiscarriedouttoquantifytheeffectsofinter-connectionofthereactorvaultwiththeadjacentbuildingsundertheassumptionsthatthereactorvaultalongwithreactorassemblyis:(1)anisolatedstructuralsystemfromtheadjacentbuildingswithinreactorcontainmentbuilding(RCB)and(2)connectedwiththeadjacentcivilstructuresthroughfloorslabs.Analysisindicatesthat,byinter-connectingthevaultwiththeNICB,thereareoverallincreasesofallthegoverningparameterswhichdecidetheseismicdesigncriteria.Thesignificanteffectsareincreasesof:(1)radialandaxialdisplacementsofcoretopandabsorberrodsandverticalaccelerationsofcoresubassemblieswhichareofconcerntoreactorsafety,(2)primarymembranestressintensitiesfortheinnervesseland(3)strainenergiesdevelopedatthecriticalportionswhichcanenhancethebucklingrisksofmainvessel,innervesselandthermalbaffles.Hence,itispreferabletoisolatethereactorvault,directlyconstructingfromthebaseraftwithoutinter-connectingitwiththeNICB,fromtheseismicloadingconsiderations.