LeakBeforeBreakapplicationforPrimaryCoolantLoopandSurgeLineofVVER-1000/320Plant:TACISProjectR2.09/96OriginalResearchArticle

ActivitieswerecarriedoutwithintheframeofTACIS-96Program—ProjectR2.09/96named“LBBApplicabilityReviewandBasicImplementationEngineeringforPrimaryCoolantLoop&SurgeLineofVVER-1000/320NuclearPowerPlant”.MainobjectiveoftheProjectwastoperformaLeakBeforeBreakassessmentfortheMainCoolantPipesandPressurizerSurgeLineoftheReactorCoolantSystemofaselected“reference”UnitofaVVER-1000,typeV-320NuclearPowerPlant,whichwasassumedtheBalakovoUnit2. Thishasincludedthefollowing: • definitionofa“reference”methodologyforprimarypipingsystemswithcladding; • verificationoftheLeakBeforeBreakconceptapplicabilitytoprimarypiping,inaccordancewiththe“reference”methodologydefined; • preparationofnecessarymaterialsdataandvalidationfiles; • evaluationofeffectivenessandreliabilityoftheLeakDetectionsystemsandtheIn-serviceInspectionPrograms(methodologiesandqualification); • preparationofarecommendationslisttoimprovetheexistinginformationanddiagnosticsystems; • transferofknow–howfromConsortiumtoSub-Contractor,integratingthefeedbackofWesternexperience. OneofthemainhighlightsoftheProjectwasthedefinitionandexecutionofacomprehensiveMaterialTestingPrograminordertoestablishtheactualtensileandfracturepropertiesoftheprimarypipingmaterials:basematerials,weldmetals,and“heataffectedzones”weretested.CompacttestsandstandardspecimensforJ–Rcurvesdeterminationwereused;specialattentionwaspaidtothedissimilartypicaljointsoftheSurgeLinepipes,beingmadebycarbonsteelbasemetalwithstainlesssteelweld.FracturepropertiesasJ–Rcurvesweredeterminedbothatroomandoperatingtemperatures. The“reference”methodologydefinedhastakenintoaccountbothWesternandRussianLeakBeforeBreakapproaches.TheanalysishasshownthatcriteriaforLeakBeforeBreakconceptapplicabilitytotheprimarypipingofBalakovoVVER-1000/320Unit2,presentedinthereferencemethodsdevelopedintheframeofthisProject,aremet.