Seismicloadsforcrackstabilityassessment,inareviewofleak-before-break(LBB)applicabilityOriginalResearchArticle

ThisstudywasperformedtodefinetheseismicloadingconditionsforuseinthecrackstabilityassessmentofaBWRfortheapplicabilityoftheleak-before-break(LBB)criterion.TheLBBhasbeenappliedtothedesignofClass1pipinginJapaneselight-waterreactors.CrackpenetratedconditionwithdetectableleakintheLBBapplicabilityreviewisclassifiedintotheLevelCservicecondition.HereanS1-earthquake(maximumdesignearthquake)iscurrentlyassumed,ratherthananS2-earthquake(extremedesignearthquake).Inordertojustifythisassumption,thefrequencyofanS1-earthquakeoccurringduringcoolantleakageduetocrackpropagationwasdetermined.ThefrequencyofcoolantleakagefromClass1pipingmustbelessthanthatoftheLevelCservicecondition(2.5×10−2to1×10−4peryear)inordertoassumethatanS1-earthquakeisappropriate.Accordingly,thefrequencyofcoolantleakagefromClass1pipingwascalculatedusingaprobabilisticfracturemechanics(PFM).TheresultsofthisanalysisindicatethatthefrequencyofcoolantleakagefromClass1pipingislessthantheexpectedoccurrenceofanS1-earthquake.Astheresults,itisconcludedthattheassumptionoftheseismicloadingemployedinanLBBapplicabilityreviewshouldbeappropriate.