DegradationassessmentofstructuresandpassivecomponentsatnuclearpowerplantsOriginalResearchArticle

Thispaperdescribesamulti-yearresearchprogramtoassessage-relateddegradationofstructuresandpassivecomponentsimportanttothesafeoperationofnuclearpowerplants(NPPs).Thepurposeoftheresearcheffortistodevelopthetechnicalbasisforthevalidationandimprovementofanalyticalmethodsandacceptancecriteriawhichcanbeusedtomakerisk-informeddecisionsandtoaddresstechnicalissuesrelatedtodegradationofstructuresandpassivecomponents.Theapproachadoptedforthisresearchprogramconsistsoftwophases.InPhaseI,specificdegradationoccurrencesatplantswerecollectedandevaluated,existingtechnicalinformationonagingwasreviewed,andascopingstudywasperformedtoidentifywhichstructuresandcomponentsshouldbestudiedinthesubsequentphasesoftheresearchprogram.BasedontheresultsofthePhaseIeffort,selectedstructuresandpassivecomponentsareevaluatedinPhaseIItoassesstheeffectsofage-relateddegradationusingexistingandenhancedanalyticalmethods.Fragilityanalysesareperformedforundegradedanddegradedstructuresandpassivecomponents.Theseresultscanthenbeusedtoassessthepotentialimpactofdegradationonoverallplantrisk.ThePhaseIIeffortalsoutilizestheresultsoftheanalysestodevelopprobabilisticdegradationacceptancecriteriaforthestructuresandpassivecomponentsstudied.Theseresearchactivitiesprovideusefultoolstosupportthecurrentgoalsofdevelopingrisk-informedandperformance-basedregulationinthenuclearindustry.