SECY 82-465l and RGl. l542 provided guidance to the utilitiesregarding an acceptable methodology for performing structuralintegrity evaluation of aging nuclear reactor pressure vessels (RPVs)subjected to pressurized thermal shock (PTS) transients.Probabilistic fracture mechanics (PFM) analysis is a major element ofthis methodology. RG l.l54 currently specifies that when performing aPFM analysis, all flaws shall be considered as surface flaws thatexist in the inner surface of the RPV wall. Recently, PTS analysiswas performed for one of the Korean PWR Vessels. As a result of PFManalysis, it was found that current RG. l.l54 methodologies were veryconservative. Therefore, to evaluate and quantify the conservatism ofRG l.l54, several PFM analyses were performed in this paper, and PFManalysis results were compared with the value from RG l.l54.
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