PLEX/TDB

Life extension studies indicate that more rigorous fatigue analysis will be required to demonstrate adequacy of reactor coolant system piping and components for more than 40 years of operation. The extent of reanalysis required can be significantly reduced, and longer RCS design life demonstrated, if the transient design basis used for evaluation of fatigue life is more realistically and accurately derived. The PLEX transient design basis proposed is based on validated operating experience and analysis which considers the probability of future occurrence based on event causes and how they change as the plant ages. The methodology proposed also requires the degree of conservatism in transient projections to be relatively uniform and consistent with the accuracy of the projection methodology used