Feedwater (FW) nozzles are often considered to be locations with the highest cumulative fatigue usage in boiling water reactors (BWRs). Despite the lack of fatigue failures of these components, application of fatigue life environmental correction factors to the usage factors, originally computed by the designers, typically result in environmentally assisted fatigue (CUFen) values greater than 1.0. The reason for this disconnect may be attributable to the differences in analytical methods, as well as the differences in severity between the idealized design transient definitions and the actual transient behavior. This paper investigates these differences by comparing the traditional design fatigue analyses with those computed using modern fatigue monitoring methods. The results support the position that the level of conservatism in those original analyses account for some, if not all, of the environmentally-assisted fatigue effects.

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