U.S. program for inspection of BWR core shroud

Assessment of the serviceability of boiling water reactor (BWR) core shroud welds will depend in part on the results of nondestructive evaluation (NDE) and on the uncertainty associated with those results. The examination results -- a description of the state of the shroud in terms of the location, length, and depth of cracking present in each weld joint -- will form one input into fracture mechanics calculations that will determine the ability of the shroud to perform its function for one or more subsequent operating cycles. These calculations incorporate several degrees of conservatism. In order to employ the NDE results in a conservative manner, an evaluation factor is added to the reported extent of cracking. Careful assessment of the uncertainty associated with various NDE techniques can help to assure that the conservatism applied is not excessive. This document presents the findings and products of the Inspection Subcommittee of the BWR Vessel and Internals Project as of December 1994. Investigations are ongoing and the reports referenced within this paper will be updated as necessary and should be referred to for the latest information. Topics include mock-up fabrication, NDE uncertainty measurements, and provision of visual examination workshops