<p>A probabilistic fracture mechanics (PFM) evaluation was performed for the nozzle blend radius and nozzle-to-shell weld of a boiling water reactor (BWR) feedwater nozzle using the PFM methodology in Electric Power Research Institute (EPRI) Boiling Water Reactor Vessel and Internals Program (BWRVIP) BWRVIP-108-A and BWRVIP-241-A, which are the technical basis for inspection relief in ASME Code Case N-702.&nbsp;&nbsp; Using a finite element model of the feedwater nozzle, stress analysis was performed for plant-specific piping loads and bounding transients, which were grouped by severity and projected cycle counts.&nbsp;&nbsp; Monte Carlo simulations were performed using the VIPER-NOZ (Vessel Inspection Program Evaluation for Reliability, including Nozzle) PFM software to determine probabilities of failure for the reactor pressure vessel (RPV) with an inspection population of 25% of the feedwater nozzles every ten years for sixty years of plant operation.&nbsp;&nbsp; The results show that the probabilities of failure for normal operation and low temperature over pressure (LTOP) event meet the acceptance criteria for RPV failure in NUREG-1806 by the U.S. Nuclear Regulatory Commission (NRC).&nbsp;&nbsp; Thus, there is potential to seek regulatory relief to reduce the inspection population of BWR feedwater nozzles from 100% to 25% every ten years using the technical basis of ASME Code Case N-702.</p>

Probabilistic Fracture Mechanics Evaluation of a BWR Feedwater Nozzle

Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2021/volume/85314

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