As plants pursue operation for longer periods (i.e. 60 years) the region of the reactor pressure vessel (RPV) which must be considered as the beltline region for generation of pressure-temperature (P-T) curves and satisfaction of 10CFR50 Appendix G requirements for prevention of brittle fracture has increased in size as the region of the vessel with a cumulative fluence greater than 1E17 n/cm has increased with plant age. In recent years nozzles have been identified as being located inside the beltline region of Boiling Water Reactors (BWRs). Consequently fracture mechanics evaluations of the nozzles in the beltline must be performed when developing beltline P-T curves. This paper evaluates adequacy of an existing simplified method for performing a Linear Elastic Fracture Mechanics (LEFM) analysis of a corner cracked, partial penetration, nozzle present in the beltline region of many BWRs. The nozzle design considered in this paper is representative of the BWR water level instrument nozzle. The results of this investigation are intended to provide a technical basis for the adequacy of the simplified nozzle solution considered in this paper for performing ASME Section XI, Appendix G evaluations of the instrument nozzle design.

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