Pressure-Temperature limit methodology is based on the rules of Appendix G in Section XI of the ASME Code in accordance with the requirements of 10 CFR 50, Appendix G, and the Appendix G in Section XI method refers to Welding Research Council (WRC) Bulletin 175 (WRC175). Flaw size is an important factor to protect the reactor pressure vessel from brittle failure but is not explicitly documented in WRC175. However, according to the recent change of Appendix G, the ¼ thickness (¼T) flaw size is postulated in the surface of the nozzle inner corner for the evaluation of Pressure-Temperature limit.

In this paper, stress intensity factor is computed by using 3D finite element analysis (FEA) considering ¼T corner cracks of inlet nozzle and outlet nozzle in reactor pressure vessel. The result is compared with the stress intensity factor using influence function in the ASME Code. The results of stress intensity factor in accordance with the ASME Code are more conservative than those of the 3-D FEA with a crack. The allowable pressure and operation region in Pressure-Temperature limit curve are affected by the calculation methods of stress intensity factor.

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