Abstract
Reactor Pressure Vessel (RPV) is one of the most important components in a nuclear power plant (NPP). The primary concern of aging mechanism for RPV is irradiation embrittlement. In order to prevent brittle fracture, during NPP heatup and cooldown processes, the pressure and temperature in RPV should be kept under the pressure-temperature (P-T) limit curve. The P-T limit curve method originated from a WRC bulletin in 1972 and was included in ASME Sec. XI App. G.. Since then, much effort for reducing the conservatism of the P-T limit curve calculation has been made in many countries. Technology developed over the last 30 years has provided a strong basis for revising the P-T limit curve methodology. Up to now, changes have been made in the latest version of the ASME and RCCM codes. In this paper, the P-T limit curve methodologies given by the ASME code, the RCCM code, and Chinese Nuclear Industry Standard EJ/T 918 are studied. The differences of the P-T curve methodologies in previous and current versions for the ASME and RCCM codes are discussed. Two P-T curve calculation methods based on the RCCM code Ver. 2007 are proposed, due to lack of specific description for the calculation method in the RCCM code. Comparison of the P-T curves obtained using methods from different codes is also performed. It shows that using static fracture toughness KIC instead of reference fracture toughness KIR to calculate P-T curves can increase acceptable operating region during NPP heatup and cooldown processes significantly. Comparing with the latest versions of the ASME and RCCM codes, the current Chinese Standard is more conservative.
Published Version
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