ALTERNATIVE REFERENCE TEMPERATURE BASED ON MASTER CURVE APPROACH IN JAPANESE REACTOR PRESSURE VESSEL STEEL

Master Curve approach is the effective method to evaluate the fracture toughness of the ferritic steels accurately and statistically. The Japan Electric Association Code JEAC 4216-2011, "Test Method for Determination of Reference Temperature, T-o,T- of Ferritic Steels" was published based on the related standard ASTM E 1921-08 and the results of the investigation of the applicability of the Master Curve approach to Japanese reactor pressure vessel (RPV) steels. The reference temperature, T-o can be determined in accordance with this code in Japan. In this study, using the existing fracture toughness data of Japanese RPV steels including base metals and weld metals, the method for determination of the alternative reference temperature RTTo based on Master Curve reference temperature T-o was statistically examined, so that RTTo has an equivalent safety margin to the conventional RTNDT. Through the statistical treatment, the alternative reference temperature RTTo was proposed as the following equation; RTTo = T-o + C-MC + 2 sigma(To). This method is applicable to the Japan Electric Association Code JEAC 4206, "Method of Verification Tests of the Fracture Toughness for Nuclear Power Plant Components" as an option item.