A new method for determining the threshold level of impact energy for reactor pressure vessel metal

This paper presents the results of validation of a novel approach for finding the threshold level of impact energy to estimate a ductile to brittle transition temperature for ferritic and ferritic-martensitic steels used for the manufacture of reactor pressure vessels (RPV). The idea of the proposed approach is that the value of the threshold level of impact energy is adjusted depending on the strength of the steel. The opportunity of increasing the threshold level of impact energy KVth as the strength of RPV steels increases is validated. The KVth correction technique is described using surveillance test data for Charpy impact and uniaxial tension tests. For highly embrittled RPV steels (transition temperature shift around 160 degrees C or more), the ASTM E185 standard method is shown to clearly underestimate the radiation shift as compared to a physically based approach.