Examination of VVER-440 RPV steel re-irradiation behavior using materials from operating units

摘要

The paper presents the results of a study on degradation of mechanical properties due to irradiation and re-irradiation of VVER-440 reactor pressure vessel (RPV) steels. The Russian regulatory approach for prediction of radiation embrittlement of VVER-440 steels is considered. Results of an investigation of materials cut out of RPVs of operating units of nuclear power plants (NPP) are discussed. Subsize V-notched impact bend specimens (5×5×27.5 mm~3) were used for ductile-to-brittle transition temperature(DBTT) evaluation of those steels. DBTT values determined using standard 10×10×55 mm~3 and subsize 5×5×27.5 mm~3 specimens are compared. The relation between these two values is validated using the results of testing trepans cut out from the RPV of Novovoronezh NPP unit 2.