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

The paper presents the results of a study on degradation of mechanical prop erties due to irradiation and re-irradiation of VVER-440 reactor pressure v essel (RPV) steels. The Russian regulatory approach for prediction of radia tion embrittlement of VVER-440 steels is considered. Results of an investig ation of materials cut out of RPVs of operating units of nuclear power plan ts (NPP) are discussed. Subsize V-notched impact bend specimens (5 x 5 x 27 .5 mm(3)) were used for ductile-to-brittle transition temperature (DBTT) ev aluation of those steels. DBTT values determined using standard 10 X 10 X 5 5 mm(3) and subsize 5 x 5 x 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. (C) 2000 Published by Els evier Science Ltd.