Application of Subsize Specimens for Re-Irradiation Embrittlement Monitoring of the First Generation of VVER-440 RPV Steels

Abstract

The first generation of VVER-440 Units were not supplied with RPV steel surveillance programs. Therefore, cutting out of samples (tem-pletes) from the inner side of RPV wall is the only possibility for re-irradiation embrittlement monitoring of the first generation of VVER-440 RPV steels. Calculations showed that it is possible to cut out a sample of 7×60×95 mm (with consequent repair) from a RPV core weld. Thus, it is impossible to machine the standard 10×10×55 mm Charpy V-notch specimens to determine RPV steel radiation embrittlement. Therefore it is necessary to use subsize specimens (5×5×27.5 mm and 3×4×27 mm) for ductile-to-brittle transition temperature evaluation of templet material. The small samples were cut out from the inner surface of the all old Russian VVER-440 RPVs to assess the actual condition of the RPV material before and after post-irradiation annealing and after re-irradiation. Special monitoring programs of periodic sampling of RPVs and re-irradiation of the templet material in surveillance channels of VVER-440∕213 RPVs were developed. The state of the art of application of subsize specimens for re-irradiation embrittlement monitoring of the first generation of VVER-440 RPV steels is discussed.