Volume 4, Issue 5 (May 2007)
Monitoring of Radiation Embrittlement of the First and Second Generation of VVER RPV Steels
The analysis of the current condition on the prediction of radiation embrittlement for VVER RPV materials of the first and second generation has been carried out. The radiation lifetime of a definite type of pressure vessel is determined by various parameters caused by operational features and the chemical composition of pressure vessel’s metal. The emphasis on re-irradiation embrittlement kinetics is given for the first generation of VVER RPV steels (VVER-440/179 and VVER-440/230 grades). The technique for the first generation RPV materials monitoring, based on sampling and studies of metal from the pressure vessel’s inner surface, is considered. The current program of cutting out templates, for the inner surface of a RPV wall, and their re-irradiation in surveillance channels of VVER-440 units with full core and dummy assembles is described. The new approaches to re-irradiation embrittlement models are analyzed. The basic problems of VVER-440/213 and VVER-1000 metal monitoring are analyzed. The representativity of VVER-440/213 and VVER-1000 RPV surveillance programs is discussed. The necessity of updating of the current standard reference dependences for the prediction of radiation embrittlement of RPV materials is shown. The most urgent questions of reactor dosimetry for VVER pressure vessel materials have been covered. The lifetime extension problem for the first and second generation of VVER units is considered.