Dose–time dependence of steel critical brittleness temperature for VVER-1000 vessel service life prediction

Abstract

The high conservativeness of the evaluation of the service life of VVER-1000 vessels is due to the operational reliability margin and the high error in determining the initial computational data. A structural analysis of the error in critical brittleness temperature investigations is presented and the factors which have a large effect on the error in constructing the dose‐time dependences of the critical brittleness temperature are determined. In constructing dose‐time curves, the use of the critical temperature of a calibration metal and heat-treatment regimes of calibration samples makes available and permits checking a wide range of structures that is characteristic for large blanks, makes it possible to take account of radiation embrittlement effects and radiation-stimulated reversible brittleness, decrease the error in determining the guaranteed values to T cr ± 5°C, and eliminate the large effect of structural nonuniformity on objective predictions made for a reactor vessel. Reliable prediction of the service life of VVER-1000 vessels with computational validation of the strength and reli