Use of the Concept of mechanical stability to estimate irradiation embrittlement of pressure vessel steels

Based on the concept of mechanical stability of metals and alloys developed earlier, new approach to estimation of irradiation embrittlement of pressure vessel steel is formulated. It is shown that the critical value of fluence may be determined not by ultimate shift of Charpy critical temperature or by Master-curve reference temperature, but by the condition of plastic state instability of steel. Applicability of the proposed approach to estimation of limiting value of fluence is demonstrated by the example of pressure vessel steel 15Kh2NMFA and its weld. The origin of errors in Master-curve approach is analyzed within the bounds of approach offered