Literature survey of the mechanisms of neutron irradiation embrittlement of PWR pressure vessel steels

In this note, the mechanisms of irradiation embrittlement in PWR pressure vessel steels is analysed and the influence of metallurgical and irradiation parameters are also discussed. The irradiation embrittlement of pressure vessel steels, as measured by transition temperature shifts, arises mainly from the formation of precipitates and clusters of point defects (dislocation loops, microvoids) within the grains. It is strongly dependent upon the chemical composition; the elements which cause the greatest embrittlement are copper, nickel and phosphorous. Embrittlement increases as the dose rate increases. This phenomenon seems to be related to the fact that the nature of damage depends on this dose rate. An increase in irradiation temperature of 1 deg C induces a decrease in the transition temperature shift of about 0.5 to 1.5 deg C