Effect of thermal ageing on impact ductility of the nuclear reactor pressure vessel steel SA533B and its weld metal

The effects of long term thermal ageing on the impact toughness of a reactor pressure vessel (RPV) steel SA533B and its submerged arc weld metal have been studied. The annealings were carried out at 350–450 °C with a duration of 1–5 years. An estimate of the degree of embrittlement at the expected end-of-life of a RPV was made. The studied base metal did not exhibit any noticeable embrittlement during the anticipated reactor life. The studied weld metal proved to be susceptible to the thermal ageing resulting in a small rise in the ductile-brittle transition temperature at the expected end-of-life of the reactor pressure vessel.