Doel 3 & Tihange 2 - Some Peer-reviewed Scientific Papers & Reports

ABSTRACT

A summary of the hydrogen and irradiation embrittlement properties of reactor pressure vessel steel and their weldments is presented. The embrittling effect of hydrogen is marked for hydrogen contents above 2 ppm in both irradiated and unirradiated steels. The effects of hydrogen are more pronounced in impure steels and they are manifested by intergranular fractures, especially when phosphorous segregation to the grain boundaries has taken place. This conjoint action is a probable reason for the anomalous fracture behaviour of the base material specimens of irradiated pressure vessel steel in surveillance tests. In general, stainless-steel cladding is considered to prevent the hydrogen-induced cracking problems in the nuclear pressure vessels. However, if the cladding is penetrated by cracks, the pressure vessel steel would come into direct contact with high temperature reactor water and may locally absorb hydrogen produced by corrosion reactions. In this case, the superimposed embrittling effects of irradiation and hydrogen absorption must be taken into account when considering the integrity of the pressure vessel.