Radiation Embrittlement of Reactor Pressure Vessel Steels

The status of the Naval Research Laboratory (NRL) embrittlement study with emphasis upon major factors, such as the effects on different steels and the effects of nuclear and thermal environment during irradiation is discussed. Post irradiation heat treatment for the restoration of notch ductility has been investigated over a range of irradiation and annealing conditions. Fracture analysis of structural-steel failures demonstrates a point of relative safety from brittle fracture at 60 degree F above the nil-ductility-transition (NDT) temperature. The results showed that the degree of embrittlement of steels irradiated in the range from 200 degree F to 450 degree F was independent of the temperature, but with successively higher irradiation temperatures, in the range from 450 degree F to 750 degree F, the degree of embrittlement was progressively smaller.