A cooperative Atomic Energy Commission/Combustion Engineering/Naval Research Laboratory (AEC/C-E/NRL) research program is exploring trends in radiation effects for commercially produced ASTM A533-B steel plates, weld deposits, and weld heat affected zones with three levels of impurity copper content control. The primary objective is to establish the trend of improved 550°F (288°C) radiation performance with progressive reductions in allowable copper content. Overall program objectives are to develop information assisting the formulation of special specifications for steels for nuclear service and the delineation of associated embrittlement trends for vessel design and operation. This report summarizes the findings on the radiation resistance of two of three series of A533-B plates and weldments. Series 1 materials contained ⩾ 0.15 percent copper, typical of nonimproved steel production (pre-1971). Series 2 materials contained 0.10 percent copper maximum, representative of improved steel production (current practice). Radiation resistance was assessed from Charpy-V (Cv) notch ductility changes with irradiation to two fluence levels, 2 to 3 × 1019 and 4 to 5 × 1019 neutrons (n)/cm2 > 1 MeV.
Data trends indicate a marked improvement in radiation resistance with the specification of 0.10 percent maximum copper. The improvement is evident both in a smaller increase in Cv 30 ft lb transition temperature and in a smaller decrease in Cv upper shelf energy with irradiation. New ASTM and American Welding Society (AWS) specifications proposing to restrict the copper, phosphorus, and sulfur contents of A533-B plates and weld deposits for nuclear service are reviewed and appear well formulated from the experimental findings presented here.
The effectiveness of postirradiation 650°F (343°C) 168-h heat treatment for notch toughness recovery was also explored.