Evaluation of Commercial Production A533-B Plates and Weld Deposits Tailored for Improved Radiation Embrittlement Resistance

Abstract

A cooperative 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 controlled levels of impurity copper content. The primary objective is to establish the trend of improved 550$sup 0$F (288$sup 0$C) radiation performance with progressive reductions in allowable copper content. 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 findings on the radiation resistance of two of three series of A533-B plates and weldments. Series 1 materials contained greater than or equal to 0.15 percent Cu, typical of nonimproved steel production (pre-1971). Series 2 materials contained 0.10 percent Cu max, representative of improved steel production (current practice). Radiation resistance was assessed from Charpy-V (Cv) notch ductility changes with irradiation to two fluence levels: 2-3 x 10$sup 19$ and 4.5 x 10$sup 19$ n/cm$sup 2$ greater than 1 MeV. Data trends indicate a marked improvement in radiation resistance with the specification of 0.10 percent max Cu. The improvement is evident both in a smaller increase in Cv 30 ft-lb transition temperature and inmore » a smaller decrease in Cv upper shelf energy with irradiation. New ASTM and AWS specifications proposing to restrict the copper, phosphorous 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 hour heat treatment for notch toughness recovery was also explored. 12 fig, 6 tables. (auth)« less