A series of advanced investigations on the radiation performance of four 6-in-thick plates from a large (30-ton) commercial melt of A533-B steel is described. The melt represented the first commercial scale demonstration test of improved radiation embrittlement resistance through the control (minimization) of selected residual impurity elements. Melt specifications emphasized the attainment of a low copper and phosphorus content; one half of the melt was modified, however, by a copper addition (0.03 percent Cu increased to 0.13 percent Cu). Initial plate tests described superior 550 F (288 C) radiation resistance, in terms of notch ductility retention, for the primary melt composition and verified the detrimental influence of impurity copper on irradiation behavior. Promising capability of the primary melt composition for very high fluence (∼2.5 × 1020 n/cm2 > 1 MeV) service is shown by the current investigations. In addition, a significant influence of copper content on radiation resistance is revealed for a broad range of exposure temperatures. A dependence of 650 F (343 C) postirradiation heat treatment response (notch ductility recovery) on copper content was also found. Charpy-V versus dynamic tear test performance and tensile strength trends with temperature are examined for low (<450 F, 121 C) and elevated (550 to 585 F, 288 to 307 C) temperature irradiation conditions.

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