Significance of Nickel and Copper Content to Radiation Sensitivity and Postirradiation Heat Treatment Recovery of Reactor Vessel Steels

Abstract

This paper describes an experimental test in confirmation of a suspected interaction between nickel alloying and copper impurities in steel radiation sensitivity development. The study was prompted by differences observed in radiation embrittlement trends for high nickel, high copper content versus low nickel, high copper content welds and for A533-B (0.4 to 0.7 percent Ni) versus A302-B (<<0.4 percent Ni) steel plates. The study also explored the influence of nickel content on notch ductility recovery attainable by a low temperature heat treatment after irradiation. Eight steel plates with variations in nickel content from 0.002 to 0.69 percent and with variations in copper content from 0.005 to 0.28 percent were used for the investigation. The plates were produced from two (4-way split) laboratory melts. Plate radiation embrittlement sensitivities were determined from Charpy-V notch ductility changes by 288/sup 0/C irradiation to approx. 2.5 x 10/sup 19/ n/cm/sup 2/. Experimental observations show that a 0.7 percent but not a 0.3 percent nickel content can be detrimental to the radiation resistance of steel; the effect, however, is clearly dependent on steel copper content. Nickel content was also found to influence the amount of transition temperature recovery produced by a postirradiation 399/sup 0/C-168 hour heatmore » treatment.« less