Effect of neutron dose and spectra, He/dpa ratio and Ni and Zn accumulation on irradiation damage of pure copper and PH and DS copper alloys

The present analysis is based mainly on the results of recently undertaken investigations of radiation resistance of copper alloys irradiated in the SM-2 and BOR-60 reactors, as well as on the results of the just accomplished collaborative spectrally tailored experiment in the SM-2 reactor. Low-temperature radiation embrittlement at T(irr)similar to 100 degrees C presents considerable problems for dispersion strengthened (DS) and precipitation-hardened (PH) copper alloys, as their total elongation at T-test=T-irr=100 degrees C drops to similar to 1% and uniform elongation to similar to 0.1%. At irradiation temperatures above 300 degrees C, the most significant mechanical property change for PH copper alloys is the softening effect due to radiation enhanced precipitate coarsening and dislocation recovery and recrystallization processes. The softening effect is sensitive to the neutron spectrum, and the threshold temperature of its manifestation in a mixed-spectrum reactor is apparently similar to 100 degrees C less than in a fast neutron reactor. The results of copper alloys irradiation in mixed-spectrum reactors serve as the basis for an analysis of the neutron spectrum effect and the problem of fission-fusion correlation. At irradiation temperatures greater than 350 degrees C, helium embrittlement associated with the high helium accumulation rate for copper alloys exposed to fusion neutrons will be one of the main problems limiting the lifetime. At increased irradiation temperatures, creep will present a special problem. It is apparent that the DS copper alloys have some advantage in their radiation resistance compared to PH alloys such as CuCrZr, this being attributable to the high-temperature stability of their hardening structure. (C) 1998 Elsevier Science S.A. All rights reserved.