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 Tirr∼100°C presents considerable problems for dispersion strengthened (DS) and precipitation-hardened (PH) copper alloys, as their total elongation at Ttest=Tirr=100°C drops to ∼1% and uniform elongation to ∼0.1%. At irradiation temperatures above 300°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 ∼100°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°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.