EFFECT OF FAST-NEUTRON IRRADIATION ON TENSILE PROPERTIES OF PRECIPITATION-HARDENED CU-CR-ZR ALLOY

High-strength, high-conductivity copper alloys are suitable heat-sink materials for the divertor of magnetically confined fusion reactors su bject to high thermal loads. Tensile specimens of a commercial high-st rength Cu, Cr, Zr alloy were irradiated in the HFR reactor in Petten a t 150 and 250 degrees C. The total accumulated damage (10 dpa) and the damage production rate (3.3 x 10(-7) dpa/s) correspond to the envisag ed operating requirements of the ITER divertor. Tensile testing after irradiation was performed in the LMA hot laboratory at JRC Ispra, at a single constant strain rate of 2.9 x 10(-4)/s. At 155 degrees C an in crease of yield strength (YS) was measured and a decrease of uniform e longation (UE) from 5% to virtually zero. Persisting high total elonga tion (TE) values of about 9% indicate that the ductile fracture mode i s not affected. Irradiation hardening at 255 degrees C is less pronoun ced. In the light of this study and of published results, the temperat ure of 275 degrees C is proposed as a conservative temperature limit f or use of fully precipitation hardened Cu-Cr-Zr (Mg) alloys to exclude irradiation softening.