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 subject to high thermal loads. Tensile specimens of a commercial high-strength Cu, Cr, Zr alloy were irradiated in the HFR reactor in Petten at 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 envisaged 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 increase of yield strength (YS) was measured and a decrease of uniform elongation (UE) from 5% to virtually zero. Persisting high total elongation (TE) values of about 9% indicate that the ductile fracture mode is not affected. Irradiation hardening at 255 degrees C is less pronounced. In the light of this study and of published results, the temperature of 275 degrees C is proposed as a conservative temperature limit for use of fully precipitation hardened Cu-Cr-Zr (Mg) alloys to exclude irradiation softening.