Porosity swelling and transmutation contributions to conductivity changes in some neutron-irradiated copper alloys

Abstract

Fast-neutron irradiation of alloys for fusion-reactor applications produces bulk changes in the density and composition via porosity swelling and transmutation which affect the do volume electrical and thermal conductivities ( σ = 1/ ϱ e and K ). For the Cu materials of our study, neutron fluences of 2 × 10 26 n/m 2 ( E > 0.1 MeV) produced increases in Ni and Zn concentrations of about 0.05 and 0.09 wt%, respectively, and porosity swelling of 0–7%; ϱ e accordingly increased as much as 18%. We also determined the individual ϱ e changes due to both swelling and transmutation via use of an appropriate mixing rule and of Matthiessen's law to unmask any residual effects present, e.g., phase or microstructural changes. For four materials — two pure copper and two alumina-dispersion-strengthened (ADS) alloys — subtraction of these δϱ e 's from the irradiated values yielded or nearly yielded the respective control values. In contrast, the two precipitation-strengthened (PS) alloys studied, MZC and AMZIRC, had relatively large negative residues, apparently indicating effective radiation-induced conductivities.