High-dose neutron-irradiation effects in fcc metals at 4.6 K

Abstract

The rate of residual-resistivity increase and the isochronal recovery have been studied on the fcc metals Al, Ni, Cu, Pd, Ag, Pt, and Au irradiated at 4.6 K with reactor neutrons to a dose of about ${10}^{19}$ fast neutrons/${\mathrm{cm}}^2$. The rate of resistivity increase is nonlinear as a function of irradiation-induced resistivity; computer analysis shows that the data are best fitted with an expression having up to third-order terms in $\Delta \rho$. There are deviations from simple damage-rate theory in all cases, but an anomalous negative deviation from a linear law (convex curvature) is observed in Ni, Pd, Pt (and Fe). This behavior is most probably caused by a decrease of the specific Frenkel-defect resistivity due to defect clustering, an effect which should contribute in all metals after fast-neutron irradiation to high doses. Saturation values of resistivity and defect concentration as well as recombination volumes have been obtained more accurately than from previous work. The isochronal recovery is compared with previous lower-dose data. Stage I decreases and stage III increases with increasing neutron dose. After high-dose irradiation, correlated recovery in stage III becomes dominant in the case of Al, Cu, Ag, and Au.