The High‐Temperature Recovery of Neutron‐Irradiated Rhenium

Abstract

The recovery of rhenium after neutron irradiation a t w 390 OK has been studied u p t o 1130 O K by means of electrical resistivity measurements a t 4.2 OK. Two irradiations were performed in the BR2 reactor a t Mol: one u p t o a fluence of 7.6 x 1018 n cm-2 (thermal) and 4.3 x lo1' n (fast, E > 1 MeV) and the other one up to a fluence of 3.2 x 1019 n cmV2 (thermal) and 1.8 x lo1* n cm-2 (fast, E > 1 MeV). The irradiation induced resistivity is only partially recovered a t 1130 OK, where the annealing of defects is supposed t o be complete. This effect is attributed to the transmutation of rhenium into osmium and tungsten. The annealing spectrum between 400 and 1130 OK consists of several peaks, the main peak occurring a t about 650 OK (0.19 Tm) preceded by a subpeak a t about 620 OK. The latter one is more clearly resolved for the lower irradiation dose. This is also the case for the minor peaks occurring a t about 490 and 540 OK. Towards higher temperature continuous recovery occurs in the temperature interval 800 t o 1000 OK, whereas a small annealing