IRRADIATION AND POSTIRRADIATION ANNEALING OF SOME ALUMINUM-BASE FUELS

Abstract

Irradiated specimens of 39 wt% U/sub 3/O/sub 8/ dispersed in aluminum and of aluminum-17.3 wt% uranium alloy were andnealed. Each specimen was partially clad with aluminum. Gross swelling was not observed for the aluminum- 39 wt% U/sub 3/O/sub 8/ dispersion specimens for burnup and annealing temperature levels ranging up to 1.0 x 10/sup 20/ fissions per cc and 550 deg C, respectively. Small volume increases were found, however, and these were attributed to the aluminum reduction of U/sub 3/O/sub 8/, which is accompanied by measurable volume increases. X-ray diffraction andalyses confirmed the reaction between the U/sub 3/O/sub 8/ and the aluminum matrix. The dispersion specimens and, in particular, the U/sub 3/O/sub 8/ particles sintered during irradiation at temperatures from 55 to 90 deg C in an effective thermal-neutron flux of between 1 and 3 x 10/sup 13/ nv. Annealing at 550 deg C produced severe localized blistering on specimens of aluminum-17.3 wt% uranium alloy having burnups of 5.9 x 10/sup 20/ fissions per cc. Similar conditions produced only a small uniform volume increase when the burnup was 1.4 x 10/sup 20/ fissions per cc. The observed stability is attributed to a defect structure in the compound UAl/sub 4/ in which unoccupied uranium sites trap fission products and, in particular, fission product gases. (auth)