Irradiation behavior of aluminum-base fuel dispersions

Miniature fuel plates were irradiated to determine factors that may influence the performance of ?lumimmi-clad aluminum-base UA1 and U3O8 dispersions in the Advanced Test Reactor (ATR) and the High Flux Isotope Reactor (HFIR)* Our primary goal was to establish whether UAl̂ .and U3O8bearing fuel plates could be irradiated to fission densities greater than 1.8 x 10 2 1 fissions/cm without failure. The experiment, designated PM capsule 1, consisted of 18 uninstrumented single-core test plates and 3 instrumented doublecore plates. It was irradiated in the permanent beryllium reflector region of HFIR for 11,613 MWd. The principal experimental variables were initial void content of the fuel dispersions as affected by the type of fuel dispersoid, dispersoid concentration, and fabrication procedure and the fuel dispersoid particle size. Two grades of U3O8, burned and high fired, and arc-cast UA1X were used at dispersoid concentrations that corresponded to current HFIR and ATR loadings am! 25Z increases in these loadings. Poscirradiation examination of the test fuel plates showed all to be in excellent condition, without evidence of either actual or incipient failure. Maximal fuel core swelling of 8.8 vol Z occurred in a UAlx-bearing plate irra­ diated to a 2 3 5 U burnup of 1.8 x 10 2 1 fissions/cm at 63 to 80°C. The swelling behavior of the aluminum-clad U3O8-AI and UA1X-A1 dispersions, however, depended primarily upon the fission density and the void contents of their cores during irradiation; it was independent of the fuel disperscid size distribution of less than 44 um particles. Variations in fuel dispersoid concentration and fuel plate fabrication procedures can alter the void content of these dispersions and, consequently, affect significant}y their irradiationinduced swelling behavior. A mathematical model considering final fission density and initial void content predicts the degree of final plate swelling adequately for most engineer­ ing applications.