Instrumented Capsule for Measuring Fission-Induced Creep of Oxide Fuels

The design, testing, and operation of an instrumented capsule used to study fission-induced creep of stoichiometric enriched UO₂ helices are described. Preliminary data are reported for a specimen of 1.82% ²³⁵U enrichment that was irradiated in the General Electric Test Reactor. A large primary creep component was observed under a load of 211 g (equivalent to an outer fiber shear stress of 2890 psi) at a fission rate of 2.6 × 10¹² fissions/(cm³ sec) and a maximum specimen temperature of 103°C. Extrapolation of the straintime creep data yielded a steady-state shear strain rate of ∼6 × 10⁻⁶/h at the outer fibers. Anelastic strain was also observed when the specimen was unloaded and subsequently irradiated.