Postirradiation Behavior of Naturally and Artificially Defected UO₂ Fuel Elements at 250°C in Air

Irradiated UO₂ fuel elements with multiple and single 0.8-mm-diam artificial defects showed significant diametral increases, bowing, and sheath cracking after <200 h at 250°C in air. An irradiated UO₂ element with a natural defect under identical conditions exhibited similar behavior. Fuel oxidation was localized in the vicinity of the defects; behavior was independent of power history.