Recent Findings on the Oxidation of UO, Fuel Under Nominally Dry Storage Conditions

Abstract

This paper is an overview of fuel-storage demonstration experiments, supporting research on UO₂ oxidation, and associated model development, in progress at AECL's Whiteshell Laboratories. The work is being performed to determine the time/temperature limits for safe storage of irradiated CANDU fuel in dry air. The most significant recent experimental finding has been the detection of small quantities of U₃O₈, formed over periods of one to several years in a variety of experiments at 150-170°C Another important finding is the slight suppression of U₃O₈ formation in SIMFUEL and other doped UO, formulations. The development of a nucleation-and-growth model for U₃O₈ formation is discussed, along with available activation energy data. These provide a basis for predicting U₃O₈ formation rates under dry-storage conditions, and hence optimizing fuel storage strategies.