Oxide fuel transients

The behavior of UO2 fuel from power reactors has been studied up to high burn-up (∝60 GWd/tU), under both steady state and power transient conditions in the range of 35 to 48 kW/m. Careful post-irradiation examination involving electron probe microanalysis, transmission and scanning electron microscopy in addition to detailed hot cell examination have provided a large data base on the radial migration and release of volatile fission products. Theoretical evaluation with different computer codes and supporting laboratory experiments established the basis for understanding the kinetics and mechanisms operative during transients in high burn-up UO2. Typical examples are given to demonstrate the degree of understanding achieved. (orig.)