Low temperature swelling and densification properties of LWR fuels

Analysis of recent data reported in the literature on low temperature swelling and densification behavior of light water reactor (LWR) fuel suggests that, at low irradiation temperatures, the extent of irradiation induced densification shows a simple exponential dependence on burnup with a rate constant that is insensitive to temperature and flux level. These data are also consistent with the view that the total porosity controls the kinetics of irradiation-induced densification process. In the same temperature range the rate of swelling was found to be constant to a burnup near 50 GWD/MTU, with a value of approximately 1% per 10 GWD/MTU. The significance of these results is discussed in terms of current theories.