Fission gas bubble behaviour in uranium dioxide
A theoretical model developed to study gas bubble evolution in nuclear materials has been used to analyse experiments on uranium dioxide irradiated to low burnup (0.1 and 0.4 at%), in which fission gas bubble size distributions were measured following out-of-pile isothermal anneals. Following irradiation, the UO(2) was annealed for 1 or 6 h at temperatures between 1303 and 1973 K and then thinned for transmission electron microscopy observation of the bubble size distributions. The model is based on the assumption that the coalescence of the moving bubbles is the main mechanism defining gas porosity development under these conditions. The gas bubbles are assumed to be in equilibrium and their motion is assumed to be caused by random migration. The calculations show that the observed bubble size distributions may be reproduced on the base of the bubble growth mechanisms considered. The joint action of bubble surface and volume diffusion mechanisms can explain both the general nature of the experimental distributions and their peculiarities, in particular the bimodal bubble size distribution observed after annealing at 1673 K. The choice of appropriate values for input parameters into the model is discussed.
Bibliographic Reference: Article: Journal of Nuclear Materials, Vol. 201 (1993) pp. 92-96
Record Number: 199311075 / Last updated on: 1994-11-29
Original language: en
Available languages: en