TOWARDS A BETTER UNDERSTANDING OF THE ROLE OF STRESS IN RESTRUCTURING OF RADIATION DAMAGE

摘要

A theoretical stress analysis is conducted in an UO2 crystal doped with an α-emitter producing intense lattice damage. For this purpose, we consider that dislocations and dislocation loops act as sources of internal stress within a poly crystalline material. The elastic energy of dislocation loops is individually calculated and compared with the released energy, measured by means of differential scanning calorimetry during annealing experiments where loops are formed from interstitial point defects. The dislocation loop density and sizes are assessed from TEM analysis. The results confirm that the energy liberated during the formation of prismatic dislocation loops during annealing of radiation damage can be reproduced, similarly to what is observed in the so-called high burnup structure (HBS) of nuclear fuel. This allows a better quantitative assessment of the different sources of internal energy in the HBS. Secondly, the theoretical elastic energy of long dislocation lines is calculated by applying Kroner's theory of discrete dislocations in a continuum (Kroner, 1958) to irradiated UO2. It is shown that the interaction forces play an important role, depending on the characteristics of the periodic configuration.