Gamma-ray Tomography of Irradiated CANDU Reactor Fuel

Abstract

Gamma ray computerised tomography (CT) methods have been developed to measure the porosity distribution, cracking pattern, and other characteristics of irradiated CANDU® power reactor fuel pellets. This paper illustrates the technique and documents a CT study of two 24-mm-long sections of CANDU reactor UO₂ fuel elements. Transmission CT was used to map porosity at various longitudinal cross-sections, and to evaluate dish filling, fuel swelling, three-dimensional cracking patterns and crack sizes. Emission CT was used to map approximate distributions of accumulated non-volatile fission products and to extract corrections for transmission scans. This work shows that we currently have a unique quantitative method of non-destructively mapping porosity and cracking in irradiated fuel. The CT techniques are non-destructive and non-invasive. The obtained information is complementary to post-irradiation examination of irradiated fuel by microscopy and ceramography.