Experience of long-term U–Al fuel performance in research reactors with low energy generation

Life cycle extension practices for U–Al fuel in Al cladding used at the OR and the IRT MEPhI research reactors are discussed. The IRT MEPhI reactor uses tube type IRT-3M FA with dispersed UO2–Al fuel meat and SAV–1 aluminum alloy as cladding. The OR reactor uses pin type fuel elements with U–Al alloy fuel meat in cladding of Al alloy AMSN. The necessity of life cycle extension for the fuel elements is caused by a large calendar time of fuel assembly operation (10–30 years) and regulatory bodies concerns about this issue. The results of fuel cladding corrosion effects estimation using available empirical correlations for the corrosion rate and the rate of oxide film growth are presented. The results of visual inspection of the fuel elements are shown. Water chemistry monitoring practises in the reactor pool and in spent fuel storage are analysed. The successful experience of the IRT MEPhI (in 2003–2007) on repeated operation of the fuel assemblies previously discharged from the core (after the storage over 5–21 years) is presented.