Fission product behaviour and fuel rod chemistry at extended burnup: Results, models and programmes of analytical experiments carried out at the CEA, Grenoble

Of the analytical experiments carried out at CEA to study fuel behaviour at high burnups, special mention should be made of the study of the effects of moderate transients on fission gas release (importance of cracking associated with power variations), and SEM examination of fracture surface of various fuels (analysis of bubble populations and precipitates of associated metallic fission products). Several factors must be considered when analysing the results: radial specific power profile and its thermal effect, fission gas creation, oxygen balance, density and open porosity, gaseous swelling. This paper describes the principle of various tools (calculations or experiments) used to obtain information on all these points. Finally, a brief discussion is given of the study programmes relating to the effect of O/M ratio on fuel behaviour and to the major problem of caesium retention. (author). 11 refs, 4 figs