CEA Preliminary Studies for Industrial MOx Reprocessing: From Laboratory Results to Successful First Industrial Campaign on UP2-800 Areva Plant

In November/December 2004, AREVA succeeded in reprocessing for the first time MOX spent fuels with a continuous dissolution process on the UP2-800 plant in La Hague. It was the industrial conclusion of preliminary and extensive studies realized by the CEA teams at the laboratory scale in Atalante facilities. The experiments were realized using MOx fuel obtained by MIMAS process and irradiated in Saint-Laurent des Eaux power reactor. The average burn-ups of the pin samples used for the studies were comprised between 28 GWd/T and 43 GWd/T. As the MOx fuel present a specific behavior versus dissolution due to the presence of PuO₂ clusters, the solubility tests were mainly focused on the Pu behavior as a function of the temperature of dissolution (from 88 °C to boiling point) and the fuel burn-up. The fixed dissolution parameters were the residence time (8 hours), the initial acidity (near 8 M) and the sample size (35 mm). Available results concern dissolution kinetics, plutonium solubility and its distribution in the different flux (insoluble solids, solution).