First assessment of a digestion method applied to recovery of plutonium from refractory residues after dissolving spent sfr mox fuel in nitric acid

Given the initial plutonium content in SFR MOX fuel, its quantitative recovery is one of the main objectives for the dissolution process. A silver (II) oxidative digestion step was studied in the Atalante facility to assess its possible application to the treatment of undissolved residues obtained after dissolving spent SFR MOX fuel in nitric acid. This process was first optimized on plutonium dioxide powders, and then tested on irradiated LWR MOX fuel residues. The digestion step permitted the recovery of up to 99% of the residual plutonium, with some slight differences depending on the position of the pin part from which the dissolution residue was obtained. Local burnup and chemical composition were found to be influential. The quantity of residues after digestion was significantly reduced by this treatment, with the final residues consisting mainly of metallic compounds including ruthenium, molybdenum, rhodium or palladium.