Monitoring the plutonium depletion in dissolution residues of a spent fuel solution using a surrogate and plutonium isotope ratio measurements

This study presents the development of an innovative experiment using a surrogate, for monitoring the depletion kinetics of plutonium dissolution residues in an irradiated fuel dissolution solution containing a high plutonium concentration. The surrogate, a (U,Pu)O₂ compound, was synthesized from a plutonium having an isotopic composition different from the dissolution solution. This helps monitoring the plutonium residue depletion by TIMS measurements of the ²⁴⁰Pu/²³⁹Pu isotope ratio. Repeatability better than 83 ppm was achieved for the ²⁴⁰Pu/²³⁹Pu ratios in each aliquot of the dissolution profiles allowing qualitative and quantitative interpretation of the kinetic evolution that could not be reached by a conventional direct concentration determination. (author)