Supercritical fluid extraction of uranium and fission products in reprocessing of simulated spent nuclear fuel in weakly acidic solutions of Fe(III) nitrate in the presence of tributyl phosphate

Abstract

The kinetics of dissolution of ceramic UO2 in aqueous solutions of Fe(III) nitrate in the presence of TBP in supercritical CO2 was studied. Quantitative recovery of U into solutions of Fe nitrate in combination with its extraction from the solution into the fluid occurs under these conditions within ∼2 h, which is by more than an order of magnitude faster than in dissolution in a Fe(III) nitrate solution without TBP under common conditions. The behavior of uranium and simulated fission products (FPs) in reprocessing of simulated spent nuclear fuel (SSNF) in weakly acidic Fe(III) nitrate solutions using supercritical CO2 containing TBP was studied. Under these conditions, SSNF dissolves quantitatively with the simultaneous recovery of the U nitrate complex into the TBP-containing fluid phase. Uranium is recovered from the fluid phase by back extraction with an H2O2 solution with simultaneous precipitation of U in the form of the peroxide UO4·2H2O. In the process, high degree of uranium decontamination from all the FPs is reached, which allows repeated use of U in the nuclear fuel cycle.