A "Two-Step" Electrochemical Approach for Recovery of Plutonium and Uranium from Aqueous Acidic Waste Solutions.

Chemical quality control of nuclear fuel, particularly the determination of Pu and U contents by chemical methods, results in analytical acidic aqueous waste solutions from which Pu and U must be recovered efficiently for the remediation of radioactive wastes. Reported methods involve several complicated steps requiring addition of chemical oxidants/reductants for valence adjustments and generation of secondary wastes, thereby making the recovery process cumbersome. Herein, we report a novel two-step electrochemical approach for Pu and U recovery from acidic aqueous waste solutions containing different metallic impurities (Fe, Cr, Mn, Cd, Al, Ni, Co, Zn, and Mg) by bulk electrolysis using a Pt gauze electrode. Pu and U are recovered from these waste solutions in a two-step process: (i) bulk electrolysis of the mixed solution at a constant potential of 0.1 V vs Ag/AgCl/3 M KCl that results in the reduction of PuO22+ to Pu3+ followed by the precipitation of Pu3+ as K2(K0.5Pu0.5)(SO4)2, which is then filtered and separated and (ii) the filtrate solution is again subjected to bulk electrolysis at a constant potential of -0.35 V vs Ag/AgCl/3 M KCl resulting in the reduction of UO22+ to U4+. The U4+ is then precipitated as K2(K0.67U0.33)(SO4)2, which is filtered and separated, leading to a Pu- and U-free aqueous acidic waste solutions. Biamperometry shows that 97.8% and 99.1% recovery of Pu and U, respectively, is possible, and emission spectrometry confirms the purity of K2(K0.5Pu0.5)(SO4)2 and K2(K0.67U0.33)(SO4)2. Because of its operational simplicity, potential for remote handling, and excellent extraction efficiency, the present methodology can easily replace traditional methods for the recovery of Pu and U from acidic aqueous waste solutions.

Electrochemical recovery of plutonium from aqueous carbonate waste solutions.

Recovery of plutonium from aqueous carbonate waste solutions generated during the reprocessing of spent nuclear fuel is a key concern for sustainable nuclear energy programmes and the remediation of radioactive waste. Reported methods proceed through secondary waste generation caused by acidification of carbonate waste and make the recovery process cumbersome. Herein, we report a simple method for the recovery of Pu as solid PuO2 powder from carbonate waste solution in a two-step process. (i) Pu was selectively electrochemically precipitated as plutonium-hydroxide in the presence of interfering U, Th, Ru, Zr, Nb, Cs and the degradation products of tri-butyl phosphate by bulk electrolysis at -0.9 V using a Pt gauze electrode and (ii) the precipitate was annealed at 973 K for conversion to pure PuO2 powder. The present approach is simple, avoids the generation of secondary waste and reduces the exposure of working personnel to radiation.