Investigations into the Hydrazine-Free Electrochemical Reduction of Pu(IV) In the PUREX Process.

摘要

In the PUREX Process applied to spent fuel element reprocessing, the separation of uranium from plutonium is achieved by Pu(III) valence-setting. In order to protect Pu(III) against oxidation by nitrous acid, hydrazine is used as a nitrate capturing compound. Instead of using nitrous acid (or nitrogen oxides) as a reductant, the attempt was made to set the valence of Pu(III) electrochemically in the absence of hydrazine in a range of low acid concentration where nitrous acid has just lost its oxidizing properties. The following dependencies and influences were studied: nitric acid concentration/current density/temperature/uranium content/electrode surface ratio/influence of extremely low hydrazine concentrations. The re-oxidation behavior was also studied of the completely reduced Pu(III)-containing solutions. Results of experiments run in pure aqueous systems were applied in a pulse column with the TBP/dodecane/HNO sub 3 system. Conclusions drawn from experiments, that electrochemical U/Pu-separation is in principle possible without adding hydrazine, were confirmed by the pulse column experiments. 33 refs., 34 figs., 20 tabs. (ERA citation 13:042732)