Reduction Stripping of Plutonium Loaded on TBP with Addition of Nitrous Acid†

Abstract

Abstract For incorporation in the process of Pu purification with TBP, a modified method is proposed for the effective reduction stripping of Pu without the use of reducing salt, whose function is replaced by excess nitrous acid in the extraction feed. The nitrous acid acts as “redox reagent” for Pu(IV) in the stripping bank and in the extraction feed. The practical applicability of this process was experimentally proved by both batchwise extraction and flowsheet studies with miniature mixer-settlers. The addition of 0.1 mol/1 of nitrous acid to the extraction feed caused about half of the nitrous acid initially added to be loaded on the TBP and be carried toward the stripping bank. Over 99.9% of Pu including 40% of Pu(III), is stripped under the conditions of 0.3 N HNO3, 0.008 N HNO2, and with a flow ratio of 1.4 (aq./org.). Basic studies related to the above flowsheet were also made on the extraction of nitrous acid with TBP and the reduction of Pu(IV) with nitrous acid. The redox potentials were also calculated.