Application of EDTA for the estimation of plutonium in organic streams and for the polishing of uranium product of purex process

Estimation of plutonium in the organic stream of purex process is normally done by stripping the plutonium from TBP phase and counting the alpha activity in the stripped solution. This scheme presupposes a quantitative recovery of plutonium from the organic phase. Most commonly adopted procedure is to reduce the Pu(IV) in TBP phase to Pu(III) using ascorbic acid of uranous nitrate. The experience is that while these reducing agents work satisfactorily with pure TBP solutions, the presence of HDBP, H2MBP, the derivatives of TBP from acid, thermal and radiolytic attack in the purex organic stream makes them less and less effective. EDTA forms a strong aqueous soluble complex with plutonium in dilute nitric acid solutions and hence effectively removes it from even heavily degraded TBP. Same principle is made use of in preferentially extracting uranium into TBP while retaining plutonium in the aqueous phase as plutonium-EDTA complex, thereby polishing the uranium product of purex process free of residual plutonium contamination. This paper describes both the schemes in detail and presents data collected using actual purex process stream solutions. (author)