SEPARATION AND RECOVERY OF URANIUM, NEPTUNIUM, AND PLUTONIUM FROM HIGH-LEVEL WASTE USING TRIBUTYL-PHOSPHATE - COUNTERCURRENT STUDIES WITH SIMULATED WASTE SOLUTION

The present work deals with countercurrent extraction studies on the p artitioning of uranium, neptunium, and plutonium using 30% tributyl ph osphate (TBP) from simulated high level waste solution generated durin g reprocessing of spent uranium fuel from pressurized heavy water reac tors. The oxidation states of neptunium and plutonium were adjusted ei ther by 0.01 M potassium dichromate or 0.01 M dioxovanadium ion. Neptu nium and plutonium, extracted in the TBP phase, were stripped together using a mixture containing 0.05 M ascorbic acid and 0.25 M hydrogen p eroxide in 2.0 M nitric acid solution. Although dioxovanadium ion is m ore effective for proper adjustment of the oxidation states of plutoni um and neptunium, subsequent recovery of these actinides from loaded T BP is better if potassium dichromate is used for the valency adjustmen t. Results of the stagewise analysis of extraction and stripping of ac tinides using mixer-settlers are presented.