Third phase formation in the extraction of plutonium IV and uranium VI nitrates with tri-N-butyl phosphate (TBP) in odourless kerosene (OK) at different diluent ratios, temperature and acidities

Third phase boundaries in HNO3/Th/TBP/OK, HNO3/PuIV/TBP/OK and HNO3/UVI/PUIV/TBP/OK have been measured using a density technique. PuIV solubilities have been determined in TBP/OK from 5 to 20 vol% TBP and temperatures 2 to 20C. The composition of the third phase formed at nitric acid levels from 0.2 to 10M indicate that the PuIV solubility curve may be related to different phase compositions. UVI increases PuIV solubility above 0.2M HNO3 but decreases it at lower levels. High levels of UVI suppress PUIV third phase formation completely. (author)