Simultaneous determinations of uranium, thorium, and plutonium in soft tissues by solvent extraction and alpha-spectrometry

A radiochemical procedure for the simultaneous determination of uranium, thorium, and plutonium, in soft tissues has been developed. The weighed amounts of tissues, spiked with 232U, 242Pu, and 229th tracers, are wet ashed. Uranium, thorium, and plutonium are coprecipitated with iron as hydroxides, dissolved in concentrated HCl and the acidity adjusted to 10 M. Uranium and plutonium are extracted into 20% TLA solution in xylene, leaving thorium in the aqueous phase. Plutonium is back-extracted by reducing to the trivalent state with 0.05 M NH4I solution in 8 M HCl, and uranium is back-extracted with 0.1 M HCl. Thorium is extracted into 20% TLA solution from 4 M HNO3 and back-extracted with 10 M HCl. Uranium, thorium and plutonium are electrodeposited separately onto platinum discs and counted alpha-spectrometrically using surface barrier silicon diodes and a multichannel analyzer. The method was developed using bovine liver and applied to dog and human tissues. The mean radiochemical recoveries of these actinides in different organs were better than 70%. 6 references, 2 tables