Rapid Bioassay Methods for Plutonium, Neptunium, and Uranium

Abstract

Very sensitive, rapid methods were developed to determine plutonium, neptunium, and enriched uranium in urine. Chloride complexes of the actinides are extracted from oxidized urine salts with the liquid ion exchanger tri-isooctylamine (TIOA). The actinides are back-extracted and then are counted on low-background solid-state counters. All three actinides are exchanged in 10 sec from an 8 N HCl solution of urine salts, with TIOA dissolved in xylene. They can be back-extracted collectively from the organic phase with 0.1 N HCl to determine total alpha, or they can be stripped individually. When stripped individually, plutonium is adjusted to Pu(III) and stripped from the TIOA with 8 N HCl containing 0.05 M NH4I; Np(IV) is stripped with 0.02 N HF in 4 N HCl; and then U(VI) is stripped with 0.1 N HCl. These procedures yield low-solid mounts (1.5 mg) containing greater than 95% of the actinides with no other radioactive contaminants; lengthy electrodeposition is eliminated. The mounts are assayed with counters having 30% efficiency and backgrounds less than 5 counts/day. Sensitivity is 0.1 dis/min of alpha per 1.5 l. for a 250-ml urine sample.