Rapid Bioassay Methods for Plutonium, Neptunium, and Uranium

Abstract

Very sensitive, rapid methods were developed to determine Pu, Np, and enriched U 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 3 actinides are exchanged in 10 sec. from an 8 N HC1 solution of urine salts, with TIOA dissolved in xylene. They can be back-extracted collectively from the organic phase with 0.1 N HC1 to determine total alpha, or they can be stripped individually. When stripped individually, Pu is adjusted to Pu(III) and stripped from the TIOA with 8 N HC1 containing 0.05 M NH4I; Np(IV) is stripped with 0.02 N HF in 4 N HC1; and then U(VI) is stripped with 0.1 N HC1. 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/ 1.5.1. for a 250-ml urine sample.