Nuclear Methods in Environmental Science SIMULTANEOUS DETERMINATION OF URANIUM AND PLUTONIUM ISOTOPES IN SOILS BY MEANS OF SINGLE ALPHA-SPECTROMET RY

A simple, rapid and reliable method was developed for the simultaneous determination of uranium and plutonium isotopes by alpha-spectrometry using a single source. A new uranium tracer a 3 o U was applied as well as the 23 ~ Pu tracer to determine overall yields of uranium and plutonium isotopes throughout the entire procedure employed. The analytical procedure consists of sample leaching with 8N HNO3 solution, purification by solvent extraction, simultaneous electrodeposition of U and Pu, and subsequent alpha-spectrometry with a silicon detector. In the solvent extraction using TOA/xylene from 8N HNO 3 solution, the preferential extractability of Pu rather than U permits to purify simultaneously the trace amounts of Pu and the macro amounts of U, as in the case of ordinary soil samples, resulting in favourable peak heights for both isotopes. From a single alpha-spectrum, the determinations of 23 s U, 234 U (and their ratio of 2 a 4 U/238 U), 239.~ 4 o Pu, and 3SPu contents were conveniently carried out after correcting the overall yields obtained from 23~ and 236Pu activities in the same spectrum. This analytical method was satisfactorily applied to the determination of U and Pu isotope contents in some soils.