Sequential Determination of ²⁴¹Am, ²³⁷Np, Pu Radioisotopes and ⁹⁰Sr in Soil and Sediment Samples

Polona Tavčar,* Rožle Jakopič, and Ljudmila Benedik
Jožef Stefan Institute, Department of Environmental Sciences, Jamova 39, 1000 Ljubljana, Slovenia

Abstract
A sensitive and reliable method for the simultaneous determination of ²⁴¹Am, ²³⁷Np, plutonium radioisotopes and ⁹⁰Sr in soil and sediment samples is described. Analysis involves leaching of the samples in conc. HNO₃, followed by radiochemical separation and purification. The radiochemical procedure begins with separation of ²⁴¹Am/⁹⁰Sr, plutonium radioisotopes and ²³⁷Np by anion exchange chromatography. ²⁴¹Am and ⁹⁰Sr from the combined effluent are separated using TRU resin and Sr resin. Counting sources for alpha spectrometric measurements were prepared by the microcoprecipitation technique. Radiochemical yields were determined using ²⁴³Am, ²³⁹Np and ²⁴²Pu tracers. Strontium recovery was determined gravimertrically and Sr counting sources were analysed by liquid scintillation counting. The method was successfully tested by analysis of six reference materials and on two sediment samples with high activities of the selected radionuclides. The results were compared with reference and literature values.

Key words: Actinides, strontium, extraction chromatography, microcoprecipitation technique, liquid scintillation counting.