Determinations of actinides in biological and environmental samples

Abstract

This paper summarises the radiochemical procedures utilised in our laboratory to determine U, Th and Pu in different sample matrices, including soft tissues, bones, urine, faeces, soil, water, air-filters, lichen, and building materials such as granite, phosphate and concrete. Sample preparation, depending upon the matrix of the sample, includes either dry ashing and/or wet ashing with a mixture of HNO 3 and H 2SO 4 or HNO 3 alone with occasional additions of a few drops of HNO 3 and H 2O 2. Uranium, Th and Pu are either co-precipitated with Fe carrier as hydroxides or with Ca as oxalates. Solvent extractions are performed from 2M HNO 3, 4M HNO 3 or 10M HCl depending upon the actinide or combination of actinides to be determined. The techniques have been very successful for most samples, with radiochemical recoveries exceeding 70%. However, radiochemical recoveries of Th from soil samples have been very poor (10–30%). Attempts are being made to improve these recoveries.