A fast and sequential method for determination of plutonium and strontium in urine samples

This paper describes a fast and sequential procedure to analyze 238-239Pu and 90Sr in urine samples. Sample preparation involves calcium coprecipitation and dissolution of the precipitate in 8M HNO3. 242Pu is employed as a tracer and stable Sr as a carrier to determine chemical yield. Urine samples from Procorad International Proficiency Exercises (Association Pour La Promotion Du Controle de Qualite Des Analyses De Biologie Medicale En Radiotoxicologie) were employed to verify this method. This procedure is advantageous for samples that do not contain high amounts of Sr or Ca. The radionuclides are sequentially separated and purified by a Dowex ion-exchange resin and Sr-Spec Eichrom resin. These separation columns can be coupled since the same nitric acid concentration is used. Pu was analyzed by Alpha Spectrometry with a typical recovery of approximately 80 to 95 %. The detection limit was determined to be 0.09 Bq/sample (in a silver planchet). Sr was analyzed using Liquid Scintillation Counting and employing a double energetic window method. The typical recovery obtained was of approximately 70 to 85 %. The detection limit for this analysis was 0.5 Bq/sample (in filter). This is a reliable optimized method for the measurement of Pu and Sr in urine samples which is more cost effective and efficient than traditional ion exchange, solvent extraction, and precipitation techniques. In emergency situations the Sr-Spec resin separation is recommended due to its simplicity. Possible uncertainty sources were identified for the Alpha Spectrometry and Liquid Scintillation Counting which contributed to the combined uncertainty in the activity concentration determined. (author)