Separation of radioactive strontium by extraction using chromatographic resin

Abstract

90Sr is generated in the nuclear fission process, and can constitute a long-term biological hazard because of the chemical similarity to calcium and long radioactive and biological half-lives of 28.6 and 49.3 yr, respectively. Moreover, 90Sr is one of the most important radionuclides in the low and medium radioactive wastes that arise from nuclear power plants. For these reasons, a fast and accurate analysis method has been developed which is based on strontium-selective extraction chromatography using macrocyclic polyethers (crown-ethers), specifically 4,4′(5′)-bis(t-butylcyclohexano)-18-crown-6, immobilized on an inert support. The strontium-selective chromatographic resin is commercially available under the name Sr-Spec (for Strontium Specific) from Eichrom Industries. After elution of 90Sr by dilute HNO 3, the concentration measurements were carried out by liquid scintillation counting. The procedure was developed on a standard solution containing 241Am, 109Cd, 57Co, 139Ce, 113Sn, 85Sr (to determine the chemical yield), 137Cs, 88Y (to quantify the 90Y separation) and 60Co. The resulting chemical yield was 88%, with all separation factors >99% (calculated as the quotient of the analyzed activities for each final eluate and the initial activities). This procedure was then applied to the analysis of 90Sr in wastes coming from Spanish nuclear power plants (ion exchange resins and evaporator concentrates), and gave separation factors >99%. The chemical yield for 90Sr range from 58 to 82%, as determined by the addition of strontium carrier and gravimetric analysis. Compared with the more conventional separation techniques the new procedure is rapid and achieves greater chemical yield and decontamination factors.