SEPARATION OF RADIOACTIVE STRONTIUM BY EXTRACTION USING CHROMATOGRAPHIC RESIN

Sr-90 is generated in the nuclear fission process, and can constitute a long-term biological hazard because of the chemical similarity to ca lcium and long radioactive and biological half-lives of 28.6 and 49.3 yr, respectively. Moreover, Sr-90 is one of the most important radionu clides in the low and medium radioactive wastes that arise from nuclea r power plants. For these reasons, a fast and accurate analysis method has been developed which is based on strontium-selective extraction c hromatography using macrocyclic polyethers (crown-ethers), specificall y 4,4'(5')-bis(t-butylcyclohexano)-18-crown-6, immobilized on an inert support. The strontium-selective chromatographic resin is commerciall y available under the name Sr-Spec (for Strontium Specific) from Eichr om Industries. After elution of Sr-90 by dilute HNO3, the concentratio n measurements were carried out by liquid scintillation counting. The procedure was developed on a standard solution containing Am-241, Cd-1 09, Co-57,Ce-139, Sn-113, Sr-85 (to determine the chemical yield), Cs- 137, Y-88 (to quantify the Y-90 separation) and Co-60. The resulting c hemical 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 Sr-90 in wastes coming from Spanish nuclear power plants (ion excha nge resins and evaporator concentrates), and gave separation factors > 99%. The chemical yield for Sr-90 range from 58 to 82%, as determined by the addition of strontium carrier and gravimetric analysis. Compare d with the more conventional separation techniques the new procedure i s rapid and achieves greater chemical yield and decontamination factor s.