Sr-90 in an Activated Concrete Core

Radiochemical methods which allow sequential determination of radionuclides are often desirable for reasons of speed and cost-effectiveness, for example in mixed waste streams or in waste characterization for nuclear decommissioning. Although a variety of methods are in use for the analysis of in concretes, they tend to use large reagent volumes and involve 

The ideal chemical separation method should be relatively simple, have few separation stages and should be time / cost effective. Itoh et al (2002) used a combined anion and cation exchange column method for the isolation of Ca from other alkaline earth metals. This 3 column separation involved 6 chemical separation techniques following two HF/HCIO4 digests. The decontamination factors for Eu and Co are quoted as 10. The final limit of detection for Ca for this method was 8 Bq/g, based on a measurement by X-ray spectrometric determination. 

Other methods currently in use for Ca determination in concretes are based entirely on precipitations for purification of the Ca. Suarez et al (2000) utilise a chromate precipitation for removal of Ba and Ra from the solution. This is a pH dependant precipitation, and the chromate solution resulting from this requires a separate waste stream. The method has a total of 9 steps after sample dissolution, and has decontamination factors of 10 for Ba and Co, 10 for Sr and 10 for Eu. The minimum detectable activity by liquid scintillation counting is 0.29 Bq/g for Ca (0.034 Bq/g Ca). 

The method described by Hou et al. (2005) utilizes a series of pH or concentration controlled precipitations for the purification of Ca, with 7 method stages, including the chemical recovery determination. The determination of Sr, however, involves a further 3 chemical separation steps, and a further 3 weeks for a result. Decontamination factors are 10 for Eu, Cs, Sr, Fe, Ni, Co. 

The method described in this paper utilizes both precipitations and ion extraction chromatography for purification of Ca and Sr, with Mn02 resin replacing the pH controlled Ba-chromate precipitation required for removal of Ba and Ra from the solution. It is a relatively fast, easy method, and as such is cost and time effective which are important considerations for a commercial laboratory. 

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Sequential Determination of Ca-41/45 and Sr-90 in an Activated Concrete Core 3 CONCLUSIONS... 

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