RADIOISOTOPES
Online ISSN : 1884-4111
Print ISSN : 0033-8303
ISSN-L : 0033-8303
Relation between Distribution Coefficient of Radioactive Strontium and Solid-Liquid Distribution Ratio of Background Stable Strontium
Toshifumi IGARASHIYasunori MAHARAMasaki OKAMURANobuo ASHIKAWA
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1992 Volume 41 Issue 7 Pages 350-356

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Abstract

Distribution coefficients (Kd) of nuclides, which are defined as the ratio of the adsorbed concentration to the solution concentration, are important in predicting nuclide migration in the subsurface environment. This study was undertaken to construct an effective method of determining the most pertinent Kd value for simulating in situ distribution phenomena between the solid and liquid phases, by using background stable isotopes. This paper describes the applicability of this method to Sr by carrying out a batch Sr adsorption experiment where stable Sr coexisted with the radioactive isotope, 85Sr, and by comparing the concentration distribution ratio of the background stable Sr with the Kd value obtained by the batch experiment. The results showed that the Kd of 85Sr (Kd85) agreed well with the Kd of the coexisting stable Sr (Kds) and that the two values decreased with an increase in the concentration of the stable Sr, when sand was used as an adsorbent. In addition, the Kd85 corresponded to the ratio of the exchangeable solid-phase concentration of background stable Sr to the concentration of the background stable Sr in groundwater when the concentration of the coexisting stable Sr approached the background level. On the other hand, when powdered rock samples were used, the Kd85 did not agree with the Kds and the concentration distribution ratio of the background stable Sr was greater than the Kd85. This discrepancy might be due to the disequilibrium resulting from grinding the rock matrices. This suggests that measurement of the background stable Sr distribution ratio between the solid and liquid phases can be an effective method of estimating the Kd of radioactive Sr when the groundwater is in satisfactory contact with the adsorption medium.

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© Japan Radioisotope Association
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