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Open Chemistry
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2011
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vol. 9
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issue 5
798-807
EN
The determination is based on the evaluation of experimentally obtained breakthrough curves using the erfc-function. The first method is founded on the assumption of a reversible linear sorption/desorption isotherm of radionuclides on solid phase with constant distribution and retardation coefficients, whereas the second one is based on the assumption of a reversible non-linear sorption/desorption isotherm described with the Freundlich equation, i.e., with non-constant distribution and retardation coefficients. Undisturbed cores of 5 cm in diameter and 10 cm long were embedded in the Eprosin-type cured epoxide resin column. In this study the so-called Cenomanian background groundwater was used as transport medium. The groundwater containing radionuclides was introduced at the bottom of the columns at about 4 mL h−1 constant flow-rate. The results have shown that in the investigated fucoidic sands: (i) the sorption was in principle characterized by linear isotherms and the corresponding retardation coefficients of 137Cs and 85Sr, depending on the type of sample, were approximately 13 or 44 and 5 or 15, respectively; (ii) the desorption was characterized by non-linear isotherms, and the retardation coefficients of the same radionuclides ranged between 23–50 and 5–25, respectively. The values of the hydrodynamic dispersion coefficients of these radionuclides varied between 0.43–1.2 cm2 h−1. [...]
Open Chemistry
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2007
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vol. 5
|
issue 3
868-879
EN
A rapid method for calculating the time dependence of activities of individual radionuclides in genetically coupled decay series has been proposed. The method is based on the mathematical procedure, in which the matrix method is used for calculating a set of decay equations given in the vector form. The developed method is computerized and uses the modern Scilab software. This simple method eliminates certain drawbacks of older methods used previously for this purpose and is applicable to even solve calculations which are not easily treatable with the older methods. Some practical examples of such calculations are presented. Moreover, the new method is universal and it also enables a more general approach to the problem of the calculation of decay series in nuclear chemistry. [...]
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