Calcium isotope fractionation in liquid chromatography with benzo-18-crown-6 resin in aqueous hydrobromic acid medium

Liquid chromatography operated in a breakthrough mode was employed to study calcium isotope fractionation in the aqueous hydrobromic acid medium. Highly porous silica beads, the inner pores of which were embedded with a benzo-18-crown-6 ether resin, were used as column packing material. Enrichment of heavier isotopes of calcium was observed in the frontal part of respective calcium chromatograms. The values of the isotope fractionation coefficient were on the order of 10^?3. The observed isotope fractionation coefficient was dependent on the concentration of hydrobromic acid in the calcium feed solution; a higher HBr concentration resulted in a smaller fractionation coefficient value. The present calcium isotope effects were most probably mass-dependent, indicating that they mostly came from isotope effects based on molecular vibration. Molecular orbital calculations supported the present experimental results in a qualitative fashion. Chromatography operated in aqueous HBr media is a better system of Ca isotope separation than that operated in aqueous HCl media.     

Calcium ion selectivity and isotope effects studied by using benzo-18-crown-6 resins

The chromatography experiments using benzo-18-crown-6 resin were carried out to study isotope effects in calcium adsorption. By the elution technique with hydrochloric acid solution, it was found that the adsorption of calcium depends on the concentration of hydrochloric acid in solution and that 9 M HCl concentration is the appropriate condition for the adsorption of calcium to the cavity of benzo-18-crown-6 of which cavity size is a little larger than the diameter of calcium ion. Thereafter, the isotope fractionation of calcium in the complex formation reaction with 18-crown-6 ether was investigated by using the breakthrough technique of chromatography with above-mentioned synthesized resin and 9 M hydrochloric acid solution. The observed isotope separation coefficient ε=−1 was 1.9 × 10⁻³ for the isotopic pair ⁴⁰Ca/⁴⁸Ca.     

Lithium Isotope Separation by Displacement Chromatography Using Cryptand Resin

This paper summarizes results of sensitivity analysis of a generic geologic disposal system for HLW, using a GSRW code and an automated sensitivity analysis methodology based on the Differential Algebra. The results of sensitivity analyses indicate that parameters related to a homogeneous rock surrounding a disposal facility have higher sensitivities to the performance measure analyzed here than those of a fractured zone and engineered barriers.

This methodology permits sensitivity analyses of a single parameter with changing values of other parameters simultaneously, and thus gives quantitative information on the interrelation- ship between the parameters: the parameters for engineered barriers are generally insensitive to the output, while they are somewhat sensitive to the output only in a case of the low solubility condition. The methodology also provides technical Information which might be basis for the optimization of design of the disposal facility.