Hidetake Kakihana

Boron isotopic composition of fumarolic condensates and sassolites from Satsuma Iwo-jima, Japan

11B/10B ratios of the high temperature fumarolic gases (>465°C) of this island were found to be constant within the limits of experimental error (11B/10B = 4.066). This value may represent the 11B/10B ratio of boron in the andesite magma. 11B/10B ratios of the low temperature fumarolic gases (<235°C) were found to vary from 4.053 to 4.077. 11B/10B ratios of some sassolites were approximately equal to that of the fumarolic condensates and the other ones were slightly enriched in 10B compared to the fumarolic condensates.

Ion exchange, isotope exchange and isotope separation

Abstract Ion-exchange and isotope-exchange reactions are discussed mainly from the theoretical point of view in order to find a general expression for the isotope separation factor (eqn. 14). The theoretical expression for the separation factor of boron isotopes is derived from eqn. 14 for the system containing aqueous boric acid with an anion-exchange resin (eqn. 20). Some experimental results for boron isotopes are given and are discussed with the use of eqn. 20. Results obtained from a small column are also presented in order to show a new, simple procedure for boron isotope separation, which needs only boric acid as raw material, a column of a weakly basic anion-exchange resin for chromatographic purposes and water as eluting agent.

Theory of chromatographic separation of isotopes. II. Theory and practical parameters for displacement chromatographies.:Theory and Practical Parameters for Displacement Chromatographies

A mathematical model for chromatographic isotope separation systems is derived starting from a simple theoretical equation for concentration profiles in an ideal displacement chromatogram. The theoretical equation is combined with appropriate material balances to develop a set of equations which relate the size, production rate and start-up time of chromatographic separation equipment to the degree of isotope enrichment. These equations are easy to use, and require a minimum of empirical data. The model incorporates a series of simplifying assumptions which are valid for displacement chromatographies where the isotopic separation coefficient is small and the degree of enrichment accomplished in a single column is not very high. Thus the model is applicable to most isotope separation systems of practical interest (including uranium enrichment), although it may be inadequate for certain special cases.

Kinetics and mechanism of the uranium(IV)-uranium(VI) electron exchange reaction in hydrochloric acid

Abstract The rate of the electron exchange reaction between U(IV) and U(VI) has been studied in high concentrations of hydrochloric acid and was found to be accelerated by large concentrations of chloride ion. From the rates at different temperatures, ranging from 30° to 70°C, an activation energy and entropy of 32·2 kcal/mole and 25·5 e.u., respectively, were calculated. Possible mechanisms consistent with the observed rate law are proposed.

THE SEPARATION FACTOR OF LITHIUM ISOTOPES WITH ION EXCHANGERS

Fundamental equations for the isotopic ion exchange reaction were derived with various degrees of approximation considering the various kinds of external solutions and ion exchangers. The separation factors of lithium isotopes S76(Li) in ethanol (or acetone)-water mixtures were determined with differently cross-linked sulphonated polystyrene-divinylbenzene copolymers and synthetic inorganic ion exchanger Ionite C (zirconium phosphate type). LiOH system gave higher separation factors than LiCl systems. The highly cross-linked resins and synthetic inorganic ion exchanger are also favourable for the higher separation factor. The highest value 1·022 was obtained for the system of 0·1 M LiOH 20 per cent acetone-water mixture using synthetic inorganic ion exchanger. These experimental results were analysed by fundamental equations.

Uranium Isotope Fractionation in Ion Exchange Chromatography Using Uranyl-Carboxylate Complexes

A systematic study on the isotope fractionation occurred in the isotopic exchange reaction has been carried out by means of ion exchange chromatography using uranyl-carboxylate complex formation reactions. On a cation exchange resin column, an isotopic plateau holding displacement chromatogram has been performed and the magnitudes of the isotope effects have been determined for the three cases of uranyl-carboxylate, uranyl-acetate, uranyl-tartrate and uranyl-citrate. The elemental separation coefficients were found to be 0.8 × 10−4 for acetate ligand, 1.2 × 10−4 for tartrate ligand and 1.8 × 10−4 for citrate ligand. The enrichment of 235U in relation to 238U was observed in the uranyl-carboxylate complexes in all times.

THERMODYNAMIC ISOTOPE EFFECT OF LITHIUM, CARBON, NITROGEN, CHLORINE, COPPER, AND URANIUM COMPOUNDS.

Few studies have so far been reported on isotopic frequency shifts, which present problems in experimentation. In this paper, the G and F matrix method is applied to theoretical calculation of the frequency shifts of linear molecules XYZ and XYZ, as well as of octahedral molecules XY 2 Using these values, reduced partition function ratios of lithium, carbon, copper, nitrogen, chlorine and uranium compounds have been calculated.

Theory of Chromatographic Separation of Isotopes, (III): Analysis of Non-Displacement Chromatography

A fundamental equation applicable to any kind of chromatography is solved on the assumption that velocity and chromatographic diffusion coefficient of the species under consideration are constant and its concentration is finite. The results can be used to describe the chromatographic behavior of the species in breakthrough, reverse break. through and band operations, covering not only the chromatographic distribution of isotopes but also that of easily separable chemical species, especially in the case of elution chromatography. Some numerical calculations are performed to show how the shapes of the isotopic mole fraction and isotopic concentration profiles in band operation of a two-isotope chromatography are influenced by the velocity ratio and chromatographic diffusion coeffi-cient ratio of the two isotopes, and by the initial band width. These calculations yield some interesting results, including a clear indication of the possibility of reverse enrich-ment.KEYWORDS: non-displacement chromatography, radioisotopes, radioactivity, diffusion coefficients, velocity ratio, isotope separation, equations, numerical solutions, mole fraction

Solvent deuterium isotope effect on hydrolysis of boric acid

Abstract The hydrolysis equilibria of boric acid in light- and heavy-water solutions containing 3 mol dm−3 of LiClO4 as an ionic medium were studied at 25°C by measuring the lyonium ion concentration with a glass electrode. Analysis of the e.m.f. data indicated the formation of analogous complexes in H2O and D2O: B(OL)4−, B4(OL)142−, and either B2(OL)7− or B3(OL)112− as a minor species. The formation constants ∗ β p,q are smaller in D2O than in H2O. These results are consistent with those previously reported for the hydrolysis of cations. It seems that the formation constants Kp,q for the heavy-water system have slightly larger values than those for the light-water system, although this solvent deuterium isotope effect for polyborate complexes is much smaller than that observed for some metal ion hydrolysis species.

Separation of Isotopes of Lithium and Uranium by Electromigration Using Cation-Exchange Membranes

Isotope separation by chromatographic electromigration has been studied for lithium (6Li and 7Li) and uranium (235U and 238U), using cation-exchange membranes as migration media. The membranes were pulled back against the direction of the movement of isotopic cations in a countercurrent manner. In both cases of the elements the lighter isotope, 6Li or 235U, was concentrated at the frontal part of a migration zone; at the extreme front the 6Li atom % increased to 16.8% from the original value of 7.5% after 386 cm migration, and the 235 U atom % rose to 0.743% from the original value of 0.723% after 200 cm migration. Isotope separation coefficients were experimentally determined: e = (3.7 ± 0.4) μ 10−3 for lithium isotopes, and two slightly different values e = (4.9 ± 1.0) μ 10−5 and (5.4 ± 1.1) μ 10−5 for uranium isotopes. The steep isotope accumulation was observed in a narrow boundary region. A mathematical expression for the isotope accumulation curve was derived, and the slope of the curve was assessed...