Keizo Kawamoto

A theoretical study on the zone mobility-pH curve in paper electrophoresis of low molecular weight compounds with a dissociable proton and its application to phosphorus compounds

Abstract It was found that the zone mobility of a compound with dissociable proton plotted against the pH value of the background solution is approximately expressed by a hyperbolic tangent function. By the use of this relation, we can easily draw the zone mobility-pH value of the background solution is approximately expressed by a hyperbolic tangent function. By the use of this relation, we can easily draw the zone mobility-pH curve of migrating species and estimate the consecutive dissociation constants. The relationships between the mobility and the molecular weight or the hydrated ionic radius were also discussed. Jokls equation is only applicable to the first dissociation of a migrating substance and the deviation increases with increasing charge number because of the hydration increment. After considering the hydration ratio, we proposed a modification of the equation. The observed relative zone mobility-pH curves of phosphorus compounds such as phosphorus oxyacids, phenylphosphorus compounds and phosphoric esters of hexoses or inosines were in fair agreement with the calculated ones. The equation proposed is useful in practice for the estimation of the dissociation constant and/or molecular weight of an unknown sample.

Asymmetrical radical formation in D- and L-alanines irradiated with tritium-β-rays

Radical formation in D- and L-alanines was studied using ESR after internal3H-β-irradiation under the situation in which the contribution of Bremsstrahlung to form the radicals is assumed to be considerably less than the case of9 0Y-β-irradiation. It was demonstrated that the relative radical concentration by the β-rays was distinguishably higher in D-alanine than in L-alanine. Thus the asymmetry found in these experiments in the radical formation of the alanines may be attributed to the different interaction between the polarized electrons and the two enantiomers.

Effect of water vapor on tritium release from ceramic breeder material

In most current designs of D-T fusion reactor breeding blankets employing Li-based ceramic as breeder materials, the use of a helium sweep gas containing 0.1% of hydrogen is contemplated to extract tritium via isotopic exchange reactions. However, at lower temperatures, the release process of tritium from the breeders is known to be rather slow. For this reason, there is still a need to develop techniques that promote the release of bred tritium. In order to improve the recovery of tritium from blankets over a wide range of temperature, the effect of the difference in sweep gas composition was investigated. Out of pile tritium release experiments were conducted using the ceramic breeders irradiated in a research reactor. The experimental results reveal the benefit of the sweep gas with water vapor, which is effective to increase the tritium release rate from ceramic breeder materials especially at comparatively lower temperatures. The experimental result was analyzed using several numerical models, and it was found that the consideration of trapping and detrapping reactions is necessary to reproduce the experimental tritium release curve.

Hot atom chemical behavior of tritium produced by 6Li (n,a)3H in Li4SiO4

The effects of irradiation damages induced by neutron irradiation on tritium release processes were studied in Li4SiO4. It was shown that the thermal annealing process of the damages consisted of two processes of a fast and a slow process. The activation energies were determined to be 0.21 eV and 1.1 eV, respectively. From the experimental results, it was suggested that the migration of tritium and displaced oxygen into the damages plays an important role in both thermal annealing processes.

Thermodynamic systematics of the formation of liquid alloys of f-elements with bismuth

Abstract In order to strengthen the comprehensive understanding of the mechanism of extraction of f-elements in a pyrometallurgical liquid–liquid extraction system, excess thermodynamic quantities of lanthanide and actinide in liquid bismuth are discussed. Excess enthalpy changes of some lanthanides and actinides in liquid bismuth were experimentally determined or estimated, and their systematic variation along the lanthanide and actinide series is examined by using a semi-empirical calculation method. Characteristic features of the thermodynamic stabilities of lanthanides and actinides in liquid bismuth are discussed.

Enhancement of tritium release from ceramic breeders with impregnated catalytic additives

Abstract In most current designs of D-T fusion reactor breeding blankets employing Li-based ceramic as breeder materials, the use of a helium sweep gas containing 0.1% of hydrogen is contemplated to extract tritium via isotopic exchange reactions. However, at lower temperatures, the release process of tritium from the breeders is known to be rather slow. For this reason, there is still a need to develop techniques that promote the release of bred tritium. In order to improve recovery of tritium from blankets over a wide range of temperature, the effect of catalytically active metal additives on the heterogeneous isotope exchange reactions at the breeder/sweep gas interface was examined, and main results are summarized in this paper. Platinum and palladium were deposited on solid breeder material pebbles (Li4SiO4) by the incipient wet impregnation method. Experiments were performed with hydrogen and predeuterated water using packed bed reactors and gas chromatographic analysis. Out of pile tritium release experiments were also conducted using ceramic breeders irradiated in a research reactor. The experimental results of this work reveal the benefit of the addition of catalytic additive metals, which is very effective to increase the tritium release rate from ceramic breeder materials especially at comparatively lower temperatures.

Solubility product of hexavalent uranium hydrous oxide

The solubility of U(VI) hydrous oxide was measured in the hydrogen ion concentration (pHc) range from 4 to 6 at 25±1°C in a NaClO4 solution. The experiment was carried out by oversaturation method at ionic strength I=0.1, 0.5 and 1.0 and by undersaturation method at I=1.0. The solid phase was found to be composed of a mixture of UO3.2H2O and UO2 (OH)2 by XRD. The concentration of U(VI) was measured by inductively coupled plasma mass spectrometry (ICP-MS), and was analyzed to obtain the solubility products (Ksp ), by taking into account the participation of the U(VI) hydrolysis species such as (UO2)2 (OH)2 2+ By using the literature values of the hydrolysis species and by using the specific interaction theory (SIT), the log Ksp ° value at the standard state (I=0) was determined to be log Ksp °=—22.46±0.10. Possible differences in the log Ksp° values due to different solid phases were recognized.

An approach to the mechanism of the asymmetrical radical formation in yttrium-90-beta-irradiated D- and L-alanines.

Several attempts were made to investigate the mechanism of the asymmetrical radical formation in yttrium-90-beta-irradiated D- and L-alanines which was reported in the preceding paper (1). The experiments demonstrated that the magnitude of the asymmetry was dependent on beta-ray dose, namely the lower the dose the larger the observed difference was, and that no difference could be detected when the alanines were irradiated in aqueous state. The results in the present study seem to that different interaction between the crystal structure of the two enantiomers and polarized beta-rays may be responsible for the observed phenomenon.

The relationship between cell killing effect and number of lanthanide atoms bound to DNA molecules in cultured HeLa cells treated with rare earth elements

HeLa S-3 cells were treated with several rare earth elements, Ce, La, and Sm, at 37 °C for 1 hour and the relationship between the lethal effects of these elements and the number of the atoms bound to DNA, RNA, and proteins was examined. Among the 3 element, only Ce gave an exponential dose-survival relationship from which the value of mean lethal concentration (D0) was determined to be 6.75 mM. By using identically treated cells, the number of Ce atoms combined with DNA, RNA and protein molecules in HeLa cells were determined after fractionation of the cells using neutron activation analysis. In this way, theD0 value given as the Ce concentration was replaced by the number of Ce atoms combined with each fraction, then the target volumes, viz., cell killing efficiency, expressed as the reciprocal ofD0 value was calculated for each fraction. The results suggested that DNA and RNA could stochiometrically be the primary target molecule for cell killing by Ce.

Effect of catalytic metals on tritium release from ceramic breeder materials

Abstract In most current designs of D–T fusion reactor breeding blankets employing Li-based ceramics as breeder materials, the use of a helium sweep gas containing 0.1% of hydrogen is contemplated to extract tritium via isotopic exchange reactions. However, at temperatures lower than 400 °C, the release process of tritium from the breeders is known to be rather slow. For this reason, there is still a need to develop techniques that promote the release of bred tritium. In order to improve the recovery of tritium from blankets over a wide range of temperature, palladium and nickel were deposited on Li 4 SiO 4 pebbles by the incipient wet impregnation method. Out-of-pile tritium release experiments were conducted using the ceramic breeders irradiated in a research reactor. The experimental results reveal the benefit of the addition of catalytic additive metals, which is effective to increase the tritium release rate from ceramic breeder materials especially at comparatively lower temperatures.