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  • Author or Editor: S. Takahashi x
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Abstract  

Spectrophotometric studies on a uranium(VI) ternary complex and its analytical application are described. Uranium(VI) reacts with 5-Br-PADAP to form an unstable chelate, which precipitates on standing in 48% ethanolic aqueous solution. The colour stability of uranium(VI) complex is greatly improved by the presence of aromatic carboxylic acids. For the present purpose, o-hydroxybenzoic acid and its derivatives are best suited. The calibration graph is linear up to 2.6 g·ml–1 of uranium(VI) at 578 nm. The role of carboxylic acid as an auxiliary ligand is discussed.

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Abstract  

Speciation and solubility of neptunium were studied using paper electrophoresis, ion exchange and ultrafiltration. Among these methods, the paper electrophoresis was found to be suitable for measuring speciation and solubility of neptunium of low concentration, if chemical species had opposite charge each other or dissolved species had a charge. Using paper electrophoresis, hydrolysis constants of NpO2OH0 and NpO 2 (OH) 2 and solubility product of NpO2 were obtained and ionic-strength dependence of speciation was observed.

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Abstract  

We observed the interference effect of electron-capture X-rays emitted by the nuclear transformations in radioisotopes. This interference is between the direct monochromatic emission from the radioactive atoms and the emission totally reflected by the substrate surface. Nanometer-level structural information about the radioactive atoms can be obtained by analyzing the measured interference fringes because the period of these fringes depends on the position of the radioactive atoms relative to the substrate surface. In this work, we used the functional protein molecules (myosin subfragment 1 (S1)) which were radioiodinated with no carrier added125I to observe the conformational changes in aqueous solutions.

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Abstract  

Binding constants of Eu(III)- and Am(III)-complexes with soil-derived humic acid were determined by solvent extraction at various pH and ionic strength. Based on the dependence of binding constants on pH and ionic strength, stabilities of the humate complexes in land water and seawater were estimated. Speciation calculation based on the binding constants indicated that Am(III) could combine with humic substances in natural water system.

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Abstract  

We have compared the 127I Mössbauer spectra of eleven organoantimony compounds with hypervalent bonding, E-Sb-I (E = O, I, N, C ). The charges on iodine atoms fall between -0.54 e for the compound with Sb-I bond length of 2.83 Å and -0.82 e for the compound with 3.34 Å. The negative charges on iodine atoms have been found to increase with the increase in the Sb-I bond lengths. Regarding to the dependence of the kind of E atoms, the negative charges on iodine atoms have been found to decrease with the increase in the electronegativities of E atoms. 121Sb Mössbauer spectra have shown the decrease of the group oxygen electronegativity of hexafluorocumyl alcohol by substituting CF3 for CH3, and this was reflected through O-Sb-I bonding as the increase in the negative charges of iodine atoms in the 127I Mössbauer spectra.

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Abstract  

Water originated from groundwater systems can have relatively high concentration of radon. In many situations, radon is released from the water and mixes with the indoor air. In the present study, laboratory experiments were conducted to characterize the airborne radon released by showering and the use of a washing machine. The followings were discussed: (1) a comparison between the loss of waterborne radon and the increase of airborne radon, (2) time-related changes in airborne radon after the water use, (3) changes in the equilibrium factor, and (4) the relationship between radon concentration and the distance from the source of radon release.

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Abstract  

The Mössbauer spectrum of LiFeVPOx, LiFeV0.5POx and LiFePOx glasses prepared by conventional melt-quenching method for cathode active material is composed of a doublet due to distorted FeIIIO4 tetrahedra. The Mössbauer spectrum of LiFePOx glass has an additional doublet due to distorted FeIIO6 octahedra. Heat treatment of LiFeVPOx and LiFeV0.5POx glasses at a given temperature close to each crystallization temperature causes a marked decrease in the value of Δ, reflecting a decrease in the distortion or an increase in the local symmetry of distorted FeIIIO4 tetrahedra. Heat treatment of LiFeVPOx glass causes an increase in the electric conductivity from the order of 10−7 to 10−3 S·cm−1, together with an increase in the specific discharge-and charge-capacity of a coin-type Li-ion cell from 50 to 150 mAh·g−1. These results prove that structural relaxation of the glass network causes an increase in the electric conductivity and an increase in the energy density of the Li-ion cell.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: K. Takamiya, T. Fukunishi, R. Tsujito, S. Fukutani, T. Takahashi, S. Shibata and S. Uchida

Abstract  

The adsorption behavior of fission products to various soils was studied using a multitracer. The multitracer was prepared by neutron irradiation of 235U. Distribution coefficients of fission products were obtained for seventeen kinds of Japanese soils. It was found that zirconium, niobium, and rare earth elements show high distribution coefficients for all soil samples, however, elements like alkali metals show varied values.

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Abstract  

For the assessment of a public impact caused by radionuclides released from nuclear facilities, a dynamic compartment model was developed for prediction of behavior of radioiodine in air, paddy field and rice plant system. The transfer coefficients among compartments were determined by some experimental data and assumptions for each chemical form of iodine. A verification of the model was carried out by some case studies.

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