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  • Author or Editor: K. Hashimoto x
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Abstract  

The recoil reactions of technetium produced by100Ru/
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\begin{gathered} Tc/ba/_2^ + + ba^ - \to Tc/ba/_3 \hfill \\ Tc/ba/^{2 + } orTc^{3 + } + xba \to Tc/ba/_3 \hfill \\ /x = 2or3/. \hfill \\ \end{gathered}$$ \end{document}
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Abstract  

The solvent extraction behavior of [TcCl6]2− in the HCl-TBP system was studied together with that of its aqua complexes. It was deduced from the dependence of the distribution coefficient of [TcCl6]2− both on the HCl and TBP concentrations that a possible form extracted into TBP is H2[TcCl6](TBP)4. The distribution coefficients of aqua complexes of [TcCl6]2− were found to be in the order of [TcCl4(H2O)2]<[TcCl6]2−<[TcCl5(H2O)].

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Abstract  

For the purpose of studying the secretion of exogenous toxic metals into hair, relation between their concentrations in hair and those in organs, and the metal shift, Hg or Mn was orally administered to guinea pigs for protracted periods, the distributions of metals in hair and organs were examined by means of neutron activation analysis. It was found that the administration of Hg at high dose resulted in abnormally high Hg levels in hair from the 2nd dosing week and in organs after 25 week dosing, and in a reduced motor activity after 25 week administration. There occurred metal shifts in hair as well. Administration of Mn at high doses, on the other hand, showed no such biological influences, although a dose-dependent increase of Mn in hair was detected with time.

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Abstract  

The solvent extraction of technetium from urine with TBP has been investigated. The distribution ratio of technetium was determined as a function of HCl concentration and reaction time. The distribution ratio in the HCl-TBP system containing urine is consistently lower than that without urine. The chemical forms of technetium in urine, analyzed by paper chromatography, indicated that pertechnetate was reduced in the presence of HCl and that the reduction of pertechnetate was enhanced by urine. The observed decrease in the distribution ratio was attributed to the enhanced reduction of pertechnetate by urine.

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Abstract  

Reactions of pertechnetate ion with thiourea (tu) in a hydrochloric acid solution have been investigated by spectrophotometry. Two consecutive reactions were observed for the formation of a technetium-thiourea complex. The intermediate is considered to be a Tc(V)-tu complex ([TcO(tu)4]3+). The observed reaction rates of these two reactions were found to be second order with respect to the concentration of thiourea. The rate-determining step in the 1st step was concluded tobe the reduction of Tc(VII) to Tc(V) and that in the 2nd step to be the reduction of Tc(V) to Tc(III).

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Abstract  

Sorption of uranium(VI) has been inbestigated using an open-cell plyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime (LIX 63). Above pH 4.5 more than 99% of uranium is sorbed onto the LIX 63 impregnated foam, and uranium can be desorbed with a dilute acid from the foam. The sorption capacity for uranium increases linearly with increasing concentration of impregnated LIX 63. Quantitative removal of uranium from salt solutions was accomplished.

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Abstract  

The cross sections of both thermal neutron capture and the (n, 2n) reaction for231Pa target have been determined by using gamma-ray and alpha-ray spectrometric methods following irradiation with neutrons possessing purely thermalized and fission-type reactor spectrum, respectively. Prior to the irradiation, a pre-chemical purification was applied to ensure the accurate determination of the target nuclide,231Pa. For the sake of alpha-spectrometric determination of the daughter230U, decayed out from parent230Pa, the chemical purification of uranium was also applied to the alpha-source preparation from the reactor-irradiated231Pa. The activity ratio of230U to232U was converted to an initial formation ratio of230Pa to232U and followed by an evaluation of cross section. The cross section value for the231Pa (n,)232Pa reaction process was estimated to be 186±13 barn for purely thermal neutrons. The231Pa(n, 2n)230Pa cross section value is 4.12±0.32 mbarn for fission type neutrons.

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Abstract  

The natural radiation levels in Niigata Prefecture were studied from the aspects of the gamma-ray dose rate in Chuetsu and Joetsu districts. The former Chuetsu district was divided into three parts (Kashiwazaki, Nagaoka and Uonuma area). In the Uonuma area, the dose rates were higher than those of the other area, probably reflecting the geological circumstances. The most of the measuring points showed radionuclide contribution to the dose rates in the order of40K>Th-series>U-series and the dose rates were significantly dependent on the different compostion of radionuclides in the soils reflecting the original base rocks. In Niigata Prefecture, annual dose equivalent due to natural radiation from ground has the same level as the 0.34 mSv average value for Japan.

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Abstract  

Since October 1983, the Niigata Prefectural Government has been carrying out the continuous measurements of gamma-emitting radionuclides in the environment around the Kashiwazaki Kariwa nuclear power station by environmental radiation monitoring telemetry system. Continuous measurements of gamma-ray spectra have been established since April 1996. As a result, the contribution of various radionuclides has been gradually clarified in the variations of the gamma-ray dose rate. In this paper, the energy spectrum of the incident gamma-ray to NaI(Tl) scintillation detector was obtained by the unfolding method using a response matrix, and the variations of the energy spectrum observed in the precipitation and snow were investigated. The increase in the dose rate in precipitation originated from the increase in the flux density of gamma-ray from 214Bi and 214Pb, daughter nuclide of 222Rn, which fell down with the precipitation. On the other hand, the reduction in the dose rate in the snowy period was confirmed due to the shielding effect of a part of gamma-rays from the natural radioactive nuclides by the snow layer, in coincidence with the decrease of the flux density in 40K and 208Tl.

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Abstract  

Environmental cumulative doses measured by a radiophotoluminescence glass dosimeter (RPLD) and a thermoluminescence dosimeter (TLD) were compared at the same monitoring points during two years. In winter season, when the mean temperature of the monitoring points dropped below 4 °C, the RPLD-sensitivity offered approximately 5% lower values in comparison with those in other seasons. From the artificial irradiation experiments under different room temperatures, the sensitivity of RPLD was found to decrease by 3-4% below 6.3 °C, while the difference was negligible above 8 °C. Based on the present results, much attention should be paid to the sensitivity changes of RPLD, whenever used in cold areas.

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