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  • Author or Editor: T. Kobayashi x
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Abstract  

The destructive determination method of alpha emitters in various combustible solid materials has been investigated by a combination of acid digestion and coprecipitation with barium sulfate. It was consequently established that the method described in the paper may be applicable to determine alpha activities in the practical wastes.

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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  

Trace amounts of transition elements (Fe, Co, Ni and Cu) in zirconium fluoride and NBS SRM's were determined by substoichiometric radioactivation analysis. The contents of impurities in sublimed sample were less than those of high-purity material and of reagent grade. The detection limits of these elements in zirconium fluoride were 10 ng/g for iron, 0.01 ng/g for cobalt, 1 ng/g for nickel and 0.1 ng/g for copper. The analytical results for iron, cobalt, nickel and copper in NBS SRM's were in good agreement with certified values.

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Abstract  

The coprecipitation behaviour of uranium or thorium with barium sulfate is investigated from the variation of yields with uranium or thorium concentration, acid and acidity, and amount of sodium and/or potassium sulfate. Uranium or thorium in quantities less than 1.5 mg is quantitatively coprecipitated with barium (5.9 mg) sulfate when using an optimum conditions. The chemical form of uranium in barium sulfate precipitates is discussed by determination of mole ratio of potassium to uranium.

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Abstract  

In this study, we aimed to recognize the body abnormalities through determining the metallic balance of hair. We determinated multiple elements of patients hair with acute chromium poisoning by burn from the worst clinical condition to complete recovery. Elements determined were Al, Au, Br, Ca, Cl, Co, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Na, S, Se, V and Zn by mondestractive neutron activation analysis. Comparing the clinical findings of a patient with acute chromium poisoning and metallic balance of his hair, we demonstrated that the metallic balance returned to the normal range with recovery from sickness, which suggested a promising possiblity to utilize this as one parameter indicative of clinical state.

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Abstract  

Carrier- and salt-free42K milked from an42Ar–42K generator was utilized for isotope dilution analysis of potassium in ultra-pure water. Potassium in the sample marked with the42K was shown to be concentrated easily 60 times by crown-ether extraction and acid back-extraction to be determined by atomic absorption spectrophotometry. The same extractions proved to be effective for removing the reagent blank. Cerenkov radiation counting was often suitable for42K measurement. The42K was used also for studying the interaction of ultra-low concentrations of potassium with vessel walls.

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Abstract  

New cubic leucite-type compounds, CsMSi2O6 (M=B0.2Al0.8,Al0.2Fe0.8), Cs2MSi5O12 (M=Cd, Mg, Ni, Zn) have been synthesized by the two-stage heat treatment of the solid-state reaction. The thermal expansion properties of the synthesized leucite-type compounds have been studied with HTXRD and LTXRD in the temperature range of 123 to 1273 K. The thermal expansion rate of CsB0.2Al0.8Si2O6 was found to be considerably smaller than that of CsAlSi2O6, while the thermal expansion property of Cs2MSi5O12 (M=Mg, Zn, Cd) was found to have a linear relationship in the temperature range of 298 to 1273 K. By using Rietveld analysis it was found that the thermal expansion rate decreased with increasing the Si—O—M(Si) angle for cubic leucite-type compounds at 298 K, and that the phase transitions of CsAlSi2O6 and Cs0.9Al0.9Si2.1O6 were due to the relationship between the bond angle of Si—O—M(Si) of the three-dimensional framework structure and the space ratio in the unit cell at 298 K.

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Abstract  

Amounts of239Pu in alpha-bearing wastes were determined by -ray measurement using a NaI/Tl/ scintillation detector. The deviations of measurement caused by the nonuniform distribution of239Pu in the wastes and by a volume factor were corrected by rotating and scanning the objects. Contribution from241Am coexisting with239Pu was also corrected by taking into account the difference of the counts between A /356–470 keV/ and B /475–620 keV/ intervals. Attenuation of -ray of239Pu was estimated from the matrix density. Thus the content of239Pu could be determined within an accuracy of about 25% at the 1 mg level in a cardboard carton of 17 1.

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Abstract  

A method of radioactivation analysis has been developed for the determination of 17 elements as impurities in high-purity optical glasses. The substoichiometric extraction of platinum with dithizone was studied and a simple procedure was proposed for the determination of platinum. Copper and manganese were also determined substoichiometrically by the extractions with dithizone and with thenoyltrifluoracetone, respectively. The non-destructive γ-ray spectrometry using a Ge(Li) detector has been applied for the determination of the other 14 elements (Ag, Co, Cr, Eu, Fe, Ir, Sc, Zn, Cs, Hf, Rb, Sb, Ta and Tb). Impurity elements at the ppb level were analysed by the proposed method and it is shown that the method is reliable for the determination of trace impurities in high-purity optical glasses.

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