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  • Author or Editor: T. Hashimoto x
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Abstract  

The optimum conditions for high electrodeposition yields of trace amounts of americium on a stainless steel plate and an aluminium foil were studied. In the case of a stainless steel cathode, the following conditions can be recommended: electrolyte, 10 ml of a 0.1M ammonium oxalate buffer solution with 0.5 ml of the americium stock solution (7∶93 v/v, HNO3); current density, 86 mA/cm2; deposition time, 60 min. The uniformity of the deposited241Am was examined with a conventional α-track method with a cellulose nitrate film as a track recording material. Clear tracks on this film were obtained with a polyester film (18 μ) as α-absorber placed between the deposited americium source and the cellulose nitrate film.

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Abstract  

Thermal diffusivity of high density polyethylene (PE) has been measured by a new a. c. Joule-heating method. The diffusivity was determined at various temperatures between room temperature and above melting point in heating and cooling processes. This method is based on the phase shift of temperature waves across film sample, so that it offers several advantages, e.g., easy measuring in polymer melts.

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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  

An attempt was made to apply a delayed coincidence method for the absolute determination of trace quantities of the thorium series. This method is based on selective counting of the relatively short lived nuclide216Po (half-life 145 ms) in the thorium series members. For this purpose, a list mode time analyzing system combined with a liquid scintillation counter was assembled by means of a conventional microcomputer. A multiple time analysis was employed in the processing and data compilation of delayed coincidences to distinguish them from the true coincidences due to random events.From a time spectrum, the decay component of216Po (145 ms) can be selectively measured. Absolute activities of its progenitors,224Ra and228Th as well as220Rn, can be determined even in the presence of the background radiations of the almost equivalent activity-strength of concomitant uranium series.

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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  

A new technique for the simultaneous measurement of higher order harmonic of temperature wave under temperature scan was proposed. The mathematical rule for the propagation of harmonies in the film shaped specimen was examined and the principle of Fourier transform thermal analysis was theoretically and experimentally justified. This principle applied to a technique called ‘Fourier transform thermal analysis’, makes it possible to determine simultaneously thermal diffusivity, heat capacity per unit volume and thermal conductivity as a function of frequency and temperature. The results on thermoplastics were shown and the glass transition and the crystallization were discussed.

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Abstract  

A new determination equipment combined with the time interval analysis (TIA) has been developed for the simultaneous determination of concomitant alpha–emitting nuclides, such as Pu, Am, Cm and natural alpha–emitters in dust samples. This discrimination technique for the determination of artificial alpha–nuclides is based on the selective subtraction of natural alpha–nuclides contribution to the total pulses by analysing the time interval distributions due to the successive alpha- and beta decay events within millisecond or microsecond orders.

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Abstract  

For versatile applications of alpha-spectrometric analysis, the geometrical counting efficiency was conveniently evaluated for a circular detector faced to a circular radiating source with a Monte Carlo simulation method using a microcomputer after checking the qualities of the random numbers. The results were tabulated as functions of the distance (Q) between the detector and the source and of the source diameter (P), normalized with the detector diameter. An application was attempted for the uniformity examination of a natural uranium source electrodeposited on a stainless steel plate.

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Abstract  

In most established method for luminescence dating, the ratio of 90Sr/90Y radionuclides has been employed to provide reference laboratory doses to sample. Recently a small X-ray irradiator (Varian VF-50J) was introduced as an alternative to the traditionally used radioactive sources. Test results are presented whether the use of the small X-ray irradiator is possible in the dating technique. Aspects of the assessment of the X-ray irradiator include consideration of the measured optically stimulated luminescence signal and the relationship between X-ray tube currents and dose rates, as well as the dependence of equivalent dose for various dose rates. The test performances are assessed in relation to use with heated quartz.

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Abstract  

A new automated OSL/TL measuring system, equipped with a small X-ray irradiator applicable to a single-aliquot method, has been developed. To ensure cross check between OSL and RTL, the naturally accumulated doses evaluated with OSL and RTL measurements were compared. The results nearly agreed with each other, although the ages estimated from the experimental data were different from the real ages of Shin-Yakushiji temple because of the uncertainty of the annual dose. Nevertheless, it was concluded that the application of this system to the dating could be performed owing to uses of the luminescence measurements.

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