RADIOISOTOPES
Online ISSN : 1884-4111
Print ISSN : 0033-8303
ISSN-L : 0033-8303
Volume 44 , Issue 4
Showing 1-13 articles out of 13 articles from the selected issue
  • Ryuhei KUROSAWA, Takeshi IIMOTO, Shinji TOKONAMI
    1995 Volume 44 Issue 4 Pages 225-235
    Published: April 15, 1995
    Released: September 07, 2010
    JOURNALS FREE ACCESS
    A measurement technique for low level concentration of individual radon decay product in open air was developed. A reliability of determined concentration was especially discussed in this study.
    In order to clearly make a distribution of radon progeny, it had been required to accurately estimate low level concentration of individual radon decay product. However a market supplied ZnS (Ag) scintillation counter did not usually have enough detection sensitivity to determine its concentration in open air because high sampling velocity was not expected due to a restriction of the filter size. The detectable limit of above mentioned detector for 218Po concentration had been only about 10 Bq⋅m-3. In order to realize a higher detection sensitivity, higher velocity and higher collection efficiency were required. In this study, the following items were regarded as important factors for sampling filter to realize a high sensitivity : a) large sampling area, b) low pressure drop and c) high collection efficiency. Under the above conditions, Fluoropore AF 07P filter (effective sampling area : 85 mmφ) combined with High Volume Air Sampler (HVAS, made by Staplex Co.) was found to achieve the highest detection sensitivity with high velocity readings of 400l⋅min-1. In addition, a large area (125 mmφ) ZnS (Ag) scintillator was applied to efficiently measure the alpha rays emanating from radon decay products collected on the surface part of the large area filter. The detection efficiency of this ZnS (Ag) scintillation counter for the alpha rays of 218Po was estimated at 24.5% and that of 214Po at 34.5%. These efficiencies were estimated by both experiments and calculation which indicated same value each other.
    The time sequence was determined as follows; Sampling time was five minutes, waiting time was one minute and measuring time was every five minutes for a total of 50 min. The least square method was introduced to estimate the concentrations.
    The detectable limits of concentration were 1.5 Bq⋅m-3 for 218Po, and 0.4 Bq⋅m-3 for 214Pb and 214Bi using this method.
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  • Akio NAKANISHI, Akira FURUSE, Nahoko SUGAHARA, Makoto TSUNEDA, Atsushi ...
    1995 Volume 44 Issue 4 Pages 236-243
    Published: April 15, 1995
    Released: September 07, 2010
    JOURNALS FREE ACCESS
    Using the strongest permanent magnet (NEOMAX), a high-sensitive portable ESR spectrometer useful for practical measurements has been developed. The spectrometer is assembled in one small case with the weight of about 25 kg and is operated by a personal computer. The spectrometer reaches a sensitivity of 2×1010 spins/0.1 mT with a resolving power below 0.045 mT. This spectrometer can be utilized for practical measurements and fundamental researches. An important field of practical measurements is the dosimetry of gamma radiations. The spectrometer is also to characterize the alanine samples irradiated from 10 Gy to 30 kGy with an accuracy of scattering lower than 2%.
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  • Kunio OOHASHI, Tomonari SUGANO
    1995 Volume 44 Issue 4 Pages 244-250
    Published: April 15, 1995
    Released: September 07, 2010
    JOURNALS FREE ACCESS
    Tritiation by the hydrogen isotope exchange in toluamides with HTO was studied in the presence of RhCl3⋅3H2O as a catalyst. It was established by chemical degradation that the exchange reaction occurred with virtually 100% regioselectivity at the o-position (s) (C2 and C6 positions) of all the toluamides. The methyl group was not tritiated. The exchange in m-toluamide was very strongly hindered at the C2 position between the methyl and the amido group. The exchange at the C6 position was more strongly prevented in o-toluamide than in m-toluamide. These findings are explained on the basis of the steric effect of the methyl group in agreement with the previously suggested mechanism that the exchange proceeds via initial coordination of the substrate compound to rhodium (III) chloride trihydrate.
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  • Tadashi YAMASAKI, Takao IIDA
    1995 Volume 44 Issue 4 Pages 251-255
    Published: April 15, 1995
    Released: September 07, 2010
    JOURNALS FREE ACCESS
    A portable integrating monitor for measuring both radon and thoron progeny concentrations was developed. The monitor gave the average equilibrium equivalent concenttrations of radon (E.E.R.) and thoron (E.E.T.) during five days. The calibration factor was calculated by Monte Carlo method. We selected four measurement locations : home, office, laboratory and outdoor. In the measurement at home, the both radon and thoron progeny concentrations in the nighttime were larger than in the daytime. On the other hand at the other locations the concentrations in the nighttime were same as in the daytime. The RT-ratio, which was defined as the ratio of E.E.T. to E.E.R., was about 0.10 indoors and about 0.02 outdoors. Therefore indoor thoron progeny concentration tends to be higher.
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  • Mamoru MEKATA
    1995 Volume 44 Issue 4 Pages 256-266
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • Tsuneo CHO
    1995 Volume 44 Issue 4 Pages 267-274
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • Koichiro SERA
    1995 Volume 44 Issue 4 Pages 275-279
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • Michiko YOSHITAKE
    1995 Volume 44 Issue 4 Pages 280-283
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • Masao MASHITA
    1995 Volume 44 Issue 4 Pages 284-294
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1995 Volume 44 Issue 4 Pages 295-296
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1995 Volume 44 Issue 4 Pages 297-298
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1995 Volume 44 Issue 4 Pages 299-300
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1995 Volume 44 Issue 4 Pages 301-302
    Published: April 15, 1995
    Released: July 21, 2010
    JOURNALS FREE ACCESS
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