Japanese Journal of Health Physics
Online ISSN : 1884-7560
Print ISSN : 0367-6110
ISSN-L : 0367-6110
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Volume 53, Issue 1
Displaying 1-8 of 8 articles from this issue
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Foreword
Technical Data
  • Air Absorbed Dose Rate Measurements and External Dose Assessment by Car-Borne Survey in the Gold Mining Areas of Betare-Oya, Eastern-Cameroon
    Louis NGOA ENGOLA, Joseph Emmanuel NDJANA NKOULOU II, Masahiro HOSODA, ...
    Article type: Technical Data
    2018 Volume 53 Issue 1 Pages 5-11
    Published: 2018
    Released on J-STAGE: June 05, 2018
    DOIhttps://doi.org/10.5453/jhps.53.5
    JOURNAL FREE ACCESS
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    In order to assess radiological exposure of the public due to natural occurring radioactive materials from gold mining areas of Betare-Oya and vicinity, Eastern Cameroon, a preliminary study was carried out in 2015 for laboratory measurements of activity concentrations of primordial radionuclides. In terms of annual effective dose, results revealed a mean value of 0.34 mSv y-1. However, it was necessary to make air absorbed dose rate contour map for a detailed evaluation of external dose. For this purpose, a car-borne survey using a 3-in × 3-in NaI(Tl) scintillation spectrometer was carried out in Betare-Oya and vicinity. Absorbed dose rates in air ranged from 23 to 80 nGy h-1 with a mean value of 44 ± 7 nGy h-1. The average values of activity concentrations in soil of 40K, 238U and 232Th were 197 ± 21 Bq kg-1, 37 ± 13 Bq kg-1 and 32 ± 7 Bq kg-1 respectively. 232Th was found to be the main contributor to the absorbed dose rate in air from outdoor terrestrial radiation in the study areas with a mean value of 43%. External annual effective dose ranged from 0.17 to 0.60 mSv y-1 with a mean value of 0.33 ± 0.05 mSv y-1, in agreement with the result (0.34 mSv y-1) of the previous study performed in the same areas using gamma spectrometry in laboratory for radioactivity measurements in soil samples. This survey first and widely revealed an aspect of natural radiation exposures in soil mining areas of Eastern Cameroon.
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  • Using Experimental Transfer Factors to Estimate the Ratio between the Committed Effective Dose from Ingestion of Radio-tellurium to that of Radio-cesium Released by the Fukushima Daiichi Nuclear Power Plant Accident
    Tomoyuki TAKAHASHI, Keiko FUJIWARA, Tadatoshi KINOUCHI, Satoshi FUKUTA ...
    Article type: Technical Data
    2018 Volume 53 Issue 1 Pages 12-16
    Published: 2018
    Released on J-STAGE: June 05, 2018
    DOIhttps://doi.org/10.5453/jhps.53.12
    JOURNAL FREE ACCESS
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    Tellurium (Te) isotopes were released into the environment with other radioactive isotopes including cesium (Cs) and iodine (I) as a result of the accident at the Fukushima Daiichi Nuclear Power Plant. There is a possibility that the ingestion of Te-127m and Te-129m with foods may cause a significant internal radiation dose for the public because the half-lives of these isotopes are relatively long 109 and 33.6 days, respectively. Data on the transfer of Te from cultivated soil to plants through roots is essential to estimate the contribution of radioactive Te to the internal radiation dose in the public. However, little is known about transfer of Te from soil to plants in the ecosystem. Therefore, we previously estimated transfer factors for stable Te and Cs from soil to radish and komatsuna by experiments. In the present study, we calculated ratios of committed effective dose for radioactive Te to radioactive Cs by using our experimentally estimated transfer factors for stable Te and Cs as well as those reported by the IAEA. Ratios calculated with transfer factors estimated by the IAEA report were two orders of magnitude higher than those calculated with our measured transfer factors. These results suggest that the committed effective dose from ingestion of radioactive Te is probably considerably lower than the dose based on IAEA results.
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  • Concentrations of Chemical Components, Including 210Pb, Present in Aerosols Collected at Naha, Okinawa Prefecture, a Sub-tropical Region of Japan
    Naofumi AKATA, Yoshitaka SHIROMA, Masahide FURUKAWA, Akemi KATO, Hidek ...
    Article type: Technical Data
    2018 Volume 53 Issue 1 Pages 17-22
    Published: 2018
    Released on J-STAGE: June 05, 2018
    DOIhttps://doi.org/10.5453/jhps.53.17
    JOURNAL FREE ACCESS
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    Aerosol samples were collected at Naha, Okinawa Prefecture, Japan during July 2001 to March 2005 to elucidate the concentrations of chemical components, including 210Pb, present in air for a sub-tropical region of Japan. The NO3-, SO42-, NH4+ and Ca2+ concentrations had clear seasonal variations and were high in winter to spring and low in summer. 210Pb concentrations ranged from 0.10 to 1.52 mBq m-3 and were low in summer and high in the other three seasons. The source of sulfur compounds in the aerosol samples was clarified by combining the sulfur isotope ratio δ34S and 210Pb concentrations. The multi-isotope method using δ34S and 210Pb concentrations was judged to be a good tool for understanding the transported sulfur source.
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