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-ray Spectrometry of Environmental Samples Collected in FukushimaSaegusa, Jun; Yoda, Tomoyuki; Maeda, Satoshi; Okazaki, Tsutomu; Otani, Shuichi; Yamaguchi, Toshio; Kurita, Yoshiyuki; Hasumi, Atsushi; Yonezawa, Chushiro*; Takeishi, Minoru
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1078 - 1085, 2017/11
After the nuclear accident at the Fukushima Daiichi Nuclear Power Plant in March 2011, the Japan Atomic Energy Agency has newly set up a laboratory for radioactivity analysis in Fukushima. At the laboratory, radioactivity concentrations of environmental samples such as soil, water, dust filter, plant, etc., approximately 1,000 samples in a month, are measured with high-resolution -ray spectrometry systems. The systems employ n-type HPGe detectors from Ortec. Since September 2012, characterization and upgrade of the systems have been performed aimed at enhancing reliability of analysis and convenience of customers. Resolving both systematic and technical issues, the laboratory has been accredited the ISO/IEC 17025 standard as a testing laboratory for radioactivity analysis.
Nishino, Sho; Hoshi, Katsuya; Tsujimura, Norio; Kowatari, Munehiko; Yoshida, Tadayoshi
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1258 - 1263, 2017/11
In order to investigate how neutron dosimeters respond in the continuous neutron fields in workplaces, we performed performance tests of four widely-used neutron survey meters in various simulated workplace neutron calibration fields established in two calibration facilities (FRS and ICF) in JAEA. As a result, we found that survey meters significantly over or underestimate neutron dose in the fields which have spectral components only in the energy range below 1 MeV, while those show good performance in the fields which have spectral components in the energy range above 1 MeV.
Yoshitomi, Hiroshi; Hagiwara, Masayuki*; Kowatari, Munehiko; Nishino, Sho; Sanami, Toshiya*; Iwase, Hiroshi*
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1188 - 1195, 2017/11
The equivalent doses to the lens of the eye and extremities for radiation workers should be assessed properly to ensure that the dose limits are not exceeded. Recently, the following two issues has pressed demand on more appropriate evaluation of the equivalent doses of the lens of the eye and extremity. One is the new occupational dose limit for the lens of the eye the ICRP recommended. The other is growing demand on handling of highly activated materials in the maintenance works of an accelerator and contaminated materials during the decommissioning works of nuclear facility, which increases the potential exposure risk to the extremities to a wider variety of radio-nuclides. Since the points to be assessed for the exposures to the lens of the eye and the extremities are apart from the trunk, the homogeneity of the radiation fields would be significantly impact on the assessment of these equivalent doses. However, there has been no sufficient and available method to identify the nonhomogeneous situations systematically in terms of the eye lens or extremity monitoring. The goal of this study is to provide the framework to identify the nonhomogeneous exposure situations. In order to fulfil this purpose, newly proposed indices to represent the homogeneity were calculated by Monte Carlo simulation incorporated with mathematical phantom, verifying the benchmark measurements. Important parameters that significantly impact on these indices were also shown from the various trials of calculations of homogeneity indices.
Kowatari, Munehiko; Yoshitomi, Hiroshi; Nishino, Sho; Tanimura, Yoshihiko; Oishi, Tetsuya; Yoshizawa, Michio
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1230 - 1238, 2017/11
The Facility of Radiation Standards (FRS) of the Japan Atomic Energy Agency (JAEA) offers various kinds of radiation calibration fields for calibration and testing for over three decades. The FRS-JAEA offers reliable X-ray, -ray, beta-ray and neutron calibration fields with a vast range of variety. The quality and a set of neutron calibration fields are particularly mentioned. Neutron calibration fields with energies ranging between 0.025 eV and 19 MeV enable users to check the whole items for performance test. Two different sets of beta-ray calibration fields were established and served for regular calibration of dosimeters mainly used in nuclear industries. Resent research accomplishments on -ray calibration fields can extend the upper limit of the energy up to 6 MeV. In addition to them, a simulated workplace neutron calibration field has been newly established for calibration of neutron dosimeters used inside the nuclear reactors.
Sakoda, Akihiro; Ishimori, Yuu
no journal, ,
Numerous studies have experimentally and numerically been made to understand the first process "radon emanation" leading to radon exposure. We made an extensive review of previous emanation measurements, including our results, for more than a thousand samples. The discussion was made with respect to issues such as the representative values of radon emanation fraction for environmental materials and the measurement method. In addition, we have numerically simulated the emanation process to investigate the impacts of environmental factors. The discrepancies between the observed and calculated data were seen depending on a factor, which should be studied further in the future.
