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Nakano, Masanao
Hoken Butsuri (Internet), 56(1), p.17 - 25, 2021/03
The Tokai Reprocessing Plant is the first reprocessing plant in Japan which started hot test in 1977, and had reprocessed 1140 tons of spent nuclear fuel by May 2007. The gaseous and liquid radioactive wastes has been discharged to the environment. Since iodine-129 (
I) is one of the most important nuclides for environmental impact assessment. Therefore, I in the exhaust and effluent has been controlled, and a precise analysis method of I in the environmental samples was developed, and the concentration of 129I in the environment was investigated. This report presents an overview of these activities. Not limited to I on reprocessing facilities, it is essential for nuclear operators to reduce the amount released to the environment in the spirit of ALARA, and to continuously develop the further upgrading environmental monitoring methods and evaluation methods in order to foster a sense of safety and security among residents living in the vicinity of the facilities.
Nagaoka, Mika; Fujita, Hiroki; Aida, Taku*; Guo, H.*; Smith, R. L. Jr.*
Applied Radiation and Isotopes, 168, p.109465_1 - 109465_6, 2021/02
Times Cited Count：0 Percentile：0.00(Chemistry, Inorganic & Nuclear)The radioactivities in the environmental samples are analyzed to monitor the nuclear power facilities. The pretreatment of radioactive nuclides of alpha and beta emitters in the environmental samples is performed with acid to decompose organic matter and extract object nuclide such as 
Sr, U and Pu. However, the pretreatment methods are time-consuming and used many concentrated acid solutions that are unsafe and hazardous. Therefore, we develop to the new pretreatment method using supercritical water instead of acid. Hydrothermal pretreatment of soils (Andosols) from Ibaraki prefecture (Japan) was used to improve methods for monitoring radioactive Sr and U. Calcined samples were pretreated with subcritical or supercritical water (SCW) followed by extraction with 0.5 M HNO
solutions. With SCW pretreatment, recoveries of Sr and U were 70% and 40%, respectively. Experimental recoveries obtained can be described by a linear relationship in water density. The proposed method is robust and can lower environmental burden of routine analytical protocols.
Sasaki, Miyuki; Sanada, Yukihisa; Yamamoto, Akio*
Radiation Protection Dosimetry, 184(3-4), p.400 - 404, 2019/10
Times Cited Count：3 Percentile：26.93(Environmental Sciences)The maximum-likelihood expectation maximization (ML-EM) method is expected to improve the accuracy of airborne radiation monitoring using an unmanned aerial vehicle. The accuracy of the ML-EM method depends on various parameters, including detector efficiency, attenuation factor, and shielding factor. In this study, we evaluate the shielding factor of trees based on several field radiation measurements. From the actual measurement, the shielding factors were well correlated with the heights of the trees. The evaluated shielding factors were applied to the ML-EM method in conjunction with the measured data obtained from above the Fukushima forest. Compared with the conventional methods used for calculating the dose rate, the proposed method is found to be more reliable.
Iwamoto, Hiroki; Nishihara, Kenji; Yagi, Takahiro*; Pyeon, C.-H.*
Journal of Nuclear Science and Technology, 54(4), p.432 - 443, 2017/04
Times Cited Count：20 Percentile：86.03(Nuclear Science & Technology)Ishii, Toshimitsu; Ooka, Norikazu; Hoshiya, Taiji; Kobayashi, Hideo*; Saito, Junichi; Niimi, Motoji; Tsuji, Hirokazu
Journal of Nuclear Materials, 307-311(Part.1), p.240 - 244, 2002/12
Times Cited Count：3 Percentile：22.77(Materials Science, Multidisciplinary)no abstracts in English
Muramatsu, Ken; Kubo, Kotaro; Takada, Tsuyoshi
no journal, ,
no abstracts in English
