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論文(リポジトリ)

論文(リポジトリ)
Nakasone, Shunya ; Yokoyama, Sumi ; Takahashi, Tomoyuki ; Ota, Masakazu ; Kakiuchi, Hideki ; Sugihara, Shinji ; Hirao, Shigekazu ; Momoshima, Noriyuki ; Tamari, Toshiya ; Shima, Nagayoshi ; Atarashi-Andoh, Mariko ; Fukutani, Satoshi ; Ishimine, Akinobu ; Furukawa, Masahide ; Tanaka, Masahiro ; Akata, Naofumi
出版情報: Plasma and Fusion Research.  15  2020-05-13.  The Japan Society of Plasma Science and Nuclear Fusion Research — プラズマ・核融合学会
URL: http://hdl.handle.net/20.500.12000/47465
概要: This paper presents an evaluation of a rapid pretreatment method for tritium analysis, that uses ion exchange resins (th e batch method). The standard water samples were prepared with river water collected in Okinawa, Japan. Powdex resin was used in this study, which is an ion exchange resins in the form of powder beads. First, 100 mL of the standard sample was stirred with the cation exchange (PCH) and anion exchange (PAO) resins, as well as with activated carbon. To determine the optimal stirring time, we tested stirring times of 5, 10, 20 and 30 min. Additionally, to determine a suitable amount of ion exchange resin for environmental water samples, variations in the amount of resin and activated carbon were tested. Under the conditions of Experiment-3 (0.3 g, 0.3 g and 0.6 g of PCH, PAO and activated carbon, respectively) and with a stirring time of 5 min, electrical conductivity values of less than 1 mSm^<−1> were achieved. These results demonstrate the effectiveness of the removal of impurities in the sample water by ion exchange resins and confirm that such an effect can be achieved during a short period of time (i.e., in 5 min).
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2.

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論文(リポジトリ)
Shiroma, Yoshitaka ; Hirao, Shigekazu ; Akata, Naofumi ; Furukawa, Masahide ; Miyake, Hitoshi ; Hayashi, Hiroshi ; Saze, Takuya ; Tanaka, Masahiro
出版情報: Plasma and Fusion Research.  14  2019-07-11.  The Japan Society of Plasma Science and Nuclear Fusion Research — プラズマ・核融合学会
URL: http://hdl.handle.net/20.500.12000/47468
概要: The latest measurement of the absorbed dose rate in air was performed at the National Institute for Fusion Science (NIFS ) site during the period for the first deuterium plasma experiment conducted in Large Helical Device (LHD). The arithmetic mean of the absorbed dose rates in air for 222 measurement points at the NIFS site was 43 nGy h^<−1>. Very little change was observed in the distribution maps of the absorbed dose rates in air before and after the deuterium experiment in the LHD. In addition, the absorbed dose rates in air around the buildings were distributed at similar high levels before and after the deuterium experiment. A radionuclide analysis of soil and broken stone was conducted using a high-purity Ge semiconductor detector. The absorbed dose rates in air at the NIFS site were mainly defined by the radiation from the ground and the building material around the measurement points. The effect of the deuterium experiment was so small that it was undetectable in this study.
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3.

論文(リポジトリ)

論文(リポジトリ)
Yokoyama, Sumi ; Takahashi, Tomoyuki ; Ota, Masakazu ; Kakiuchi, Hideki ; Sugihara, Shinji ; Hirao, Shigekazu ; Momoshima, Noriyuki ; Tamari, Toshiya ; Shima, Nagayoshi ; Atarashi-Andoh, Mariko ; Fukutani, Satoshi ; Nakasone, Shunya ; Furukawa, Masahide ; Tanaka, Masahiro ; Akata, Naofumi
出版情報: Plasma and Fusion Research.  14  2019-06-03.  The Japan Society of Plasma Science and Nuclear Fusion Research — プラズマ・核融合学会
URL: http://hdl.handle.net/20.500.12000/47466
概要: To estimate the environmental transfer of tritium into the atmosphere and to establish tritium analysis techniques, this study improves our previous compartment model and proposes new analytical technique based on the microwave heating method and a water-sample purification technique using ion resin. This article introduces a new conceptual approach for estimating environmental tritium behavior.
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4.

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Akata, Naofumi ; Kakiuchi, Hideki ; Tanaka, Masahiro ; Shima, Nagayoshi ; Shiroma, Yoshitaka ; Tokonami, Shinji ; Hosoda, Masahiro ; Ishikawa, Yoshio ; Furukawa, Masahide ; Sanada, Tetsuya
出版情報: Plasma and Fusion Research.  13  2018-06-12.  The Japan Society of Plasma Science and Nuclear Fusion Research — プラズマ・核融合学会
URL: http://hdl.handle.net/20.500.12000/47467
概要: We have developed a rapid sampling system for measuring the tritium in atmospheric water vapor. The system consists of a high-efficiency particulate air filter cartridge, an oil-free compressor, a water-vapor-separating module with hollow fiber membranes, two cold traps, and an oil-free rotary pump. Compressed air (0.4 - 0.7MPa) is introduced into the water-vapor-separation module, which consists of a stainless steel column containing polyimide membrane tubes. Water vapor permeates through the tubes and is collected by cold traps cooled with dry ice and ethanol. The module is heated with a flexible heater to control its temperature. We have determined the recovery yields under various sampling conditions and find that this system can collect atmospheric water vapor with a recovery yield of >99%. This system can thus be a useful tool for understanding short-term observations of tritium in atmospheric water vapor.
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5.

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論文(リポジトリ)
仲宗根, 峻也 ; 石津, 裕二 ; 池本, 憲弘 ; 城間, 吉貴 ; 赤田, 尚史 ; 田中, 将裕 ; 古川, 雅英 ; Nakasone, Shunya ; Ishizu, Yuji ; Ikemoto, Norihiro ; Shiroma, Yoshitaka ; Akata, Naofumi ; Tanaka, Masahiro ; Furukawa, Masahide
出版情報: 保健物理.  53  pp.65-71,  2018.  日本保健物理学会
URL: http://hdl.handle.net/20.500.12000/47470
概要: In this study, to estimate the recent tritium concentration and its variation with latitude and time in Japan, environme ntal water samples were taken monthly from June 2014 to October 2016 in Okinawa Island, subtropical region of Japan. The inland water samples were taken from two springs and the drop water samples were taken in a limestone cave. The samples were distilled to remove impurities and then electrolysed using electrolytic enrichment system. Each of the enrichment samples was mixed with the liquid scintillation cocktail, and the tritium concentration was measured with a low background liquid scintillation counter. Arithmetic mean ± standard deviation for the tritium concentration of Morinokawa (spring water), Kakinohanahikawa (spring water) and Gyokusendo (cave drop water) samples were estimated to be 0.13 ± 0.04 Bq L^<-1>, 0.12 ± 0.03 Bq L^<-1> and 0.13 ± 0.03 Bq L^<-1>, respectively. The comparison between these results and reported data suggested that the latitude effect is one of factors in the relatively low tritium concentration observed in Okinawa Island.
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