Design and commissioning of the exhaust detritiation system for the Large Helical Device

Tanaka, Masahiro; Suzuki, Naoyuki; Kato, Hiromi; Kondo, Tomoki; Yokosawa, Minoru; Kawamata, Tomonori; Ikeda, Mitsuru; Meguro, Tsuyoshi; Tanaka, Tomonari; Sonoi, Kazuro

doi:10.1016/j.fusengdes.2017.12.034

Cited by 28 publications

(25 citation statements)

References 18 publications

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“…A small amount of tritium was produced by a fusion reaction in the deuterium plasma experiment. Although the deuterium and the tritium gases were exhausted from the vacuum vessel of the LHD and recovered by the exhaust detritiation system (EDS) [15], a part of the tritium was released into the environment through the main stack. In the first year of the deuterium plasma experiment, the annual tritium yield was permitted up to 3.7 × 10 10 Bq for commissioning of the deuterium plasma experiment.…”

Section: Introductionmentioning

confidence: 99%

Isotope Composition and Chemical Species of Monthly Precipitation Collected at the Site of a Fusion Test Facility in Japan

Tanaka

Iwata

Kato

et al. 2019

IJERPH

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The deuterium plasma experiment was started using the Large Helical Device (LHD) at the National Institute for Fusion Science (NIFS) in March 2017 to investigate high-temperature plasma physics and the hydrogen isotope effects towards the realization of fusion energy. In order to clarify any experimental impacts on precipitation, precipitation has been collected at the NIFS site since November 2013 as a means to assess the relationship between isotope composition and chemical species in precipitation containing tritium. The tritium concentration ranged from 0.10 to 0.61 Bq L−1 and was high in spring and low in summer. The stable isotope composition and the chemical species were unchanged before and after the deuterium plasma experiment. Additionally, the tritium concentration after starting the deuterium plasma experiment was within three sigma of the average tritium concentration before the deuterium plasma experiment. These results suggested that there was no impact by tritium on the environment surrounding the fusion test facility.

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Section: Introductionmentioning

confidence: 99%

Isotope Composition and Chemical Species of Monthly Precipitation Collected at the Site of a Fusion Test Facility in Japan

Tanaka

Iwata

Kato

et al. 2019

IJERPH

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“…After a deuterium plasma experiment in the LHD is started, tritium is exhausted from the vacuum vessel. An EDS was installed prior to performing the deuterium plasma experiment [13]. Because the EDS is connected to all exhaust gas lines from the LHD system, the inlet of the EDS is suitable for observing exhaust gas composition, including hydrogen isotopes.…”

Section: Monitoring Exhaust Gas From the Lhd And The Wall Conditioning Proceduresmentioning

confidence: 99%

Detection of Ammonia and Deuterated Hydrocarbons in Exhaust Gas by Infrared Absorption Spectroscopy during Wall Conditioning

Tanaka

Kato

Suzuki

et al. 2021

Plasma and Fusion Research

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To detect ammonia and deuterated hydrocarbons in exhaust gas from the Large Helical Device (LHD), infrared absorption spectrometry, FTIR with a long optical path gas cell, was applied. Ammonia (NH 3 ) and deuterated hydrocarbons (C x H y D z ) could be detected during the first operations of wall baking at 368 K and the D 2 glow discharge conducted after vacuum vessel closure. The concentration of ammonia increased with increasing baking temperature, and deuterated ammonia was not detected. Thus, the ammonia, which likely originated from sweat of workers produced during vacuum vessel maintenance activities, was released from the vacuum vessel wall. Hydrocarbons were likely produced by chemical sputtering of carbon tiles and were deuterated by a hydrogen isotope exchange reaction due to D 2 glow discharge, while H 2 O was released from the vacuum vessel during wall baking. It was confirmed that ammonia and various types of deuterated hydrocarbons could be measured discriminately by an FTIR spectroscopy system using a long optical path gas cell.

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“…These armor tiles can be damaged by the high heat and particle fluxes of high temperature plasma, which are normally confined by the magnetic field but can be fluctuated by the experimental conditions. Also, the investigation of tritium retention in the vacuum vessel is significantly important in the deuterium experiments from the radiation control point of view [9][10][11] . Therefore, the armor tiles have been replaced frequently due to damage or for analyses.…”

Section: Introductionmentioning

confidence: 99%

The Evaluation of a Simple Measurement Method using NaI(Tl) Scintillation Survey-Meter for Radiation Safety Management of Radioactivated Armor Tiles of LHD Vacuum Vessel

Kobayashi

Suzuki

Saze

et al. 2021

Radiat. Saf. Manage.

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In this study, the application of a simple measurement method using NaI(Tl) scintillation survey-meter to detect the gamma-rays in the armor tiles of LHD vacuum vessel exposed to fast neutrons during deuterium plasma experiments was evaluated to control the occupational exposure for the storage of huge numbers of the armor tiles. The gamma-ray spectrometry for an activated armor tile by high-purity germanium detector (HPGe) showed the gamma-ray peaks from 58 Co, 54 Mn and 60 Co. The detection efficiencies of these nuclides for HPGe were evaluated by PHITS to estimate the concentrations of these nuclides. The radiation transport model for HPGe in PHITS were validated by the gamma-ray measurements for sealed gamma-ray sources. Then, the detection efficiencies of these nuclides for NaI(Tl) scintillation survey-meter were also evaluated by the same manner using PHITS. The predicted dose rate of the activated armor tiles in NaI(Tl) scintillation survey-meter was consistent with the actual measurement. The predicted count rate in NaI(Tl) scintillation survey-meter for 60 Co, which will be a deterministic nuclide in the armor tile due to longer half-life, in the clearance level was sufficiently higher than the minimum detectable count rate of NaI(Tl) scintillation survey-meter with a simple shielding for environmental radiation.

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Design and commissioning of the exhaust detritiation system for the Large Helical Device

Cited by 28 publications

References 18 publications

Isotope Composition and Chemical Species of Monthly Precipitation Collected at the Site of a Fusion Test Facility in Japan

Isotope Composition and Chemical Species of Monthly Precipitation Collected at the Site of a Fusion Test Facility in Japan

Detection of Ammonia and Deuterated Hydrocarbons in Exhaust Gas by Infrared Absorption Spectroscopy during Wall Conditioning

The Evaluation of a Simple Measurement Method using NaI(Tl) Scintillation Survey-Meter for Radiation Safety Management of Radioactivated Armor Tiles of LHD Vacuum Vessel

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