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JAEA Reports

Tritium removal of heavy water system and helium system in FUGEN

Takiya, Hiroaki; Kadowaki, Haruhiko; Matsushima, Akira; Matsuo, Hidehiko; Ishiyama, Masahiro; Aratani, Kenta; Tezuka, Masashi

JAEA-Technology 2020-001, 76 Pages, 2020/05

JAEA-Technology-2020-001.pdf:6.06MB

Advanced Thermal Reactor (ATR) FUGEN was operated for about 25 years, and now has been proceeding decommissioning after the approval of the decommissioning plan in Feb. 2008. The reactor, heavy water system and helium system are contaminated by tritium because of neutron absorption of heavy water, which is a moderator. Before dismantling these facilities, it is necessary to remove tritium from them for not only reducing the amount of tritium released to surrounding environment and the risk of internal exposure by tritium but also ensuring the workability. In first phase of decommissioning (Heavy Water and Other system Decontamination Period), tritium decontamination of the reactor, heavy water system and helium system started in 2008 and completed in 2018. This report shows the results of tritium decontamination of the reactor, heavy water system and helium system.

Journal Articles

Study of radiation-induced primary process by ion pulse radiolysis

Yoshida, Yoichi*; Yang, J.*; Kondo, Takafumi*; Seki, Shuhei*; Kozawa, Takahiro*; Tagawa, Seiichi*; Shibata, Hiromi*; Taguchi, Mitsumasa; Kojima, Takuji; Namba, Hideki

JAEA-Review 2005-001, TIARA Annual Report 2004, p.183 - 185, 2006/01

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2005-001-p0127-p0267.pdf

A heavy-ion-pulse radiolysis technology was developed using a single-photon-counting system. In the system, the ion beam was injected a thin scintillator before irradiating the sample. The light emitted from the scintillator by the ion irradiation was used as analyzing source to detect the absorption of primary species in water. Measurement of time-dependent absorption of hydrated electrons in water was achieved using the system, which demonstrates the usefulness of this technique.

Journal Articles

Re-emission of heavy water vapour from soil to the atmosphere

Yokoyama, Sumi; Noguchi, Hiroshi; Ichimasa, Yusuke*; Ichimasa, Michiko*

Journal of Environmental Radioactivity, 71(3), p.201 - 213, 2004/01

https://doi.org/10.1016/S0265-931X(03)00169-3

Times Cited Count：10 Percentile：22.56(Environmental Sciences)

The reemission process of tritiated water (HTO) deposited on a soil surface is an important process to assess tritium doses to the general public around nuclear fusion facilities. A field experiment using heavy water (HDO) as a substitute for HTO was curried out in the summertime to investigate the reemission process of HTO from soil to the atmosphere. In the experiment, the time variations of the depth profiles of HDO concentrations in soil exposed to HDO vapour and soil mixed with HDO were measured during the reemission process on the field. The decrease of HDO concentration insoil water of exposed soil was much greater than that of mixed soil. The reemission process was analysed using a model including the evaporation of HDO from soil, the exchange between the soil HDO and air H $_{2}$ O, and the diffusion of HDO in soil. It was found that the model is applicable to calculating the time variations of detailed depth profiles of HDO concentration in soil water in surface soil layers.

JAEA Reports

JRR-2 decommissioning activity, 1

Nakano, Masahiro; Arigane, Kenji; Okawa, Hiroshi; Suzuki, Takeshi; Kishimoto, Katsumi; Terunuma, Akihiro; Yano, Masaaki; Sakuraba, Naotoshi; Oba, Nagamitsu

JAERI-Tech 2003-072, 92 Pages, 2003/08

JAERI-Tech-2003-072.pdf:6.99MB

The decommissioning plan of the Japan Research reactor No2(JRR-2), decommissioning activities until the first half of phase-3, radioactive wastes and exposure dose of workers are described in this report. Since the first criticality in October 1960, JRR-2 had been operated about 36 years for various experiments. However, JRR-2 was permanent shutdown in December 1996 based on JAERI's long term plan, and the decommissioning of the JRR-2 was started in August 1997. Decommissioning of the JRR-2 was planed for 11 years from 1997 to 2007 and the program was divided into 4 phases. The decommissioning activities of the phase-1, phase-2 and the first half of phase-3 had already completed as planned in March 1998, February 2000, March 2002, respectively. The decommissioning activities of the later half of Phase-3 (dismantling of the reactor cooling systems) are carrying out at present time with planed 2002 and 2003 fiscal years.

Journal Articles

An Application to Intraoperative BNCT using epithermal neutron of new JRR-4 mode "Epi-12"

Matsushita, Akira*; Yamamoto, Tetsuya*; Matsumura, Akira*; Nose, Tadao*; Yamamoto, Kazuyoshi; Kumada, Hiroaki; Torii, Yoshiya; Kashimura, Takanori*; Otake, Shinichi*

Research and Development in Neutron Capture Therapy, p.141 - 143, 2002/09

A thermal-epithermal mixed beam "Thermal Neutron Beam Mode I" was used in the eleven sessions of boron neutron capture therapy which have been performed at JRR-4 from 1998. We are planning to use an epithermal beam for the treatment of deeper tumors in the next trial of the intraoperative BNCT. In this study, "Epi-12" which was made by putting up a cadmium shutter of "Thermal Neutron Beam Mode I" was investigated for the clinical benefits and safety by epithermal beams. Decrease of fast neutron contamination ratio in Epi-12 mode is the advantage for BNCT, particular in the intraoperative BNCT. Because fast neutron on the brain surface is one of the critical factors in the intraoperative BNCT in which the plain beam directly interacts the normal structures. Furthermore a mixture of mode Epi-12 and Th-12 will provide various dose distribution designs. It may be used as a new method to control the best distribution for individual tumors.

JAEA Reports