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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

Technology demonstration of sampling from reactor core structure of FUGEN Decommissioning Engineering Center

Iwai, Hiroki; Soejima, Goro; Takiya, Hiroaki; Awatani, Yuto; Aratani, Kenta; Miyamoto, Yuta; Tezuka, Masashi

Dekomisshoningu Giho, (61), p.12 - 19, 2020/03

FUGEN Decommissioning Engineering Center received the approval of the decommissioning plan in 2008, and we have been progressing the decommissioning. The first phase of decommissioning (Heavy Water and Other System Decontamination Period) finished in March 2018, and FUGEN has entered into the second phase of decommissioning (Reactor Periphery Facilities Dismantling Period). This report outlines the technology demonstration of sampling from reactor core structure of FUGEN that to prepare for reactor dismantlement in the third phase.

Journal Articles

Characteristic analysis on generativity of staffs in nuclear power plant in decommissioning project

Zhao, Q.*; Taruta, Yasuyoshi; Kobayashi, Shigeto*; Hashimoto, Takashi*

Chishiki Kyoso (Internet), 9, p.III 1_1 - III 1_9, 2019/06

no abstracts in English

Journal Articles

Calculation of low-energy electron antineutrino spectra emitted from nuclear reactors with consideration of fuel burn-up

Riyana, E. S.*; Suda, Shoya*; Ishibashi, Kenji*; Matsuura, Hideaki*; Katakura, Junichi*; Sun, G. M.*; Katano, Yoshiaki

Journal of Nuclear Science and Technology, 56(5), p.369 - 375, 2019/05

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Nuclear reactors produce a great number of electron antineutrinos mainly from beta-decay chains of fission products. Such neutrinos have energies mostly in MeV range. We are interested in neutrinos in a region of keV, since they may have information on fuel burn-up and may be detected in future with advanced measurement technology. We calculate reactor antineutrino spectra especially in the low energy region. In this work we present neutrino spectra from various reactors such as typical PWR reactor and others types of reactors for comparison. Our result shows the electron antineutrino flux in the low energy region increases with burn-up of nuclear fuel by accumulated nuclides with low Q values in beta decay.

Journal Articles

Status of decommissioning of FUGEN Decommissioning Engineering Center

Takiya, Hiroaki; Aratani, Kenta; Awatani, Yuto; Ishiyama, Masahiro; Tezuka, Masashi; Mizui, Hiroyuki

Dekomisshoningu Giho, (59), p.2 - 12, 2019/03

FUGEN Decommissioning Engineering Center received the approval of the decommissioning program in 2008, and we have been progressing the decommissioning. The first phase of decommissioning (Heavy Water and Other system Decontamination Period) finished in May 2018, and FUGEN has entered into the second phase of decommissioning (Reactor Periphery Facilities Dismantling Period). This report outlines the results obtained in the first phase of decommissioning of FUGEN.

Journal Articles

Distance information display system for supporting decommissioning work of nuclear power plants

Miki, Naoya*; Harazono, Yuki*; Ishii, Hirotake*; Shimoda, Hiroshi*; Koda, Yuya

International Electronic Journal of Nuclear Safety and Simulation (Internet), 9(2), p.162 - 171, 2018/12

Kyoto University reports on the distance information display system developed in collaboration between "Fugen" and Kyoto University. In the distance information display system, the worker can easily measure the distance of the object. In this presentation, we report the test results carried out with "Fugen" and the questionnaire results of the subjects.

Journal Articles

Investigation for dust behavior of cutting in air and cutting underwater by thermal cutting methods

Soejima, Goro; Iwai, Hiroki; Nakamura, Yasuyuki; Tsuzuki, Satoshi*; Yasunaga, Kazushi*; Kume, Kyo*

Heisei-29-Nendo Koeki Zaidan Hojin Wakasawan Enerugi Kenkyu Senta kenkyu Nempo, 20, P. 80, 2018/11

We investigated the behavior of the dust generated by Laser and Plasma-arc cutting underwater and in air aimed at the simulant material of reactor components (SUS304) and the pressure and calandria tube (Zr-2.5%Nb, Zry-2) of the prototype reactor "FUGEN".

Journal Articles

Pipe cutting method at high radiation area in FUGEN

Takiya, Hiroaki; Ishiyama, Masahiro; Tezuka, Masashi; Kitayama, Naoki

Proceedings of International Conference on Dismantling Challenges; Industrial Reality, Prospects and Feedback Experience (DEM 2018) (Internet), 8 Pages, 2018/10

In FUGEN, we had isolated the reactor core by cutting pipes of the periphery systems (e.g. reactor cooling system, heavy water system, and helium system) between 2015 and 2017, as preparation for dismantling the reactor core and taking some samples from the reactor core structures. There are three issues to be solved at this isolation work; (1) to shorten the working time at high radiation area which is 1-5mSv/h at air and 10mSv/h at contact, (2) to prevent tritium spreading to working area at cutting work because tritium air is existing with 20-30Bq/cm$$^{3}$$ inside of the heavy water system and helium system, and (3) to minimize the influence of contaminated fume for the accurate radioactivity evaluation of reactor core structure. In this study, considering these problems, we discussed the method for cutting the pipes of heavy water system and helium system at the high radiation area and carried out the pipe cutting in the way.

Journal Articles

Distance Information Display System using augmented reality for supporting decommissioning work

Miki, Naoya*; Harazono, Yuki*; Ishii, Hirotake*; Shimoda, Hiroshi*; Koda, Yuya

Proceedings of 2nd International Conference on Computer-Human Interaction Research and Applications (CHIRA 2018) (USB Flash Drive), p.134 - 140, 2018/09

In this study, in order to make measuring lengths of the objects and the gaps at NPPs more efficient, the Distance Information Display System was developed, which make it easy for the dismantling workers to measure them. The results showed that the Distance Information Display System developed in this study can be used easily with extremely simple operation by the dismantling workers at NPPs, and the workers can also measure the lengths in a short time.

Journal Articles

Adaptation for knowledge management to nuclear research fields

Taruta, Yasuyoshi; Yanagihara, Satoshi*; Iguchi, Yukihiro; Kitamura, Koichi; Tezuka, Masashi; Koda, Yuya

Chishiki Kyoso (Internet), 8, p.IV 2_1 - IV 2_12, 2018/08

no abstracts in English

Journal Articles

Development of program for improving generativity of staffs in nuclear power plant

Zhao, Q.*; Taruta, Yasuyoshi; Kobayashi, Shigeto*; Hashimoto, Takashi*

Chishiki Kyoso (Internet), 8, p.V 13_1 - V 13_2, 2018/08

no abstracts in English

Journal Articles

Research concept of decommissioning knowledge management for the Fugen NPP

Taruta, Yasuyoshi; Yanagihara, Satoshi*; Iguchi, Yukihiro; Kitamura, Koichi; Tezuka, Masashi; Koda, Yuya

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 6 Pages, 2018/07

The IAEA are developed the discussion for those situations and pointed out the importance of nuclear knowledge management. The nuclear knowledge management is developing a database as nuclear knowledge management. In recent years, the IAEA has also advanced knowledge taxonomies on nuclear accidents. These studies are attempts to appropriately arrange and utilize huge amounts of information. Even in nuclear facilities in Japan, it is pointed out that veteran staff aging and loss of knowledge and skill caused by retirement. Therefore, we created a prototype database system to utilize past knowledge and information for ATR Fugen. Now, there are few cases of past decommissioning that can be utilized. This study of pilot model concept revealed that it is not sufficient to just prepare a past data and information. This is what information other than the construction report requires the decommissioning and what kind of information should be gathered.

Journal Articles

The Initiative towards construction of Knowledge Management System in FUGEN Decommissioning Engineering Center

Tezuka, Masashi; Taruta, Yasuyoshi; Koda, Yuya

Dekomisshoningu Giho, (56), p.46 - 54, 2017/09

Implementation of decommissioning needs much plant information in period of Design, construction and operation. In addition, it is essential for efficient dismantling works to advance the technologies, data, lessons and learns, experiences and documents by getting through the decommissioning process. On the other hands, as workers who operated or maintained the plant are aging and retiring, their empirical knowledge has been lost. For the purpose of safety and reasonability of further decommissioning activities, Knowledge Management System (KMS) has been producing in FUGEN which is now under decommissioning. KMS is an initiative of human resources development and to pass on expertise and knowledge to the younger generations. The system based on the prototype of FUGEN aims a high versatility system available for further decommissioning facilities.

Journal Articles

Technology development on reactor dismantling and investigation of contamination in FUGEN

Soejima, Goro; Iwai, Hiroki; Nakamura, Yasuyuki; Hayashi, Hirokazu; Kadowaki, Haruhiko; Mizui, Hiroyuki; Sano, Kazuya

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 5 Pages, 2017/07

no abstracts in English

Journal Articles

Efforts in the "Fugen"; The History of up to termination of operation and Efforts of decommissioning measures

Morishita, Yoshitsugu

Denki Hyoron, 101(11), p.24 - 29, 2016/11

no abstracts in English

Journal Articles

Tritium decontamination of contaminated system with tritiated heavy water by drying treatment

Kadowaki, Haruhiko; Matsushima, Akira; Nakajima, Yoshiaki

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 6 Pages, 2016/06

Advanced thermal reactor "FUGEN" is a heavy water-moderated boiling light water-cooled pressure tube-type reactor. Because tritium had been generated in the heavy water during the reactor operation, the heavy water system and helium system were contaminated by tritium. The chemical form of the tritium was water molecule in FUGEN. Air-through drying and vacuum drying were applied to the system drying, and it was demonstrated that both methods were effective for drying treatment of heavy water in system. Helium system, low-contamination and non inclusion, could finish the vacuum drying rapidly. However, Heavy water purification system needed long period for drying treatment. The result showed that it needed long period to dry up if the objects include the adsorbent of water such as alumina pellet, resin and silica gel. But it can be accelerated by replacement absorbed heavy water to light water from the result of drying treatment of the rotary type dehumidifier.

JAEA Reports

Applicability test of abrasive water jet cutting technology for dismantling of the core internals of Fukushima Daiichi NPS

Nakamura, Yasuyuki; Iwai, Hiroki; Tezuka, Masashi; Sano, Kazuya

JAEA-Technology 2015-055, 89 Pages, 2016/03

JAEA-Technology-2015-055.pdf:17.54MB

It was reported that Fukushima Daiichi Nuclear Power Station (1F) had lost the cooling function of the reactor by the Tohoku Earthquake. It is assumed that the core internals became narrow and complicated debris structure mixed with the molten fuel. In consideration of the above situations, the AWJ cutting method, which has features of the long work distance and little heat effect for a material, has been developed for the removal of the molten core internals through cutting tests for 3 years since FY 2012. And it was confirmed that AWJ cutting method is useful for the removal of the core internals etc. The results in FY 2012 were reported in "R&D of the fuel debris removal technologies by abrasive water jet cutting technology (JAEA-Technology 2013-041)" and this report summarizes the results of FY 2012, 2013 and 2014 in this report. It was confirmed the possibility to apply the removal work of the fuel debris and the core internals.

JAEA Reports

A Study on optimization of dismantling scenarios in Fugen decommissioning project; Preliminary evaluation of dismantling scenario of the heat exchangers, etc.

Koda, Yuya; Tezuka, Masashi; Yanagihara, Satoshi*

JAEA-Technology 2015-050, 74 Pages, 2016/03

JAEA-Technology-2015-050.pdf:3.43MB

The implementation of the decommissioning work is accompanied by long-term period and considerable expense, so it is important that we make the most optimized work scenario in consideration of safety or the work and effectiveness. For this reason, we are studying selection method of the optimal work scenarios as a management index of the manpower and dose etc., in dismantling work for Fugen. In this report, results of a study shows the method of selecting the best scenarios for the heat exchangers of the reactor coolant purification system by evaluating execution multiple work scenarios, as well as evaluating the manpower and dose, etc., moreover by setting the importance of each evaluation item.

JAEA Reports

Applicability test of plasma cutting technology for dismantling of the core internals of Fukushima Daiichi NPS

Tezuka, Masashi; Nakamura, Yasuyuki; Iwai, Hiroki; Sano, Kazuya

JAEA-Technology 2015-047, 114 Pages, 2016/03

JAEA-Technology-2015-047.pdf:46.17MB

It was reported that Fukushima Daiichi Nuclear Power Plant had been lost the function of cooling the reactor by the Tohoku Earthquake. It is assumed that the original shapes of the internal core are not kept and the inside of the reactor makes so narrow in the space, however the fuel debris and the molten internal core will have to be removed for the decommissioning of 1F. We concerned the suppression of dross by optimization of cutting conditions, in using some moderated test pieces. And we can improve the cutting capability by heating the objects in advance. Moreover, it's possible that plasma arc cutting can cut off the mixed material the fuel debris and the molten internal core by using the cooperation cutting technique both the plasma arc and the plasma jet cutting. From these results, we have got the prospect that plasma cutting method can apply the removal of the fuel debris and the molten internal core.

JAEA Reports

The Development of the basic dismantling procedure of the reactor of FUGEN

Iwai, Hiroki; Nakamura, Yasuyuki; Mizui, Hiroyuki; Sano, Kazuya

JAEA-Technology 2015-046, 110 Pages, 2016/03

JAEA-Technology-2015-046.pdf:85.22MB

Advanced Thermal Reactor (ATR) FUGEN is a proto-type heavy water moderated, boiling light water cooled, pressure tube-type reactor with the thermal power of 557 MW and the electrical power of 165 MW. The reactor of FUGEN is classified into the core region and the shielding region. The core region is highly activated owing to the long term operation, and characterized by its tube-cluster construction that contains 224 fuel channels arranging both the pressure and the calandria tubes coaxially in each channel closely. And the shielding region surrounding the core region has the laminated structure composed of up to 150 mm thickness of carbon steel. The reactor is planning to be dismantled under water remotely in order to shield the radiation around the core and prevent airborne dust generated by the cutting, and firing of zirconium material. This paper reports on the result of development of the basic dismantling procedure of the reactor of FUGEN.

264 (Records 1-20 displayed on this page)