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Yamamoto, Keisuke; Nakagawa, Takuya; Shimojo, Hiroto; Kijima, Jun; Miura, Daiya; Onose, Yoshihiko*; Namba, Koji*; Uchida, Hiroaki*; Sakamoto, Kazuhiko*; Ono, Chika*; et al.
JAEA-Technology 2024-019, 211 Pages, 2025/02
The uranium enrichment facilities at the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency (JAEA) were constructed sequentially to develop uranium enrichment technology with centrifugal separation method. The developed technologies were transferred to Japan Nuclear Fuel Limited until 2001. And the original purpose has been achieved. Wastewater Treatment Facility, one of the uranium enrichment facilities, was constructed in 1976 to treat radioactive liquid waste generated at the facilities, and it finished the role in 2008. In accordance with the Medium/Long-Term Management Plan of JAEA Facilities, interior equipment installed in this facility had been dismantled and removed since November 2021 to August 2023. This report summarizes the findings obtained through the work related to the contamination inspection methods cancellation the controlled area of Wastewater Treatment Facility from September 2023 to March 2024.
Sano, Kyohei; Tameta, Yuito; Akuzawa, Tadashi; Kato, Soma; Takano, Yugo*; Akiyama, Kazuki
JAEA-Technology 2024-018, 68 Pages, 2025/02
High Active Solid Waste Storage Facility (HASWS) at the Tokai Reprocessing Plant (TRP) is a facility for storing highly radioactive solid waste generated from the reprocessing operation. Wet cells in HASWS store hull cans that contain fuel cladding tubes (hull) and fuel end pieces remained after the spent nuclear fuel shearing and dissolving, as well as used filters and contaminated equipment. Dry cells in HASWS store analytical waste containers that contain waste jugs and the other waste generated from analytical operation of samples in TRP. Since HASWS does not have waste recovery equipment from the cells, it is considered that recovery equipment to be installed. In the wet cells, methods of recovery wet-stored waste are being considered that utilize a ROV, which has been used in decommissioning in the UK, and a lifter, which is used in the marine industry to float and transport items sinking to the bottom of the sea. To confirm the feasibility of the recovery method that combines the functions of the ROV and the lifter, tests for removing waste were conducted in steps that came closer to the real environment: a "unit test" to confirm the functions required of each of the ROV and the lifter, a "combination test" to combine the ROV and the lifter to move waste underwater, and a "comprehensive test" to retrieve waste in an environment simulating the hull storage facility. Through this test, the ROV and the lifter were able to perform a series of tasks required to recovery waste - cutting the wires attached to the waste, attaching a lifter to the waste, moving the waste to under the opening, and attaching the recovery device to the moved waste - in series, confirming the feasibility of the method for recovery wet-stored waste using the ROV and the lifter.
Owada, Mitsuhiro; Nakanishi, Yoshiki; Murokawa, Toshihiro; Togashi, Kota; Saito, Katsunori; Nonaka, Kazuharu; Sasaki, Yu; Omori, Koji; Chinone, Makoto; Yasu, Hideto; et al.
JAEA-Technology 2024-013, 221 Pages, 2025/02
The uranium enrichment facilities at the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency (JAEA) were constructed sequentially to develop uranium enrichment technology with centrifugal separation method. The developed technologies were transferred to Japan Nuclear Fuel Limited until 2001. And the original purpose has been achieved. Wastewater Treatment Facility, one of the uranium enrichment facilities, was constructed in 1976 to treat radioactive liquid waste generated at the facilities, and it finished the role in 2008. In accordance with the Medium/Long-Term Management Plan of JAEA Facilities, interior equipment installed in this facility had been dismantled and removed since November 2021 to August 2023. This report summarizes the findings obtained through the work related to dismantling and removal of interior equipment for decommissioning of Wastewater Treatment Facility.
Shimada, Asako; Tsukahara, Takehiko*; Nomura, Masao*; Takeda, Seiji
Journal of Radioanalytical and Nuclear Chemistry, 333(12), p.6297 - 6310, 2024/12
Times Cited Count:0 Percentile:0.00(Chemistry, Analytical)Koda, Yuya; Nakamura, Yasuyuki; Iguchi, Yukihiro*; Yanagihara, Satoshi*
Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 10 Pages, 2024/11
"Fugen" has been proceeding with decommissioning work since receiving approval for the decommissioning plan in 2008, and is currently in the second step of dismantling the reactor peripheral equipment. In decommissioning, project management is important to select strategies and optimize processes, waste, safety, costs, etc. In Japan, it is expected that decommissioning work for nuclear facilities will become more serious in the future, and the knowledge and project management data obtained from the decommissioning work carried out at "Fugen" to date will be useful for planning. Since the dismantling and removal of the main turbine equipment and the peripheral equipment in preparation for the reactors have been completed so far, the actual data has been organized and analyzed and compiled into unit work coefficients. The project management data, collected during the decommissioning work carried out at "Fugen" is organized and calculated as a unit work coefficient.
Sato, Hinata; Mori, Amami; Kuno, Sorato; Horigome, Kazushi; Goto, Yuichi; Yamamoto, Masahiko; Taguchi, Shigeo
JAEA-Technology 2024-011, 56 Pages, 2024/10
Flush-out, which recovers remaining nuclear materials in the process and transfer it to a highly radioactive liquid waste storage tank, has been performed at main plant of Tokai Reprocessing Plant. The flush-out has been composed from three steps: first step is to remove of spent fuel sheared powder, second step is to collect plutonium solution stored in the process, and third step is to convert uranium solution into uranium trioxide powder. The first step of flush-out activity has been completed in 2022. Second and third steps of flush-out have been completed from March 2023 to February 2024. Process control analysis has been performed for operation of the facility, and material accountancy analysis has been performed to control the accountancy of nuclear materials. In addition, related analytical work such as pretreatment for transporting inspection samples for safeguards analysis laboratories in IAEA has been also performed. This report describes results of analytical work performed in collections of plutonium and uranium solutions in second and third steps of the flush-out, including calibration of analytical equipment, waste generation, and education and training of analytical operator.
Shimada, Taro; Kabata, Kazuhiko*; Takai, Shizuka; Takeda, Seiji
Proceedings of Probabilistic Safety Assessment and Management & Asian Symposium on Risk Assessment and Management (PSAM17 & ASRAM2024) (Internet), 10 Pages, 2024/10
Nuclear regulatory inspections during the decommissioning phase of nuclear power plants need to be conducted based on risk information, but a method for quantitatively evaluating this risk has not been developed. Therefore, in this study, an event tree of accident events that may occur in the decommissioning phase has been developed, and a code DecAssess-R has been developed to evaluate the exposure risk, which is expressed as the product of the exposure dose and probability of occurrence according to the accident sequence for each equipment to be dismantled. In particular, we have taken into account that the amount of mobile radioactivity that may accumulate in HEPA filters and be released all at once during an accident varies temporally and spatially with the progress of dismantling work. The event tree was constructed based on the results of the survey of domestic and international trouble information in the decommissioning phase and similar dismantling and replacement operations. The event frequencies are based on information from general industries, and the event progression probabilities are based on the equipment failure probabilities in the operation phase. The safety functions to be reduced with the progress of decommissioning were taken into account according to the dismantling work schedule. As a result of the exposure risk assessment for dismantling operations of BWRs and PWRs in Japan, the exposure risk for fire events was the largest. In particular, the exposure risk was greater for the dismantling of components in the reactor building by airborne cutting than for the dismantling of reactor internals, which has the greatest radioactivity in underwater dismantling.
Sato, Nobuaki*; Kameo, Yutaka; Sato, Soichi; Kumagai, Yuta; Sato, Tomonori; Yamamoto, Masahiro*; Watanabe, Yutaka*; Nagai, Takayuki; Niibori, Yuichi*; Watanabe, Masayuki; et al.
Introduction to Dismantling and Decommissioning Chemistry, 251 Pages, 2024/09
This book focuses on the dismantling and decommissioning of nuclear facilities and reactors that have suffered severe accidents. In Part 1, we introduce basic aspects ranging from fuel chemistry, analytical chemistry, radiation chemistry, corrosion, and decontamination chemistry to waste treatment and disposal. Then, Part 2 covers the chemistry involved in the decommissioning of various nuclear facilities, and discusses what chemical approaches are necessary and possible for the decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Plants, how decommissioning should be carried out, and what kind of research and development and also human resource development are required for this.
Yokochi, Masaru; Sasaki, Shunichi; Yanagibashi, Futoshi; Asada, Naoki; Komori, Tsuyoshi; Fujieda, Sadao; Suzuki, Hisanori; Takeuchi, Kenji; Uchida, Naoki
Nihon Hozen Gakkai Dai-20-Kai Gakujutsu Koenkai Yoshishu, p.1 - 4, 2024/08
Tokai Reprocessing Plant, which is shifted to decommissioning stage, stores large amount of high-level radioactive liquid waste (HLLW) generated by reprocessing of spent nuclear fuels in High-level Active Waste facility (HAW). Radioactive risk related to HLLW has been concentrated in HAW until the completion of vitrification. Natural disasters such as earthquake may damage cooling function of HAW. Therefore, HAW must improve earthquake resistance, as exchanging the ground around HAW facility and pipe trench by concrete. This earthquake resistance construction starts from July of 2020 and completed in March 2024. This report summarizes the construction work and describes the inspection results after the construction.
Nakamura, Shoji; Endo, Shunsuke; Rovira Leveroni, G.; Kimura, Atsushi; Shibahara, Yuji*
KURNS Progress Report 2023, P. 46, 2024/07
The present work is an attempt to measure the thermal-neutron capture cross-sections for some nuclides which are of importance in decommissioning to evaluate produced radioactivity. This work selected some of objective nuclides for decommissioning, such as Fe,
Er and
Hf, and measured thermal-neutron capture cross-sections for these nuclides by a neutron activation method at Kyoto University Research Reactor. The present results were obtained as follows:1.23
0.03 barn for
Fe(n,
)
Fe reaction, 8.19
0.35 barn for
Er(n,
)
Er reaction and 13.57
0.14 barn for
Hf(n,
)
Hf reaction. As a by-product, the measurement of Hf sample also presented 0.427
0.006 barn for
Hf(n,
)
Hf reaction. It has been revealed that the data adopted in an evaluated data library differ from the present results by more than experimental uncertainties.
Koda, Yuya; Matsuno, Hiroki; Matsushima, Akira; Kubota, Shintaro; Toda, Keisuke; Nakamura, Yasuyuki
JAEA-Review 2024-003, 38 Pages, 2024/06
"Fugen Decommissioning Engineering Center", in planning and carrying out our decommissioning technical development, organizes "Technical special committee on Fugen decommissioning" which consists of the members well-informed, aiming to make good use of Fugen as a place for technological development which is opened domestic and international, as the central place in research and development base of Fukui prefecture, and to utilize the outcome in our decommissioning to the technical development effectively. This report consists of presentation paper are "The current status of Fugen decommissioning", "Regarding dismantling and decontamination of steam drums", "Knowledge of radiation management in dismantling contaminated equipment", "Achievements and considerations for identifying and separating contaminated parts of nonradioactive waste" and "Regarding technology development plans for nuclear reactor dismantling" which is presented in the 41st Technical Special Committee on Fugen Decommissioning.
Taruta, Yasuyoshi; Aratani, Kenta; Miyashita, Shinichi; Tomoda, Koichi; Fujiwara, Wataru
JAEA-Review 2024-002, 31 Pages, 2024/06
"Fugen Decommissioning Engineering Center", in planning and carrying out our decommissioning technical development, organizes "Technical special committee on Fugen decommissioning" which consists of the members well-informed, aiming to make good use of Fugen as a place for technological development which is opened domestic and international, as the central place in research and development base of Fukui prefecture, and to utilize the outcome in our decommissioning to the technical development effectively. This report consists of presentation paper are "The current status of Fugen decommissioning", "Comparative consideration of dismantling method for fuel exchanger", "Status of consideration for installation of backup power supply equipment" and "Streamlining decommissioning operations by utilizing digital technology" which is presented in the 40th Technical Special Committee on Fugen Decommissioning.
Shimada, Taro; Shimada, Asako; Miwa, Kazuji*; Nabekura, Nobuhide*; Sasaki, Toshihisa*; Takai, Shizuka; Takeda, Seiji
JAEA-Research 2024-004, 115 Pages, 2024/06
We have studied the confirmation method for the termination of decommissioning of nuclear facilities based on the site release flow presented at the Nuclear Regulation Authority (NRA) study team meeting in 2017, and organized it as a procedure for the site soil. First, the effects of radionuclides released by the Fukushima Daiichi Nuclear Power Station accident are excluded as background radioactivity, and the distribution of radioactivity concentration of facility origin on the site is evaluated using geostatistical method kriging. Then, considering the downstream transport of sediment by surface runoff generated by rainfall that exceeds the infiltration capacity of the ground surface, a series of evaluation procedures are presented to evaluate the exposure dose reflecting future changes from the evaluated radioactivity concentration distribution, and a comparison method with the assumed 0.01 mSv/y as a dose criterion is proposed. Furthermore, an example of the procedure for evaluating the distribution of contamination in the subsurface was also presented for the case where groundwater is affected.
Otsuka, Kaede*; Shimada, Taro; Takahashi, Hiroaki*
NTEC-2024-3001, p.1 - 17, 2024/05
Based on the Act on Regulation of Nuclear Source Materials, Nuclear Fuel Materials and Reactors (Act No. 166 of 1957), licensee shall develop decommissioning plan and submit it to the Nuclear Regulation Authority (hereinafter referred to as "NRA") when a nuclear power reactor or nuclear power business is to be decommissioned. When the decommissioning is completed, the result shall be confirmed by the NRA as being in compliance with the "criteria specified by the NRA", but no specific method has been established. As a result of Integrated Regulatory Review Service which was conducted in 2016, the International Atomic Energy Agency advised that criteria be established for site release after the completion of decommissioning. In response of the advice, the NRA issued "The guide for determining the condition of site soil etc." in 2022. To properly implement the Guide, it was considered that a specific method for collecting samples should be identified. Moreover, the Guide does not cover facilities affected by the fallout from the TEPCO's Fukushima Daiichi Nuclear Power Plant accident (hereinafter referred to as "1F fallout"). The Secretariat of the NRA had commissioned the research to the Japan Atomic Energy Agency (hereinafter referred to as "JAEA") between 2019 and 2022, in order to develop determination methods of condition of soil etc., of the decommissioning facility affected by 1F fallout. This report proposes the determination methods of condition of soil etc. on confirmation of completion of decommissioning, based on the result of commissioning research conducted by the JAEA.
Hirako, Kazuhito; Sawazaki, Hiromasa; Goto, Takehiro
Hozengaku, 23(1), p.9 - 13, 2024/04
The decommissioning of the prototype fast breeder reactor Monju, which started in 2018, has completed the extraction and solidification of the secondary sodium and the removal of the fuel body, which are the main processes in the first stage of decommissioning, and has moved to the second stage of decommissioning from 2023. This report provides an overview of the Monju decommissioning programme and the first stage of Monju decommissioning as "Trends of Monju decommissioning, Part 1". The actions in the second stage of Monju decommissioning will be explained in the next issue, including the outline and the review of the performance maintenance facilities that will change with the progress of the decommissioning and the construction of the maintenance programme accordingly.
Nakano, Hiroko; Fujinami, Kyoko; Yamaura, Takayuki; Kawakami, Jun; Hanakawa, Hiroki
JAEA-Review 2023-036, 33 Pages, 2024/03
A practical training course using the JMTR (Japan Materials Testing Reactor) and other research infrastructures was held from November 29 to December 2 in 2021 for Asian young researchers and engineers. This course was adopted as International Youth Exchange Program in Science (SAKURA SCIENCE Exchange Program) which is the project of the Japan Science and Technology Agency, and this course aims to enlarge the number of high-level nuclear researchers/engineers in Asian countries which are planning to introduce a nuclear power plant, and to promote the use of facilities in future. In this year, from the viewpoint of preventing the spread of COVID-19 infection, it was decided to hold the event online. 53 young researchers and engineers joined the course from 6 countries. In FY2022, training programs with invitations were held due to the easing of restrictions on entry into Japan from overseas. 7 young researchers and engineers from4 Asian countries participated in the training from February 1 to 10, 2023. The common curriculum in the training course of FY2021 and FY2022 included lectures on nuclear energy, irradiation testing, safety management, JMTR decommissioning plan, etc. In the online session, conducted in FY2021, information exchange on the energy situation in each country was conducted. On-site training conducted in FY2022, included practical training on operation using simulations, environmental monitoring, etc. and facility tours of the JMTR, etc. Many participants could join the online training course, they created a diversity of expertise and made lively discussions during the information exchange. On-site training, while limited in number of participants, provided a good opportunity for personnel exchange through practical training and face-face communication. It is desirable to hold on-site training as long as circumstances permit. This report summarizes the training conducted in FY2021 and FY2022.
Takiya, Hiroaki
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 30(2), p.66 - 71, 2023/12
A half of unclear facilities in Japan Atomic Energy Agency (JAEA) has been transferred to decommissioning phase because of achieving the expected goals for the research and development, aging of buildings and equipment, etc. JAEA must safely, efficiently, and rationally implement back-end measures related to decommissioning, from the dismantling of nuclear facilities to the processing and disposal of radioactive waste generated by dismantling. The decommissioning and radioactive waste management head office collaborates with each JAEA's site to plan and promote comprehensive back-end measures and promote near surface disposal of low-level radioactive waste generated from research, medical, and industrial facilities, and to work on research and development aimed at solving common issues related to back-end measures, human resource development, etc. Since decommissioning is a long-term project, it is important to secure specialized human resources for the future. This article presents a summary of human resource development for decommissioning.
Machida, Masahiko; Iwata, Ayako; Yamada, Susumu; Otosaka, Shigeyoshi*; Kobayashi, Takuya; Funasaka, Hideyuki*; Morita, Takami*
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(4), p.119 - 139, 2023/11
We estimate monthly discharged inventory of Sr from port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2022 by using the Voronoi tessellation method inside the port, following the monitoring of
Sr sea water radioactivity concentration inside the port. The results suggest that the closure of sea side impermeable wall is the most effective for the reduction of discharged one. In addition, the results roughly reveal the monthly discharged inventory required to observe visible enhancement of the sea radioactivity concentration from the background level in each area. Such outcome is significant for considering environmental impacts on the planned future releasing of the treated water accumulated in 1F site.
Nakazawa, Osamu; Takiya, Hiroaki; Murakami, Masashi; Donomae, Yasushi; Meguro, Yoshihiro
JAEA-Review 2023-012, 6 Pages, 2023/08
The selection of back-end technology development issues to be prioritized and their schedule of the Japan Atomic Energy Agency (JAEA) have been put together as the "Strategic Roadmap for Back-end Technology Development." The results of questionnaires on development technologies (seeds) and technical issues (needs) within JAEA conducted in FY2022 were reflected in the selection. The issues were extracted from among those that match the seeds and needs, from the perspective of early implementation in the work front and the perspective of common issues, and nine themes were selected. We will build a cross-organizational implementation framework within JAEA and aim to implement the development results in the work front as well as social implementation.
Sato, Yuji; Miyamoto, Yuta; Awatani, Yuto; Yamamoto, Kosuke; Hatakeyama, Takumi
JAEA-Review 2023-002, 59 Pages, 2023/08
"Fugen Decommissioning Engineering Center", in planning and carrying out our decommissioning technical development, organizes "Technical special committee on Fugen decommissioning" which consists of the members well-informed, aiming to make good use of Fugen as a place for technological development which is opened domestic and international, as the central place in research and development base of Fukui prefecture, and to utilize the outcome in our decommissioning to the technical development effectively. This report consists of presentation paper are "Achievements and Considerations for Sampling and Analysis of Reactor Core Components", "Treatment of liquid scintillator waste liquid" and "Results and issues of rationalization of decontamination related to the clearance and considerations related to surface contamination monitoring" which is presented in the 39th Technical Special Committee on Fugen Decommissioning.