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JAEA Reports

Accident consequence analysis for JMTR as a decommission facilities

Nagata, Hiroshi; Omori, Takazumi; Maeda, Eita; Otsuka, Kaoru; Nakano, Hiroko; Hanakawa, Hiroki; Ide, Hiroshi

JAEA-Review 2023-033, 40 Pages, 2024/01

JAEA-Review-2023-033.pdf:1.39MB

Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. In order to submit the decommissioning plan to the Nuclear Regulation Authority, the type of accident assumed in the first stage of the decommissioning plan was selected, and the public exposure dose was evaluated. A fuel handling accident and a fire accident during storage of waste were selected as assumed accidents in the first stage of the decommissioning plan. An evaluation of the public exposure dose from the radioactive materials released into the atmosphere due to these accidents was estimated to be a maximum of 0.019 mSv (due to a fire accident during storage of waste). This estimated value was found to be sufficiently smaller than the judging criteria (5 mSv), and not to pose a significant risk of radiation exposure to the general public.

JAEA Reports

Evaluation on secondary radioactive contamination remaining in JMTR Reactor Facility

Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Hanakawa, Hiroki; Ide, Hiroshi

JAEA-Technology 2022-029, 55 Pages, 2023/02

JAEA-Technology-2022-029.pdf:2.77MB

Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. The activation activity of secondary radioactive contamination remaining in the reactor facility was evaluated in order to submit the decommissioning plan to the Nuclear Regulation Authority. Total activation activity was 2.73$$times$$10$$^{12}$$Bq after 12 years, 1.46$$times$$10$$^{12}$$Bq after 21 years, respectively. The system with high activation activity was the primary cooling system in JMTR. The relatively large radionuclide was H-3, Fe-55, Co-60, Ni-63, Sr-90 and Cs-137. The radioactivity level was classified based on the values of the obtained radioactivity concentration. As a result, the primary cooling system and the drain system was classified as L2, and others was classified as L3. The nuclide that affected classification result was only Co-60 in irradiation facility of HR-1 and OSF-1. H-3, Co-60, Sr-90, Cs-137 and so on were affected classification in other system. When treating and disposing of radioactive waste, evaluation will be carried out based on appropriate methods.

JAEA Reports

Evaluation on activation activity of radioactive materials remaining in JMTR Reactor Facility

Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Ide, Hiroshi

JAEA-Technology 2022-017, 113 Pages, 2022/08

JAEA-Technology-2022-017.pdf:6.17MB

Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. The activation activity of radioactive materials remaining in the reactor facility was evaluated in order to submit the decommissioning plan to the Nuclear Regulation Authority. Total activation activity was 9.3$$times$$10$$^{18}$$ Bq after the permanent shutdown of reactor, 2.7$$times$$10$$^{16}$$ Bq after 21 years, 1.0$$times$$10$$^{16}$$ Bq after 40 years and 2.4$$times$$10$$^{15}$$ Bq after 100 years. The structure with high activation activity was the core structural materials in JMTR such as beryllium frame, aluminum reflector, etc., and the material was stainless steel, beryllium, etc. The ratio of nuclides to the total amount of activated radioactivity was highest in H-3 until about 40 years after the reactor shutdown, and then in Ni-63. For reference, the radioactivity level was classified based on the results of the obtained radioactivity concentration. The ratio of the weight of each radioactivity level to the total weight was 0.3-0.4% (10-13t) for L1, 0.0-0.4% (0-14t) for L2, 1.0-1.2% (32-39t) for L3 and 98.0-98.7% (about 3200t) for CL until 100 years after the reactor shutdown. It was found that those classified as CL account for more than 90% of the total. When treating and disposing of radioactive waste, evaluation will be carried out based on appropriate methods, including evaluation results of secondary pollutants.

Journal Articles

Radiochemical research for the advancement of $$^{99}$$Mo/$$^{rm 99m}$$Tc generator by (n, $$gamma$$) method, 4

Fujita, Yoshitaka; Seki, Misaki; Ngo, M. C.*; Do, T. M. D.*; Hu, X.*; Yang, Y.*; Takeuchi, Tomoaki; Nakano, Hiroko; Fujihara, Yasuyuki*; Yoshinaga, Hisao*; et al.

KURNS Progress Report 2021, P. 118, 2022/07

no abstracts in English

Journal Articles

Development of stabilization treatment technology for radioactive aluminum waste

Seki, Misaki; Fujita, Yoshitaka; Fujihara, Yasuyuki*; Zhang, J.*; Yoshinaga, Hisao*; Sano, Tadafumi*; Hori, Junichi*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; et al.

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 29(1), p.2 - 9, 2022/06

no abstracts in English

JAEA Reports

Investigation on soundness of JMTR Facility piping by ultrasonic thickness measurement

Omori, Takazumi; Otsuka, Kaoru; Endo, Yasuichi; Takeuchi, Tomoaki; Ide, Hiroshi

JAEA-Review 2021-015, 57 Pages, 2021/11

JAEA-Review-2021-015.pdf:6.3MB

The JMTR reactor facility was selected as a decommissioning one in the Medium/Long-Term Management Plan of JAEA Facilities formulated on April 1, 2017. Therefore, the decommissioning plan was submitted to Nuclear Regulation Authority on September 18, 2019, and the approval was obtained on March 17, 2021 after two amendments. Currently, preparations for decommissioning are underway. The JMTR reactor facility has been aged for more than 50 years since the first criticality in March 1968. However, some of the water piping systems has not been updated since its construction, and there is a possibility of pipe wall thinning due to corrosion, etc. Therefore, the integrity of the water piping was investigated for the facilities that circulate cooling water and pump radioactive liquid waste. In this investigation, the main circulation system of the reactor primary cooling system, the pool canal circulation system, the CF pool circulation system, the drainage system of the liquid waste disposal system, and the hydraulic rabbit irradiation system of the main experimental facility were measured for the pipe wall thickness using the Ultrasonic Thickness Measurement (UTM) method. These values satisfied the technical standards for research and test reactor facilities. No loss of integrity is expected to occur during the upcoming decommissioning period. In the future, we will periodically confirm that there is no wall thinning in the piping of the cooling water circulation and the water transmission system during the decommissioning period by using this result as basic data.

Journal Articles

Development of the treatment method for difficult wastes aimed at decommissioning of JMTR; Structural materials of reactor and used ion-exchange resins

Seki, Misaki; Nakano, Hiroko; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Takeuchi, Tomoaki; Ide, Hiroshi; Tsuchiya, Kunihiko

Dekomisshoningu Giho, (62), p.9 - 19, 2020/09

Japan Materials Testing Reactor (JMTR) has been contributing to various research and development activities such as the fundamental research of nuclear materials/fuels, safety research and development of power reactors, and radioisotope production since the beginning of the operation in 1968. JMTR, however, was decided as a one of decommission facilities in April 2017 and it is taken an inspection of a plan concerning decommissioning because the performance of JMTR does not confirm with the stipulated earthquake resistance. As aluminum and beryllium are used for the core structural materials in JMTR, it is necessary to establish treatment methods of these materials for the fabrication of stable wastes. In addition, a treatment method for the accumulated spent ion-exchange resins needs to be examined. This report describes the overview of these examination situations.

Journal Articles

Research on activation assessment of a reactor structural materials for decommissioning, 2

Seki, Misaki; Ishikawa, Koji*; Sano, Tadafumi*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Hanakawa, Hiroki; Ide, Hiroshi; Tsuchiya, Kunihiko; Fujihara, Yasuyuki*; et al.

KURNS Progress Report 2019, P. 279, 2020/08

no abstracts in English

Journal Articles

Research on activation assessment of a reactor structural materials for decommissioning

Seki, Misaki; Ishikawa, Koji*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Hanakawa, Hiroki; Ide, Hiroshi; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; et al.

KURNS Progress Report 2018, P. 257, 2019/08

no abstracts in English

Journal Articles

Status of JMTR decommissioning plan formulation, 2

Otsuka, Kaoru; Ide, Hiroshi; Nagata, Hiroshi; Omori, Takazumi; Seki, Misaki; Hanakawa, Hiroki; Nemoto, Hiroyoshi; Watanabe, Masao; Iimura, Koichi; Tsuchiya, Kunihiko; et al.

UTNL-R-0499, p.12_1 - 12_8, 2019/03

no abstracts in English

Journal Articles

Preliminary analysis for demolition of secondary cooling system and pool canal cycling system secondary piping

Hanakawa, Hiroki; Kawamata, Takanori; Ogasawara, Yasushi; Otsuka, Kaoru; Omori, Takazumi; Ide, Hiroshi; Tsuchiya, Kunihiko

UTNL-R-0499, p.11_1 - 11_7, 2019/03

no abstracts in English

Journal Articles

Status of JMTR decommissioning plan formulation

Otsuka, kaoru; Hanakawa, Hiroki; Nagata, Hiroshi; Omori, Takazumi; Takeuchi, Tomoaki; Tsuchiya, Kunihiko

UTNL-R-0496, p.13_1 - 13_11, 2018/03

no abstracts in English

Oral presentation

Examination of stabilization treatment method of radioactive aluminum waste

Seki, Misaki; Ishikawa, Koji*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Suzuki, Yumi*; Tanaka, Atsushi*; Kawakami, Tomohiko*; Ide, Hiroshi; Tsuchiya, Kunihiko

no journal, , 

no abstracts in English

Oral presentation

Examination of stabilization treatment method of radioactive aluminum waste, 2; Removal properties of impurities in the stabilization treatment process

Seki, Misaki; Ishikawa, Koji*; Fujihara, Yasuyuki*; Sano, Tadafumi*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Ide, Hiroshi; Hori, Junichi*; Tsuchiya, Kunihiko

no journal, , 

no abstracts in English

Oral presentation

Development of exposure reduction technologies by digitalization of environment and radioactive source distribution, 6; Computational method validation and effectiveness evaluation of an estimation system of radiation sources and dose rates

Aoki, Yuto; Ito, Rintaro; Kitamura, Akihiro; Omori, Takazumi; Taniguchi, Tatsuro; Ide, Hiroshi

no journal, , 

In this report, we present the validation results of the radiation source inverse estimation computation method and the effectiveness evaluation method of the "estimation system of radiation sources and dose rates" developed by JAEA. As for the validation test, the JMTR was used as the evaluation site, and the results of radiation source inverse estimation computations were compared with measured data. As a result, it was confirmed that the hot spot could be estimated approximately well. As for the effectiveness evaluation, the test field to be established at the NARREC and at the JMTR were used as the evaluation sites, and the effectiveness evaluation items such as the functions of each tool and the process of the system were summarized.

Oral presentation

LASSO reconstruction scheme to predict radioactive source distributions inside reactor building rooms; Evaluation activities

Aoki, Yuto; Ito, Rintaro; Kitamura, Akihiro; Machida, Masahiko; Suzuki, Masahiro; Omori, Takazumi; Taniguchi, Tatsuro; Ide, Hiroshi

no journal, , 

Patent

放射性アルミニウム廃棄物処理方法

関 美沙紀; 井手 広史; 永田 寛; 大塚 薫; 大森 崇純

石川 幸治*; 川上 智彦*; 田仲 睦*; 鈴木 祐未*

JP, 2019-149027  Patent licensing information  Patent publication (In Japanese)

【課題】放射性アルミニウム廃棄物に含まれるアルミニウムを、化学的に安定である酸化アルミニウムに変換する放射性アルミニウム廃棄物処理方法を提供する。 【解決手段】本発明に係る放射性アルミニウム廃棄物処理方法は、放射性アルミニウム廃棄物に含まれるアルミニウムを酸化アルミニウムに変換する放射性アルミニウム廃棄物処理方法であって、放射性アルミニウム廃棄物を、アルカリ金属の水酸化物の水溶液で溶解し、不純物を沈殿させる溶解工程(工程S1)と、前記溶解工程で得られた溶液を、固液分離し不純物を除去する第1固液分離工程(工程S2)と、前記第1固液分離工程で得られた溶液に酸性水溶液を添加し、水酸化アルミニウムを主成分とする固体を沈殿させる中和工程(工程S3)と、前記中和工程で得られた溶液を、固液分離し固体を得る第2固液分離工程(工程S4)と、前記第2固液分離工程で得られた固体を焼成する焼成工程(工程S6)と、を含むことを特徴とする。

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