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Sakasegawa, Hideo; Nomura, Mitsuo; Sawayama, Kengo; Nakayama, Takuya; Yaita, Yumi*; Yonekawa, Hitoshi*; Kobayashi, Noboru*; Arima, Tatsumi*; Hiyama, Toshiaki*; Murata, Eiichi*
Progress in Nuclear Energy, 153, p.104396_1 - 104396_9, 2022/11
Times Cited Count:1 Percentile:0.00(Nuclear Science & Technology)When dismantling centrifuges in uranium-enrichment facilities, decontamination techniques must be developed to remove uranium-contaminated surfaces of dismantled parts selectively. Dismantled uranium-contaminated parts can be disposed of as nonradioactive wastes or recycled after decontamination appropriate for clearance. previously, we developed a liquid decontamination technique using acidic electrolyzed water to remove uranium-contaminated surfaces. However, further developments are still needed for its actual application. Dismantled parts have various uranium-contaminated surface features due to varied operational conditions, inhomogeneous decontamination using iodine heptafluoride gas, and changes in long-term storage conditions after dismantling. Here, we performed liquid decontamination on specimens with varying uranium-contaminated surfaces cut from a centrifuge made of low-carbon steel. From the results, the liquid decontamination can effectively remove the uranium-contaminated surfaces, and radioactive concentrations fell below the target value within twenty minutes. Although the required time should also depend on dismantled parts' sizes and shapes in their actual application, we demonstrated that it could be an effective decontamination technique for uranium-contaminated steels of dismantled centrifuges.
Sakasegawa, Hideo
ENEKAN, 20, p.20 - 23, 2022/07
no abstracts in English
Yagi, Naoto; Mita, Yutaka; Kanda, Nobuhiro
Dekomisshoningu Giho, (61), p.2 - 11, 2020/03
Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency has been conducting research and development on uranium exploration, uranium mining, uranium refining / conversion, and uranium enrichment. Currently, our Center has completed its initial mission and is conducting decommissioning of facilities used for R&D, and R&D for decommissioning. Of the three main facilities of our Center, the refining conversion facility and the enrichment engineering facility have already begun dismantling equipment in the facilities. The uranium enrichment demonstration plant is in the process of applying for a decommissioning plan. This report provides an overview of the current status of our Center's decommissioning.
Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*; Sugitsue, Noritake
Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 8 Pages, 2019/05
Clearance of contaminated metal is important for recycling and volume reduction of radioactive waste. Among applicable decontamination technologies, immersion method with ultrasonic cleaning is considered to be effective for metal materials having various shapes. in this study is to demonstrate decontamination of carbon steel contaminated by uranium hexafluoride to the target level for clearance (less than 0.04 Bq/cm), and minimize secondary waste. In this test, acidic electrolytic water, dilute hydrochloric acid, dilute sulfuric acid and ozone water with various pH and redox potential were used as decontamination solutions to be tested. We found that acidic electrolytic water is effective solution for decontamination of carbon steel contaminated by uranium hexafluoride. It could be decontaminate less than target level for clearance, and reduced secondary waste relatively.
Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 10(3), p.194 - 204, 2011/09
This paper shows the investigation result of the reasonable IF treatment condition and the full-scale examination result by using this IF
treatment condition. As a result, it could confirm 99% of the intermediate uranium fluoride in the cascade was removed for 60 days. Further, this paper shows the investigation result of the reasonable IF
production condition and the full-scale examination result. As a result, it could be proved 3,355 kg-IF
gas was produced.
Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 10(3), p.205 - 215, 2011/09
This paper shows we constructed theoretically the methodology using the -ray measured outside the gas centrifuge and MCNP code. Further, this paper shows the investigation result of the reasonable separation condition and the full-scale examination result. As a result, it could be proved IF
weight of 86% can separate and refine from UF
and IF
mixture gas.
Hyakutake, Toru*; Muto, Akinori*; Sasakura, Mariko*; Minowa, Hirotsugu*; Suzuki, Kazuhiko*; Yokoyama, Kaoru; Takahashi, Nobuo; Hata, Haruhi; Sugitsue, Noritake
JAEA-Research 2010-032, 32 Pages, 2010/10
System decontamination has been generally carried out with the aim of reducing the amount of radioactive waste generated and minimizing human exposure to radiation released from nuclear fuel facilities. At the Ningyo-Toge Environmental Engineering Center, metal surfaces that are contaminated by uranium are dry decontaminated by using iodine heptafluoride (IF) as a system decontaminator. In this dry decontamination technique, a chemical reaction occurs between the uranium compound attached to the metal surface and IF
. Only a few studies have been carried out on the decontamination efficiency, mechanism, level, etc. of dry decontamination techniques that use a decontamination gas. Therefore, the generalization of dry decontamination technique was assessed by a numerical method using decontamination data obtained at the Ningyo-Toge Environmental Engineering Center. A concrete analytical content is a depositing of Uranium Hexafluoride.
Hyakutake, Toru*; Muto, Akinori*; Sasakura, Mariko*; Minowa, Hirotsugu*; Suzuki, Kazuhiko*; Yokoyama, Kaoru; Takahashi, Nobuo; Tsunashima, Yasumichi; Ema, Akira; Sugitsue, Noritake
JAEA-Research 2009-047, 92 Pages, 2010/01
System decontamination has been generally carried out with the aim of reducing the amount of radioactive waste generated and minimizing human exposure to radiation released from nuclear fuel facilities. At the Ningyo-Toge Environmental Engineering Center, metal surfaces that are contaminated by uranium are dry decontaminated by using iodine heptafluoride (IF) as a system decontaminator. In this dry decontamination technique, a chemical reaction occurs between the uranium compound attached to the metal surface and IF
. Only a few studies have been carried out on the decontamination efficiency, mechanism, level, etc. of dry decontamination techniques that use a decontamination gas. Therefore, the generalization of dry decontamination techniques is required. In the present study, the efficiency of a dry decontamination technique was assessed by a numerical method using decontamination data obtained at the Ningyo-Toge Environmental Engineering Center.
Ema, Akira; Sugitsue, Noritake; Zaitsu, Tomohisa
Proceedings of 2007 ANS Topical Meeting on Decommissioning, Decontamination and Reutilization & Technology Expo (DD&R 2007) (CD-ROM), 3 Pages, 2007/09
When we decommission the equipments contaminated by the uranium, the dismantling process of the equipments and the disposal process of the radioactive waste will be carried out. However, costs of these processes will be very expensive. In order to minimize these costs, we have developed new decontamination technology to decontaminate below the clearance level without dismantling.
Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Sugitsue, Noritake; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*
no journal, ,
For metal exposed to uranium hexafluoride, as a study of a method of reasonably decontaminating radioactive substances attached to a corrosion layer and a base material generated after opening to the atmosphere, removal using a simulated sample and an actual sample Based on the dyeing test results, evaluation of decontamination efficiency, secondary waste generation amount, etc. was carried out. As a result, it was confirmed that acidic functional water decontamination is totally superior to other dilution decontamination.
Aoki, Katsumi; Kihara, Yoshiyuki; Takahashi, Tetsuo; Yagi, Naoto; Ohara, Yoshiyuki; Hinoda, Shingo
no journal, ,
no abstracts in English
Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Sugitsue, Noritake; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*
no journal, ,
The metal surface exposed to uranium hexafluoride corrodes covering radioactive materials. We studied reasonably decontamination method. In this test, decontamination characteristics using water, diluted acid, functional electrolyzed water were evaluated using a simulated sample. As a result, we found that the oxidation-reduction potential of functional electrolyzed water affects decontamination performance.
Nakayama, Takuya
no journal, ,
Facilities that have completed their missions of research activities or have become obsolete will be systematically decommissioned. The dismantling of these facilities is expected to generate a large amount of metal waste with contaminated surfaces. In particular, a large amount of ferrous metal wastes, such as carbon steel, are generated. In order to reduce the disposal cost of radioactive wastes, it is required to reduce the volume of radioactive wastes by efficient decontamination. Therefore, as a rational decontamination method, we evaluated decontamination characteristics using acidic electrolyzed water containing hypochlorous acid, diluted hydrochloric acid, and diluted sulfuric acid on a sample simulating a corrosion layer. As a result, it was found that acidic electrolyzed water is a decontamination solution with an appropriate balance between the effects of dissolving the base metal and dissolving and removing the corrosion layer.
Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*
no journal, ,
In the nuclear industry, when the nuclear facilities are dismantled, the decontamination work of the radioactive substances is carried out. The selection of the decontamination method is a big problem because the enlargement of decontamination plant and increases of disposal cost is caused. In this study, we propose the new decontamination method of the uranium compounds by IF gas. In this presentation, we show the full-scale exam result and so on by using the actual uranium enrichment plant.
Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*
no journal, ,
In this study, we suggest the new technology decontaminates equipments by reacting the uranium compounds with IF gas in the uranium treatment facilities. This presentation shows the decontamination experiment result of the uranium enrichment plant, which is composed of a lot of gas centrifuges. Also, we shows the method for quantifying the uranium weight in the interior of gas centrifuge.
Yoshitsugu, Yuichi; Tsujinaka, Hideyuki; Goto, Hirohito; Fujita, Masato; Nishimura, Yoshiyuki; Okui, Masahiro; Ito, Kimio; Ono, Takayuki
no journal, ,
At Ningyo-toge Environmental Engineering Center, Various actions are considered to be it for nuclear fuel plant decommissioning and to take a step. It is excepted that a large quantity of waste is occurred by equipments and buildings decommissioning. In our center, it is introduced a system of "Non radioactive Waste" to reduce quantity of radio waste. I introduce our system.
Daiten, Masaki
no journal, ,
Main equipment of the uranium refining and conversion facility had been dismantled from 2008 to 2013. The uranium enrichment pilot plant has been dismantled since 2014. Removal treatment of uranium residue in equipment of the uranium enrichment demonstration plant commenced from 2001. Based on the technological result of uranium removal treatment, removal treatment of uranium from the first operation unit commenced, and it will be completed in FY 2016. Measurement and evaluation of radioactivity concentrations of equipment for clearance level commenced in May 2013. After the radioactivity concentrations were confirmed, and the certificates were issued by Nuclear Regulation Authority, clearance objects were carried out from the uranium facility and aluminum materials were reused for the first time in Japan.
Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Sugitsue, Noritake; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*
no journal, ,
no abstracts in English
Nakamura, Hironobu
no journal, ,
In accordance with the Japan-IAEA safeguards agreement, domestic operator has to declare the Design Information Questionnaire (DIQ) when the operator change the design information for the facilities of themself. In the IAEA, though they already released the procedure to make the DIQ from the construction to operation, unfortunately, they did not release the procedure from shutdown to decommission. So, the operator of all over the world is asking IAEA to release the common DIQ making guidelines as soon as possible. Therefore, IAEA hold the specialist meeting to make the DIQ guideline under decommissioning, and JAEA also attend to discuss the meeting because JAEA has several types of facilities and proposes subjects to be solve in order to revise the DIQ smoothly. In this paper, regarding the discussion for the decommissioning DIQ in the main nuclear fuel cycle facilities such as reprocessing, we present and propose about simple revise, clarification between stage of decommissioning and DIQ procedure, revision of nuclear material accountancy procedure and the termination of safeguards.