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Journal Articles

Current status of JAEA Ningyo-toge Decommissioning Project

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.

Journal Articles

Study on decontamination of steel surface contaminated with uranium hexafluoride by acidic electrolytic water

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$$^{2}$$), 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.

Journal Articles

Decontamination performance evaluation of IF$$_{7}$$ treatment technology and proof of IF$$_{7}$$ production method

Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 10(3), p.194 - 204, 2011/09

This paper shows the investigation result of the reasonable IF$$_{7}$$ treatment condition and the full-scale examination result by using this IF$$_{7}$$ 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$$_{7}$$ production condition and the full-scale examination result. As a result, it could be proved 3,355 kg-IF$$_{7}$$ gas was produced.

Journal Articles

Proposal of method for quantifying uranium weight in the interior of gas centrifuge, and performance evaluation of IF$$_{7}$$ treatment reaction product separation and refinement

Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 10(3), p.205 - 215, 2011/09

This paper shows we constructed theoretically the methodology using the $$gamma$$-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$$_{5}$$ weight of 86% can separate and refine from UF$$_{6}$$ and IF$$_{5}$$ mixture gas.

JAEA Reports

Study on efficiency of dry decontamination technique by numerical method, 2 (Joint research)

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

JAEA-Research-2010-032.pdf:1.72MB

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$$_{7}$$) as a system decontaminator. In this dry decontamination technique, a chemical reaction occurs between the uranium compound attached to the metal surface and IF$$_{7}$$. 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.

JAEA Reports

Study on efficiency of dry decontamination technique by numerical method (Joint research)

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

JAEA-Research-2009-047.pdf:5.13MB

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$$_{7}$$) as a system decontaminator. In this dry decontamination technique, a chemical reaction occurs between the uranium compound attached to the metal surface and IF$$_{7}$$. 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.

Journal Articles

System chemical decontamination technology by the IF$$_{7}$$ gas

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.

Oral presentation

Basic study on system decontamination by iodine heptafluoride, 1; Estimation of deposition rate and mechanism based uranium enrichment plant operation data

Yokoyama, Kaoru; Hata, Haruhi; Sugitsue, Noritake; Hyakutake, Toru*; Muto, Akinori*; Sasakura, Mariko*; Minowa, Hirotsugu*; Suzuki, Kazuhiko*

no journal, , 

The decontamination technique using the iodine heptafluoride is known as a system decontamination technique of facilities like the uranium enrichment plant where the uranium hexafluoride was handled. In this report, the mechanism of the system decontamination using the iodine heptafluoride is clarified at a molecular level. The generation process of the uranium tetrafluoride is estimated using the plant operation data. In addition, the generation speed of the uranium tetrafluoride and the activation energy are of the uranium tetrafluoride and iodine heptafluoride reaction are estimated.

Oral presentation

Basic study on system decontamination by iodine heptafluoride, 2; Formulate of potential model for deposition mechanism of uranium compound

Hata, Haruhi; Yokoyama, Kaoru; Sugitsue, Noritake; Hyakutake, Toru*; Muto, Akinori*; Sasakura, Mariko*; Minowa, Hirotsugu*; Suzuki, Kazuhiko*

no journal, , 

As a first step to elucidate the molecular mechanism of decontamination systems for iodine heptafluoride, uranium hexafluoride and the metal (iron), the possibility of physical adsorption and chemical reactions with uranium hexafluoride and uranium tetrafluoride (solid), we investigate the possibility of physical adsorption and chemical reactions of this. Therefore, the intermolecular of uranium hexafluorides, iron and uranium hexafluoride, uranium tetrafluoride and uranium hexafluoride (solid) and evaluated by molecular orbital method to the intermolecular potential between, based on this data, MD law adhesion mechanism was estimated by uranium hexafluoride.

Oral presentation

The Experimental study for decontamination performance evaluation of IF$$_{7}$$ treatment technology

Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*

no journal, , 

When uranium enrichment plant decommissioning is carried out, a reasonable gas centrifuge decontamination technology is required. The present study proposes a dry treatment technology using Iodine Heptafluoride (IF$$_{7}$$) gas. As a result, we observe experimental decontamination performance.

Oral presentation

Proposal for the decontamination method of the radioactive substances by the chemical reaction

Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*

no journal, , 

In the nuclear industry, when the nuclear facilities is 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$$_{7}$$ gas.

Oral presentation

The Study of the decontamination technology for the radioactive waste reduction

Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*

no journal, , 

We carried out the full-scale exam of the IF$$_{7}$$ production for the study of the decontamination technology using IF$$_{7}$$ gas. As a result, it could be proved 3,355kg-IF$$_{7}$$ gas was produced.

Oral presentation

Proposal for the decontamination method of the radioactive substances by the chemical reaction, 2

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$$_{7}$$ gas. In this presentation, we show the full-scale exam result and so on by using the actual uranium enrichment plant.

Oral presentation

The Study of the nuclear facility decontamination technology by using the chemical reaction of the iodine heptafluoride gas

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$$_{7}$$ 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.

Oral presentation

Proposal for the decontamination method of the radioactive substances by the chemical reaction, 3

Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko*

no journal, , 

In this study, we propose the decontamination method of plant equipments by using the chemical reaction with IF$$_{7}$$ gas as the prior study for the decommissioning of the uranium enrichment plant. This presentation shows the IF$$_{7}$$ treatment examination result for the actual uranium enrichment plant. Further, we show the full-scale examination result about IF$$_{7}$$ production technology and the reaction product separation refinement technology, too.

Oral presentation

The Introduce of "Non radioactive Waste" at Ningyo-toge Environmental Engineering Center

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.

Oral presentation

Recent status of decommissioning on uranium facilities and application of clearance

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.

Oral presentation

A Decontamination characteristic of the metal surface with uranium hexafluoride, 1; Basic test used simulation sample

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.

Oral presentation

A Decontamination characteristic of the metal surface with uranium hexafluoride, 3; Evaluation of rational for decontamination technique

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.

Oral presentation

A Decontamination characteristic of the metal surface with uranium hexafluoride, 2; Basic test used actual sample

Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Sugitsue, Noritake; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*

no journal, , 

no abstracts in English

Oral presentation

Discussion for the decommissioning DIQ in the main nuclear fuel cycle facilities such as reprocessing

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.

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