Liquid decontamination using acidic electrolyzed water for various uranium-contaminated steel surfaces in dismantled centrifuge

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

https://doi.org/10.1016/j.pnucene.2022.104396

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.

Current status of JAEA Ningyo-toge Decommissioning Project

Yagi, Naoto; Mita, Yutaka; Kanda, Nobuhiro

Dekomisshoningu Giho, (61), p.2 - 11, 2020/03

http://www.randec.or.jp/publish/documents/gihou/Decommissioning%20gihou_61.pdf

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.

Decontamination performance evaluation of IF treatment technology and proof of IF production method

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

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

https://doi.org/10.3327/taesj.J10.026

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.

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) 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.

System chemical decontamination technology by the IF 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.

Ningyo-toge Environmental Engineering Center; Reiwa 3rd year business plan

Aoki, Katsumi; Kihara, Yoshiyuki; Takahashi, Tetsuo; Yagi, Naoto; Ohara, Yoshiyuki; Hinoda, Shingo

no journal, , 

no abstracts in English

Decontamination method using acidic electrolyzed water for metals contaminated with radioactive materials

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.

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

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.

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