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.

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

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

Nippon 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.

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.

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 gas.

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.

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 gas as the prior study for the decommissioning of the uranium enrichment plant. This presentation shows the IF treatment examination result for the actual uranium enrichment plant. Further, we show the full-scale examination result about IF production technology and the reaction product separation refinement technology, too.

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.

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.

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.