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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.

JAEA Reports

Current status of a decommissioning project in the Enrichment Engineering Facility; Results in the second-half of the fiscal year of 2014

Matsumoto, Takashi; Takahashi, Nobuo; Hayashibara, Kenichi; Ishimori, Yuu; Mita, Yutaka; Kakiya, Hideyoshi

JAEA-Technology 2016-020, 80 Pages, 2016/11

JAEA-Technology-2016-020.pdf:17.8MB

The Enrichment Engineering Facility of the Ningyo-toge Environmental Engineering Center was constructed in order to establish the technological basis of plant engineering for uranium enrichment in Japan. Uranium enrichment tests, using natural and reprocessed uranium, were carried out from 1979 to 1989 with two types of centrifuges in the facility. According to the decommissioning plan of the facility, UF$$_{6}$$ handling equipment and supplemental equipment in these plants are intended to be dismantled by 2019 in order to make vacant spaces for future projects use, for example, inventory investigation, precipitation treatment, etc. This report shows the current state of the decommissioning project in the second-half of the fiscal year of 2014.

JAEA Reports

Current status of a decommissioning project in the Enrichment Engineering Facilities; Results in the first-half of the fiscal year of 2014

Matsumoto, Takashi; Morimoto, Yasuyuki; Takahashi, Nobuo; Takata, Masaharu; Yoshida, Hideaki; Nakashima, Shinichi; Ishimori, Yuu

JAEA-Technology 2015-036, 60 Pages, 2016/01

JAEA-Technology-2015-036.pdf:9.15MB

The Enrichment Engineering Facilities of the Ningyo-toge Environmental Engineering Center was constructed in order to establish the technical basis of the uranium enrichment plant in Japan. Uranium enrichment tests, using natural and reprocessed uranium, were carried out from 1979 to 1990 at two types of plants in the facilities. UF$$_{6}$$ handling equipment and Supplemental equipment in these plants are intended to be dismantled by 2019 in order to make places for future projects, for example, inventory investigation, precipitation treatment, etc. This report shows the basic plan of this decommissioning project and presents the current state of dismantling in the first-half of the fiscal year of 2014, with indicating its schedule, procedure, situation, results, and so on. The dismantled materials generated amounted to 37 mesh containers and 199 drums, and the secondary waste generated amounted to 271.4 kg.

JAEA Reports

The Uranium waste fluid processing examination by liquid and liquid extraction method using the emulsion flow method

Kanda, Nobuhiro; Daiten, Masaki; Endo, Yuji; Yoshida, Hideaki; Mita, Yutaka; Naganawa, Hirochika; Nagano, Tetsushi; Yanase, Nobuyuki

JAEA-Technology 2015-007, 43 Pages, 2015/03

JAEA-Technology-2015-007.pdf:5.33MB

The centrifuge which has the subtlety information concerning the nuclear nonproliferation used for uranium enrichment technical development exists in the uranium enrichment facilities of Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency. This centrifugal is performing separation processing of the radioactive material adhering to the surface of parts by wet decontamination of ultrasonic cleaning by dilute sulfuric acid and water, etc. By removing the uranium contained in waste fluid, generated sludge reduces activity concentration. And the possibility of reduction of sludge processing is examined. For this reason, from the 2007 fiscal year, Nuclear Science and Engineering Directorate and cooperation are aimed at, and development of the extraction separation technology of the "uranium" by the emulsion flow method is furthered. The test equipment using the developed emulsion flow method was tested. And dilute sulfuric acid and water were used for the examination as actual waste fluid. The result checked whether the various performances in Basic test carried out in Nuclear Science and Engineering Directorate would be obtained.

Journal Articles

Application of ionic liquid as a medium for treating waste contaminated with UF$$_{4}$$

Ohashi, Yusuke; Asanuma, Noriko*; Harada, Masayuki*; Wada, Yukio*; Matsubara, Tatsuo; Ikeda, Yasuhisa*

Journal of Nuclear Science and Technology, 46(8), p.771 - 775, 2009/08

Most of the metal or bed material wastes generated from uranium enrichment facilities or uranium refining and conversion plants are contaminated by uranium fluoride compounds such as UF$$_{4}$$. The UF$$_{4}$$ powder was completely dissolved in BMICl(1-buthyl-3-methylimidazolium chloride). The uranium concentrations of metal waste dropped below the temporary proposed clearance level (1.0 Bq/g) using BMICl. In the cyclic voltammogram of BMICl solution when dissolving UF$$_{4}$$, uncoupled reduction and oxidation peaks were observed and the reduction peak was considered to correspond to the reduction of uranyl(VI) + e$$^{-}$$ $$rightarrow$$ uranyl(V) followed by further reduction to UO$$_{2}$$.

JAEA Reports

Alpha radioactivity measurement technology with ionized air type measurement; Applicability evaluation to verification of the clearance level

Mita, Yutaka; Matsumura, Toshihiro; Yokoyama, Kaoru; Sugitsue, Noritake

JAEA-Technology 2008-061, 35 Pages, 2008/10

JAEA-Technology-2008-061.pdf:3.87MB

In Ningyo-toge Environmental Engineering Center. The equipments and radioactive waste which were contaminated with uranium are generated so much in future dismantling stage. In our plan, some of equipments and radioactive waste are decontamination to a clearance level, and cut down on decommission and disposal expense. This plan needs the alpha-rays measurement technology of the very low level. We think that ionized Air transfer measurement technology is promising as of clearance verification technology. The ionized Air transfer measurement technology applied to the Ionized Air Type Measurement can measure alpha radioactivity of a very low level. Moreover, as compared with a direct survey, there is the merit which can be measured in a short time. However ionized Air transfer measurement technology is new technology. Therefore, there is almost no measurement track record. Furthermore, the date about the influence of a background, a detection limit, measurement performance, and reliability is insufficient. So, this measurement test estimated applicability as clearance level verification of an Ionized Air Type Measurement.

JAEA Reports

Fundamental Research for Utilization of Uranium Compound as the Magnetic Materials

Kimura, Akihiro; Yokoyama, Kaoru*

JNC-TN6400 2004-006, 167 Pages, 2004/09

JNC-TN6400-2004-006.pdf:2.47MB

Numerous uranium compounds were synthesized and those physical properties have been measured until now, and it is known that those parts show the ferromagnetism. Moreover, it is reported the part of them also has the strong magnetic anisotropy by contribution of uranium. Since it is the indispensable requirements to have strong magnetic anisotropy for obtaining large coercive force required for a permanent magnet, the uranium compound may have possibility as an outstanding permanent magnet with depending on the combination of uranium and else addition elements. This research estimated the application possibility as permanent magnet materials by observing the magnetism with vibrating magnetization measurement equipment and the magnetic balance by preparing the ferromagnetic uranium compounds. Furthermore, magnetic field press, sintering and so on was carried out for the compounds with this possibility, and those magnetisms were evaluated. Through the above examination, it was cleared that UFe10Si2B0.25 satisfies the requirements as materials of a permanent magnet, and UFe13Si4 may be able to be also used as the materials by addition of boron because coercive force and residual magnetization increase, and so on. However, about the permanent magnets which were made from these materials, no sufficient coercive force and residual magnetization can be shown. It is thought that a processing method and so on will need to be improved.

JAEA Reports

Technology developments for the decommissioning of uranium fuel facilities and the treatments of uranium wastes at Ningyo-toge Environmental Engineering Center

Annen, Sotonori; Ishimori, Yuu; Ema, Akira; Takanobu, Osamu; Nagayasu, Takaaki; Mita, Yutaka

JNC-TN6400 2003-001, 35 Pages, 2003/10

JNC-TN6400-2003-001.pdf:2.78MB

Technology developments for the decommissioning of uranium fuel facilities and the treatments of uranium wastes are one of the current main projects in the Ningyo-toge Environmental Engineering Center of the Japan Nuclear Cycle Development Institute (JNC Ningyo-toge). In order to carry out the project reasonably and safely, all techniques from decommissioning to waste treatment should be unified systematically. Thus, the JNC Ningyo-toge is aiming at the establishment of a 'decommissioning engineering'. This booklet illustrates the decommissioning engineering, especially four engineering elements; that is, a removal technology for uranium compounds, a decommissioning technology of the centrifuges, an application of CaF2 precipitate and a decommissioning engineering system.

Oral presentation

Development of uranium recovery technique from uranium contaminated materials by using ionic liquids, 1; Solubility of uranium contaminated materials in ionic liquids

Ohashi, Yusuke

no journal, , 

We propose ways to use ionic liquid as reaction media in order to separate uranium and to recover uranium from contaminated materials that is generated from nuclear fuel institutions. By using BMICl and eutectic mixtures of choline chloride-urea we did decontamination tests of waste NaF adsorption materials and metal wastes. We confirmed the solubility of uranium included in NaF into ionic liquids. The decontamination effect of ionic liquids to metal wastes were also confirmed. As a result it was confirmed that 86% of uranium included in NaF is soluble in BMICl after 3 hours soaking. 64% of uranium included in NaF was soluble in eutectic mixtures of choline chloride-urea under the same condition. On the other hand, after we have soaked contaminated metal materials into BMICl for 3 hours, the density of surface radioactivity became lower than 1/10 of levels at which we can bring it out from restricted areas.

Oral presentation

Alpha radioactivity measurement technology with ionized air type measurement apparatus, 2; Measurement test for decontaminated components

Mita, Yutaka; Matsumura, Toshihiro; Sugitsue, Noritake; Yamaguchi, Hiromi; Sano, Akira*; Naito, Susumu*; Maekawa, Tatsuyuki*; Yoshimura, Yukio*; Matsumoto, Takashi*

no journal, , 

By using Ionized Air Type Measurement Apparatus which was designed to measure clearance level of dismantled large-scale things which generate from nuclear plants, after chemical decontaminating machinery and materials which are used in plants, we experimented on a real-scale measurement of clearance level of them. We evaluated performance of detection and confirm applicability as a system of measurement of clearance level.

Oral presentation

Buckling fracture of PVC ventilation duct by the in-line monitor sampling

Matsubara, Tatsuo; Endo, Yuji; Yamanaka, Toshihiro; Kuramoto, Takao; Daiten, Masaki; Sugitsue, Noritake

no journal, , 

The hard vinyl chloride ventilation duct of the local ventilation equipment for used centrifuge decommissioning system had fractured despite the ventilation stopping. As a result of investigation of the causes, it was found that negative pressure in the isolated duct with the damper valve exceeded buckling limit because the air sampling of air-sniffer was not stopped. For experimental proof of this, we investigated of attained negative pressure, analyzed buckling stress and confirmed that hard vinyl chloride ventilation duct was fractured quickly by negative pressure buckling with the mock-up examination device.

Oral presentation

Development of decontamination technology using ionic liquid as a medium for treating waste contaminated with uranium

Ohashi, Yusuke

no journal, , 

In this study we estimated the applicability of process using BMICl and chorin chloride-urea ionic liquid (CCU) for metal waste and NaF waste contaminated with uranium. Dissolution experiments were carried out by adding UF$$_{4}$$ samples in BMICl and CCU in air. UF$$_{4}$$ samples were completely dissolved in BMICl after around 6h at 100$$^{circ}$$C. 38% samples were also dissolved in CCU after 5h at 100$$^{circ}$$C. 86% of uranium in Sodium fluoride (NaF) waste was also dissolved in BMICl after 3h at 100$$^{circ}$$C in air. 64% of uranium in NaF also dissolved in CCU after 3h at 100$$^{circ}$$C. Cyclic voltammograms of the sample solutions prepared by dissolving steel waste into BMICl were measured. The result suggests that electrolytic deposit of iron could not get mixed in with uranium deposit.

Oral presentation

Result of the environmental monitoring around Ningyo-toge

Ono, Takayuki; Ishimori, Yuu; Kawasaki, Satoru; Ando, Masaki

no journal, , 

Ningyo-toge Environmental Engineering Center concluded an environmental conservation agreement between Okayama in 1979 to operate an uranium-enrichment facility. Then, the center has conducted environmental radiation monitoring. We report the results.

Oral presentation

Solidification and leaching property by time progress of the sludge containing fluoride

Tsunashima, Yasumichi; Ohashi, Yusuke; Shimazaki, Masao; Nomura, Mitsuo; Tanaka, Yoshio

no journal, , 

The operation waste of uranium conversion plant and uranium enrichment plant is called sludge, and contains many fluoride which is deleterious material. For disposal, elution of fluoride is a problem. Moreover, sludge contains many calcium sulfate and we are anxious about expansion of cement solidification object by superfluous generation of Ettringite. In order to solve these subjects, the solidification examination of the sludge which used calcium hydrogen phosphate is considered as magnesium oxide system solidification material. The solidification and leaching property by time progress of the sludge containing fluoride are reported.

Oral presentation

Operational results of clearance system in the uranium using facility

Mita, Yutaka; Sugitsue, Noritake; Ogura, Hiroaki; Daiten, Masaki; Ishimori, Yuu; Ema, Akira

no journal, , 

In enrichment engineering facilities of Ningyo-toge Environmental Engineering Center, make reports on the investment performance that was that there is no need (clearance) dealing with the centrifuge that was contaminated with uranium that was used to technological development of uranium enrichment as radioactive waste. Casings centrifuge was reused metal about 10ton by carrying the decontamination and radioactivity concentration measurement as a flower bed in the center.

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

About an analysis in Ningyo-toge environmental engineering center

Nomura, Mitsuo

no journal, , 

no abstracts in English

Oral presentation

Statistical analysis of dust monitoring data for air discharged from a nuclear facility using environmental data; Pilot study

Watanabe, Taisuke; Sakoda, Akihiro; Miyauchi, Toru; Kanzaki, Norie; Tanaka, Hiroshi

no journal, , 

no abstracts in English

18 (Records 1-18 displayed on this page)
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