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JAEA Reports

Decommissioning report for Wastewater Treatment Facility (Part 2); Chapter on contamination inspection section

Yamamoto, Keisuke; Nakagawa, Takuya; Shimojo, Hiroto; Kijima, Jun; Miura, Daiya; Onose, Yoshihiko*; Namba, Koji*; Uchida, Hiroaki*; Sakamoto, Kazuhiko*; Ono, Chika*; et al.

JAEA-Technology 2024-019, 211 Pages, 2025/02

JAEA-Technology-2024-019.pdf:35.35MB

The uranium enrichment facilities at the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency (JAEA) were constructed sequentially to develop uranium enrichment technology with centrifugal separation method. The developed technologies were transferred to Japan Nuclear Fuel Limited until 2001. And the original purpose has been achieved. Wastewater Treatment Facility, one of the uranium enrichment facilities, was constructed in 1976 to treat radioactive liquid waste generated at the facilities, and it finished the role in 2008. In accordance with the Medium/Long-Term Management Plan of JAEA Facilities, interior equipment installed in this facility had been dismantled and removed since November 2021 to August 2023. This report summarizes the findings obtained through the work related to the contamination inspection methods cancellation the controlled area of Wastewater Treatment Facility from September 2023 to March 2024.

Journal Articles

Eco-friendly carboxymethyl cellulose nanofiber hydrogels prepared via freeze cross-linking and their applications

Sekine, Yurina; Nankawa, Takuya; Yunoki, Shunji*; Sugita, Tsuyoshi; Nakagawa, Hiroshi; Yamada, Teppei*

ACS Applied Polymer Materials (Internet), 2(12), p.5482 - 5491, 2020/12

 Times Cited Count:66 Percentile:94.22(Materials Science, Multidisciplinary)

We developed a cross-linking method using freeze concentration and used it to synthesize a new type of carboxymethyl cellulose nanofiber (CMCF) hydrogel with high compressive strength ($$>$$ 80 MPa) and high compressive recoverability. The hydrogels were prepared by adding an aqueous solution of citric acid (CA) to a frozen CMCF sol and then thawing the sol. The reaction between the freeze-concentrated CMCF and CA created a rigid porous structure that reflected the ice crystal structure. Their cross-linked structure has a high stability to compressive stress. Bentonite was immobilized on a CMCF hydrogel by adding bentonite to the CMCF sol before freeze cross-linking. The CMCF-bentonite hydrogel showed high adsorptivity for chemical dyes. The physically cross-linked CMCF hydrogels are non-toxic, metal-free, and simple to prepare, and thus they may be useful as sustainable materials in various fields.

Journal Articles

Design and trial fabrication of a dismantling apparatus for irradiation capsules of solid tritium breeder materials

Hayashi, Kimio; Nakagawa, Tetsuya; Onose, Shoji; Ishida, Takuya; Nakamichi, Masaru; Takatsu, Hideyuki; Nakamura, Mutsumi*; Noguchi, Tsuneyuki*

Journal of Nuclear Materials, 386-388, p.1083 - 1086, 2009/04

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Investigation and design of the dismantling process of irradiation capsules containing tritium, 2; Detailed design and trial fabrication of capsule dismantling apparatus and investigation of glove box facility

Hayashi, Kimio; Nakagawa, Tetsuya; Onose, Shoji; Ishida, Takuya; Nakamichi, Masaru; Katsuyama, Kozo; Iwamatsu, Shigemi; Hasegawa, Teiji; Kodaka, Hideo; Takatsu, Hideyuki; et al.

JAEA-Technology 2009-007, 168 Pages, 2009/03

JAEA-Technology-2009-007.pdf:31.88MB

In-pile functional tests of breeding blankets have been planned by Japan Atomic Energy Agency (JAEA), using a test blanket module (TBM) which will be loaded in the International Thermonuclear Experimental Reactor (ITER). In preparation for the in-pile functional tests, JAEA has been being performed irradiation experiments of lithium titanate (Li$$_{2}$$TiO$$_{3}$$), which is the first candidate of solid breeder materials for the blanket of the demonstration reactor (DEMO) under designing in Japan. The present report describes (1) results of a detailed design and trial fabrication tests of a dismantling apparatus for irradiation capsules which were used in irradiation experiments by the Japan Materials Testing Reactor (JMTR) of JAEA, and (2) results of a preliminary investigation of a glove box facility for post-irradiation examinations (PIEs). In the detailed design of the dismantling apparatus, datailed specifications and the installation methods were examined, based on results of a conceptual design and basic design. In the trial fabrication, cutting tests were curried out by making a mockup of a cutting component. Furthermore, a preliminary investigation of a glove box facility was carried out in order to secure a facility for PIE work after the capsule dismantling, which revealed a technical feasibility.

JAEA Reports

Investigation and design of the dismantling process of irradiation capsules containing tritium, 1; Conceptual investigation and basic design

Hayashi, Kimio; Nakagawa, Tetsuya; Onose, Shoji; Ishida, Takuya; Kodaka, Hideo; Katsuyama, Kozo; Kitajima, Toshio; Takahashi, Kozo; Tsuchiya, Kunihiko; Nakamichi, Masaru; et al.

JAEA-Technology 2008-010, 68 Pages, 2008/03

JAEA-Technology-2008-010.pdf:11.31MB

In-pile functional tests of breeding blankets for fusion reactors have been planned by Japan Atomic Energy Agency (JAEA), using a test blanket module (TBM) which will be loaded in ITER. The present report describes a conceptual investigation and a basic design of the dismantling process for irradiation capsules which were used in irradiation experiments by the Japan Materials Testing Reactor (JMTR) of JAEA. In the present design, the irradiation capsule is cut by a band saw; the released tritium is recovered safely by a purge-gas system, and is consolidated into a radioactive waste form. Furthermore, adoption of the inner-box enclosing the dismantling apparatus has brought a prospect to be able to utilize an existing hot cell (beta-$$gamma$$ cell) equipped with usual wall material permeable to tritium, without extensive refurbishing of the cell. Thus, the present study has indicated the feasibility of the present dismantling process for the irradiated JMTR capsules containing tritium.

Oral presentation

Effect of electron irradiation on the property of electrochemical hydrogen absorption by a Mm-Ni based alloy

Muraki, Keita*; Nakagawa, Takuya*; Kishimoto, Masahiko*; Abe, Hiroshi; Hiraki, Takeshi*; Uchida, Hirohisa*

no journal, , 

In this study, we examined the effect of electron irradiation on the surface of a hydrogen storage alloy in order to improve the initial activation. We measured the initial rate of hydrogen absorption in an electrochemical process, and found that the electron irradiation treatment in the atmosphere is more effective than that in the vacuum or helium gas. Based on results of surface analysis of the alloy by ESCA, we found the existence of non-stoichiometric oxides of rare earths. As well known, non-stoichiometric rare earth oxides such as CeO$$_{x}$$ and LaO$$_{x}$$ has a high ability to dissociate covalent molecules like H$$_{2}$$O. This paper demonstrates an effective surface treatment of electron irradiation, and the important catalytic actions of rare earth oxides in the surface to improve the initial activation of the alloy.

Oral presentation

Performance tests of a mask fitting tester for use in nuclear facilities

Nakagawa, Masahiro; Kato, Takuya; Nojima, Shun; Sakai, Toshiya; Shishido, Nobuhito; Umehara, Takashi

no journal, , 

Mask fitting tester "MT-03" is widespread as educational equipment in medical institution and industrial organization. However, there are few examples introduced in order to check the protection performance of purifying respirators in nuclear facilities. In this study, we compared protection factors obtained by MT-03 and those obtained by Mask-man test apparatus "MT-100N". As a result, although the change of measurement result is larger and measured value is higher than that of MT-100N, it was found that protection performance can be checked appropriately.

Oral presentation

Decommissioning of uranium facility, 3; Contamination inspection for cancellation the controlled area in Wastewater Treatment Area

Yamamoto, Keisuke; Nakagawa, Takuya; Matsuo, Kazuomi; Suguro, Toshiyasu

no journal, , 

Wastewater Treatment Area was constructed to treat radioactive liquid waste generated at the uranium enrichment facilities. The interior equipment installed in this facility was to be dismantled and removed by 2023. After that, contamination inspection for cancellation the controlled area was conducted, and it was confirmed that there was no contamination in the targeted area. In addition, to reduce the amount of radioactive waste, contamination inspection and investigation of building usage history for confirmation of non-radioactive waste was performed on concrete and other building materials, and the results were found to be below the lower detection limit. This presentation shows the findings obtained through the work related to contamination inspection for cancellation the controlled area.

Oral presentation

Phytoremediation of radioactive contaminated soil; Screening for plant species with high absorption capacity of Cs and Sr

Goto, Yukari*; Nakagawa, Takuya*; Makino, Yuko*; Yamada, Satoshi*; Yamada, Mina*; Sakoda, Akihiro; Ishimori, Yuu

no journal, , 

Tottori University and Japan Atomic Energy Agency started a joint study to develop an environmental remediation technique for agricultural soil. Nine plants were water-cultured and examined for screening. A few were selected as candidates for demonstrations in fields. Preselected plants were mainly halophytes. Easily cultivated and harvested plants without harmful effect on new agriculture were also considered. Seedings prepared were first grown for a certain term. Additive-free, $$^{133}$$Cs and $$^{88}$$Sr groups, which are both stable isotopes, were then made. Stems, leaves and roots were harvested, in principle, two weeks after the addition, to measure K, Ca, Mg, Sr and Cs concentrations in them. It was concluded that New Zealand spinach and ice plant were most adequate for removing contaminants from surface soil. The two accumulate Cs and Sr mostly in the shoots, are prostrate, and spread the roots shallowly. For valid application, growth-phase dependences of absorption and distribution, growth property and root distribution should be elucidated. Finally, the application study plan was developed based on screening test results.

Oral presentation

Evaluation of radiation resistance of activated sludge used for nitrate ion decomposition

Nakagawa, Akinori; Kogawara, Takafumi; Onizawa, Takashi*; Hanada, Keiji; Nakayama, Takuya; Meguro, Yoshihiro

no journal, , 

no abstracts in English

Oral presentation

Development of high-strength cellulose nanofiber hydrogels by freeze-crosslinking

Sekine, Yurina; Nankawa, Takuya; Miura, Daisuke*; Yunoki, Shunji*; Sugita, Tsuyoshi; Nakagawa, Hiroshi; Yamada, Teppei*

no journal, , 

We developed a crosslinking method using freeze concentration and used it to synthesize a cellulose nanofiber hydrogel with high compressive strength. The reaction between the freeze-concentrated cellulose nanofiber and citric acid created a rigid porous structure. Without the freeze crosslinking method, the complex of the cellulose nanofiber sol and citric acid produced hydrogels, which easily collapsed under compressive stress. We will give a presentation on the crosslinking method and the chemical and physical properties of the hydrogel.

Oral presentation

Renovation of building L

Nakagawa, Takuya; Yamamoto, Keisuke; Suguro, Toshiyasu; Sone, Tomoyuki

no journal, , 

no abstracts in English

Oral presentation

Steam assisted pyrolysis system for mineralization and volume reduction of radioactive liquid organic waste

Koyama, Hayato; Kijima, Jun; Shimojo, Hiroto; Nakagawa, Takuya; Owada, Mitsuhiro; Sone, Tomoyuki

no journal, , 

Spent tri-n-butyl phosphate/n-dodecane contaminated with uranium and spent fluorine oil are stored in the Japan Atomic Energy Agency (JAEA). The purpose of this study is to reduce the volume of these wastes, convert it into a stable chemical form, and reduce the amount of storage using the steam assisted pyrolysis system we are developing. We report on the results of treatment of several organic liquid wastes and explain the corrosion prevention methods of this system.

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