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Journal Articles

Effects of heterogeneity of geomechanical properties on tunnel support stress during tunnel excavation

Okazaki, Yasuyuki*; Hayashi, Hisashi*; Aoyagi, Kazuhei; Morimoto, Shingo*; Shinji, Masato*

Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12

In the design of tunnel support, the behavior of the rock mass around a tunnel and the stress acting on the tunnel support may be predicted using a numerical analysis. However, in such a numerical analysis, it is common to assume that each stratum comprises a homogeneous material, ignoring the heterogeneity of the geomechanical properties inherent to the rock mass. For this reason, it is not unusual for the results of the numerical analysis to differ from the actual behavior. We performed a tunnel excavation analysis considering the heterogeneity of the geomechanical properties in the rock mass to investigate the local increase in the tunnel support stress obtained in the 350 m gallery at the Horonobe Underground Research Laboratory. The results revealed that, in order to predict the locally increased support stress in advance, it is necessary to carry out a tunneling excavation analysis considering the heterogeneity of the geomechanical properties. It was also revealed that the scale at which the geomechanical properties fluctuate is an important factor.

Journal Articles

Uranium waste engineering research at the Ningyo-Toge Environmental Engineering Center of JAEA

Umezawa, Katsuhiro; Morimoto, Yasuyuki; Nakayama, Takuya; Nakagiri, Toshio

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05

In December 2016, the Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency (JAEA Ningyo-toge) announced new concept of "Uranium and Environmental Research Platform". As part of the concept, uranium waste engineering research are now undergoing. The objective of the research is to establish the processing technology for safely and reasonable disposal of uranium waste. In particular, estimation of the amount of uranium and harmful substances and development of technologies to reduce their concentration in the waste to the permissive level for the disposal in shallow ground disposal are needed. We are now developing the technologies to reduce the concentration of uranium and harmful substances shown below. (1) Survey on uranium inventory. Uranium waste is now stored in 10-odd thousands of 200 L drums. We are surveying amount and chemical form of uranium in the drums. (2) Development of decontamination technology of metal and concrete waste. We are investigating decontamination methods for metals and concrete contaminated with uranium. (3) Development of technologies to remove, detoxify and fix the harmful substances. We are surveying the types and amounts of harmful substances in waste. In addition, we are investigating the method to remove, detoxify, and fix harmful substances. (4) Measurement technology of uranium radioactivity. We are investigating and examining ways to improve the quantitative accuracy of measurement and shorten the measurement time. (5) Development of uranium removal technology from sludge. We are investigating new processing method to remove uranium from sludge which is applicable for several kind of sludge. The results of these technological developments and environmental research will be reflected to "small-scale field test" and "disposal demonstration test" which are planned for demonstration of the uranium waste disposal technology.

JAEA Reports

Uranium and environmental research platform; Social gathering of uranium and environmental research

Nakayama, Takuya; Yagi, Naoto; Sato, Kazuhiko; Hinoda, Shingo; Nakagiri, Toshio; Morimoto, Yasuyuki; Umezawa, Katsuhiro; Sugitsue, Noritake

JAEA-Review 2018-005, 163 Pages, 2018/03

JAEA-Review-2018-005.pdf:72.95MB

The Ningyo-toge Environmental Engineering Center of JAEA has been working together with local communities for more than 60 years. Through our R&D projects on from uranium exploration to uranium enrichment as a part of the nuclear fuel cycle (i.e., front-end), we have accumulated experiences in the fields of management of uranium related technology. Taking advantage of such our potential, we will start new R&D program on "Research on Uranium and the Environment." In December 2016 we announced our new concept of the "Uranium and Environmental Research Platform" as a framework aimed at contributing to regional and international society through R&D programs (environmental research and uranium waste engineering research) that are needed to steadily carry out decommissioning of uranium handling facilities.

JAEA Reports

Decommissioning activities and R&D of nuclear facilities in the second midterm plan

Terunuma, Akihiro; Mimura, Ryuji; Nagashima, Hisao; Aoyagi, Yoshitaka; Hirokawa, Katsunori*; Uta, Masato; Ishimori, Yuu; Kuwabara, Jun; Okamoto, Hisato; Kimura, Yasuhisa; et al.

JAEA-Review 2016-008, 98 Pages, 2016/07

JAEA-Review-2016-008.pdf:11.73MB

Japan Atomic Energy Agency formulated the plan to achieve the medium-term target in the period of April 2010 to March 2015(hereinafter referred to as "the second medium-term plan"). JAEA determined the plan for the business operations of each year (hereinafter referred to as "the year plan"). This report is that the Sector of Decommissioning and Radioactive Waste Management has summarized the results of the decommissioning technology development and decommissioning of nuclear facilities which were carried out in the second medium-term plan.

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

Evaluation formulas of manpower needs for dismantling of equipments in uranium refining and conversion plant

Izumo, Sari; Usui, Hideo; Kubota, Shintaro; Tachibana, Mitsuo; Kawagoshi, Hiroshi; Takahashi, Nobuo; Morimoto, Yasuyuki; Tokuyasu, Takashi; Tanaka, Yoshio; Sugitsue, Noritake

JAEA-Technology 2014-021, 79 Pages, 2014/07

JAEA-Technology-2014-021.pdf:22.8MB

Japan Atomic Energy Agency has developed PROject management data evaluation code for DIsmantling Activities (PRODIA) to make an efficient decommissioning for nuclear facilities. PRODIA is a source code which provides estimated value such as manpower needs, costs, etc., for dismantling by evaluation formulas according to the type of nuclear facility. Evaluation formulas of manpower needs for dismantling of equipments about reprocessed uranium conversion in Uranium Refining and Conversion Plant are developed in this report. In the result, 7 formulas for prepare process, 24 formulas for dismantling process and 8 formulas for clean-up process are derived. It is confirmed that an unified evaluation formula can be used instead of 8 formulas about dismantling process of steel equipment for uranium conversion process, and 3 types of simplified formula can be used for preparation process and clean-up process respectively.

Journal Articles

Existing status of uranium refining and conversion plant decommissioning project

Sugitsue, Noritake; Morimoto, Yasuyuki; Tokuyasu, Takashi; Tanaka, Yoshio

Nippon Genshiryoku Gakkai Wabun Rombunshi, 12(3), p.242 - 256, 2013/09

This technical report showed the situation of the dismantling of the main equipment in the radiation controlled area of a uranium refining and conversion plant. And, the dismantling which we did is the work of the beginning of a uranium refining and conversion plant decommissioning project. We started dismantling in April 2008, and finished dismantling of the main equipment in a radiation controlled area in 29 September 2011. The dismantling waste and equipment was stored in the 200 little drum. All the contamination equipment can be sealed and kept in this stage. The radioactivity inventory of a uranium refining and conversion plant does not change in this stage. However, the risk of contamination by aged deterioration of this facility became remarkable small. Moreover, we were able to get many information and experience about dismantling.

Journal Articles

Development of evaluation models of manpower needs for dismantling the dry conversion process-related equipment in Uranium Refining and Conversion Plant (URCP)

Izumo, Sari; Usui, Hideo; Tachibana, Mitsuo; Morimoto, Yasuyuki; Takahashi, Nobuo; Tokuyasu, Takashi; Tanaka, Yoshio; Sugitsue, Noritake

Proceedings of 15th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2013) (CD-ROM), 9 Pages, 2013/09

 Times Cited Count:0 Percentile:100

Journal Articles

Study on evaluation of project management data for decommissioning of uranium refining and conversion plant

Usui, Hideo; Izumo, Sari; Shibahara, Yuji; Morimoto, Yasuyuki; Tokuyasu, Takashi; Takahashi, Nobuo; Tanaka, Yoshio; Sugitsue, Noritake; Tachibana, Mitsuo

Proceedings of International Waste Management Symposia 2012 (WM 2012) (CD-ROM), 13 Pages, 2012/02

Dismantling of dry conversion facility in the uranium refining and conversion plant at Ningyo-toge began in 2008. During dismantling activities, project management data have been collected. Establishment of the calculation formula for dismantling of each kind of equipment makes it possible to evaluate manpower for dismantling the whole facility. However, it is not easy to prepare calculation formula for all kinds of equipment in the facility. Therefore, a simpler evaluation method was considered to calculate manpower based on facility characteristics. The results showed promise for evaluating dismantling manpower with respect to each chemical process. To create an effective dismantling plan, it is necessary to carefully consider use of a GH preliminarily. Thus, an evaluation method of project management data such as manpower and secondary waste generation was considered. The results showed promise for evaluating project management data of GH by using established calculation formula.

Journal Articles

Uranium refining and conversion plant decommissioning project

Zaima, Naoki; Morimoto, Yasuyuki; Sugitsue, Noritake; Kado, Kazumi

Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.311 - 320, 2010/10

JAEA Reports

Radiation environment account before dismantling the conversion facilities; Evaluation of the uranium inventory and air dose rate in the dismantling facilities, 2

Takahashi, Nobuo; Yokoyama, Kaoru; Morimoto, Yasuyuki; Shimaike, Masamitsu; Ikegami, Sohei; Sugitsue, Noritake

JAEA-Technology 2010-003, 92 Pages, 2010/06

JAEA-Technology-2010-003.pdf:10.76MB

At the reprocessed uranium conversion facilities, Hydration and Conversion room-1,2,3, Dehydration and Conversion room-1,2, Dry process filter room have been dismantled according to the schedule, in 2009 fiscal year. The $$gamma$$-ray measurement had been carried out before dismantlement to evaluate the radioactivity inventory. As a result, the uranium recovery work was forecasted for reasonable dismantlement. In addition, the feature nuclide affecting the results of the measurement on the air dose was evaluated. Additionally, as the waste data, $$gamma$$-ray analysis results are shown.

Journal Articles

Decay properties of $$^{266}$$Bh and $$^{262}$$Db produced in the $$^{248}$$Cm + $$^{23}$$Na reaction

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi*; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.

Journal of the Physical Society of Japan, 78(6), p.064201_1 - 064201_6, 2009/06

 Times Cited Count:27 Percentile:20.59(Physics, Multidisciplinary)

Decay properties of an isotope $$^{266}$$Bh and its daughter nucleus $$^{262}$$Db produced by the $$^{248}$$Cm($$^{23}$$Na,5$$n$$) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. $$^{266}$$Bh was clearly identified from the correlation of the known nuclide, $$^{262}$$Db. The obtained decay properties of $$^{266}$$Bh and $$^{262}$$Db are consistent with those observed in the $$^{278}$$113 chain, which provided further confirmation of the discovery of $$^{278}$$113.

Oral presentation

Proposal of uranium bearing waste disposal

Kawatsuma, Shinji; Takebe, Shinichi; Ouchi, Masaru; Kozawa, Kazushige; Yagi, Naoto; Sato, Kazuhiko; Morimoto, Yasuyuki; Fukushima, Tadashi; Ishibashi, Makoto*

no journal, , 

no abstracts in English

Oral presentation

A Consideration on clearance level of natural uranium nuclide

Kawatsuma, Shinji; Ishibashi, Makoto*; Morimoto, Yasuyuki

no journal, , 

no abstracts in English

Oral presentation

Decommissioning project of uranium conversion plant, 2; Evaluation of the nuclide composition in the spent bed material and the external exposure

Takahashi, Nobuo; Shimaike, Masamitsu; Morimoto, Yasuyuki; Ikegami, Sohei; Sugitsue, Noritake

no journal, , 

no abstracts in English

Oral presentation

Decommissioning project of uranium conversion plant, 1; Master plan

Morimoto, Yasuyuki; Ikegami, Sohei; Sugitsue, Noritake

no journal, , 

no abstracts in English

Oral presentation

Decommissioning project of uranium conversion plant, 3; Evaluation of the nuclide composition in the cold trap and the external exposure

Shimaike, Masamitsu; Takahashi, Nobuo; Morimoto, Yasuyuki; Ikegami, Sohei; Sugitsue, Noritake

no journal, , 

no abstracts in English

Oral presentation

Decommissioning project of uranium conversion plant, 4; Dismantling operation data management

Tokuyasu, Takashi; Morimoto, Yasuyuki; Ikegami, Sohei; Sugitsue, Noritake; Tachibana, Mitsuo; Tanimoto, Masataka; Ishigami, Tsutomu

no journal, , 

no abstracts in English

Oral presentation

Decommissioning project of uranium conversion plant, 5; Evaluation of the relation between the drum storage rate and the work rate

Ikegami, Sohei; Tokuyasu, Takashi; Morimoto, Yasuyuki; Sugitsue, Noritake

no journal, , 

no abstracts in English

Oral presentation

Decommissioning project of uranium conversion plant, 6; Analysis of work management data

Tanimoto, Masataka; Ikegami, Sohei; Tokuyasu, Takashi; Morimoto, Yasuyuki; Sugitsue, Noritake; Tachibana, Mitsuo; Ishigami, Tsutomu

no journal, , 

no abstracts in English

44 (Records 1-20 displayed on this page)