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Saegusa, Hiromitsu*; Funaki, Hironori; Kurikami, Hiroshi; Sakamoto, Yoshiaki; Tokizawa, Takayuki*
Insights Concerning the Fukushima Daiichi Nuclear Accident, Vol.4; Endeavors by Scientists, p.170 - 187, 2021/10
Removed contaminants including soil, grass and trees are to be stored safely at temporary storage facilities for several years, after which they will be transferred to a planned interim storage facility. The decontamination pilot project was carried out in both the restricted and planned evacuation areas in order to assess decontamination methods and demonstrate measures for radiation protection of workers. Fourteen temporary storage facilities of different technical specifications were designed and constructed under various topographic conditions and land use. In order to support the design, construction and monitoring of temporary storage facilities for removed contaminants during the full-scale decontamination within the prefecture of Fukushima, technical know-how obtained during the decontamination pilot project has been identified and summarized in this paper.
Tanaka, Masaru*; Kawara, Osami*; Ishizaka, Kaoru*; Ohata, Yuki*; Fukuike, Iori*; Kawase, Keiichi; Tokizawa, Takayuki; Miyagawa, Hiroshi*; Ishimori, Yuu
JAEA-Research 2018-001, 98 Pages, 2018/06
JAEA-Research-2018-001.pdf:2.49MB
In the 2016 fiscal year, communication cases on general waste disposal facility construction plans in recent years were surveyed. Results suggested as follows: (1) Existing long-term relationships or agreements in local area promote local accepting. (2) An operator needs to consider alternative plans and explain reasons for the decision making to local stakeholders. (3) Even after first announcement of a new plan, an operator needs to review the plan depending on local concerns. (4) Announcement of a new plan will activate communications on local development including the site redevelopment.
Tanaka, Masaru*; Aoyama, Isao*; Ishizaka, Kaoru*; Ohata, Yuki*; Fukuike, Iori*; Kawase, Keiichi; Watanabe, Masanori; Tokizawa, Takayuki; Miyagawa, Hiroshi*; Ishimori, Yuu
JAEA-Research 2017-003, 65 Pages, 2017/06
JAEA-Research-2017-003.pdf:2.92MB
JAEA Ningyo-toge Environmental Engineering Center and Fukushima Environmental Safety Center have same challenges in risk communication. As reference, similar domestic cases were investigated by our two Centers, and requirements for building long-term relationship were clarified. As follows; (1) Develop new relationship with various stakeholders in the region. (2) Make better use of existing resources (personnel, land and facilities, etc.). (3) Make a concerted effort to create new values with local stakeholders. (4) Make an opportunity which local stakeholders confirm safety and build confidence to the project. These efforts will enhance the opportunities for operators and residents to learn about environment management and environmental protection.
Saegusa, Jun; Tagawa, Akihiro; Kurikami, Hiroshi; Iijima, Kazuki; Yoshikawa, Hideki; Tokizawa, Takayuki; Nakayama, Shinichi; Ishida, Junichiro
Mechanical Engineering Journal (Internet), 3(3), p.15-00609_1 - 15-00609_7, 2016/06
After the Fukushima nuclear accident, JAEA lead off demonstration tests to find out effective decontamination methods for various school facilities in Fukushima. It included (1) dose reduction measures at schoolyards, (2) purification of swimming pool water and (3) removal of surface contamination of playground equipments. Through these tests, they established practical methods suitable for each situation; (1) At school yards, dose rates were drastically reduced by removing topsoil which was then placed in trenches of 1 m deep; (2) For the purification of pool water, the flocculation-coagulation treatment was found to be effective for collecting radiocesium dissolved in the water; (3) Demonstration tests for playground equipments, such as horizontal bars and a sandbox wood frame, suggested that effectiveness of decontamination considerably varied depending on the material, paint or coating condition. This paper reviews these demonstrations.
Saegusa, Jun; Tagawa, Akihiro; Kurikami, Hiroshi; Iijima, Kazuki; Yoshikawa, Hideki; Tokizawa, Takayuki; Nakayama, Shinichi; Ishida, Junichiro
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05
After the Fukushima nuclear accident, JAEA lead off demonstration tests to find out effective decontamination methods for various school facilities in Fukushima. It included (1) dose reduction measures at schoolyards, (2) purification of swimming pool water and (3) removal of surface contamination of playground equipments. Through these tests, they established practical methods suitable for each situation; (1) At school yards, dose rates were drastically reduced by removing topsoil which was then placed in trenches of 1 m deep; (2) For the purification of pool water, the flocculation-coagulation treatment was found to be effective for collecting radiocesium dissolved in the water; (3) Demonstration tests for playground equipments, such as horizontal bars and a sandbox wood frame, suggested that effectiveness of decontamination considerably varied depending on the material, paint or coating condition. This paper reviews these demonstrations.
Watanabe, Masahisa; Umemiya, Noriko; Tagawa, Akihiro; Kawase, Keiichi; Noguchi, Shinichi; Sakazume, Yoshinori; Watanabe, Masanori; Tokizawa, Takayuki
JAEA-Review 2013-052, 232 Pages, 2014/03
JAEA-Review-2013-052.pdf:26.42MB
To discover technologies that can be utilized for decontamination work and verify their effects, economic feasibility, safety, and other factors, the Cabinet Office, Government of Japan launched the FY2012 Decontamination Technology Demonstrations Project to publicly solicit decontamination technologies that would be verified in demonstration tests and adopted 15 candidates. JAEA was commissioned by the Ministry of the Environment, Government of Japan to provide technical assistance related to these demonstrations. JAEA carried out technical advice of demonstration test and evaluation of 15 technologies (e.g., decontamination technology of Burned ash washing and Pond Dredging) to perform decontamination of the environment.
Miyahara, Kaname; Tokizawa, Takayuki; Nakayama, Shinichi
Materials Research Society Symposium Proceedings, Vol.1518, p.245 - 256, 2013/10
After the Fukushima Dai-ichi accident, Japan Atomic Energy Agency (JAEA) was chosen by the Government to conduct decontamination model projects at selected sites. Despite tight boundary conditions in terms of timescale and resources, the decontamination model projects provide a good basis for developing recommendations on how to assure clean-up efficiency and reduce time, cost, subsequent waste management and environmental impact. This can be summarised in terms of site characterisation and data interpretation, clean-up and waste minimisation and storage.
Yoshikawa, Hideki; Iijima, Kazuki; Sasamoto, Hiroshi; Fujiwara, Kenso; Mitsui, Seiichiro; Kitamura, Akira; Kurikami, Hiroshi; Tokizawa, Takayuki; Yui, Mikazu; Nakayama, Shinichi
Materials Research Society Symposium Proceedings, Vol.1518, p.269 - 275, 2013/10
Following the release of radionuclides into the environment as a result of the accident at Fukushima Daiichi Nuclear Power Plant, Japan Atomic Energy Agency (JAEA) had to develop an immediate and effective method of reducing the dose rate received by students in school facilities. A demonstration of a reducing method was carried out by JAEA at a junior high school ground and kindergarten yard in the center of Fukushima-city. Dose rates of the released radionuclides are largely controlled by the ground level contamination and accumulation of mainly cesium-137 (
Cs) and cesium-134 (
Cs) in populated areas. An effective means of reducing dose rate was to remove the surface soil and to bury it on-site under fresh uncontaminated soil or soil collected under deep depth at the site for shielding. The dose rate at1 m above ground level was reduced from 2.5 
Sv/h to 0.15 Sv/h.
Iijima, Kazuki; Funaki, Hironori; Tokizawa, Takayuki; Nakayama, Shinichi
Proceedings of 15th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2013) (CD-ROM), 6 Pages, 2013/09
In decontamination pilot projects conducted by Japan Atomic Energy Agency (JAEA), many different techniques were tested to determine their applicability to remediate areas evacuated after the Fukushima Daiichi nuclear accident. The projects evaluated the radioactive contamination of trees and the effectiveness of decontaminating a highly contaminated evergreen forest. As the first step, three Japanese cedar trees and three fir trees were cut down and the distributions of radioactive cesium (Cs) were measured in each. The total concentrations of Cs and Cs in the leaves and branches were about 1 MBq/kg for both cedar and fir trees, and were appreciably higher than in the bark for cedar. The concentrations in the outer part of the trunks (under the bark) were lower, on the order of 10 kBq/kg, and those in the core of the trunks were lower than 1 kBq/kg for both kinds of trees. The observation that the Cs concentrations are higher in the outer part of trees, is compatible with the assumption that radio-Cs was mostly adsorbed on the surface of trees and partly penetrated into the trunks through the bark. Evolution of air dose rates in a 100
60 m pasture adjacent to the forest was monitored during decontamination of the forest and of the pasture itself. The dose rates in the pasture decreased drastically after stripping contaminated topsoil from the pasture and decreased slightly more after stripping contaminated topsoil of the forest floor and pruning the trees. Cutting down and removing 84 trees in the outermost area (10-m width) of the forest also slightly decreased these dose rates. After decontamination, the residual dose rates around the highly contaminated forest were mostly attributed to radioactive Cs existing in or on trees and topsoil in the untouched forest beyond the decontaminated area.
Saegusa, Jun; Kurikami, Hiroshi; Yasuda, Ryo; Kurihara, Kazuo; Arai, Shigeki; Kuroki, Ryota; Matsuhashi, Shimpei; Ozawa, Takashi; Goto, Hiroaki; Takano, Takao; et al.
Health Physics, 104(3), p.243 - 250, 2013/03
Times Cited Count：3 Percentile：25.73(Environmental Sciences)After the Nuclear accident on March 2011, water discharge from many outdoor swimming pools in the Fukushima prefecture was suspended out of concern that radiocesium in the pool water would flow into farmlands. We have reviewed the existing flocculation method for decontaminating pool water and established a practical decontamination method by demonstrating the process at several pools in the Fukushima prefecture.
Saegusa, Hiromitsu; Funaki, Hironori; Kurikami, Hiroshi; Sakamoto, Yoshiaki; Tokizawa, Takayuki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 12(1), p.1 - 12, 2013/03
Since the Fukushima Daiichi Nuclear Power Plant accident caused by the Tohoku Region Pacific Coast Earthquake, decontamination work has been conducted. Decontamination wastes including removed soil, grass and trees are to be stored safely at temporary storage facilities for up to three years, after which they will be transferred to a planned interim storage facility. The decontamination pilot project was carried out in both the restricted and planned evacuation areas in order to assess decontamination methods and demonstrate measures for radiation protection of workers. Temporary storage facilities of different technical specifications were designed and constructed under various topographic conditions and land-use. In order to support designing, constructing and monitoring of temporary storage facilities for decontamination wastes during the full-scale decontamination, technical know-how obtained during the decontamination pilot project has been identified and summarized in this paper.
Kurikami, Hiroshi; Yoshikawa, Hideki; Sasamoto, Hiroshi; Iijima, Kazuki; Zaima, Naoki; Munakata, Masahiro; Tokizawa, Takayuki; Nakayama, Shinichi
JAEA-Review 2012-045, 129 Pages, 2013/01
JAEA-Review-2012-045.pdf:15.94MB
This report shows the records of JAEA's investigation on dose rate reduction at the Fukushima University Junior High School and Kindergarten. The main outcomes are as follows. (1) 
experiments were performed to investigate intrusion depth of radiocesium in the soil. Based on the experiment, we proposed a countermeasure to reduce air dose rates. (2) The action we proposed allowed dose rate reduction to about one tenth to one twentieth at playgrounds. (3) Follow-up monitoring was performed after one year, and shows no obvious evidence of recontamination at the playgrounds. (4) Decontamination of a tree was tested. Radiocesium was accumulated around the root. By removing the soil, the air dose rate at about one-meter distance from the tree was decreased.
Miyahara, Kaname; Tokizawa, Takayuki; Nakayama, Shinichi
IAEA-CN-211 (Internet), 2 Pages, 2013/01
After the Fukushima Dai-ichi nuclear accident, Japan Atomic Energy Agency (JAEA) was chosen by the Government to conduct decontamination pilot projects at selected sites in Fukushima prefecture. Despite tight boundary conditions in terms of timescale and resources, the demonstration projects have served their primary purpose of development of a knowledge base to support more effective planning and implementation of stepwise regional remediation of the evacuated zone. A range of established, modified and newly developed techniques have been tested under realistic field conditions and their performance characteristics determined. The results of the project can be summarised in terms of site characterisation, clean-up and waste management.
Tanaka, Masaru*; Gofuku, Akio*; Ishizaka, Kaoru*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Research 2010-054, 76 Pages, 2011/02
JAEA-Research-2010-054.pdf:4.46MB
To obtain public understanding on the uranium mining sites reclamation at Ningyo-toge Environmental Engineering Center, it is necessary to conduct appropriate Risk Communication (RC). In this study, to discuss the appropriate Risk communication method on the uranium mining sites reclamation, making of explanatory material by university student, and questionnaire survey on the risk perception were conducted.
Ishizaka, Kaoru*; Tanaka, Masaru*; Suzuki, Kazuhiko*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Research 2008-086, 64 Pages, 2008/12
JAEA-Research-2008-086.pdf:1.99MB
In this study, to discuss the appropriate Risk Communication (RC) method on the uranium mining sites reclamation, comparative investigation of RC cases which concern the siting of solid waste management facilities and nuclear facilities, and questionnaire survey on the risk perception of landfill were conducted. As a result of comparative investigation, information disclosure and supplement are important factor to obtain public trust on the siting plan and developer. As assumption of the public participation, it is necessary the safety assurance of the siting plan and regional development plan cover a long period. As a result of questionnaire survey, it was shown that the almost people worried about health and the environmental impact of radioactive waste; moreover, there are a lot of ratios of the peoples who felt a dangerous and scary sensuously.
Yabuta, Naohiro*; Kawai, Jun*; Hikawa, Tamae*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Review 2008-015, 92 Pages, 2008/11
JAEA-Review-2008-015.pdf:11.88MB
On the closure of uranium mine site at Ningyo-Toge Environmental Engineering Center Japan Atomic Energy Agency, the action plans for risk communication with residence and local governments were developed and implemented. Under a practical program of the risk communication, an ethnographical research on Ningyo-Toge Environmental Engineering Center has been conducted by local high school students. The research was focused on several social groups such as engineers at the Center and residents around Ningyo-Toge and described their circumstances from the past to the present, since the discovery of the uranium outcrop 1955. In the second year of the program, the results of the research were presented at symposium and the students had opportunities to exchange their views with others from different high schools that held in similar programs. Through those activities, the importance of the program was rediscovered and some new issues were also identified.
Yabuta, Naohiro*; Kawai, Jun*; Hikawa, Tamae*; Tokizawa, Takayuki; Sato, Kazuhiko; Koga, Osamu
JAEA-Review 2008-014, 133 Pages, 2008/11
JAEA-Review-2008-014.pdf:11.04MB
On the closure of uranium mine site at Ningyo-Toge, the action plans for risk communication with residence and local governments were developed and implemented. Under a practical program of the risk communication, an ethnographical research on Ningyo-toge has been conducted by local high school students. The research was focused on several social groups such as engineers at the Center and residents around Ningyo-toge and described their circumstances from the past to the present. In addition, it should be noted that as a results, the research project led several effects listed below; (1) High school students understood significance of the uranium development projects implemented at Ningyo-toge, (2) Differences of standpoints between local residents and Ningyo-toge became clearer, (3) Foundation to communicate between local communities and Ningyo-toge was found out, (4) The educational program on an ethnographical research was conducted autonomously by local high school students.
Ota, Masakazu*; Iida, Takao*; Yamazawa, Hiromi*; Nagara, Shuichi; Ishimori, Yuu; Sato, Kazuhiko; Tokizawa, Takayuki
Journal of Nuclear Science and Technology, 44(5), p.791 - 800, 2007/05
Times Cited Count：16 Percentile：70.27(Nuclear Science & Technology)A study on the effectiveness of clay-mixed soil as a barrier against radon exhalation from soil surface was carried out at a closed uranium mine in Japan. Continuous observations of radon flux at a clay-covered soil surface and a bare soil surface, radon concentration in soil air and soil moisture content were carried out for 80 days. The mean of radon flux of the clay-covered plot was one fifth of that of the bare plot. This result indicates that clay-mixed soil worked effectively for reduction of radon exhalation from the soil surface. A numerical analysis with a one-dimensional radon transport model for unsaturated soil was carried out to evaluate the effectiveness of the barrier under dry weather conditions. Calculation results suggested that the barrier works effectively even under the dry condition.
Koga, Osamu; Nagara, Shuichi; Sato, Kazuhiko; Tokizawa, Takayuki
JNC TN6410 2005-001, 38 Pages, 2005/03
JNC-TN6410-2005-001.pdf:1.33MB
Mesh models are formed to carry out simulations of the groundwater flow and the solute transport at around former Yotsugi Open-Pit Mine and Yotsugi Mill Tailings Dam. Also, hydraulic field survey and literature survey are carried out to set boundary conditions and property values for the simulations.Mesh models are formed for Yotsugi Open-Pit Mine, Yotsugi Mill Tailings Dam and the wide area so that boundary conditions could be given to the model for Yotsugi Mill tailings Dam. These three models are confirmed to perform properly for analyses.Hydraulic field survey is carried out in the wide area to estimate the groundwater distribution and to understand the top hydraulic head boundary of the model. As result, groundwater level at the ridge used as a boundary of the model is set to be twenty meters depth.Values of effective diffusion coefficient, specific storage and absolute density are set to be used for the simulation of the solute transport by the literature survey.
Sugitsue, Noritake; Tanaka, Yoshio; Tokizawa, Takayuki; Annen, Sotonori; Yonekawa, Shigeru; Nakakura, Hiroyuki*; Tokuyasu, Takashi*; Aritomi, Tadahiko*
Dekomisshoningu Giho, (30), p.53 - 66, 2004/09
In the Ningyo-Toge Environmental Engineering Center, we clarify a relation of all works about the decommissioning. And, as an information base to plan promotion of efficiency of a work, we develop the Decommissioning Engineering System. The Decommissioning Engineering System consists of the function to do work support of a decommissioning, the function to gather the results information the decommissioning technology and the general evaluation function of the decommissioning plan on the basis of facilities information collected by three-dimensional CAD. The decommissioning of the nuclear fuel cycle facility has the characteristics that a period from the plan to the decommissioning is long in comparison with the general chemical plant. And the peculiarity to handle radioactive waste is a reason. In addition the System Decontamination, Dismantling, Treatment and Waste disposal are each other influence it closely in the decommissioning process. Therefore as for the decommissioning process, system engineering is important.
