Skyrmion creation and annihilation by electric current vorticity

Fujimoto, Junji*; Funaki, Hiroshi*; Koshibae, Wataru*; Matsuo, Mamoru; Maekawa, Sadamichi*

IEEE Transactions on Magnetics, 58(8), p.1500407_1 - 1500407_7, 2022/08

https://doi.org/10.1109/TMAG.2021.3139638

Design, construction and monitoring of temporary storage facilities for removed contaminants

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.

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018) (Translated document)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2020-007, 249 Pages, 2020/10

JAEA-Research-2020-007.pdf:15.83MB

The accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Evaluation of sediment and Cs redistribution in the Oginosawa River catchment near the Fukushima Dai-ichi Nuclear Power Plant using integrated watershed modeling

Sakuma, Kazuyuki; Malins, A.; Funaki, Hironori; Kurikami, Hiroshi; Niizato, Tadafumi; Nakanishi, Takahiro; Mori, Koji*; Tada, Kazuhiro*; Kobayashi, Takamaru*; Kitamura, Akihiro; et al.

Journal of Environmental Radioactivity, 182, p.44 - 51, 2018/02

https://doi.org/10.1016/j.jenvrad.2017.11.021

The Oginosawa River catchment lies 15 km south-west of the Fukushima Dai-ichi nuclear plant. The General-purpose Terrestrial Fluid-flow Simulator (GETFLOWS) code was used to study sediment and Cs redistribution within the catchment. Cesium-137 input to watercourses came predominantly from land adjacent to river channels and forest gullies. Forested areas far from the channels only made a minor contribution to Cs input to watercourses, total erosion of between 0.001-0.1 mm from May 2011 to December 2015. The 2.3-6.9% y decrease in the amount of Cs in forest topsoil over the study period can be explained by radioactive decay (approximately 2.3% y), along with a migration downwards into subsoil and a small amount of export. The amount of Cs available for release from land adjacent to rivers is expected to be lower in future than compared to this study period, as the simulations indicate a high depletion of inventory from these areas.

Numerical study of sediment and Cs discharge out of reservoirs during various scale rainfall events

Kurikami, Hiroshi; Funaki, Hironori; Malins, A.; Kitamura, Akihiro; Onishi, Yasuo*

Journal of Environmental Radioactivity, 164, p.73 - 83, 2016/11

AA2015-0827.pdf:2.61MB

https://doi.org/10.1016/j.jenvrad.2016.07.004

We performed simulations using the three-dimensional finite volume code FLESCOT to understand sediment and radiocesium transport in generic models of reservoirs with parameters similar to those in Fukushima Prefecture. The simulations model turbulent water flows, transport of sediments with different grain sizes, and radiocesium migration both in dissolved and particulate forms. To demonstrate the validity of the modeling approach for the Fukushima environment, we performed a test simulation of the Ogaki Dam reservoir over a typhoon. We simulated a set of generic model reservoirs systematically varying features such as flood intensity, reservoir volume and the radiocesium distribution coefficient. The results ascertain how these features affect the amount of sediment or Cs discharge downstream from the reservoirs, and the forms in which Cs is discharged. Silt carries the majority of the radiocesium in the larger flood events, while the clay-sorbed followed by dissolved forms are dominant in smaller events. The results can be used to derive indicative values of discharges from Fukushima reservoirs under arbitrary flood events.

Design, construction and monitoring of temporary storage facilities for removed contaminants

Saegusa, Hiromitsu; Funaki, Hironori; Kurikami, Hiroshi; Sakamoto, Yoshiaki; Tokizawa, Takayuki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 12(1), p.1 - 12, 2013/03

https://doi.org/10.3327/taesj.J12.028

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.

Prediction of groundwater flow rate into shaft to the depth of 50m

Shibano, Kazunori; Orukawa, Go*; Yasue, Kenichi; Funaki, Hironori; Kurikami, Hiroshi

JAEA-Research 2008-033, 27 Pages, 2008/06

JAEA-Research-2008-033.pdf:2.33MB

The hydrogeological model of shallow zone was built by using the data of core observation and permeability tests in the shallow boreholes drilled prior to the shaft excavation. Then, groundwater flow analysis of shaft excavation was performed using the hydrogeological model. By making a comparison between inflow rate into the shaft obtained by the analysis and measured inflow rate to the depth of 50m, the hydrogeological model and the performance of the cut-off wall established around the shaft were evaluated. The prediction analysis showed that the cut-off wall was the adequate performance and the hydraulic conductivity of fresh rock in the Koetoi Formation directly influenced the inflow rate below the cut-off wall. The simplified model in the report is efficient to reflect the excavation execution of the underground facility.

Basic approach to solute transport analysis utilizing information from surface-based investigations at two generic underground research laboratories

Maekawa, Keisuke; Sawada, Atsushi; Ota, Kunio; Kurikami, Hiroshi; Kunimaru, Takanori; Funaki, Hironori; Hama, Katsuhiro; Takeuchi, Shinji; Amano, Kenji; Saegusa, Hiromitsu; et al.

JAEA-Review 2007-011, 8 Pages, 2007/03

JAEA-Review-2007-011.pdf:0.66MB

In the current programme for research and development on the technical aspects of geological disposal, it is of significance to establish techniques for evaluating solute transport with a direct link to surface-based investigations through the processes of data interpretation, modelling and parameter designation within the immediate five years following the H17 Project. This report presents a basic approach to promoting multidisciplinary research activities involving field investigations and relevant solute transport analysis.

Horonobe underground research laboratory project; The present understanding of geological environment

Funaki, Hironori; Matsui, Hiroya; Hama, Katsuhiro; Kunimaru, Takanori; Ishii, Eiichi; Kurikami, Hiroshi

Proceedings of International Workshop on Waste Management in Sapporo, p.125 - 128, 2005/08

Japan Nuclear Cycle Development Institute (JNC) has been conducted an underground research laboratory (URL) project for the sedimentary rock (Neogene) in Horonobe, Hokkaido. The main aims are to understand the geological environment and to confirm reliability of technologies for geological disposal of High-Level Radioactive Waste (HLW) under actual sedimentary rock. This is an investigation project which is planned over 20 years and it is divided into three phase; surface-based investigation phase, construction phase and operation phase. In this paper, we report the present understanding of geological environment.