Demonstrative experiments on the migration of radiocesium from buried soil contaminated by the accident at Fukushima Daiichi Nuclear Power Station

Yamaguchi, Tetsuji; Shimada, Taro; Ishibashi, Makoto*; Akagi, Yosuke*; Kurosawa, Mitsuru*; Matsubara, Akiyoshi*; Matsuda, Yuki*; Sato, Shigeyoshi*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 22(2), p.21 - 27, 2015/12

https://doi.org/10.3327/jnuce.22.2_21

It is predictable from previous studies that radiocesium hardly migrate into surrounding soils and groundwater from soils contaminated by the Fukushima Daiichi Nuclear Power Plant accident if they are buried and covered with indigenous soils. This study demonstrated the prediction by performing in-situ migration experiments over a year in a public park in Miho, Ibaraki prefecture and in two public parks in Misato, Saitama prefecture. Contaminated soils were buried at a depth range of 0.3 - 1.0 m or at 0.3 - 1.3 m and covered with indigenous soil layer of 0.3 m, and were sprinkled with water to accelerate the radiocesium migration. Migration of radiocesium was not observed from radiometric analyses of boring cores and soil water samples. Laboratory column and sorption experiments revealed that the radiocesium hardly leach out of the soil and even if they leach out from the contaminated soil, radiocesium is sorbed on surrounding soils and hardly migrate through the soli layer. Simulation of Cs-137 migration for 100 years by an advection-diffusion model showed that Cs-137 hardly migrate and decay out in the contaminated soil.

XUV-FEL spectroscopy; He two-photon ionization cross-sections

Sato, Takahiro*; Iwasaki, Atsushi*; Ishibashi, Kazuki*; Okino, Tomoya*; Yamanouchi, Kaoru*; Adachi, Junichi*; Yagishita, Akira*; Yazawa, Hiroki*; Kannari, Fumihiko*; Aoyama, Makoto; et al.

Europhysics News, 42(5), P. 10, 2011/09

The resonant and non-resonant two-photon single ionization processes of He were investigated using intense free electron laser light in the extreme ultraviolet (XUV) region (53.4-61.4 nm) covering the 1s-2p and 1s-3p resonant transitions of He. On the basis of the dependences of the yield of He on the XUV light-field intensity at 53.4, 58.4, 56.0 and 61.4 nm, the absolute values of the two-photon ionization cross sections of He at the four different wavelengths and their dependence on the light-field intensity were determined for the first time.

Irradiation history of Itokawa regolith material deduced from noble gases in the Hayabusa samples

Nagao, Keisuke*; Okazaki, Ryuji*; Nakamura, Tomoki*; Miura, Yayoi*; Osawa, Takahito; Bajo, Kenichi*; Matsuda, Shintaro*; Ebihara, Mitsuru*; Ireland, T.*; Kitajima, Fumio*; et al.

Science, 333(6046), p.1128 - 1131, 2011/08

https://doi.org/10.1126/science.1207785

A steroid surface materials record regolith processes and a history of cosmic-ray irradiation. Noble gas isotopes in three rocky grains from Itokawa have been determined. High concentrations of solar He, Ne, and Ar, as high as those in lunar soils, are released at variable temperatures from each sample. The isotopic compositions are essentially identical to those of solar wind but distinguishable in He relative abundance. These noble gas characteristics can be explained by repeated implantation and preferential loss of solar He by removal of weathered He-rich rim on the grain surface through friction among regolith grains on Itokawa. Residence time of regolith materials on Itokawa is alculated to be shorter than 10 Myr, suggesting that regolith materials of small asteroids would escape easily to space.

Uranium distribution in the environment and its contribution to environmental radioactivity

Sato, Kazuhiko; Ishibashi, Makoto*; Kawatsuma, Shinji

Dekomisshoningu Giho, (38), p.2 - 10, 2008/11

http://www.randec.or.jp/publish/documents/gihou/Decommissioning%20gihou_38.pdf

Clearance of materials and disposal of radioactive waste generated from uranium utilizing facilities which include uranium conversion and enrichment facilities, and fuel fabrication facility among the nuclear fuel cycle has been discussed in Japan. These materials are supposed to be contaminated with long-lived natural nuclide, i.e. uranium. Uranium is widely distributed among the environment, e.g. soil, rock, river-water, groundwater and so on. Furthermore, uranium is also contained in some building materials and consumer goods. Literature survey about distribution of uranium in the environment and measurement of uranium concentration in some materials were carried out. As a result, it is revealed that range of U-238 activities in soils in Japan is from 0.001 Bq/g to about 1 Bq/g. Addition to that, the range of building materials is overlapped by that of soils, while some consumer goods showed relatively high activities. Futermore, dose contribution of uranium series nuclides to the environmental radiation dose were discussed. It is suggested that, sum of environmental radiation dose in Japan is about 1.5 mSv/yr and dose contribution of uranium series nuclides is about 0.8 mSv/yr.

Study of sub-surface disposal concepts for uranium waste, 3

Tsujimura, Seiichi; Funabashi, Hideyuki; Ishibashi, Makoto*; Takase, Toshio*; Kurosawa, Mitsuru*

JAEA-Research 2007-030, 105 Pages, 2007/03

JAEA-Research-2007-030.pdf:7.72MB

Uranium waste has characteristics that it is rarely expected to decay its radioactivity and it is not almost recessary to consider external exposure to radiation from waste package. We studied resonable sub-surface disposal concepts for uranium waste considering the characteristics. It showed feasibility of this system. In 2006, the study was done to evaluate the correlation between dose to the public and the parameter in consideration of the uncertainty of the parameter by comprehensive sensitivity analysis calculating repeatedly dose with the data sets by random sampling in parameter ranges given adequately, because last year's study was an evaluation intended for a limited site. The result was that two parameters, "flow velocity of underground water of repository neighborhood" and "distribution coefficient of uranium in natural barrier", had correlation with dose to the public.

Study of Subsurface Disposal Concepts for Uranium Waste

Yamamoto, Masayuki*; Ishibashi, Makoto*

JNC TJ8440 2005-001, 72 Pages, 2005/03

JNC-TJ8440-2005-001.pdf:0.49MB

Uranium waste has features that the main nuclide is long-lived uranium and it is not almost necessary to consider radiation influence from waste package. Although the many studies for subsurface disposal concept of uranium waste have been done, the wastes features were not carefully considered in the former studies. The following reasonable disposal concepts have been designed considering the features in this study. (1) Concrete vault disposal concept in rock cavern (2) Monolithic disposal concept in rock cavern (3) Trench disposal concept in rock cavern / The safety of the disposal concepts during operation and after control phase has been investigated in this study. As the result, it has been shown that the exposure dose of workers due to waste package is not high. And it has been shown that the exposure dose of the public does not change so much, even if the engineered barrier has been reduced. Besides some issues regarding regulation, operation and monitoring have been picked up.

A Consideration on clearance level of natural uranium nuclide

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

no journal, , 

no abstracts in English

Uranium contribution in the environmental radiation, 2; Dose from environmental uranium

Yagi, Naoto; Ishibashi, Makoto*; Sato, Kazuhiko; Kawatsuma, Shinji

no journal, , 

no abstracts in English

Solute transport analysis using discrete fracture network model, 3

Hosoya, Shinichi*; Seno, Shoji*; Nakajima, Makoto*; Atsumi, Hiroyuki*; Ishibashi, Masayuki; Morikawa, Keita; Onoe, Hironori; Kunimaru, Takanori

no journal, , 

Discrete Fracture Network (DFN) model provides the basis of groundwater flow analysis and solute transport analysis for crystalline rock. Due to its complexity, it is difficult to estimate how the input parameters influence the result of the analysis. In this study, using the data obtained in the Mizunami Underground Research Laboratory (MIU) project conducted by Japan Atomic Energy Agency (JAEA), we examined how the modeling methodology influenced the result of groundwater flow analysis and solute transport analysis.

Study of high resolution spectroscopy of LX-rays emitted from TRU using TES microcalorimeter

Nakamura, Keisuke; Aoki, Katsunori; Takasaki, Koji; Maeda, Makoto*; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English