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Journal Articles

Evaluation of hydrogeochemical processes provoked by tunnel excavation and closure based on simulated experiment in a mock-up test drift

Hayashida, Kazuki; Kato, Toshihiro*; Kubota, Mitsuru*; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki

Chikyu Kagaku, 52(1), p.55 - 71, 2018/03

In this study, the simulated experimental drift was constructed in the granite of 500 m depth at Mizunami Underground Research Laboratory, and the hydrochemical process after the drift closure was observed. The groundwater chemistry around the drift changed with the change of the groundwater flow in the fractures when the gallery was constructed. The redox potential increased due to the infiltration of oxygen from the drift into the rock. After closing the drift, the redox potential of the groundwater plunged due to microbial activity, while the groundwater became alkalized conditon due to the influence of cement material such as shotcrete. The amount of cement material consumed for this alkalization was small, and it was considered that its influence would last long in accordance with the amount of cement used.

Journal Articles

Retention of rare earth elements, thorium and uranium in sedimentary rocks; A Case study in the Horonobe area of Hokkaido, Japan

Murakami, Takuma; Sasamoto, Hiroshi; Mizuno, Takashi

Chikyu Kagaku, 50(4), p.299 - 317, 2016/12

Development of techniques for investigating the long-term migration of elements in deep underground is important with respect to safety assessment for the geological disposal of high-level radioactive waste. As one study of the migration of elements in deep underground, the distribution of REE, Th and U in sedimentary rock of Horonobe area in Hokkaido was investigated, and discussed whether the difference of hydrogeological structure and lithofacies influences on the distributions. As the results, it was considered that REE and Th were mainly retained in minerals originating from terrigenous clastic and secondary mineral occurred in early diagenesis, and their distributions were relatively homogenous in both the Koetoi and Wakkanai formations. Uranium was indicated to be maintained in the sedimentary rock until now after depositing in deep-sea sediment. It was considered that the U deposition was occurred by adsorption on organic matter and reductive precipitation with decomposition of organic matter. In addition, it was confirmed that the distributions of these elements were not influenced by the difference of hydrogeological and lithofacies.

Journal Articles

Geochemistry for the Fukushima Dai-ichi Nuclear Power Plant accident; Production, dispersion and migration of radionuclides

Tanaka, Kazuya; Takahashi, Yoshio*; Fukushi, Keisuke*; Utsunomiya, Satoshi*

Chikyu Kagaku, 49(4), p.169 - 171, 2015/12

Many studies have been carried out since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This paper introduces the special issue on the FDNPP accident which includes contributions from various fields covering aerosols, soil, forest, river, ocean and application of new analytical technique to samples collected in Fukushima.

Journal Articles

Development of low-temperature thermochronology and its application to uplift and denudational history of Japanese mountains

Sueoka, Shigeru; Tsutsumi, Hiroyuki*; Tagami, Takahiro*

Chikyu Kagaku, 69(1), p.47 - 70, 2015/01

Thermochronology is a discipline to determine the timing/temperature of past thermal events based on radiometric ages, which can be used to reconstruct denudation history of mountains by converting from cooling history and have been successfully applied to major orogens worldwide in the past 40 years. It has been however difficult to apply the method to relatively young/low-relief mountains in Japan. Nonetheless, the recent development of low-temperature thermochronology has greatly expanded its applicability. In this review paper, we introduce (1) fundamentals of thermochronology, (2) recent developments of low-temperature thermochronology, (3) analytic procedures, (4) previous studies in mountains ranges abroad, (5) previous studies about uplift/denudation of Japanese mountains, (6) previous thermochronometric studies in Japanese mountains, (7) case studies of the Kiso and Akaishi Ranges by the authors, and (8) the applicability and usefulness of thermochronology in Japanese mountains.

Journal Articles

Atmospheric releases of radionuclides, 2.1$$sim$$2.4

Chino, Masamichi; Nagai, Haruyasu

Gempatsu Jiko Osen; Fukushima Daiichi Gempatsu No Chikyu Kagakuteki Sokumen, p.36 - 44, 2014/10

The book to be published is a summary of the latest knowledge on environmental contaminations due to the Fukushima Dai-ichi nuclear accident. Here, we describe the releases of radionuclides into the atmosphere which have been investigated by JAEA until now. Furthermore, it is addressed that the accuracy of estimated source term by comparing with other researches related to the source term, the problem to be solved in future.

Journal Articles

Dispersion modeling of radioactive materials

Nagai, Haruyasu; Yamazawa, Hiromi*

Gempatsu Jiko Osen; Fukushima Daiichi Gempatsu No Chikyu Kagakuteki Sokumen, p.175 - 187, 2014/09

no abstracts in English

Journal Articles

Fluctuation of radiation dose-rate during winter thunderstorm

Torii, Tatsuo; Okuyama, Shinichi; Nozaki, Tatsuo; Okubo, Koichi; Sugita, Takeshi*; Muraki, Yasushi*

Chimondai Ni Yoru Saiensu; Kyokugen Enerugi Uchubutsuri Kara Chikyukagaku Made, p.211 - 217, 2008/00

The dose rate of the $$gamma$$-rays increases in association with the activities of the thunderstorm. They were observed on the ground in the winter season of Japan. In addition to the measurement by the environmental radiation monitors set up around the fast breeder reactor, Monju, the radiation detectors were prepared which consist of the long proportional counters. The results were compared with the results measured at the same time by the environmental radiation monitors. The following two types of the radiation enhancements have been found during the winter thunderstorm activities; the gradual variation of photon intensity with energy up to a few MeV, and the burst type of the radiation that is attributed to the injection of high energy photons with the energy over 10 MeV. In this paper, we present the observed results during winter thunderstorms, and mention the runaway breakdown produced by the incidence of energetic radiation into thunderclouds.

Journal Articles

Long-term stability of geochemical environment at deep underground; Case study of minor elements in carbonate minerals

Mizuno, Takashi; Iwatsuki, Teruki

Chikyu Kagaku, 40(2), p.33 - 45, 2006/05

On a basis of Generation IV nuclear energy system, various R&D project plans for sodium cooled reactor have been drawn up including component design and balance of plant (CD and BOP). At present, CD and BOP for the reference SFR systems can be largely established from the existing knowledge and operation experience. Therefore, the project plan for CD and BOP R&D for Generation IV system is related to the system performance and the development of alternatives to the reference systems for enhanced performance with innovative technologies. This paper gives an outline of the SFR CD & BOP project plan that is examined as Generation IV R&D. The project plan covers advanced in-service inspection and repair, improved steam generator more reliability, advanced energy conversion system for higher efficiency, and leak-before-break assessment. The total schedule of the project plan consists of three steps: a viability study of proposal concepts (till 2006), performance tests for detail design specification (till 2010) and demonstration of system performance (till 2015). The R&D activities are carried out with international cooperation between France, Japan, Republic of Korea, the United Kingdom and the United States in the framework of Generation IV International Forum under the supervision of its SFR steering committee.

Journal Articles

Convenient method of UV-absorbing organic materials in river waters by high-performance gel permeation chromatography

Nagao, Seiya; Matsunaga, Takeshi; Suzuki, Yasuhiro*; Hiraki, Keizo*

Chikyu Kagaku, 35(3), p.107 - 120, 2001/08

no abstracts in English

Journal Articles

Characteristics of the fluorescent substances in the Yodo river system by three-dimensional excitation emission matrix spectroscopy

Suzuki, Yasuhiro*; Nakaguchi, Yuzuru*; Hiraki, Keizo*; Nagao, Seiya; *; *

Chikyu Kagaku, 32, p.21 - 30, 1998/00

no abstracts in English

Journal Articles

Overview of seismic safety and disaster mitigation frontier research

Ebisawa, Katsumi; Shibata, Katsuyuki; Muramatsu, Ken; Umemoto, Michitaka

Chikyu Wakusei Kagaku Knren Gakkai 1998-Nen Godo Taikai Yokousyu, p.22 - 23, 1998/00

no abstracts in English

Journal Articles

Spectroscopic properties of fluorescent substances in natural waters, 1

Suzuki, Yasuhiro*; Nagao, Seiya; Nakaguchi, Yuzuru*; Matsunaga, Takeshi; Muraoka, Susumu; Hiraki, Keizo*

Chikyu Kagaku, 31, p.171 - 180, 1997/00

no abstracts in English

Journal Articles

Gole,silver and rare earth elements in quartz-calcite veins distributed over Kushikino district

Sasaki, Yuji; *; *; *; *

Chikyu Kagaku, 23, p.97 - 103, 1989/00

no abstracts in English

13 (Records 1-13 displayed on this page)
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