Earth Science (Chikyu Kagaku)

Special issue on "Earth scientific challenge of Nuclear power Station"

Organizer group of Special issue

Article type: Article
2015 Volume 69 Issue 5 Pages 253-254
Published: September 25, 2015
Released on J-STAGE: May 12, 2017

DOIhttps://doi.org/10.15080/agcjchikyukagaku.69.5_253

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Seismic safety for the nuclear power plants in Japan(<Special issue>Earth scientific challenge of Nuclear power station)

Masaaki TATEISHI

Article type: Article
2015 Volume 69 Issue 5 Pages 255-266
Published: September 25, 2015
Released on J-STAGE: May 12, 2017

DOIhttps://doi.org/10.15080/agcjchikyukagaku.69.5_255

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Since the severe accident of the Fukushima Daiichi nuclear power station, it has been passed more than 4 years. This accident had been caused by the 2011 off the Pacific coast of Tohoku earthquake and its associated tsunami. The mechanism of this great earthquake and tsunami has been still investigated and analyzed by many scientists. Even though, many nuclear power stations will be run again, contrary to the people's wishes of decommissioning of nuclear power station. In this paper, the criteria ground motion to be most important and the accreditation of active faults to be base for seismic safety of nuclear power station, were examined. Earth scientists must contribute aggressively to ask the seismic safety of nuclear power plant in Japan. Today when disasters have happened so frequently in Japan that people are holding a big fear for earthquakes and volcanoes threatening the safety of nuclear power plant. We must further advance the study about regional geology, underground structure, active faults and volcanism together with the residents and citizens from a standpoint of protecting their lives and living.

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Contaminated water issues at Fukushima Daiichi Nuclear Power Station : Its geological background and challenges(<Special issue>Earth scientific challenge of Nuclear power station)

Naoaki SHIBASAKI

Article type: Article
2015 Volume 69 Issue 5 Pages 267-282
Published: September 25, 2015
Released on J-STAGE: May 12, 2017

DOIhttps://doi.org/10.15080/agcjchikyukagaku.69.5_267

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The contaminated water issues at the Fukushima Daiichi Nuclear Power Station (NPS) of the Tokyo Electric Power Company, Incorporated (TEPCO) have not been solved yet even after 4 years since the severe nuclear accident triggered by the 2011 off the Pacific coast of Tohoku Earthquake. The issues are crucial for the safe decommissioning of the Fukushima Daiichi NPS, however, there have been many problems related to the contaminated water. The groundwater bypass, that has been employed as one of the countermeasures to reduce the ingress of groundwater into the reactor and turbine buildings is not effective as expected. These are due to the lack of investigations and understanding on the complex geology and hydrogeology at the site. The hydrogeological profiles and subsequent groundwater simulation models prepared by the TEPCO and the Government of Japan are very simple. Although the disclosed columnar sections in the NPS site are limited, it was revealed that the facies of the D4 unit of the Dainenji Formation, which is mainly composed of mudstone and sandstone, significantly changes even in a local scale. In this paper, the author reviewed the geological background of the NPS site, brief history of the contaminated water issues, subsurface ground conditions below the contaminated water tanks, and problems on geological and hydrogeological data with subsequent groundwater modeling analysis. The author also pointed out the geological challenges of the on-going measures to reduce groundwater ingress, such as groundwater bypass, frozen (ice) wall, and the activating of the subdrain system in the NPS.

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Queries with effect of the groundwater bypass as countermeasures for contaminated water in Fukushima Daiichi Nuclear Power Plant(<Special issue>Earth scientific challenge of Nuclear power station)

Kazuyuki SUENAGA

Article type: Article
2015 Volume 69 Issue 5 Pages 283-288
Published: September 25, 2015
Released on J-STAGE: May 12, 2017

DOIhttps://doi.org/10.15080/agcjchikyukagaku.69.5_283

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The "Mid-and-Long-Term Roadmap" for the reactor decommissioning of Fukushima Daiichi Nuclear Power Plant (hereafter referred to "FDNPP") is drastically behind schedule due to the inadequate management by Tokyo Electric Power Co., Inc. (hereafter referred to "TEPCO"). The contaminated water has been increasing with 400m3 /day on average continuously by the groundwater inflow into the reactor buildings after the earthquake disaster due to loss for the pumping function of the sub-drain which was originally installed by TEPCO. TEPCO and the Committee on Countermeasures for Contaminated Water Treatment (hereafter referred to as "CCCWT") have only considered the groundwater in the upper permeable layer as the inflow of groundwater into the reactor buildings, so that TEPCO excludes the role of the groundwater in the lower permeable layer as another source of contaminated water. The groundwater in the lower permeable layer plays an important role in flow into the reactor buildings based on the information in regards to the existing geological cross-section and groundwater table publicly announced by TEPCO. The data also suggest that the upper permeable layer is contiguous to the lower permeable layer in some parts. In addition, as the result of the analysis for the data measured by TEPCO, the amount of retaining water has not ever reduced after operation of the Groundwater Bypass. Not only the effective countermeasures by the Groundwater Bypass will not be expected, but also the expansion of the contaminated water into the sea area will be occurred by the misunderstanding of the aquifer structure by TEPCO. TEPCO and CCCWT should reconsider the method of the Groundwater Bypass for the protection of the contaminated water in FDNPP.

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Damage of the reclaimed land in Fukushima Daiichi Nuclear Power Station by the 2011 off the Pacific coast of Tohoku Earthquake(<Special issue>Earth scientific challenge of Nuclear power station)

Toshiaki SHIONO

Article type: Article
2015 Volume 69 Issue 5 Pages 289-292
Published: September 25, 2015
Released on J-STAGE: May 12, 2017

DOIhttps://doi.org/10.15080/agcjchikyukagaku.69.5_289

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Some facilities of the Fukushima Daiichi Nuclear Power Station (NPS) have been constructed on the reclaimed land. According to the disaster photos disclosed by the Nuclear and Industrial Safety Agency (NISA) and the Tokyo Electric Power Company, Incorporated (TEPCO), the damage caused by the earthquake motion was found at the facilities of water supply, drainage, and power supply systems. As a result, it is presumed that leakage paths of the contaminated water become complicated. To examine countermeasures against the contaminated water issues, it is indispensable to investigate the seismic damage of the reclaimed land and the facilities by the earthquake motion in detail to clarify the leakage paths of the contaminated water.

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Some traces of evolution in a human body(Introduction to Earthscience)

Haruto KODERA

Article type: Article
2015 Volume 69 Issue 5 Pages 293-300
Published: September 25, 2015
Released on J-STAGE: May 12, 2017

DOIhttps://doi.org/10.15080/agcjchikyukagaku.69.5_293

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