Reassessment of the geological condition of the ground beneath Kashiwazaki-Kariwa Nuclear Power Plant. Nuke Info Tokyo No. 143
Niigata Prefecture should hold an earthquake and ground condition subcommittee meeting as soon as possible.
Although more than 100 days have passed since the accident, nobody knows when and how the problems of the Fukushima Daiichi Nuclear Power Plant (NPP) will be resolved. However, we now see the effects of what the government calls the peaceful use of atomic energy – the continuing trial and error in the work to remove radioactive materials from heavily contaminated water; the danger of further releases of tons of radioactive materials; the difficulties of cooling down the nuclear fuel which has already gone into a state of meltdown; the nuclear reactors, the reactor containments and the reactor buildings in a seriously damaged state; the workers at the plants being exposed to high levels of radiation; children being exposed to radiation on a day-to-day basis; the people of Fukushima distraught as they have little option but to roam from town to town; and many tons of radioactive debris at the accident site.
When the Niigata Chuetsu-Oki Earthquake struck in July 2007, all seven nuclear reactors at the Kashiwazaki-Kariwa NPP shut down. As Niigata Prefecture’s technical committee on the safety control of nuclear power plants endorsed the restart of the nuclear plants, four reactors are now operating. However, the four reactors are not safe to run even though they have been restarted, with pro-nuclear people supporting the restart of the reactors and anti-nuclear power people opposing the restart. The people of Niigata Prefecture, for their safety and assurance, wanted the committee to reconsider, pointing out a number of matters the committee had not sufficiently discussed. However, the chairman of the technical committee and each chairman of the other two subcommittees which discuss technical matters repeated only the engineering points of view without due consideration for safety issues, and thus the reactors were restarted. We should not allow the members of these committees to get away with the excuse that the disaster at Fukushima Daiichi NPP was “unforeseeable.”
Seismic activity possible in the Madogasaka Fault and the fault immediately beneath the Kashiwazaki-Kariwa NPP
The Great East Japan Earthquake on March 11th was a magnitude 9.0 earthquake, which lead to large crustal disturbances. It is likely that these have altered the stress fields over a wide area of the Japanese archipelago.
The next morning, March 12th, an M6.7 earthquake occurred in the area between Niigata and Nagano Prefectures. The ground under the Iiyama Line, running along the Shinano River collapsed, leaving the railroad track hanging in the air. Heavy damage occurred in Sakae Village, Nagano Prefecture, and in Tsunan Machi and Tokamachi City, Niigata Prefecture. Furthermore, on April 11th, an M7.0 earthquake occurred in Iwaki City, Fukushima Prefecture. A new earthquake fault has shown up on the surface of the ground along the Yunotake and Idotani faults in Iwaki City. From government back-checks concerning earthquakes for the Fukushima NPPs, the government had judged that the Yunotake fault was not active.
The Nuclear and Industrial Safety Agency (NISA) therefore sent an official notice to all electric power companies asking them to report two matters to NISA by May 31st: 1. Reassess the faults, fault geometries, and lineaments which should be considered for seismic design; 2. If there is a fault which will affect the ground under nuclear plants, reassess the potential seismic movements.
Tokyo Electric Power Company (TEPCO) reported to NISA that they had summarized the information about other faults which they did not consider when the nuclear plants were built based on former investigations. They also reported that they would gather data concerning the impacts of the Great East Japan Earthquake and the relationship between earthquakes and faults, which they would reflect in future assessments.
This official NISA notice revealed that nationwide a total of 432 faults were ignored in assessments. NISA issued an additional official notice on June 3rd, to which reports must be submitted by August 31st.
On May 31st, TEPCO reported three faults which were not considered when Kashiwazaki-Kariwa NPP was designed: 1. Hosogoe fault (7 km in length); 2. Madogasaka syncline (11.5km in length); and 3. a fault inside the Kashiwazaki-Kariwa NPP. This fault inside the NPP includes many sub-faults such as alpha-faults, beta-faults, F-faults, and V-faults. If these faults move, reactor buildings or turbine buildings may begin to tilt. The Madogasaka syncline is a fault that runs into the power station from the northwest. If this fault moves, it will probably cause a serious earthquake in which the ground will move. While the local anti-nuclear movement has repeatedly asserted this concern since August 1974, it has been disregarded by the Japanese government and by TEPCO and scholars who support nuclear power in the Niigata Prefecture’s subcommittee on earthquakes and the geological condition of the ground.
Discussion in the Japanese Parliament
If the fault inside the Kashiwazaki-Kariwa NPP or the Madogasaka syncline were active, this would have prevented the Kashiwazaki-Kariwa NPP from being built. The government and TEPCO have therefore repeatedly asserted that these faults will not move as they are old faults.
On November 22nd, 1991, the following discussion was held at the Senate’s Science and Technology Special Committee.
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If the fault directly under the Kashiwazaki-Kariwa NPP reactor core moves, is the Kashiwazaki-Kariwa nuclear power plant safe? Or is it safe because the fault does not move?
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Because we recognize that the fault does not move, the plant is safe.
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What are the grounds for asserting that the fault does not move?
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The fault passes through the Nishiyama fault and the lower part of the Yasuda fault, but does not go through the upper part of the Nishiyama fault and the Banjin sand stratum. Based on guidelines for seismic design that the fault should not have moved for over 50,000 years, we concluded that the fault will not move in the future.
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On September 2006, the Regulatory Guide for Aseismic Design of Nuclear Power Reactors was revised. The basis for judging an active fault was changed from 50,000 years to 130,000 years in the past; the Late Pleistocene. After the Niigata Chuetsu-Oki earthquake in July 2007, anti-nuclear power representatives asked NISA the following.
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The standard was changed from 50,000 years to 130,000 years in the past. The existence of the fault inside the Kashiwazaki-Kariwa NPP indicates that the plant is in an inappropriate location for a nuclear power plant, doesn’t it?
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A:
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The upper Yasuda layer was accumulated after the Late Pleistocene (130,000 years ago). Since the fault does not pass through the Yasuda layer the guideline for plant location has not been contravened.
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However, on April 11th 2011, the fault which does not pass through the layer accumulated in the Late Pleistocene moved, suggesting that the standard is clearly deficient. Therefore, although the May 31st TEPCO report disregarded the three faults discussed above for Kashiwazaki-Kariwa NPP, it is possible that the fault inside the Kashiwazaki-Kariwa NPP will cause the most serious damage to the power plant.
Niigata Prefecture’s technical committee on nuclear power plant safety held a second meeting on June 21st. Several members pointed out that the government has absolutely no grounds for guaranteeing that other nuclear power plants besides Hamaoka NPP are safe. Some of the members who had formerly agreed with the government also spoke up.
We are seriously concerned for the future of Kashiwazaki-Kariwa NPP, and so since the Fukushima disaster we shall be paying close attention to the discussion in Niigata Prefecture in order to ensure that the details are correctly handled without any further deception.
Kazuyuki Takemoto (Kashiwazaki Alliance Against Nuclear Energy), Yukio Yamaguchi (CNIC Co-Director)
