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"Almost certainly active"

February 19, 2013


Nuclear watchdog: Fault lines under Higashidori plant are active





By RYUTA KOIKE/ Staff Writer

Geological fault lines that run beneath Tohoku Electric Power Co.'s Higashidori nuclear power plant in Aomori Prefecture are almost certainly active, according to an expert panel of the Nuclear Regulation Authority.

The assessment was part of a draft report presented when the panel met on Feb. 18. The panel also called for further studies on the activity of two separate fault lines that extend directly beneath the plant's key facilities. Tohoku Electric, meanwhile, continues to argue that the faults are inactive.

In December, the panel conducted an on-site survey that mostly focused on two fault lines, called F-3 and F-9, respectively.

"These faults are likely active and should be taken into account during earthquake preparedness planning," the draft report said.

The F-3 fault runs 400 meters west of the Tohoku Electric Higashidori nuclear plant's reactor building and extends onto the premises of Tokyo Electric Power Co.'s nuclear plant of the same name, which is under construction on an adjacent plot of land to the north.

The draft report pointed out the need for a safety assessment of the seismic ground motions and ground surface displacements that would be expected in case the F-3 and F-9 faults slipped.

Apart from these fault lines, a smaller fault runs directly beneath the nuclear reactor building, while another cuts across a coolant water intake channel and other key safety equipment. The panel said more studies are necessary to determine the activity of those smaller fault lines. It called on Tohoku Electric to present documents and other material from the time the nuclear plant was built to make up for the paucity of available data.

"We have not been able to hold detailed discussions, partly because of the limited time available during our on-site survey (in December)," NRA deputy chairman Kunihiko Shimazaki said.

The government's guidelines do not allow key nuclear power plant equipment to be built directly above an active fault.

Tohoku Electric officials held a news conference following the NRA panel meeting and insisted there are no active fault lines beneath the premises of the nuclear plant.

They said they will conduct additional surveys "to confirm the inactivity of the faults" and release the survey results in December.

The Tohoku Electric officials remained noncommittal on whether the utility will follow the recommendation of the draft report and conduct the safety assessment of the seismic ground motions and ground surface displacements in case of potential fault movement.

Tohoku Electric could be ordered to conduct further "additional surveys" if it fails to present sufficient material. That could significantly delay, or even compromise, the restart of the Higashidori nuclear plant, which Tohoku Electric has scheduled for July 2015.

Faults under Higashidori N-plant active


A Nuclear Regulation Authority expert panel Monday effectively judged some crush zones on the premises of the Higashidori nuclear power plant in Aomori Prefecture to be active faults, a decision likely to delay the restart of the plant's reactors.

With the draft assessment report on an on-site inspection of Tohoku Electric Power Co.'s nuclear power plant, which was announced at a meeting of the NRA, the plant's operator will be obliged to review its quake intensity predictions and the facility's quake resistance, as several crush zones run near the site's reactor building.

But the experts did not say whether other shorter crush zones running directly under the reactor building are active faults, and called for additional inspection.

With the draft assessment report, it is highly likely Tohoku Electric will not be able to reactivate its reactors in July 2015 as initially planned.

The Higashidori plant is the second facility after Japan Atomic Power Co.'s Tsuruga nuclear power plant in Fukui Prefecture on which the team has issued a draft assessment report confirming crush zones on the premises as active faults.

Japan Atomic Power may have to decommission the Tsuruga reactors, since they conflict with the government safety standards, as active faults were found to be running directly under the site's reactor building.

Tohoku Electric is expected to submit more data, including details on geological conditions. But the company may also be obliged to decommission its reactors, depending on the contents of the additional data.

In the draft assessment report, based on an on-site inspection conducted in December, five experts mostly agreed on the assessment of the crush zones.

The NRA is expected to ask other experts to study the scientific validity of the draft assessment report. Based on the results of that study, the NRA will make a comprehensive judgment about the safety of the Higashidori plant.

The NRA will not allow Tohoku Electric to reactivate its plants until the safety of the facility is confirmed.

In the draft assessment report, the experts determined it is highly likely two crush zones running north to south on the premises of the Higashidori plant are active faults that moved sometime during the past 110,000 years, given the characteristics of the strata observed in trenches dug for the inspection and features of lifted terrain.

The experts also said a set of active faults were created as more crush zones expanded from the first two like a network.

An accurate picture of the active faults is needed to predict the intensity of quakes. The report said a broader-scope inspection is necessary to grasp the distribution and activity of the crush zones.

Tohoku Electric had said changes in terrain were caused by a swelling effect, in which the land becomes swollen due to the influence of groundwater.

But the draft said that cannot be the reason, as there are no known examples where slips of faults were caused by the swelling effect.

In Aomori Prefecture, which hosts Japan Nuclear Fuel Ltd.'s plant for reprocessing spent nuclear fuel, Electric Power Development Co. is also building a nuclear power plant in Omamachi, which will use recovered plutonium as fuel.

The latest draft assessment report may affect the seismic assessment of core facilities involved in the nuclear fuel cycle.

Faults may be active under Aomori plant
Higashidori reactor restart won't be soon, NRA panel hints






Significant portions of major geological faults running under Tohoku Electric Power Co.’s one-reactor Higashidori nuclear power plant in Aomori Prefecture are probably active, a Nuclear Regulation Authority panel said in a draft report Monday.

The faults apparently do not run directly beneath the complex’s reactor but the assessment indicates the unit may have to remain offline for quite some time because the utility will need to reassess the plant’s quake resistance and take measures to reinforce the facilities.

The draft report, which was a summary of discussions among panel members, also touched on the need to further study other smaller faults that run underneath an area close to the reactor building.

Nuclear plant operators are banned from building reactors and related facilities important for safe atomic power output directly above active faults, and it’s possible that some faults were not detected or identified as active at the time plants were built, as suggested by recent fault probes at other atomic facilities.

Officials of Tohoku Electric, who also attended the discussions, said the utility will conduct additional geological surveys, taking into account the opinions it has received from the panel.

But the utility maintained its argument that there are no active faults on the plant’s premises. Executive Vice President Takeo Umeda said later in the day that one of the major purposes of the surveys is to “properly explain that there are no activities” in the faults. The utility plans to compile the results of the surveys in December.

The panel plans to finalize the draft report after listening to the opinions of other experts who have been tasked by the NRA to cooperate in the investigation of faults at other nuclear plants.

Government in lawsuit

The central government was named Monday in a lawsuit filed by local residents seeking the decommissioning of Chubu Electric Power Co.’s Hamaoka nuclear power plant.

The plaintiffs are demanding that the government bar Chubu Electric from restarting the nuclear plant in the coastal city of Omaezaki, Shizuoka Prefecture.

The demand on the government was added to the complaint when it was updated the same day. The update, the lawsuit’s fifth, was submitted by the plaintiffs’ lawyers to the Hamamatsu branch of the Shizuoka District Court.

The update listed an additional 155 plaintiffs, bringing the total number suing to 336.



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