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.
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.