Investigation of a fault at Tomari nuclear power plant in Hokkaido, Japan
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The Nuclear Regulatory Commission, which conducts screening that is a prerequisite for the restart of the Hokkaido Electric Power Tomari Nuclear Power Station, conducted a field survey on the 15th to determine whether the fault on the site was an active fault. Since the evaluation of the fault is largely related to the results of the Tomari Nuclear Power Plant review, the future decisions of the committee will be noted.
Hokkaido Electric Power is aiming to restart all Units 1 to 3 of the Tomari nuclear power plant in Tomari, Hokkaido, which has been stopped after the Great East Japan Earthquake, and has filed an application for review with the Nuclear Regulatory Commission.
On the 15th, 11 members including Akira Ishiwatari of the Regulatory Committee visited Tomari Nuclear Power Plant and investigated a fault called F-1 fault running north and south on the west side of Unit 1.
Regarding this fault, Hokkaido Electric Power said it was not an active fault as a result of the evaluation, but in February the regulatory committee expressed the view that the data was insufficient, and additional drilling investigations were being conducted. .
The committee members were observing the cross section of the fault around 5 meters deep while receiving explanations from the person in charge of Hokkaido Electric Power.
Based on the information obtained in this survey, the regulatory committee will again evaluate whether this fault is an active fault.
Under the new regulatory standards of nuclear power plants, faults recognized as moving after the “Late Pleistocene” era from 120,000 years ago to 130,000 years ago are active faults, and it is judged that the safety of facilities cannot be secured when an earthquake occurs If you do, you will not be able to pass the examination.
After the investigation, Ishiwatari of the Nuclear Regulatory Commission said, “There is no big objection to the explanation of Hokuden, but there is still insufficient data, so I would like to ask for an explanation in future examinations.”
Tomari nuclear power plant F-1 fault
The F-1 fault is a fault of approximately 360 meters in length that runs north and south through the west side of the Tomari Nuclear Power Station. It has become a big point in deliberation.
Regarding active faults, the Regulatory Committee considers active faults to be faults that appear to have moved after the “Late Pleistocene” period of 120,000 to 130,000 years ago.
Hokkaido Electric initially was based on the information on the volcanic ash of the stratum, but from the middle it was evaluated based on the stepped topography on the sea side, and the F-1 fault There are no traces of active activity, explaining that it is not an active fault.
Under such circumstances, the Regulatory Committee informed the opinion that in February the geological data was insufficient and “it cannot be denied that it is an active fault”, and Hokkaido Electric Power conducted an additional drilling survey.
Based on the new data obtained from this excavation survey, Hokkaido Electric Power has shown this month that the F-1 fault is not an active fault.