Tohoku Electric Power Co. Inc.

02/09/2018 | Press release | Distributed by Public on 02/09/2018 03:16

Building an Intake Facility for Reactor Building Closed Cooling Seawater System at Higashidori Nuclear Power Station

TOHOKU ELECTRIC POWER CO., INC.

February 9, 2018

Building an Intake Facility for Reactor Building Closed Cooling Seawater System at Higashidori

Nuclear Power Station

Tohoku EPCO has decided to build an intake facility for reactor building closed cooling seawater system (RSW) at Higashidori Nuclear Power Station, which is to installed on a different location from the place where the existing intake facility is installed.

In the conformity assessment of Higashidori Nuclear Power Station, the faults on the premises have been under assessment. The new regulatory standards set by the Nuclear Regulation Authority (NRA) requires that an intake facility for RSW should not be built above any faults that might be active for the foreseeable future*.

The existing intake facility is installed above the m-a fault. Based on the results of the surveys of trenching and drilling, we have judged this fault is inactive for the foreseeable future. We expressed our judgement in conformity assessment meetings. Moreover, we launched an additional survey, such as trenching and boring cores, in May 2017 to enhance data to confirm the judgement. In November 2017, an on-site survey was conducted by the NRA.

The NRA has commented that it cannot admit our judgment because even the additional survey could not strictly prove the relationship between the m-a fault and its upper layers.

Our judgment on the m-a fault remains unchanged, but it is practically difficult to further survey the upper layers on the fault; therefore, we have decided to build an intake facility for RSW not just above the m-a fault.

We are resolved to make continuous efforts to improve safety at our nuclear power stations beyond the framework of the new regulatory standards.

*: Faults that might be active for the foreseeable future mean faults with activities later than the

Quaternary Late Pleistocene (120,000 to 130,000 years ago).

(Attached) Figures of the intake facility for reactor building closed cooling seawater system (RSW) at

Higashidori Nuclear Power Station

Attached

Figures of the Intake Facility for Reactor Building Closed Cooling Seawater System (RSW) at

Higashidori Nuclear Power Station

Ground plan of Higashidori Nuclear Power Station