Overview of Work related to Earthquake Countermeasures for Hamaoka Nuclear Power Station Units 3 and 4
September 25, 2013
Chubu Electric Power Co.,Inc.
Because Hamaoka Nuclear Power Station is located within the hypocentral region of a projected Tokai earthquake, earthquake-resistant design was applied from the initial stages of construction of the station in order to provide a margin of safety. Since then, Chubu Electric Power has worked constantly to reflect the very latest findings and increase the safety of the plant, for instance by voluntarily conducting work aimed at increasing earthquake resistance.
More recently, we have proceeded with the examination of concrete plans for construction work related to further earthquake countermeasures at Hamaoka Nuclear Power Station based on the status of Cabinet Office Committee for Modeling a Nankai Trough Megaquake reviews and new regulatory requirements. (Press Released Friday, April 26, 2013)
We have now decided on construction plans for earthquake countermeasures to be introduced to Units 3 and 4. An overview of these plans is provided below.
１. Setting of seismic ground motion for earthquake countermeasures
The source fault model generating strong ground motion formulated by the Cabinet Office's Committee for Modeling a Nankai Trough Megaquake (termed the "Cabinet Office model" below) assumes an earthquake of the greatest magnitude that could occur along the Nankai Trough, based on the latest research findings and other data. The model is formulated with consideration of uncertainty regarding the location of the strong motion generation area, in which seismic waves will be particularly intense.
We therefore set a seismic ground motion of 1,200 gals for earthquake countermeasures, a figure exceeding the maximum of approximately 1,000 gals based on the Cabinet Office model. We further reflected the amplification of ground motion observed at Unit 5 during the Suruga Bay earthquake in the Cabinet Office model, producing a maximum figure of approximately 1,900 gals, and we therefore set an amplified seismic ground motion of 2,000 gals for earthquake countermeasures.
２. Work to be performed
We examined the necessity for work to introduce new measures to facilities important to earthquake-resistant design* based on the seismic ground motion for earthquake countermeasures (1,200 gals). As a result of these considerations, we have decided to perform work including work to reinforce supports for pipes and cable-related equipment. In addition, based on records from seismic observation points within the station site, we have decided to perform work to reinforce facilities including the tsunami protection wall at Unit 5 and the Unit 4 water intake pond based on the amplified seismic ground motion for earthquake countermeasures (2,000 gals).
*The reactors themselves, associated pipes, equipment designed to shut down and cool the reactors, equipment designed to seal in radioactive materials, fuel-related equipment, tsunami protection facilities, flooding-prevention facilities, facilities for response to severe accidents and other major events, power sources and electrical equipment related to these facilities, and buildings and structures housing these facilities and equipment