Withstanding a Megaquake
Establishing preparedness against the Nankai Trough Megaquake
Additional measures are implemented for Units 3 and 4 to establish preparedness against the Nankai Trough Megaquake, which is expected to be even greater than the triple megaquake, for further enhancement of quake resistance (Announced in September 2013).
1. Setting Seismic Motion for Earthquake Countermeasures
We set the seismic motion for earthquake countermeasures based on the seismic motion calculated from 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") announced in September 2013.
Seismic ground motion for earthquake countermeasures (around up to 1,200 gals) is set, based on the seismic ground motion determined under the Cabinet Office Model (around up to 1,000 gals)
Amplified seismic ground motion for earthquake countermeasures (2,000 gals) is set based on the seismic ground motion hypothetically reflecting the amplification observed at Unit 5 in the earthquake at Suruga Bay to the Cabinet Office Model (around up to 1,900 gals)
The Committee for Modeling the Nankai Trough Megaquake
The Committee for Modeling the Nankai Trough Megaquake was set up at the Cabinet Office in August 2011 in response to the Tohoku-Chihou-Taiheiyou-Oki Earthquake. The Committee consists of scientists and engineering researchers to comprehensively organize and analyze existing scientific insight and model largest quakes and tsunamis that could result from the Nankai Trough Megaquake.
(Note) Go to the link below for further details.
2. Overview of Construction About Earthquake Countermeasures for Units 3 and 4
Based on seismic observation results on the site, the need for earthquake countermeasures on key facilities in seismic design was examined, using the seismic motion of 1,200 gals for facilities near observation points that showed no significant amplification, and 2,000 gals for facilities near observation points that reported notable amplification. The following measures are implemented accordingly.
Work to reinforce supports of pipes and electric circuits at Units 3 and 4
Supports for pipes and electric circuits will be reinforced or added.
Work to reinforce slopes within the site
Slope reinforcement work is applied to the areas along power supply routes extending from the gas turbine generators on the high ground to the reactor buildings, etc.
Work to remove the crest of slope within the site
Work to lower the slope on the north side of the water intake pond for Unit 4 is carried out.
Work to reinforce ground around Unit 4 water intake pond
Surrounding soil foundation is improved.
Work to reinforce the ground around tsunami protection wall
The ground around the foundation for the tsunami protection wall at Unit 5 is improved.