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Power Plant Status at the Time of the Chuetsu-Oki Earthquake in Niigata

[Time of occurrence]

10:13 PM July 16, 2007

[Hypocenter]

  • Jo-Chuetsu-Oki ,Niigata(Depth 17 km)
  • Lat. 35°33.4' N. Long. 138°36.5' E.
  • Horizontal distance from power station: Approx. 16 km
  • Magnitude: 6.8
  • Seismic intensity: Upper 6: Kashiwazaki, Kariwa
  • Units 3, 4, 7 stopped operation safely.
  • (Units 1, 2, 5 and 6 were undergoing periodic inspection)

Measures Implemented from the Chuetsu-Oki Earthquake

<Addition/enhancement of piping support>
We added and expanded support for piping (conduit tubes, cable trays, air conditioning ducts).

<Reinforcement of reactor building roofing>
We reinforced the roofing of reactor buildings by adding steel materials to reinforce the supporting truss framework (steel framework).

<Improvements to exhaust tubes>
Supports were added around exhaust tubes used for building ventilation, etc. to give exhaust tubes a more robust structure to bolster their capability to withstand earthquakes.

<Reactor building/ceiling enhancements>
Reinforcing materials were added to, and derailment prevention fittings were enlarged on the travel rail support structure for overhead cranes used to open the reactor vessel lid to prevent them from toppling over.

<Improvements to refueling equipment>
Reinforcing materials were also added to, and derailment prevention fittings were enlarged and expanded on refueling equipment in a similar manner to that for overhead cranes.

<Seismic isolation ERC construction>
A "seismic isolation ERC" was built, integrating equipment and facilities vital for implementing emergency measures and maintaining power and communications to ensure that an emergency response is not hindered in any way in the event of an earthquake (the potential for using this facility autonomously is currently under review)

Geological Surveys and Other Reviews

Earthquake proofing was improved in light of the Chuetsu-Oki Earthquake.
Earthquake proofing improvement works implemented as a result of new standards introduced in the aftermath of the Chuetsu-Oki Earthquake in Niigata (in July 2007) were completed on all units by September 2012.

Addition/enhancement of Piping Support, etc.

Internal piping and conduit supports were added or improved at between 1,400 to 3,000 sites across each plant.

Improvements to Exhaust Tubes

Supports and vibration damping equipment were added to exhaust tubes used for building ventilation, etc.

Improved Earthquake Proofing for Facilities that Open and Close

Improvements have been made to facilities receiving power from external power sources. Anchor frames and other facilities have undergone earthquake proofing improvements.

Reinforcement of Reactor Building Roofing Truss

We reinforced the roofing of reactor buildings by adding copper materials to reinforce the supporting truss framework (steel framework).

Reactor Building/overhead Crane Enhancements

Reinforcing materials were added to, and derailment prevention fittings were enlarged on the travel rail support structure for overhead cranes used to open the reactor vessel lid to prevent them from toppling over.

Refueling Equipment

Reinforcing materials were also added to, and derailment prevention fittings were enlarged and expanded on refueling equipment in a similar manner to that for overhead cranes.

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