Evaluation of Impact On Power Station and Responses based on "Concerning the Distribution of Seismic Intensity and Tsunami Height in the Event of a Massive Earthquake in the Nankai Trough," issued by the Cabinet Office(Report in Response to Directive from the Nuclear and Industrial Safety Agency, Ministry of Economy, Trade and Industry)
April 16, 2012
Chubu Electric Power Co.,Inc.
Based on a directive(*1) issued by the Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry, Chubu Electric Power Co., Inc. has produced a report in response to "Concerning the Distribution of Seismic Intensity and Tsunami Height in the Event of a Massive Earthquake in the Nankai Trough," published on March 31, 2012 by the Committee for Modeling a Nankai Trough Megaquake(*2) established by the Cabinet Office. This report compiles the results of an evaluation of the impact of a possible earthquake on the Hamaoka Nuclear Power Station at its current status, and discusses the responses that would be mounted. The report was submitted to the Nuclear and Industrial Safety Agency today.
1 Outline of report
At present, Hamaoka Units No. 1 and 2 are undergoing decommissioning work, and Units No. 3, 4, and 5 are shut down. The units are in a state of stable cold shutdown, and this state was made a premise of the evaluation.
In addition, given that the Cabinet Office's announcement indicated that the maximum height of a tsunami striking Omaezaki City, Shizuoka Prefecture, would be 21.0 meters, the evaluation was conducted based on the assumption that only equipment positioned at the highest points of the facility would be able to be used.
The evaluation showed that in the event that cooling functions for the reactors and the spent fuel storage pools were lost and water injection also ceased to function, it would take a minimum of six days (in the case of Unit No. 5) for the water level to drop to the apex of the effective length of the fuel (the upper end of the fuel pellets when fitted). In addition, safety could be ensured by the injection of water up to the apex of the effective length of the fuel rods by the portable power pumps that have been prepared as an emergency safety measure(*3).
2 Future responses
We will make continuous improvements to our emergency response procedures and conduct continuous training, working to increase our capacity to respond in an emergency.
In addition, we will conduct detailed reviews of findings generated by studies of the accident at the Fukushima Daiichi Nuclear Power Station, the considerations of the Central Disaster Council, and other sources, and implement the necessary measures on that basis.
(*1) The Directive from the Nuclear and Industrial Safety Agency was entitled "Concerning Evaluation of Impact on Chubu Electric Power Co. Inc.'s Hamaoka Nuclear Power Station and Responses Mounted based on "Concerning the Distribution of Seismic Intensity and Tsunami Height in the Event of a Massive Earthquake in the Nankai Trough," published by the Central Disaster Council (Directive)" (04.02.2012, NISA No. 1), issued by the Ministry of Economy, Trade and Industry on April 02, 2012. Based on this directive, the Nuclear and Industrial Safety agency will verify the compiled results of an evaluation of impact and a survey of responses to be mounted, assuming the current status of the Hamaoka Nuclear Power Station as a precondition.
(*2) A committee formed in response to the Interim Report (September 28, 2011) of the Specialist Committee on Earthquake and Tsunami Countermeasures in the Wake of the Great East Japan Earthquake, established by the Cabinet Office's Central Disaster Council. The committee's purpose is to organize and analyze a variety of scientific studies and to examine guidelines for the setting of the maximum class of target earthquakes, towards the establishment of new hypothetical scenarios for a Nankai Trough megaquake comprising Tokai, Tonankai and Nankai earthquakes.
(*3) Based on "Concerning the Implementation of Emergency Safety Measures at Nuclear Power Stations in view of the Accidents at the Fukushima Daiichi and Daini Nuclear Power Stations in 2011 (Directive)," issued by the Ministry of Economy, Trade and Industry on March 30, 2011, measures to ensure the recovery of reactor facility cooling functions while preventing the release of radioactive substances even in the event of the loss of (1) Function of all equipment supplying AC power; (2) All reactor facility cooling functions; and (3) Function of all equipment for cooling the spent fuel pools.