On November 27th, the NHK special series titled "The Nuclear Crisis: The Safety Myth- The Truth as Spoken by Involved Eyewitnesses" reported that the results of a trial calculation for tsunamis was not disclosed due to the societal impact that may have ensued.
The following represents the facts we have confirmed.
The "Wave source" of a tsunami, which refers to the location, size, and crustal movement etc. of earthquakes that cause tsunamis, is usually based on the past record of tsunamis caused by earthquakes. Therefore, it is impossible to predict a tsunami minus a fixed "wave source" model.
Our countermeasures were implemented in response to potential tsunami occurrences based on the accumulated knowledge of confirmed "wave source" data gathered to date. Specifically, in utilizing the "wave source" data released by the Japan Society of Civil Engineers, we estimated that the maximum height of future tsunamis that could impact Fukushima Daiichi Nuclear Power Station would not exceed 5.7 meters in February, 2002. Hence, the reinforcements at Fukushima Daiichi Nuclear Power Station were constructed accordingly.
We have also been proactive in studying the latest developments and yet unconfirmed theories as they emerge. The "Trial calculation" that NHK mentioned in its broadcast refers to one of these experimental studies dealing with hypothetical "wave sources". The estimations that resulted from this research were purely for internal reference purposes and it was understood that essential information such as wave source models needed to conduct a proper evaluation was not available. In other words, this study was not conclusive and did not serve as the foundation for the tsunami countermeasures.
We have recognized the necessity of further studies by experts on practical wave source models in order to utilize the new knowledge for tsunami countermeasures and have asked the Japan Society of Civil Engineers to confirm the wave source models etc.
© Tokyo Electric Power Company Holdings, Inc.
