Officials of Chubu Electric Power Co. are arguing in court that an 18-meter high breakwater wall now being constructed at its Hamaoka nuclear power plant would be sufficient to withstand even a 23-meter high tsunami.
That's even exceeding the 19-meter height experts have said a massive tsunami could reach in Omaezaki, Shizuoka Prefecture, where the plant is located.
The argument was made on Sept. 20 in a closed session of the Tokyo High Court considering a lawsuit by citizens seeking an injunction against plant operations. The session allows the two sides to air out points, often technical, that they want to bring up during court proceedings.
Citizens countered and asked what the utility would do should an even bigger tsunami engulf the area and the plant.
The effectiveness of the breakwater wall is expected to become a point of contention in the lawsuit.
Two expert panels commissioned by the government to offer a realistic assessment of what Japan can expect if a Nankai Trough earthquake strikes released reports in late August that estimated tsunami of up to 19 meters could strike the Omaezaki area. The Nankai Trough is an oceanic trench that stretches for about 700 kilometers off the coast of Shizuoka Prefecture in central Honshu to Kyushu. It is a region where quakes frequently occur when the oceanic plate slips under the continental plate.
At the Sept. 20 session, Chubu Electric officials reported on an experiment that recreated what would happen should a 23-meter high tsunami strike the area. The experiment confirmed that even a tsunami of that size would not severely damage the 18-meter high breakwater wall.
Utility officials also said that waterproof doors being installed at reactor buildings within the nuclear plant would prevent water from the tsunami that flooded the plant grounds from entering the buildings and causing major damage.
However, the Nuclear Safety Commission has come out with a fundamental policy of not allowing the flooding of plant grounds by a tsunami. Chubu Electric officials will have to decide if additional measures are necessary to meet that policy.
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