It appears that most if not all Japanese nuclear power plants are on the coast, presumably to take advantage of the sea for cooling.
About an hour after the earthquake March 11 (sequence of events), tsunamis inundated both the Fukushima Daiichi and Daini nuclear power plants. The effect was to stop cooling systems at both plants including ECCS (except at Unit 3 at Daini), to shut down the backup power generators at Daiichi, and to wash away diesel fuel tanks.
WNN reports that the the Fukushima power plants were required by regulators to withstand a certain height of tsunami. The Daiichi plant was designed to withstand a tsunami of up to 5.7 meters and Daini up to 5.2 meters.
TEPCO’s tentative assessment of the height of the tsunamis is over 10 meters at Daiichi and over 12 meters at Daini.
Apparently in Japan many jurisdictions have built tsunami walls of up to 4.5 metres to protect populated coastal areas. But the height of tsunamis is difficult to predict. Waves of up to 30 metres in height were reported at Okushiri Island of Hokkaidō on July 12, 1993 after an earthquake. The highest tsunami ever recorded was 524 meters, which occurred after a large landslide at Lituya Bay.
Be the first to comment