On March 11 both the Fukushima Daini and Daiichi Nuclear Power Plants were hit by a 15 meter tsunami which disabled backup power and reactor cooling systems. By March 12 off-site power was restored to the Daini plant, and by March 15 all four reactors had been brought safely to a cold shut down. At Daiichi off-site power to cooling systems wasn’t restored until April 4, with the result that Units 1-3 reactors and Unit 1-6 spent fuel pools could not be adequately cooled for weeks. (Image WNN)
On April 11 there was a magnitude 7 earthquake that resulted in a failure of off-site power at Daiichi. It appears that there are no operational backup diesel power generators at Daiichi, and the power outage resulted in an interruption of reactor and spent fuel cooling for 50 minutes.
TEPCO has just reported that it is planning multiple backup power sources to ensure that cooling at the plant will not be interrupted. On Thursday emergency diesel generators and pumps for Units 1 to 3 were relocated to positions 23 meters above sea level. In addition provision has been made for mobile backup power, on trucks and fire engines. Work has already begun to rewire the transmission power lines to the plant. In addition TEPCO is considering setting up a second system for pumping water into the reactors.
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