Back-up power supply a key difference between Canadian and Fukushima nuclear plants

Back-up energy supplies mark a key difference between Canadian nuclear power reactors and the reactors at the Fukushima Daiichi plant that were damaged in the March 2011 Honshu earthquake, said John Honey, a specialist engineering consultant with the Nuclear Insurance Association of Canada.
Honey spoke as a panel member at the Property Casualty Underwriters Club (PCUC) luncheon in Toronto on June 22. The discussion topic was ‘Fukushima, A Canadian Perspective.’
During his presentation, Honey said the Fukushima incident was worse than Three Mile Island, but not nearly as severe as Chernobyl. The Mar. 11 earthquake that struck Japan was three to four times the size of the earthquake that the reactor was built to withstand, Honey observed.
Also, the reactor was designed to withstand a tsunami with five-metre-high waves. But the tsunami following the Mar. 11 earthquake was approximately 11 metres (or 37 feet) high, hitting the reactor head-on.
The plant withstood the earthquake, he told delegates, but the tsunami ultimately caused the damage that led to explosions in three of the reactors and a contamination leak from a fourth.
“Fukushima had a total of 15 diesel generators and they all failed,” Honey said. “They were all the same kind of generator, and they were all located in the same place – in the basement of the turbine buildings. So the tsunami hit, they were all flooded and they all went,” he said. “Placing the back-up power source in the basement was a major design flaw.”
Canadian reactors, on the other hand, have two redundant and completely diverse sources of power, so they wouldn’t be subjected to that, he said.