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Hurricane Irene poses problem of electricity supply to nuclear reactors

Overall, hurricanes have prompted less cause for concern at nuclear plants than other issues, such as the NRC’s delay in assessing the risk from earthquakes near the nation’s reactors and recurring fires that could trigger a series of cataclysmic events — again, for instance, because of the loss of electricial connections or dependable switches.

Industry watchdogs concerned about power supplies – to reactors, not just homes, iWatch, 28 Aug 11, By Corbin Hiar As Hurricane Irene bore down on the East Coast, the nuclear industry assured the public that the storm wouldn’t damage the dozens of reactors in its path. The industry’s watchdogs also expressed less concern about the hurricane’s potential impact on nuclear reactors than about the vulnerability of the exposed connections between them and the rest of the world.

One concern surrounds the electric grid – the lines that transmit power to cities and homes. Another concern is the reliability of electricity that supplies the reactors themselves, and ensures safe operation of the plant. (For other more likely nightmare scenarios, see iWatch News ‘ investigations of the risk of earthquakesand fires.)……

“It’s counterintuitive for most people that nuclear power plants need electricity from the outside for the safety systems to function,” said Jim Riccio, an energy policy analyst at Greenpeace, which opposes nuclear power. “But as we’ve seen from Fukushima, if you don’t cool the core, you have serious trouble on your hands and eventually a meltdown.”

Nuclear reactors require constant cooling, even when plants are not generating electricity, as will be the case for nuclear plants along the East Coast during Hurricane Irene. The Nuclear Regulatory Commission (NRC) requires reactors to go into shutdown mode at least two hours before the onset of hurricane-force winds, typically between 70 and 75 miles per hour.

But if these plants lose power in the course of the storm – as in Japan, where an earthquake followed by a tsunami knocked out the backup generators at the Fukushima Daiichi nuclear plant – the fuel rods can overheat, causing an uncontrolled nuclear reaction. The massive amount of radiation released during the partial meltdown at Fukushima may soon force the Japanese government to declare the area around the plant uninhabitable.…..

If the power goes out along the Eastern seaboard for a long period of time, there is a risk that nuclear plants’ backup generators could run out of fuel. Or, Riccio added, the backup power could fail like one of them did Tuesday after the earthquake knocked out electricity to the North Anna nuclear power plant in Virginia.

That recent earthquake may have also put facilities at greater risks during Hurricane Irene. Nuclear plants have sensitive leak detection systems, but “if the earthquake caused piping to become weak, then that’s something that the hurricane could take the rest of the way to failure,” said David Lochbaum, a former nuclear engineer and director of the Union of Concerned Scientists’ nuclear safety project.

Even if the generators stay on or the power doesn’t go out to the nuclear reactors, there’s another risk – human error. For example, when restarting the St. Lucie nuclear power plant in Florida after Hurricane Jeanne, the utility company found that reactor auxiliary building doors had been left open during the storm. Although this mistake did not harm the public, an NRC report on the 2004 hurricane season noted that the doors provided access to an important cooling water surge tank.

Overall, hurricanes have prompted less cause for concern at nuclear plants than other issues, such as the NRC’s delay in assessing the risk from earthquakes near the nation’s reactors andrecurring fires that could trigger a series of cataclysmic events — again, for instance, because of the loss of electricial connections or dependable switches.

August 28, 2011 - Posted by Christina Macpherson | safety, USA