The U.S. Nuclear Regulatory Commission has ordered the operators of nearly 70 nuclear power plants to report back by Friday on whether the reactors at their facilities are safe to keep in operation. The order came after regulators discovered that acid in cooling water had almost burned through a six-inch lid on a reactor in Ohio. At the Davis-Besse nuclear power station, a 25-year-old plant near Toledo, only a 3/8-inch-thick stainless-steel liner was left to hold back cooling water that was under more than 2,200 pounds of pressure per square inch. If the liner had given way, thousands of gallons of slightly radioactive water would have been released. The NRC says safety systems would have kicked in and cooled the reactor. But anti-nuclear activists say the problem could have escalated into a core meltdown. Of the country’s 104 nuclear reactors, 68 others are of the same design as the one outside Toledo. Corrosion “was never considered a credible type of concern” prior to the latest development, according to the NRC’s Brian Sheron.

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