Ohio nuclear plant's study says cracks in shield could grow during freeze-and-thaw cycles

The operator of an Ohio nuclear plant along Lake Erie said cracks first discovered three years ago have grown in the concrete building that protects the plant and its reactor.

The findings do not mean the structure at the Davis-Besse plant near Toledo is unsafe, FirstEnergy Nuclear Operating Corp. said.

Independent experts determined the cracks have not compromised the building, Jennifer Young, a company spokeswoman, told the Sandusky Register (http://bit.ly/1qCuxAN).

FirstEnergy told the Nuclear Regulatory Commission in July that a study showed the cracks could grow 0.4 inches to 0.7 inches during freeze-and-thaw cycles.

The company said nearly a year ago that it found several more cracks in the concrete building and that some cracks detected earlier had grown.

The reinforced concrete shield building surrounds a 1½-inch thick carbon steel vessel containing the reactor and is intended to protect the public from a catastrophe.

The company has said high-definition cameras now used for inspecting core samples provide greater clarity and mobility and have identified cracks that weren't visible with previous inspection equipment.

Several hairline cracks were found in the structure's 2.5-foot-thick concrete in 2011. FirstEnergy determined that they were caused by wind-blown moisture seeping into the concrete during blizzards and freezing weather and that the building's structural integrity has not been affected.

Anti-nuclear groups have said the cracks call into question the soundness of the structure.

Davis-Besse is in Oak Harbor, about 25 miles east of Toledo.

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Information from: Sandusky Register, http://www.sanduskyregister.com/cgi-bin/liveique.acgi$sch=frontpage?frontpage