http://www.abc2news.com/dpp/news/region/eastern_shore/hurricane-irene-knocked-a-nuclear-reactor-offline-at-calvert-cliffs

“Late last night, a large gust of wind sent a piece of aluminum siding, which dislodged from a nearby building, into contact with the main transformer at our Calvert Cliffs nuclear power facility in Lusby, Maryland.

The Unit 1 reactor automatically and safely went off-line, as designed. Because of the situation, an Unusual Event was declared Saturday night. UE is the lowest of four emergency classifications by the NRC. We will exit the UE when we have safely completed all the actions in the site’s emergency response plan. We will update you when we safely exit the UE.”