A transformer struck by flying debris triggered an automatic shutdown at a Calvert Cliffs reactor Saturday, and New Jersey’s Oyster Creek nuclear plant was taken offline the day before as a precaution. But most of the 20-plus reactors in the region continued to operate safely last weekend while Irene became the worst storm to hit the Atlantic seaboard in a decade.
At the two-reactor Calvert Cliffs plant in Maryland, aluminum siding blown from a building struck a main transformer at unit 1. Plant safety systems shut the reactor down automatically, with Constellation Energy declaring an unusual event at 11:02 p.m. EST, Saturday, according to a company release. Unit 2 continued to operate at full power.
At Oyster Creek near Philadelphia, operators manually shut down its single reactor at 8 p.m. Saturday. Exelon indicated in a release that it took the precaution in anticipation of high sustained winds speeds, which can require a manual shutdown under plant procedures.
Six other reactors continued to operate but reduced power during the storm, according to a Nuclear Energy Institute tally Sunday night. Progress Energy reduced power at both its Brunswick reactors in North Carolina to about 65 percent power Friday night. In Connecticut, Dominion halved power at Millstone units 2 and 3 at the request of ISO-New England for grid stability, according to the NEI. And in Pennsylvania, Exelon reduced power by less than 10 percent at Limerick 1 and 2. Dominion’s two-unit North Anna plant in Virginia remained offline following automatic shutdowns during last week’s earthquake.
The majority of nuclear plants online in the affected states, though, continued to operate at full power throughout the weekend.