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Safety trigger takes Prairie Island nuclear plant's Unit 2 off line

Unit 2 at Prairie Island nuclear plant went into automatic shutdown Thursday morning when what officials described as "an inadvertent initiation signal" went to safety equipment that was being tested, causing the nuclear reactor to "trip" or "scram" at 9:08 a.m.

"All plant systems responded to shut the plant down as designed," said Arline Datu, spokesman for Nuclear Management Co., which operates the Prairie Island plant.

The plant is located just north of Red Wing.

No one was injured and there was no radiological release as the result of the shutdown, which affects only Unit 2. Unit 1 was not involved; it continues to operate at 100 percent power.

"There is no threat to the public, and this event did not meet any emergency plan classification criteria," Datu said.

An unplanned shutdown is not a routine event and does not occur frequently, she said. "We try to operate continuously until there is a planned outage. These things do happen."

Plant operators were conducting routine testing when the signal caused the reactor to shut down and selected safety equipment to start up. They spent the day investigating what caused the scram, but no determination had been reached late Thursday afternoon.

When operators have figured out what happened, they will make any necessary repairs before returning the plant to service. It could be an equipment issue, she said.

"Most like it will not be a lengthy outage," she said. "We're going to try to get this back on line as quickly as possible."

Prairie Island generates 1,076 megawatts of electricity, enough electricity to power approximately 1 million homes. Xcel Energy owns the plant, which is one of six reactors operated by Nuclear Management Co., headquartered in Hudson, Wis.