Reactor at San Onofre Shut Down in Accident

An employee making repairs to electrical equipment at the San Onofre nuclear power plant inadvertently caused the Unit 2 reactor to shut down Thursday morning.

The reactor, which stopped about 8 a.m., is expected to be brought back to power in about two days, according to David Barron, a spokesman for Southern California Edison Co., the plant’s operator.

Barron said the shutdown occurred when an employee assigned to repair equipment on the plant’s Unit 3 reactor, which is being refueled, mistakenly went to work inside a cabinet holding electrical equipment that helps run Unit 2.

“He went into the wrong cabinet,” Barron said. “It was an honest mistake. We work hard to not have those kinds of problems.”

The unit shut down safely and there was no release of radiation, Barron said. The electrical equipment the employee erroneously tinkered with is part of a system that runs the reactor’s feed-water pump, which flushes a non-radioactive stream of water into the steam generator.

In an unrelated incident, plant officials discovered that a worker had been exposed to a small dose of radiation, Barron said Thursday.

San Onofre safety inspectors discovered the microscopic fragment on the employee’s sweat shirt as he arrived at work Wednesday morning. A monitoring device that all employees must pass through alerted inspectors, who then located the particle using hand-held monitoring instruments.

The worker, who is assigned to refueling operations in the Unit 3 reactor, apparently picked up the particle when he wore the same sweat shirt on Tuesday, Barron said. As he left work that day, the employee set off the monitoring device. Inspectors, however, could not locate any particle using the more sensitive hand-held equipment, and the employee was allowed to go on his way, Barron said.

After the radioactive particle was finally found Wednesday morning, workers with monitoring devices were dispatched to the employee’s home, but no traces of radiation were found there, Barron said.

Barron said plant officials estimated that the employee was exposed to 1 to 10 rems of radiation, but that it posed no health risk. The estimated dangerous limit of exposure during a three-month period is 18.75 rems, he said.

The Nuclear Regulatory Commission was informed of the matter, Barron said, adding that such low-level contamination is not uncommon during refueling work. Typically, however, workers make sure to clean off such particles before leaving the plant, he said.