A watchdog group's report Tuesday on nuclear plant safety cites Duke Energy's Oconee plant, which regulators say relied for 28 years on a backup emergency cooling system that didn't work.
The Union of Concerned Scientists report reviews the 15 special inspections the Nuclear Regulatory Commission made last year in response to safety, security or other problems at nuclear plants. Among them was an inspection of Oconee, Duke's oldest nuclear plant, near Seneca, S.C.
Plant workers had discovered a problem with a backup system designed to cool the reactor after an accident. The Union of Concerned Scientists said Duke had installed the system in 1983, a few years after the partial meltdown at Pennsylvania's Three Mile Island plant. The two plants share a similar design.
The problem was in electrical breakers that are part of the plant's Standby Shutdown Facility, a backup control room that could be used to stabilize the plant in an emergency. The breakers were designed to open if they sensed overheating but turned out to open at too-low temperatures inside the reactor building.
If an accident occurred, the open breakers could hurt the system's ability to cool the reactor core.
The breakers Duke used had not been tested to verify they would work at elevated temperatures, the NRC said. "As a result, the (standby facility) was inoperable from 1983 until June 1, 2011," the agency said in citing Duke for a violation in December.
The NRC rated the incident as being of "substantial safety significance." Duke corrected the problem, it said.
'Oconee is a safe plant'
The problem "posed no danger to the public," Oconee spokeswoman Sandra Magee said by email. "We have more than one method for cooling the reactor system. Oconee is a safe plant."
The problem would occur only if the breakers were operated from the standby facility, which has never been needed in Oconee's 38 years in operation, Magee said. They're normally operated from the plant's control room. Duke replaced the breakers with fuses, she said.
The Union of Concerned Scientists report said many such problems occur "because reactor owners either tolerated known safety problems or took inadequate measures to correct them."
While NRC inspectors uncovered some problems, it charged that the agency itself failed to enforce some regulations, including those covering fire safety.
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