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I-98-80
July 8, 1998
FOR VIOLATIONS INVOLVING INEFFECTIVE VALVE REPAIRS AT LIMERICK
The Nuclear Regulatory Commission has proposed a $55,000 fine against PECO Energy Company for violations of agency requirements involving equipment operability at the Limerick nuclear power plant. PECO owns and operates the twin-reactor facility, which is located in the Philadelphia suburb of Limerick, Pa.
Identified during NRC inspections conducted between October 20, 1997, and March 16 of this year, the violations were discussed during a predecisional enforcement conference held on June 10 at the NRC Region I office in King of Prussia, Pa.
One of the infractions involves PECO's failure to aggressively and comprehensively fix a Unit 2 valve that was experiencing difficulties. Part of the high-pressure coolant injection (HPCI) system -- one of the plant's emergency core cooling systems -- the exhaust valve failed to close during testing on five occasions between March 1994 and January 1998.
Despite efforts to fix the problem, ineffective corrective action led to the valve being inoperable for an extended period of time.
"Although the valve does not have an automatic isolation function, it is necessary to isolate HPCI system leakage and is considered an extension of the (plant's) containment boundary," NRC Region I Administrator Hubert J. Miller wrote in a letter to PECO notifying it of the enforcement action. "In each of the first four occurrences, root cause analyses were not adequate to detect the root cause of the problem. Of particular concern is the fact that after the fifth failure on January 8, 1998, the valve was not declared inoperable even though subsequent data revealed internal binding of the valve."
Another violation was a failure to effectively troubleshoot a problem affecting a Unit 2 residual heat removal system valve. One function of the residual heat removal system is to maintain water level in the reactor vessel following a loss-of-coolant accident. Part of that system is a minimum flow valve, which is designed to open when a residual heat removal pump is in operation with the system's flow at low levels in order to prevent pump damage.
However, between Sept. 1, 1997, and Jan. 21, 1998, PECO efforts to prevent recurrent failures of the valve proved ineffective. The valve was not declared inoperable even though it was found closed four times, with the flow at less than the required 1,500 gallons per minute, during that period.
"The NRC considers this violation significant since pump damage could occur under no flow conditions in as little as three minutes. The NRC is particularly concerned that similar to the issue concerning the high-pressure coolant injection system exhaust valve, this problem revealed a lack of comprehensive troubleshooting by the engineering staff, as well as improper acceptance by the operators that the pump was operable even though the cause of the problem was not identified," Mr. Miller said.
The two violations have been categorized in the aggregate as a Severity Level III problem. (The NRC issues four levels of violations, ranging from Level I, which is the most significant, to Level IV, which is the least significant.) A fine of $55,000 is being issued for those infractions.
In addition, the NRC cited, but did not fine, PECO for a Level IV violation. It pertained to a failure to promptly identify and correct a misinstalled bearing in one of the plant's emergency diesel generators.
PECO has 30 days to pay the fine or to request in writing that all or part of the penalty be withdrawn.
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