NRC NEWS

 U.S. NUCLEAR REGULATORY COMMISSION

 2443 Warrenville Road

 Lisle IL 60532

 Web Site: http://www.nrc.gov E-mail: opa3@nrc.gov

No. III-06-027 June 30, 2006

CONTACT: Jan Strasma (630) 829-9663 

Viktoria Mitlyng (630) 829-9662 

NRC FINDS INADEQUATE VALVE ANALYSIS PRIOR TO POWER UPRATE

TO BE OF LOW TO MODERATE SAFETY SIGNIFICANCE

The Nuclear Regulatory Commission staff has issued its final determination that the Quad

Cities Nuclear Power Station failed to ensure that Unit 1 electromatic relief valves function properly

when exposed to the increased vibrations. Increased vibrations occurred following Quad Cities

implementing a 2002 extended power uprate of both reactor units. The NRC determined the failure to

ensure the electromatic relief valves function properly to be of low to moderate safety significance.

The plant is operated by Exelon Generation Co.

Electromatic relief valves perform safety-significant functions of protecting the reactor vessel

from overpressure and of depressurizing the reactor quickly in certain conditions.

Quad Cities staff identified the degradation of electromatic relief valve actuators in December

2005 and January 2006. 

In January 2006, the NRC conducted a special inspection to understand the reasons for the

degradation, review the historical usage and maintenance of the valves, evaluate the plant’s response to

previously identified indications associated with suspect valve operability, and assess the Quad Cities

staff’s efforts to determine the extent of the problem.

A follow-up inspection, conducted in May 2006, focused on reviewing the plant’s

understanding of the root cause for the electromatic relief valve actuator degradation.

The NRC found that Quad Cities failed to establish design controls to ensure that the

electromatic relief valve actuators would function properly when exposed to increased vibrations of the

main steam line that occurs as a result of an extended reactor power uprate. Even though this finding

did not present an immediate safety concern because the reactor was shut down when the issue was

identified, the NRC determined that Quad Cities had likely operated for a period of time with multiple

electromatic relief valves being inoperable.

“The NRC’s finding shows how important it is to thoroughly review the design of safetysignificant equipment that could be vulnerable to increased main steam line vibrations before

implementing an extended power uprate,” said James Caldwell, NRC Regional Administrator. “It is

also important for plant staff to pay attention to early indicators of a problem and to address them in a

timely and efficient manner.”
The company’s corrective actions included replacing the Unit 1electromatic relief valve

actuators, installing new electromatic relief valve actuators designed to withstand the increased

vibrations, and installing an additional modification to reduce the overall main steam line vibration

levels.

White findings normally result in additional NRC inspections and meetings with the utility.

Based on the white finding, the NRC issued a Notice of Violation to Exelon Generation Co. for its

failure to ensure that the application of the electromatic relief valve actuators, which perform important

safety-related functions, remained suitable for operation prior to implementing an extended power

uprate. The company is required to respond to the Notice of Violation within 30 days, describing its

corrective actions and steps it is taking to prevent a recurrence of the violation.

The letter notifying Exelon of the white finding will be available from the NRC’s Region III

Office of Public Affairs or in the NRC’s online document library at:

http://www.nrc.gov.reading-rm/adams/web-based.html . 

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