No: I-15-021 April 27, 2015

CONTACT: Diane Screnci, 610-337-5330 

 Neil Sheehan, 610-337-5331 

NRC Finalizes ‘Yellow,’ ‘White’ Inspection Findings for Oyster Creek

Nuclear Power Plant; Level of Oversight to be Increased

The Nuclear Regulatory Commission will increase its level of oversight at the Oyster Creek 

nuclear power plant following the finalization of one “yellow” and one “white” inspection finding for 

the Lacey Township (Ocean County), N.J., facility. A “yellow” classification indicates substantial 

safety significance while a “white” connotes low to moderate safety significance.

The “yellow” finding involves design aspects of electromatic relief valves, or EMRVs, for the 

Exelon-owned and -operated plant. The “white” finding pertains to the maintenance of an emergency 

diesel generator at the facility.

“These enforcement actions underscore the need for plant owners to be vigilant when it comes 

to maintaining essential safety equipment,” NRC Region I Administrator Dan Dorman said. “In the 

case of these issues, two components that can play an important role during a reactor shutdown either 

experienced or may have experienced material failures that could have prevented them from performing 

their functions when needed. The company has since corrected the equipment problems. The NRC will 

now carry out additional inspections to ensure the underlying issues have been fully addressed.”

With respect to the “yellow” finding, the EMRVs would be used to depressurize the reactor 

during a pipe break to allow coolant to be injected into the reactor core. This is necessary to keep the 

nuclear fuel in the reactor covered and cooled as the shutdown progresses.

During refurbishment work in June 2014 on two EMRVs removed from the plant in 2012, the 

company found an alignment problem with the valve’s actuator. When the valves were tested, they did 

not open.

Once the issue was identified, Exelon immediately tested five of its then-installed EMRVs. All 

five actuated successfully. Further, the company installed redesigned actuators for the valves during a 

refueling and maintenance outage at the plant in October 2014.

Even though the violation involving the EMRVs has been classified as “yellow,” the NRC has 

determined it represents an old design issue. That is, the issue stems from an inspection finding 
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involving a past design-related problem and does not reflect a current performance deficiency 

associated with existing programs, policies or procedures used by the company.

As a result, the finding will not lead to Oyster Creek moving into the Degraded Cornerstone 

Column of the NRC’s Action Matrix. However, the NRC will carry out a team inspection that will 

review Exelon’s root-cause evaluation and corrective actions for the issue.

On the issue involving one of the plant’s emergency diesel generators, the back-up power 

source may not have been available to operate because of the degradation of its cooling fan drive shaft.

Oyster Creek, like other nuclear power plants, transmits power to the grid but also receives 

power from the grid for the operation of safety systems. When that off-site power is unavailable, the 

plant’s emergency diesel generators activate to provide power to key safety systems.

On July 28, 2014, during a bi-weekly test of one of the plant’s emergency diesel generators, 

alarms involving the generator were received. Following the generator’s shutdown, Oyster Creek 

personnel discovered the belt-driven cooling fan drive shaft had sheared into two pieces, resulting in 

the generator becoming inoperable. The fan keeps the generator from overheating when operating.

Plant personnel replaced the fan shaft and performed a failure analysis on the damaged shaft. It 

was determined that fatigue was the cause of the shaft’s failure.

NRC inspectors learned that in May 2005, Exelon changed the method for tensioning the 

generator’s cooling fan belt but did not adequately verify the acceptance criteria for the change. The 

company did not detect that the change left the shaft subject to fatigue and, as a result, the failure 

occurred on July 28, 2014. Further, the period of inoperability for the generator exceeded its allowable 

outage time in violation of the plant’s technical specifications. Unlike the EMRV design issue, the

tensioning issue was identified by the NRC.

Exelon took immediate steps to address the issue, including performing a failure analysis on the 

broken shaft, examining the cooling fan drive shaft for the plant’s other emergency diesel generator and 

correcting the tensioning method.

For both issues, the NRC offered Exelon an opportunity to take part in a regulatory conference, 

to provide additional information in writing or to accept the findings as characterized. The company 

provided written responses on March 13 for each issue. The company disagreed with some aspects of 

the NRC’s analysis of the EMRV issue, concluding that the issue was less significant than 

characterized by the agency. The NRC considered the points raised by Exelon and concluded that the 

EMRV issue was appropriately characterized as “yellow.” For the EDG “white” finding, the company 

accepted the finding and its significance determination.

The NRC will perform team inspections in response to both inspection findings once Exelon 

notifies the agency of its readiness for the reviews.

The reports regarding the enforcement actions can be found in the NRC’s electronic documents 

system, ADAMS.