No. IV-12-040

Contact: Victor Dricks (817) 200-1128

 Lara Uselding (817) 200-1519

 

 Sept. 21, 2012

E-Mail: OPA4.Resource@nrc.gov

NRC ISSUES A “YELLOW” FINDING TO WOLF CREEK NUCLEAR PLANT IN 

CONNECTION WITH LOSS OF OFF-SITE POWER EVENT

The Nuclear Regulatory Commission staff has determined that an inspection finding at 

the Wolf Creek nuclear power plant related to a loss of off-site power event is “yellow,” meaning 

the issue has substantial safety significance and will result in additional NRC inspections and 

oversight. The plant, located near Burlington, Kan., is operated by Wolf Creek Nuclear 

Operating Corp.

On Jan. 13, operators at the plant declared an Unusual Event, the lowest of four levels of 

nuclear emergency, after the failure of a main generator electrical breaker, followed by an 

unexplained loss of power to a transformer. This caused the switchyard to lose power, which 

removed the plant’s connection to the electrical power grid. All safety systems responded as 

expected and emergency diesel generators automatically powered safety-related equipment.

The NRC conducted an Augmented Inspection and determined that actions by the 

licensee set the stage for the incident because the company failed to provide adequate oversight 

of contractors while they performed work that could affect safety-related equipment in April 

2011. As a result, the licensee failed to identify that electrical maintenance contractors had 

improperly connected wires on an electrical component. This allowed an electrical short to 

prevent transfer of power to a transformer on Jan. 13.

The NRC held a public meeting on March 6 in New Strawn, Kan., to discuss the 

preliminary results of the Augmented Inspection. Following further review, the NRC staff has 

concluded that the inspection finding is appropriately characterized as “yellow,” which has been 

accepted by the licensee.

Under the NRC reactor oversight process, inspection findings are evaluated using a

significance determination process and assigned a color indicating its safety significance.

Findings with very low safety significance are labeled "green." "White" findings have low to

moderate safety significance, "yellow" findings have substantial safety significance, and "red"

findings have high safety significance.

NRC NEWS

U.S. NUCLEAR REGULATORY COMMISSION

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Blog: http://public-blog.nrc-gateway.gov
The “yellow” finding moves Wolf Creek into the “degraded cornerstone” column of the

NRC action matrix, resulting in a higher level of NRC oversight. This is the third highest level of

NRC oversight and Wolf Creek joins six other U.S. nuclear units in that column. The position of 

all nuclear units within the NRC Action Matrix is available on the NRC web site at:

http://www.nrc.gov/NRR/OVERSIGHT/ASSESS/actionmatrix_summary.html#am_summary .

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