NRC NEWS

U.S. NUCLEAR REGULATORY COMMISSION

Office of Public Affairs Region III

2443 Warrenville Road

Lisle IL 60532

Site: www.nrc.gov

Blog: http://public-blog.nrc-gateway.gov

No. III-12-023

Contact: Viktoria Mitlyng (630) 829-9662

 Prema Chandrathil (630) 829-9663

June 21, 2012

E-Mail: OPA3@nrc.gov 

NRC CONCLUDES ITS REVIEW OF FENOC’S ROOT CAUSE ANALYSIS

OF DAVIS-BESSE SHIELD BUILDING CRACKS

The Nuclear Regulatory Commission has completed its review of FirstEnergy Nuclear 

Operating Co.’s (FENOC) causal analysis of, and proposed corrective actions for, cracks in the 

shield building at the Davis-Besse Nuclear Power Station. The NRC has determined the report

established a sufficient basis for its conclusions. The plant is located in Oak Harbor, Ohio, 

approximately 21 miles southeast of Toledo.

FENOC concluded that cracks in the shield building were caused by environmental 

factors that resulted from the 1978 blizzard; the lack of moisture protective coating; and certain 

aspects of the shield building’s design. The company submitted the root cause analysis of shield 

building cracks, which includes the company’s proposed corrective actions and long-term 

monitoring program of the shield building, on Feb. 28 in compliance with commitments the 

company made to the NRC.

“Our inspectors conducted a thorough and independent review of FENOC’s root cause 

determination to make sure that the reasons for the internal cracks in the shield building are well 

understood. We evaluated the effectiveness of the company’s proposed actions to ensure the 

continued safety of the shield building going forward,” said NRC Region III Administrator 

Charles Casto. “We will schedule a public meeting shortly to discuss this issue and the NRC’s 

plans to monitor the plant’s corrective actions.”

The NRC also conducted a detailed analysis of the company’s corrective actions to 

ensure shield building safety going forward. These actions included additional tests and 

laboratory analysis of the shield building; applying a protective moisture coating on the building; 

and plans to restore the plant’s design and licensing basis. 

These reviews were performed by a team of four NRC inspectors who took a wide range 

of actions to make sure the company’s data and analysis were thorough and rigorous. The NRC 

team concluded that the actions proposed by the company going forward would prevent 

recurrence of the laminar cracking if properly implemented. 
The NRC documented the results of its independent inspection in a document that will be 

publically available at: http://adams.nrc.gov/wba/; enter ML12173A023 as a search term. The 

report can also be obtained from the NRC Region III Office of Public Affairs.

The NRC began looking at the issue on Oct. 10, 2011, when the NRC was informed by 

FENOC that its workers identified cracks in the shield building while the plant was shut down to 

replace the reactor vessel head. The shield building is a 2.5-foot thick reinforced concrete 

building that surrounds a 1.5-inch thick steel containment vessel that encloses the reactor. The 

two buildings are separated by a 4.5-foot space.

The NRC thoroughly reviewed the cracks after they were discovered and determined that 

they did not pose an imminent safety issue. The NRC issued an inspection report documenting 

the agency’s review of the shield building’s operability on May 7. Before the plant returned to 

service, the NRC issued a Confirmatory Action Letter to FENOC documenting its commitments 

to determine the cause of the shield building cracks.

The NRC’s license renewal experts are evaluating the implications of this issue in the 

context of Davis-Besse’s request to extend its operating license.

The NRC is developing a program of short-term and long-term inspections to make sure 

FENOC implements the corrective actions outlined in the root cause analysis in a thorough and 

timely manner.

Documents associated with shield building cracking can be found at:

http://www.nrc.gov/info-finder/reactor/davi.html.

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