FirstEnergy Corp. said an investigation of damage to the concrete outer shell of its Davis-Besse nuclear power plant unearthed additional hairline cracks.
The sub-surface cracks on the shield building don’t “affect the facility’s structure integrity or safety,” Akron, Ohio-based FirstEnergy said in a letter to investors today. The company said the 913-megawatt reactor, shut since Oct. 1, will resume producing power in late November.
FirstEnergy shut the plant to install a new reactor vessel head three years earlier than previously planned. The U.S. Nuclear Regulatory Commission in 2005 imposed a $5.45 million fine, its largest ever, for FirstEnergy’s failure to discover corrosion had eaten a hole in a prior vessel head.
Contractors found the newest cracks on the shield building, a 30-inch-thick (76 centimeters) reinforced concrete structure that protects the reactor’s containment building from wind and tornadoes.
FirstEnergy previously discovered a hairline crack measuring about 30 feet (9 meters) on Oct. 10 after it cut a hole in the side of building to allow for installation of the new vessel head.
The company is still studying two other cracks found as it tested the shield building and continues “to assess their implications, if any,” she said.
FirstEnergy is seeking regulatory permission to extend its operating license for Davis-Besse, which has been in service since 1977, by another 20 years. The commission is scheduled to issue its decision on the application next year.