(Reuters) - FirstEnergy Corp said on Monday a small area of degradation found in the steel containment liner in one of the reactors at Pennsylvania's Beaver Valley nuclear power plant poses no harm to the public, workers or the environment.
FirstEnergy spokeswoman Jennifer Young said workers found the flaw on Friday during an inspection of the inside walls of the containment building in the 892-megawatt Unit 1, which has been shut since September 30 for a refueling and maintenance outage.
The containment building is comprised of a 4.5-foot thick concrete wall with a domed top and a 3/8-inch thick steel liner.
The degraded area is located about 7 inches from the floor and measures about 0.4 inches by 0.28 inches, she said.
Young did not say when the unit would return to service but noted the company expects to fix the degraded area within the current outage schedule.
Refueling outages usually last about a month but power traders noted this outage could take up to two months because the company is replacing the unit's two low pressure steam turbine rotors. Each rotor weighs about 153 tons and measures about 15 feet in diameter and about 30 feet in long.
Workers discovered the degraded area under a small paint blister. The company determined there was a fibrous material - most likely wood - inside the concrete touching the steel liner.
The company said the degradation likely occurred when the material decayed.
Young said a similar event occurred in 2009 when workers found a small area of degradation in another part of the steel liner. In that case, the damage was caused by a wood spacer left over from the concrete pour during construction.
She said the company in 2009 removed and replaced the damaged steel and the area has not experienced any additional degradation.
(Reporting by Scott DiSavino; Editing by Alden Bentley)