A report filed with the Nuclear Regulatory Commission says "ultrasonic examinations identified a flaw in a head penetration nozzle" of the vessel. The report says the problem was discovered November 18.
The reactor was not in operation at the time. It had been shut down for refueling, and the flaw was found during a routine inspection. The report says there was no leak.
"We saw a very small flaw, indication of one of 66 nozzle penetrations that go into the reactor vessel head," said Duke Progress Energy's Kim Crawford. "There was no leakage anywhere on the vessel head. It's very small. It's in a weld. We're going to repair it concurrent with other outage work and it will be repaired before we start the plant back up."
Crawford won't say if the repair will keep the plant out of service longer than originally expected or when it is going to restart.
Officials with the NRC told ABC11 that at some point utilities have to consider replacing the entire vessel head when cracks keep showing up.
In May, the plant was shut down after an inspection revealed early signs of corrosion and cracking in the reactor vessel. The quarter inch crack was not all the way through the reactor vessel wall and no radioactive material escaped.
The plant - which began operations in 1987 - is located in New Hill, about 20 miles southwest of Raleigh near Jordan Lake.