Oyster Creek’s reactor nozzle, which leads into the power plant’s reactor, will need repairs prior to returning online, Nuclear Regulatory Commission (NRC) officials said.
The plant shut down in October for a refueling and maintenance outage in which plant components and systems undergo inspection. During those inspections, officials found two “indications” on a nozzle attached to the reactor vessel, said NRC spokesman Neil Sheehan.
“An indication is not a crack but rather a flaw that, left unaddressed, could eventually develop into a crack. One of the indications found at Oyster Creek was 2.5 inches in length, the other 1.5 inches in length,” he said.
The nozzle is associated with the plant’s control rod drive mechanisms.
“The goal is to identify any flaws at an early stage before they can develop into a crack,” Sheehan said.
The indications identified are surface or slightly subsurface, Sheehan said.
“An indication does not pose any risk of an accident or represent any immediate safety issues for the public or plant workers,” he said.
They found the indications using dye penetrate, he said.
Plant personnel must adhere to engineering codes regarding the repair from the American Society of Mechanical Engineers (ASME), Sheehan said.
Oyster Creek specifically developed a plan to grind down the indications, he said, and as a precaution, will do a weld overlay. Exelon Corp., the owner and operator of the nuclear power plant, will be welding metal on top of the entire section of piping.
“This will help ensure the structural integrity of the piping,” he said.
While the recent Hurricane Sandy did present issues in the region, these flaws are not the result of the storm, Sheehan said. The nozzle attaches to the reactor vessel located inside the plant’s containment structure, he said.
“The containment building has walls that consist of several feet of steel-reinforced concrete, plus a steel liner inside. As such, the storm would not have had any impacts on those components inside the structure,” he said.
One incident during the storm caused Oyster Creek operators to declare an “Unusual Event” when water levels topped 4.5 feet above mean sea level. An alert went out at 8:45 p.m. when water was 6 feet above mean sea level at the plant’s water intake structure. Early Oct. 30, the water level dropped enough to eliminate the need for emergency classifications.