Oyster Creek’s reactor nozzle, which leads into the power plant’s reactor, will need repairs prior to returning online, Nuclear Regulatory Commission (NRC) Spokesman Neil Sheehan said.
The plant was shut down in October for a refueling and maintenance outage in which numerous plant components and systems are inspected. During those inspections, two “indications” were identified on a nozzle attached to the reactor vessel, Sheehan said.
“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.
The indications were identified by 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 Corporation, 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.
The flaws on the reactor nozzle are unrelated to Hurricane Sandy, Sheehan said. The nozzle is attached to the reactor vessel, which is located inside the plant's containment structure, he explained.
"The containment building has walls 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.
For the superstorm, Oyster Creek was already shut down for its refueling and maintenance outage. But Oyster Creek operators declared an "Unusual Event" (the lowest of four levels of emergency classification) on Oct. 29 when water levels topped 4.5 feet above mean sea level. An alert was then declared 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 had declined enough to eliminate the need for emergency classifications.
The NRC’s three-member inspection team will be developing a complete sequence of events during the plant’s response to the storm, including, but not limited to, emergency declarations and off-site notifications, determining the circumstances related to the emergency declarations; evaluating the activation of the plant’s emergency response organization and evaluation the plant’s preparedness for the storm, Sheehan said.
Once the inspection is completed, the NRC has 45 days to issue a report summarizing the findings.
The NRC is also conducting inspections involving the refueling and maintenance outage, he said.
“NRC inspectors will continue to closely follow the company's evaluations of the indications and the repair work,” Sheehan said. “We would want to ensure the repairs are consistent with ASME code and that the company has also checked other similar components for indications/cracks.”
Oyster Creek is the oldest operating nuclear plant in the country and provides enough around-the-clock electricity for 600,000 New Jersey homes and began commercial operations in 1969.