Restart of Ocean County's Oyster Creek Nuclear Power Plant has its second false start within a week, following Sunday's discovery of a flaw in the generating station's steam-retention-and-transfer system.

Oyster Creek Nuclear Plant (Exelon)

According to documents filed with the Nuclear Regulatory Commission, the Sunday shutdown - also known as a scram - was triggered by operators. An initial scram late last week was automatic and attributed by NRC's Neil Sheehan to faulty wiring that created noise that interfered with power-production readings.

Sheehan says that Sunday's decision was triggered when operators discovered a loss of vacuum capacity in the generator's main condenser. "Oyster Creek, like all large-scale nuclear plants, [uses] a condenser to cool down and condense back into water the steam that's been circulated through the turbine," says Sheehan.

The airless condition, Sheehan explains, maximizes heat-transfer efficiency. Monitors, seeing the degradation when power reached 20 percent, opted to shut down the reactor. He says that no radiation was subject to leakage in the other direction.

Following repairs, the systems once more undergo a checklist examination before restarting yet again. However, says Sheehan, two shutdowns in a matter of days does raise concerns among regulators.

"If you look at the number of years Oyster Creek's been in operation, there's a lot of heating and cooling that can have an effect on...an expansion joint," Sheehan says. "This really has more to do with the power-production side of the plant than the nuclear side."

"We will capture this through the performance indicator for uplanned shutdowns," he continues. "They've had two in short order. If they have more than three during the previous 7,000 hours, we will ratchet up our level of oversight."

Emergency steps at and around the nuclear plant undergo testing Tuesday. Procedures must meet criteria set by the NRC and the Federal Emergency Management Agency.