Dec 09 - The Daily News of Newburyport, Mass.


NextEra Energy's Seabrook nuclear power plant was shut down early Monday due to a vibration in a low pressure turbine on the non-nuclear side of the building, an official at the Nuclear Regulatory Commission said yesterday.

Neil Sheehan, spokesman for Region 1 of the Nuclear Regulatory Commission, said neither the public nor employees at the plant were ever in danger due to the vibration. Sheehan said Seabrook Station was shut down to replace the low pressure turbine rotor that was experiencing "a torsional vibration issue."

Sheehan said the power plant has been running at 65 percent power for about the past two weeks as plant officials observed the problem and readied to fix it.

Seabrook's nuclear power plant is a pressurized water reactor that heats water into steam, which in turn is piped to the turbine and funneled under pressure through as series of rotors, turning the rotors and creating energy, Sheehan said.

"Seabrook replaced the rotor when they shut down for refueling (earlier this fall), but they detected a problem when the plant went back online," Sheehan said. "They cut back to 65 percent to observe the problem, and they needed to shut down now to replace the rotor. They have another on site."

The smallest anomalies in torsional vibration, if not noted early and fixed, could lead to a crack in the rotor shaft.

Even though the issue relates to the non-nuclear side of the pant, Sheehan said the NRC is involved because it relates to the overall "balance of plant control." Plant management responded correctly to this situation, he added.

"They handled this properly because they detected the problem and developed a plan to deal with it," Sheehan said.

Al Griffith, spokesman for NextEra Energy's Seabrook nuclear power station, said the plant is safe and stable as the company works to fix the issue.

"Turbine rotation is measured within thousandths of an inch, and we have extremely narrow parameters for the turbine to be operating in the most efficient manner," Griffith said yesterday. "Since coming out of our fall refueling outage, we had been monitoring a small, but higher-than-expected vibration on the turbine. We operated safely at reduced power and are now in the process of fixing the rotor."

Griffith would not estimate when the plant would come back online, saying that as a merchant power plant, it's common practice not to publicly share outage duration information.

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