July 16, 2012 / 3:28 PM / 5 years ago

UPDATE 2-NextEra cuts N.H. Seabrook output due to solar activity

* First time Seabrook reduced for solar activity

* Solar activity peaks about every 12 years

* 2013 expected to be the peak of the solar storms

By Scott DiSavino

July 16 (Reuters) - NextEra Energy Inc said it expects to be able to increase power at the 1,247-megawatt Seabrook nuclear power plant in New Hampshire after reducing output Sunday night due to solar magnetic activity, a plant spokesman said Monday.

"The conditions that caused the power reduction Sunday night have gone away," said David Barr, a spokesman for the plant, noting this was the first time plant operators reduced the Seabrook reactor because of solar activity.

He could not say, due to competitive reasons, when the plant would return back to 85 percent, where it was operating before the power reduction.

Plant operators reduced the plant from 85 percent power Sunday morning to 68 percent Monday morning.

The reduced output at Seabrook came at a time when the power grid was already stressed as homes and businesses across the U.S. Northeast and Midwest crank up their air conditioners to escape another brutal heat wave.

ISO New England, which operates the power grid in the six New England states, said despite the Seabrook reduction, system conditions remained normal.

Solar storms from the sun can affect power grids, communications and global positioning system (GPS) satellites.

Major disruptions from solar activity are rare but have had serious impacts on power systems in the past. In 1989, a solar storm took down the power grid in Quebec, Canada, leaving about six million people without electricity for several hours.

Power companies receive alerts from the U.S. Space Weather Prediction Center, which is part of National Weather Service, to tell them when to prepare for solar events, which peak about every 12 years.

The Center said the next peak, called a solar maximum, is expected in 2013. The Center said it expects solar storms to continue over the next three to five years.

Seabrook spokesman Barr said the company has had procedures in place to monitor and collect data on geomagnetically induced currents during solar storms for a long time but this was the first time the data showed that the prudent thing to do was back the unit's power off.

The geomagnetically induced currents, which are variations in the Earth's magnetic field, can damage power transformers and other electrical equipment.

The solar storms Sunday night caused high circulating currents in the Seabrook transformers, according to the U.S. Nuclear Regulatory Commission (NRC).

MONITOR FOR NOW

For now, NextEra will continue to monitor the solar activity. In the future, Barr said, the company has a plan to replace the plant's three transformers, which are each as big as a small house, with equipment that would not be as affected by solar activity.

Barr, however, could not say when the transformers would be replaced.

Seabrook has been operating at less than full power, mostly at 85 percent, since December, due to a problem with the generator cooling system.

Barr could not say when the company would fix the generator cooling system.

Power traders guessed the company would fix the cooling system during the plant's next refueling outage, expected in September.

The NRC said the only other nuclear plant in the Northeast that has warned about the solar activity was Entergy Corp's 855-MW FitzPatrick nuclear plant in New York. But FitzPatrick was still operating at full power Monday morning.

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