Rising temperatures in Long Island Sound for the first time forced a shutdown of one of two nuclear reactors at Millstone Power Station in Waterford.
One of Millstone’s two units uses water from the Sound to cool its operations. On Sunday, the Sound water temperatures went above the acceptable threshold of 75 degrees to adequately cool the reactor, forcing the shutdown that continues Monday.
“This year, Long Island Sound has been the warmest on record,” Millstone spokesman Ken Holt said.
This is the first time in the reactor’s history it had to be shut down because of hot Sound water, Holt said.
Millstone is the largest power generator in New England, with its two reactors supplying 13 percent of the region’s power. The unit shutdown on Sunday is the smaller of the two, generating 880 megawatts.
As nuclear power is among the lowest cost electricity in the region, the loss of the reactor can causes prices to rise as more expensive generators are needed to meet power demand. On Monday afternoon, New England had 21,070 megawatts of power demand, well below the demand when temperatures are hotter.
Millstone is conducting an evaluation on when the station can restart the reactor, but the nuclear crew is waiting to make sure the water temperatures will be below 75 degrees for the long-term, as it is an involved process to shutdown and restart a reactor, Holt said.
The Sunday shutdown came two days after the U.S. Nuclear Regulatory Commission granted Millstone a special provision to keep operating as Sound temperatures rose.
Millstone has three gauges to judge the Sound temperature and typically uses the highest of the three to make sure the water is safe to use. On Friday, NRC said Millstone could use the average of the three gauges to determine Sound temperature, which by Sunday read the Sound water as too hot.
