Waterford - Because water temperatures in Long Island Sound have been averaging 1.7 degrees above normal this summer, the Millstone Power Station has been granted an emergency amendment to its license related to cooling water used for Unit 2.

The amendment, issued Friday by the Nuclear Regulatory Commission, gives Millstone permission to use an average of three temperatures from three locations to ensure that the water drawn into the plant to cool instruments in the nuclear reactor building and the emergency diesel generators is no higher than 75 degrees. Previously the company was required to use a single measure of the highest temperature.

NRC spokesman Neil Sheehan said the agency agreed that taking an average would be a valid way to ensure the temperature was within safety limits. If the water exceeds 75 degrees, Millstone would be required to scale back operations, and if the water reaches 77 degrees, the plants would be required to shut down.

Water that is 77 degrees or higher does not sufficiently cool the plant to keep it within the margin of safety, Millstone spokesman Ken Holt said.

Nationwide, July air temperatures have been the hottest on record since record-keeping began in 1895, according to the National Oceanic and Atmospheric Administration, and are expected to continue to remain high through August. Long Island Sound water temperatures also are elevated because of a mild winter. Sheehan said other nuclear plants recently have been granted similar emergency amendments related to the temperature of cooling water.

Holt said the difference between the highest temperature and the average of three temperatures taken at different locations is just a few tenths of a degree, but it can make the difference when it comes to the water being within the limits.

Intake water used to cool Unit 3 is drawn from a deeper part of Long Island Sound, so it is a few degrees colder than the intake water used for Unit 2, he said.

j.benson@theday.com