Waterford — Millstone Power Station engineers are being asked to respond to 11 questions posed by the Nuclear Regulatory Commission on its application to modify its permit so that it can use cooling water from Long Island Sound up to 80 degrees.

The NRC notified Millstone Thursday that it needs additional information and clarification on the engineering analysis it submitted with the application by Jan. 31. Under Millstone's current permit, cooling water for the nuclear power plants cannot exceed 75 degrees. The NRC accepted the application in July and has requested additional information at least once before.

"It's a complicated engineering task they're reviewing," said Ken Holt, spokesman for Millstone owner Dominion.

He said the company will comply with the new request and hopes the NRC will grant the modification before Long Island Sound water temperatures rise above 75 degrees again.

"We'd like it to be in place before it gets hot again," he said.

In the summer of 2012, Millstone 2 was shut down for three weeks because water temperature at the Long Island Sound intake pipe to the plant exceeded 75 degrees. Millstone 3, which draws intake water from a cooler, deeper part of the sound, continued to operate. Temperatures at the intake pipes did not exceed 75 degrees last summer.

Holt said equipment needed to monitor higher water temperatures has already been installed, so the company could begin drawing in warmer water as soon as the NRC grants the permit modification.

j.benson@theday.com