Millstone’s Unit 2 nuclear reactor reopened Friday and regained full power on Saturday, after it was following historically warm water in Long Island Sound.
Millstone Spokesman Ken Holt confirmed the plant reopened on Friday after water temperatures in Long Island Sound dropped to 72 degrees. Millstone had to shut down its Unit 2 reactor on Sunday, Aug. 12, after the Sound’s water temperature was above 75 degrees for the first time since the plant has been in existence.
Millstone uses water from Long Island Sound to cool “key safety components” of the reactors, Holt said. The Nuclear Regulatory Commission mandates that if the water temperature of Long Island Sound rises above 75 degrees, it is deemed too warm to cool the reactor and the reactor must be shut down.
For the first time in the plant’s history, the water at Long Island Sound was above 75 degrees for a 24-hour period, Holt said. That forced the shut down of Unit 2, with it not reopening until Friday, when water temperatures dropped to 72 degrees.
Holt said the reactor was not restarted immediately after the temperature dropped below 75 degrees because Millstone wanted to ensure it would stay below 75 degrees. The Unit 3 reactor never shut down for several reasons, largely because it intakes deeper water, which is generally colder, Holt said.
Millstone is considering doing an engineering study that would show that Unit 2 could use water warmer than 75 degrees to cool the reactor, which would have to be approved by the NRC, Holt said. That is still months away though, he said.
The summer is the peak time for energy producers, and having the reactor shut down for 12 days will impact earnings, Holt said.