NRC agrees to Millstone request for higher maximum temperature for cooling water

Two summers after the Dominion (NYSE:D) Millstone station in Connecticut was forced to suspend operations because of warm water temperatures in Long Island Sound, the Nuclear Regulatory Commission (NRC) has agreed to adjust the cooling water standard for Millstone 3.

In an NRC document published July 11, the agency approved raising the maximum temperature limit for the Long Island Sound from 75-to-80 degrees F. The sound serves as the ultimate heat sink (UHS) for Millstone 3, and when the water temperature exceeds the maximum limit approved by NRC the reactor unit must prepare to cease power generation.

The additional five degrees “has no adverse impact on the piping and pipe support and equipment nozzle analyses,” the NRC said in its amendment to the plant’s “technical specification” for the ultimate heat sink.

The amendment is in response to an application that Dominion Nuclear Connecticut had filed in May 2013.

As the Ultimate Heat Sink for Millstone 3, Long Island Sound supports heat removal from both safety related and non-safety related cooling systems during normal operation, shutdown, and accident conditions via the Service Water (SW) and Circulating Water (CW) systems, NRC noted.

The UHS serving multiple units should be capable of providing sufficient cooling water to permit simultaneous safe shutdown and cool down of all units it serves and to maintain them in a safe shutdown condition. Also, in the event of an accident in one unit, the UHS should be able to dissipate the heat for that accident safely, to permit the concurrent safe shutdown and cool down of the remaining units, and to maintain all units in a safe shutdown condition, according to the NRC document.

Millstone 3 is roughly 1,200-MW facility while Millstone 2 has a capacity of roughly 900 MW. Both are pressurized water reactors.

About Wayne Barber 4201 Articles
Wayne Barber, Chief Analyst for the GenerationHub, has been covering power generation, energy and natural resources issues at national publications for more than 20 years. Prior to joining PennWell he was editor of Generation Markets Week at SNL Financial for nine years. He has also worked as a business journalist at both McGraw-Hill and Financial Times Energy. Wayne also worked as a newspaper reporter for several years. During his career has visited nuclear reactors and coal mines as well as coal and natural gas power plants. Wayne can be reached at