Dominion Millstone 3 trips offline over weekend

Dominion (NYSE:D) experienced an unplanned outage at its non-utility Millstone Unit 3 nuclear unit in Connecticut during the evening of Sunday, June 12, according to an event report filed with the Nuclear Regulatory Commission (NRC).

The high water level in a steam generator at the nuclear reactor apparently figured into the incident, according to the language of the NRC event report. It says:

“At 2337 EDT on 6/12/16, a manual reactor trip was initiated on Unit 3 following feedwater isolation. As expected, Aux Feedwater system (AFW) initiated on the reactor trip. The trip was uncomplicated and the plant is currently in Mode 3 with a normal electric line-up and decay heat is being removed via steam dumps to the condenser.”

“The Feedwater isolation occurred due to high Steam Generator water level,” the NRC event report goes on to say.

Millstone Unit 2 continues, however, to run at 100%, according to NRC data.

Millstone 2, which was commissioned in the 1980s, is listed with an operating capacity of more than 1,200 MW, making it the bigger of the two pressurized water reactors (PWRs) located at the station in Waterford, Connecticut.

GenerationHub records indicate that Millstone 3 also experienced an unplanned outage in January.

“Last night, operators at Unit 3 identified that a portion of the seal on the “A” reactor coolant pump had failed,” said a Dominion spokesperson.

“The failed portion resulted in a leak of approximately two gallons per minute. The plant’s technical specification limit is less than one gallon per minute,” the spokesperson said. “The reactor was shut down safely in accordance with its technical specifications. The plant is in the process of cooling down and preparations for repairs are underway,” the spokesperson added. 

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