When the second reactor opened at Connecticut’s Millstone Nuclear Power Station on Sept. 26, 1975, nuclear power was at the height of a golden age in the United States.
Millstone, situated on a section of coastline in Waterford that extends into Long Island Sound, had been under construction for nearly a decade. Its first boiling-water reactor, Unit 1, came online in 1970. Unit 2 soon followed, a more advanced pressurized-water reactor designed by Combustion Engineering Inc. in Windsor.
The plant would add its third and final reactor, Unit 3, in 1986.
The intervening years, however, had brought about the infamous 1979 accident at Pennsylvania’s Three Mile Island — and with it, growing public anxiety over the safety of nuclear power. By the late 1990s, the number of new reactors being built in the U.S. had plummeted to zero.
Millstone Unit 1 was powered down in 1995, joining a wave of decommissioning for older nuclear power plants in Connecticut, Massachusetts, Vermont and Maine.
Units 2 and 3 continued operating, however. In 2005 the federal Nuclear Regulatory Commission renewed both licenses, allowing the reactors to continue operating until 2035 and 2045, respectively.
Virginia-based Dominion Energy, which owns the plant, sent several of its leaders to Connecticut last month to commemorate the 50th anniversary of Unit 2. They gathered with local and state leaders, along with hundreds of current and former employees, at what is now New England’s oldest and largest nuclear power plant.
Connecticut Mirror reporters were later allowed inside to view a portion of the operation and observe round-the-clock staff.
Like most of the nuclear reactors still operating in the U.S., Millstone Units 2 and 3 are pressurized-water reactors that rely on steam to spin a turbine and generate electricity. Its operation relies on three separate networks of pipes to heat and cool water. (A boiling water reactor, by contrast, utilizes only two systems of pipes.)
The first, or primary system, is a closed loop that absorbs energy from nuclear fission within the reactor core, heating water to high temperatures but preventing it from boiling due to pressure within the pipes. The hot, pressurized water then passes through the second system, a steam generator, where water under less pressure is allowed to evaporate into steam to power the turbine. The third system, or cooling system, pumps colder water from outside the plant to condense the steam back into water that is then circulated back through the steam generator.
The advantages of maintaining the separate systems is that the water inside the primary and secondary loops never mixes, preventing the spread of radiation.
When both of Millstone’s reactors are operating at full capacity, they circulate 1.55 million gallons of water a minute through the plant’s cooling system which ends up depositing the water back into the Sound.
At any given time, a team of five operators oversee Unit 2’s nuclear and electrical systems from a control room lined with hundreds of knobs, switches, levers, digital monitors and other analog devices that are recording the plants’ myriad functions.
There are five teams assigned to each of Millstone’s two control rooms. They work in shifts to ensure the plant can operate 24 hours a day for up to a year and a half before refueling.
Operators must undergo an extensive 18-month training program overseen by the NRC that is specific to each control room. Even a crew member on Unit 2 would have to be re-trained in order to transfer to Unit 3.
Mike Watson, one of the shift managers at Unit 2, has been at the plant for more than 18 years. Like many of the roughly 800 Dominion employees at Millstone, Watson previously served on nuclear-powered ships in the U.S. Navy.
“I still learn things every day,” Waston said. “Comfort is a matter of perspective.”
Just down the hall from the room where Watson and his team work is the now-abandoned control room for Millstone’s first reactor, Unit 1. Most of the extensive control devices and monitors have been removed from the seafoam-green electrical paneling.
“We get asked a lot if we’re ever going open up Unit 1 again,” said Susan Adams, Millstone’s State Policy Director. “I think if anyone ever saw this, they’d know its not going to happen.”
Millstone’s Units 2 and 3 have a peak output of 2,100 megawatts of electricity, enough to power roughly 2 million homes.
The reactors themselves are located within thick concrete containment structures that are separate from the buildings housing Millstone’s offices, control rooms and turbine generators.
Spent nuclear fuel from Millstone’s reactors is stored on site within large cooling pools — and later moved to dry steel casks sealed within concrete vaults.
With the U.S. government’s plans for a long-term nuclear repository currently at a standstill, the spent fuel will remain at Millstone indefinitely. As of 2021, a total of 2,441 metric tons of spent uranium fuel was being stored at Millstone and the former site of the Connecticut Yankee Nuclear Power Plant in Haddam, according to the Nuclear Energy Institute.
A half-century after Millstone’s Unit 2 opened, the plant still produces roughly one-third of all electricity generated within Connecticut and the vast majority of the state’s carbon-free power.
For that reason, the plant’s future has been the source of great interest and speculation in Hartford.
In 2022, state lawmakers voted to lift the state’s moratorium on new nuclear facilities, opening the door for Dominion to look to Millstone as a location to deploy the next generation of smaller, modular reactors.
During the anniversary event last month, Gov. Ned Lamont floated an expansion of nuclear power at Millstone, saying, “I don’t know whether it’s fission or fusion, or mega or modular, but it’s going to be here.”
Dominion officials, however, have made clear they’re focusing their efforts around newer modular reactors near the company’s Virginia headquarters, as well as states with fully-regulated utility markets. In the meantime, the company’s plans for Millstone will involve seeking an extension of its current license from the NRC, allowing the plant to continue operating until 2065.
Bob Blue, Dominion’s president and chief executive officer, said the company is planning to invest over $1 billion in Millstone over the next decade as part of that effort.
“We’re eager to have a long-term certainty to make the investments necessary to ensure that it provides even more value for a long time to come,” Blue said.