Why a cold snap makes nuclear count for more

A hard cold morning in January, somewhere along the Connecticut shoreline. The baseboard heat or the heat pump has been running since before dawn, the forecast says single digits down by the water, and the electric bill you will see next month is already climbing. Out past Niantic Bay, in Waterford, a pair of reactors at the Millstone Power Station keeps turning out power at close to full tilt, the way it does in almost any weather. Those two reactors supply something on the order of 40 percent of the electricity Connecticut uses in a normal year, at last public report.

New England's grid leans heavily on natural gas to make electricity. In a deep cold snap, pipeline gas gets pulled toward heating homes first, which can leave gas-fired power plants competing for whatever is left. Millstone runs on fuel already loaded inside the reactor, so it does not bid against furnaces for that gas. ISO New England (the independent operator that runs the six-state regional grid and its power markets) has flagged winter reliability as its hardest problem for years, and a roughly 2,000-megawatt nuclear station that runs straight through a nor'easter is close to the center of that worry.

The 40 percent, and the fuel-security argument

Start with the plant itself. Millstone's two working reactors, Unit 2 and Unit 3, together carry roughly 2,000 megawatts of capacity at last public report, with Unit 3 the larger of the pair, on the order of 1,200 megawatts. An older Unit 1 shut down back in the late 1990s and is not part of this. Dominion, the owner, reports the station makes about half of New England's carbon-free electricity, a figure worth treating as a round claim rather than a precise one.

The fuel-security argument turns on a simple what-if. If Millstone ever came offline, the power would have to come from somewhere, most likely more natural gas or imports over the lines from New York and Canada, which is exactly the winter squeeze the grid operator keeps warning about. Officials and studies have disagreed for years about how close that risk really is, and how much ratepayers should pay to avoid it. That disagreement is the honest state of things, not a settled answer.

The contract and the two clocks

Dominion Energy owns and runs Millstone. The reason it is still running, and not retired like some other Northeast reactors, traces back to a state decision: under Connecticut's zero-carbon procurement law, the Department of Energy and Environmental Protection (DEEP) ran a process that selected Millstone for a long-term power deal, beginning around 2019 and running roughly ten years. By that math the contract reaches into the latter part of this decade, and what happens when it ends is an open question this desk is watching.

The licenses are the second clock. Each reactor holds a federal operating license from the Nuclear Regulatory Commission, and those run on different timelines, with one into roughly the mid-2030s and the other into roughly the mid-2040s at last public report. Pushing either plant past its current license would mean a fresh NRC application for what the agency calls a subsequent license renewal, the step that can extend a reactor toward 80 years of operation. No such filing changes the picture until it actually lands on the docket.

Worth watching this month

1. Whether Dominion signals any move toward a subsequent license renewal application for its earlier-expiring Millstone unit, since that license runs only into roughly the mid-2030s; watch the NRC's license renewal pages, and treat it as routine until a real filing appears.

2. ISO New England's winter outlook and any cold-weather operating alerts this season, which the grid operator posts publicly and which are mostly routine but occasionally matter.

3. Any state conversation at DEEP or the Public Utilities Regulatory Authority about what follows the current Millstone power contract as it nears its end later this decade; this is the one that actually matters for your bill.

4. Dominion's scheduled refueling outages at Millstone, which are planned and routine but briefly take a reactor offline and dent that 40 percent share.

5. The U.S. Energy Information Administration's monthly Connecticut electricity figures, a plain public check on whether the nuclear share is holding near 40 percent or drifting.

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Questions we expect

Short answers, plain language
How much of Connecticut's power really comes from Millstone?

On the order of 40 percent in a normal year, at last public report. The exact share moves with demand and with refueling outages, so treat it as a round number rather than a fixed one.

Could Millstone close soon?

Not on any announced schedule. Both reactors hold NRC operating licenses running into the 2030s and 2040s, and the state power contract runs into the latter part of this decade. What happens after that contract is the real open question.

Why does nuclear matter more here in winter?

Because the regional grid leans on natural gas, and in a cold snap that gas is pulled toward heating homes first. Millstone runs on fuel already in the reactor, so it keeps producing when gas-fired plants are squeezed.

Does Millstone's power go only to Connecticut?

No. It feeds the regional grid run by ISO New England, so its output serves the whole six-state market. Even so, a large share of what Connecticut consumes effectively comes from it.

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Sources of record

Primary documents only

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