Millstone 2 trips offline, unscheduled outage underway

[Core Content]

Millstone 2, Waterford, Connecticut.

Millstone 2 entered a forced short outage on August 4, 2026. This event ended a 51 day unscheduled outage free streak for the 863 MW Combustion Engineering pressurized water reactor.

This forced outage marks the second such event for Millstone 2 during 2026, following a year in 2025 with zero forced outages. Dominion Energy Nuclear Conn operates this unit and one other U.S. nuclear unit. Across the industry, 94 units are currently maintaining a 97.7 percent capacity factor. There are two units in unscheduled outages nationwide, with River Bend 1 being the only other unit currently offline.

WATERFORD, CT. Millstone 2 entered an unscheduled outage on Aug 4, 2026. The NRC has not yet issued an event notification for this trip; a follow-up reply will be posted here if one is filed.

This is the second unscheduled outage of 2026 for the unit.

Across the U.S. fleet of 94 commercial reactors, today's combined capacity factor is 97.7% (2 units in unscheduled outages), below the 97.9% baseline for this month over the past five years. At the same site, Millstone 3 is running at full power. River Bend 1 also had an unscheduled outage within the past week. While the unit is down, that takes about 690,000 homes' worth of generation off the grid.

Millstone 2 is an 863-MW COMB CE PWR operated by Dominion Energy Nuclear Conn (commercial operation since 1975). The utility operates 1 other U.S. nuclear unit. Its operating license runs through 2035 (renewed in 2005).

View Millstone 2's ratings, history, projections, and current status on NukeWorker. This thread will be updated when the unit returns to service.

Want the full picture? Subscribe to the NukeWorker outage schedule for every current and upcoming U.S. nuclear outage.

Sources: NRC Daily Reactor Power Status reports, utility-published outage schedules, and NukeWorker's projections.

[Core Content]

Follow-up: the NRC has filed its event notification for the Millstone 2 trip first reported in this thread. The agency classifies it as a manual reactor trip (docket 05000336).

MANUAL REACTOR TRIP The following information was provided by the licensee via phone and email: "On August 3, 2026, at 1420 EDT, with Millstone Unit 2 operating in Mode 1 at approximately 100 percent power, operators manually tripped the reactor following an 'A' steam generator feedwater pump trip. The reactor trip was uncomplicated, and all plant systems responded as expected. Operations responded and stabilized the plant. The auxiliary feedwater system automatically actuated as designed following the reactor trip and provided feedwater to the steam generators. Decay heat removal is being maintained by the main steam system. "This event is reported pursuant to 10 CFR 50. 72(b)(2)(iv)(B) as a four-hour, non-emergency notification due to the actuation of the reactor prot...

View Millstone 2's ratings, history, projections, and current status on NukeWorker.

Source: NRC event notification.

[Core Content]

Millstone 2 returned to service following a two-day unscheduled outage caused by a scram. The unit resumed operations on August 5, 2026, after the event began on August 4, 2026.

The actual duration of the outage was two days shorter than the initial four-day projection. This event marks the second forced outage for the 863-MW Combustion Engineering pressurized water reactor in 2026, compared to zero forced outages in 2025. Dominion Energy Nuclear Conn operates this unit and one other nuclear unit in the United States. Across the industry, 94 units currently maintain a 97.4 percent capacity factor with only one other unit, River Bend 1, in an unscheduled outage.

Millstone 2 returned to service on Aug 5, 2026 after a 2-day unscheduled outage that began on Aug 4, 2026. A short forced outage like this typically reflects a controlled response to a single issue rather than a major component problem.

NukeWorker's projection had this at about 2 days at outage start; actual duration matched within a day.

The 2-day outage removed roughly 38,000 MWh from the grid, worth approximately $2 million at recent wholesale prices, equivalent to a year's electricity for about 3,500 homes.

View Millstone 2's ratings, history, projections, and current status on NukeWorker.

Want the full picture? Subscribe to the NukeWorker outage schedule for every current and upcoming U.S. nuclear outage.

Sources: NRC Daily Reactor Power Status reports, utility-published outage schedules, and NukeWorker's projections.