Millstone 2 trips offline, unscheduled outage underway

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Millstone 2 began an unscheduled forced short outage on 2026-06-05. This event ended the unit's unscheduled-outage-free streak at 1591 days.

This forced outage is the first for the 853-MW Combustion Engineering pressurized water reactor in 2026, following a year with zero forced outages in 2025. Dominion Energy Nuclear Conn operates this unit and one other U.S. nuclear unit. Across the 94 units in the current fleet, the capacity factor is 97.3 percent, with one unit currently in refueling and one unit in an unscheduled outage.

WATERFORD, CT — Millstone 2 entered an unscheduled outage on Jun 5, 2026. The NRC has not yet issued an event notification for this trip; this post will be updated if one is filed.

This is the first unscheduled outage of 2026 for the unit. The unit had just returned to service on May 13, 2026 from a 31-day refueling outage.

Across the U.S. fleet of 94 commercial reactors, today's combined capacity factor is 97.3% (1 currently in refueling, 1 in unscheduled outages), above the 95.3% baseline for this month over the past five years. At the same site, Millstone 3 is running at full power.

Millstone 2 is an 853-MW COMB CE PWR operated by Dominion Energy Nuclear Conn (commercial operation since 1975). At full power, it supplies enough electricity for roughly 682,000 homes. 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.

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

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Millstone 2 returned to service on June 14, 2026, following a 10-day forced extended outage that began on June 5. This event marks the first forced outage for the 863-MW Combustion Engineering pressurized water reactor during the 2026 calendar year.

The unit, which has been in commercial operation since 1975, recorded zero forced outages throughout 2025. Dominion Energy Nuclear Conn operates this unit along with one other U.S. nuclear unit. Across the current fleet of 94 units, the industry maintains a 98 percent capacity factor with one unit currently in an unscheduled outage and zero units in refueling.

Millstone 2 returned to service on Jun 14, 2026 after a 10-day unscheduled outage that began on Jun 5, 2026. A multi-day outage in this range typically points to a single equipment fix rather than a major component issue.

The 10-day outage removed roughly 191,000 MWh from the grid, worth approximately $8 million at recent wholesale prices, equivalent to a year's electricity for about 18,000 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.

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Follow-up: the NRC has filed an event notification on Jun 10, 2026 for the Millstone 2 trip first reported in this thread. NRC scram report (type: P, code: M, docket 05000336). View the NRC event notification.

MANUAL REACTOR TRIP The following information was provided by the licensee via phone and fax: "At 0339 EDT on June 11, 2026, control element assembly '14' dropped to the bottom of the core. "To stabilize plant conditions, the reactor was manually tripped at 0341. This resulted in the actuation of the reactor protection system (RPS) when the reactor was critical and is being reported as a four-hour non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). "There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. "There has been no impact to Unit 3 which remains at 100 percent power."

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

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