Seabrook 1 completes Spring refuel in 33 days, caps 499-day B2B run

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Seabrook 1 completed its refueling outage in 33 days, which was 9 days longer than the planned 24 days. Despite the schedule variance, the duration was 5.6 days below the average of the unit's 18 prior refuels. This event ended a streak of 5273 days without an unscheduled outage.

33 days outage · 9 days past schedule · tenth B2B run complete · 1,250 MW back online

Seabrook 1 resumed power production on May 6, 2026 after a 33-day Spring 2026 refueling outage that began Apr 4, 2026.

The published schedule had it at 24 days (Apr 4, 2026 to Apr 28, 2026), so the actual ran 9 days longer than planned.

The outage ran about 6 days shorter than the unit's 18-cycle average of 38.6 days. It also capped a 499-day breaker-to-breaker run (over the 455-day threshold for an 18-month cycle), the unit's tenth qualified B2B run. Going into the refueling, the unit had run for more than 14 years without an unscheduled outage.

The 33-day outage removed roughly 911,000 MWh from the grid, worth approximately $36 million at recent wholesale prices, equivalent to a year's electricity for about 84,000 homes.

Across the U.S. fleet of 94 commercial reactors, today's combined capacity factor is 91.3% (5 currently in refueling), above the 87.0% baseline for this month over the past five years. Salem 2, Braidwood 2, Palo Verde 2, and Susquehanna 1 also completed refueling outages within the past week.

Seabrook 1 is a 1,250-MW Westinghouse 4-loop PWR operated by NextEra Energy Seabrook (commercial operation since 1990). At full power, it supplies enough electricity for roughly 1 million homes. Its operating license runs through 2050 (renewed in 2019). The unit ran at a 99.9% capacity factor in 2025, among the unit's strongest cycles.

View Seabrook 1's ratings, history, predictions, and current status on NukeWorker.

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