Seabrook 1
Online · 100% powerNextEra Energy·Seabrook, NH·PWR·1,250 MWe
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Composite Operational Excellence Score (0-100) — average percentile rank across 7 dimensions in three sub-scores: Reliability (capacity factor, forced outage days, B2B avg streak), Efficiency (fuel utilization, refuel duration), and Discipline (startup duration, scram count). 5-year window. Higher = more operationally excellent. Click to see the full breakdown.
Excellence
Rank locked · 93 units
Subscribers
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Current reactor power level from the most recent NRC daily report.
100%
Power
ONLINE
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Days of continuous operation since the last outage ended. Ranked against all operating units.
181
Current Run
days
#48 of 95
Mid Quartile
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Longest recorded period of continuous operation between outages.
528
Record Run
days
#89 of 95
Bottom Quartile
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (455 days for this 18-month cycle unit) with no trips to 0% power.
10
B2B Runs
#12 of 86
Top Quartile
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power). Ranked against all NRC-tracked units.
90.5%
Capacity Factor
#44 of 95
Mid Quartile
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Net electricity actually generated over the most recent 12 months reported by the U.S. Energy Information Administration (Form EIA-923). These are authoritative actuals, not an estimate.
9.88 TWh
Net Generation
EIA-923 · 12 mo to 2026-07
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Total NRC-reported scram events (emergency reactor shutdowns). Ranked fleet-wide — fewer scrams = better rank.
9
Scrams
#69 of 94
Mid Quartile
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Years since commercial operation began. License remaining: 23.4 years.
36.2
Operating Age
years
23.4 yrs remaining
Excellence Score, Records & Plant Facts
B2B CHAMPION
713 days without a trip
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10 Career Runs · 1 since last trip
Champion since Feb 19, 2026
Breaker-to-Breaker Runs 10 runs
Breaker-to-breaker runs measure continuous operation between refueling outages using a cycle-adjusted threshold (90% of cycle length minus RFO duration). An active streak means the unit has been running continuously since the last refueling with no trips to 0% power.
Seabrook 1 has logged 10 breaker-to-breaker runs, continuous stretches from one refueling to the next with no trip to zero power. Its longest ran 525 days, and its runs average 504 days.
525
Best Run (days)
OR16 (2014-04-24) → OR17 (2015-10-01)
504
Avg Run (days)
★ Quadruple breaker-to-breaker
OR18 → OR19 → OR20 → OR21 → OR22
All Runs
| 2024-11-21 | 2026-04-04 | 499 days | OR23 → OR24 |
| 2021-11-05 | 2023-04-01 | 512 days | OR21 → OR22 |
| 2020-06-11 | 2021-10-02 | 478 days | OR20 → OR21 |
| 2018-10-28 | 2020-04-01 | 521 days | OR19 → OR20 |
| 2017-05-01 | 2018-10-01 | 518 days | OR18 → OR19 |
| 2014-04-24 | 2015-10-01 | 525 days | OR16 → OR17 |
| 2012-10-30 | 2014-04-01 | 518 days | OR15 → OR16 |
| 2009-12-17 | 2011-04-01 | 470 days | OR13 → OR14 |
| 2008-05-08 | 2009-10-01 | 511 days | OR12 → OR13 |
| 2002-05-31 | 2003-10-04 | 491 days | OR8 → OR9 |
About This Site
Written by NukeWorker from public records: facts that do not change. Operator, status and capacity come from the live data elsewhere on this page. Sources: Wikipedia: Seabrook Station Nuclear Power Plant.
Seabrook Station is on the Atlantic coast at Seabrook, New Hampshire, about 40 miles north of Boston and about 10 miles south of Portsmouth. Seawater from the Atlantic provides its cooling.
Read more
It has one Westinghouse four-loop pressurized water reactor. Construction began in 1976. The Clamshell Alliance formed that year, and in May 1977 more than 2,000 protesters occupied the construction site, with 1,414 arraigned on criminal trespass charges. A second unit was cancelled in 1984 at about 25 percent complete, after roughly $800 million had been spent. Public Service Company of New Hampshire, the original owner, went bankrupt in 1988. The reactor connected to the grid on May 29, 1990, and entered commercial operation on August 19, 1990.
Facility Statistics
Key performance and lifecycle metrics calculated from NRC operational data. Includes operating age, construction timeline, capacity factor, efficiency, generation totals, and reliability records.
Seabrook 1 has operated for about 36.2 years and averaged a 90.5% lifetime capacity factor, generating roughly 275.2 TWh of electricity. Its longest unbroken run reached 528 days.
Lifecycle & Tenure
Operating Age: 36.2 Yrs
Build Time: 14.1 Yrs
Lic. Remaining: 23.4 Yrs
Production & Power
Lifetime CF: 90.5%
Efficiency: 34.3%
Generated: 275.2 TWh
Reliability & Outages
Record Run: 528 Days
Refuelings: 19
Avg Startup: 7.1 Days
Ownership & Construction
The utility or company that owns and operates the facility, the architect-engineer responsible for plant design, and the primary construction contractor. Click names to view all facilities by that entity on the map.
Ownership, operation and management history
| Date | Change | From | To |
|---|---|---|---|
| Nov 1, 2002 | Sold | North Atlantic Energy | NextEra (FPL) |
NEE
NextEra Energy, Inc.
NYSE
$84.32
▼ -0.71 (-0.83%)
Previous Close
85.03
Day's Range
83.80 – 85.01
52-Week Range
74.41 – 98.75
Volume
1,922,184
Delayed quote as of Nov 3, 2026 10:38 AM ET.
Source: Yahoo Finance.
Full quote on Yahoo Finance
NextEra Energy and Dominion Energy (D) announced a merger on 2026-05-18, subject to regulatory and shareholder approval.
Operational Excellence Score Subscribers
Seabrook 1 is rated 0 to 100 on how well it actually runs, scored against every other operating reactor in the US fleet from its own operating record. Subscribers see the score, the three sub-scores behind it, and each of the seven measured inputs.
- This unit's composite score and fleet rank
- Reliability, Efficiency and Discipline sub-scores
- All seven measured inputs, with fleet percentiles
- Rank against comparable units, not just the fleet
- Three-year, five-year and lifetime windows
- Five-year trend, and every other operating US reactor
Included with every outage subscription and with NukeWorker Gold membership. Trading the outage rather than working it? The same record, cut by power market, is on NukeGryd.
Scram History 9 events since 2011
Automatic and manual reactor scram (emergency shutdown) events reported to the NRC since 2011. Includes event dates, trip type, and average recovery time. Click the title to view the full fleet scram dashboard.
Seabrook 1 has recorded 9 reactor scrams, or emergency shutdowns, since 2011 (4 automatic, 5 manual). On average the unit was back to full power about 15.1 days after each trip.
Technical Specs
Reactor design specifications including type (PWR/BWR), containment design, nuclear steam supply system manufacturer, thermal and electrical power ratings, and current operational status.
Reactor Type:
PWR
Containment:
PWR-DRYAMB
NSS Supplier:
WEST 4LP
Turbine Supplier:
GENERAL ELECTRIC CO. IAEA
Thermal Power:
3648 MWt
Net Capacity:
1250 MWe
Gross Capacity:
1,296 MWe IAEA
Design Capacity:
1,149 MWe IAEA
Efficiency:
34.3%
Status:
Operating
Lifetime Output:
330.7 TWh through 2025 IAEA
Licensing
NRC licensing history including docket number, license type and number, construction permit date, operating license issuance, commercial operation date, license renewal, and expiration date.
Docket #:
05000443
License #:
NPF-86
License Type:
OL-FP
Const. Permit:
1976-07-07
Construction Start:
1976-07-07 IAEA
Operating Lic:
1990-03-15
First Criticality:
1989-06-13 IAEA
Grid Connection:
1990-05-29 IAEA
Commercial Op:
1990-08-19
License Renewed:
2019-03-12
License Exp:
2050-03-15
Market & Region
EIA market and grid-region classifications: NERC reliability region, U.S. Census region, balancing authority responsible for grid operations, and whether the unit operates as a rate-regulated utility or a competitive merchant generator. Hover any value for the full name.
NERC Region:
NPCC
— Northeast Power Coordinating Council
Census Region:
NEW
— New England
Balancing Authority:
ISNE
— ISO New England (ISO/RTO)
Market Structure:
Merchant
— Competitive generator selling into wholesale markets