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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.
27
Excellence
#82 of 94 →
Bottom Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
183
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2000-11-14 to 2002-04-15).
517
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (400 days for this 18-month cycle unit) with no trips to 0% power.
6
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
88.3%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data.
17
Outages
since 1999
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Average time from first power generation (>0%) to sustained full power (≥95% for 2+ days) across the last 3 scheduled outages. Click to compare against the fleet on the Operator Efficiency Leaderboard.
17
Avg Startup
days (last 3)
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Average fuel utilization — percent of the designed fuel cycle that this unit consumes before refueling, derived from the historical burn-down trajectory. Higher = more efficient operator (refuels with less margin remaining; closer to coastdown). Computed as 100% minus the unit's average refuel-point fuel %, using the last 3 years where available, otherwise lifetime average. Click to compare against the fleet on the Operator Efficiency Leaderboard.
93.6%
Fuel Utilization
3yr avg
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NukeWorker's Operational Excellence Score is a composite 0–100 ranking of every active US nuclear unit across 7 publicly observable performance metrics, grouped into three sub-scores:
• Reliability — capacity factor, forced outage days, B2B avg streak
• Efficiency — fuel utilization, refuel duration
• Discipline — startup duration, scram count
Each unit's metric is converted to a percentile across the active fleet. Sub-score = average of its components; composite = average of the three sub-scores. Use the time-window toggle below to switch between 3yr / 5yr / lifetime.
• Reliability — capacity factor, forced outage days, B2B avg streak
• Efficiency — fuel utilization, refuel duration
• Discipline — startup duration, scram count
Each unit's metric is converted to a percentile across the active fleet. Sub-score = average of its components; composite = average of the three sub-scores. Use the time-window toggle below to switch between 3yr / 5yr / lifetime.
Time window
— change how far back we look
NukeWorker's
Operational
Excellence Score
Operational
Excellence Score
27/100
Bottom Quartile · #82/94
5-year window
Sequoyah 2 ranks #82 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Scrams (5-year) (48th percentile). Weakest: B2B Avg Streak (5th percentile).
Reliability
10
Capacity factor + Forced outages + B2B streaks
Efficiency
28
Fuel utilization + Refuel duration
Discipline
44
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#57 of 61
PWR
Containment:
#8 of 10
Ice Condenser
Cycle length:
#49 of 54
18-month cycle
Fleet rank above (82 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
8th
80.4% (higher better, Reliability)
Forced Outage Days/yr
17th
9.4d (lower better, Reliability)
B2B Avg Streak
5th
483d (higher better, Reliability)
Fuel Utilization
28th
97.0% (higher better, Efficiency)
Refuel Duration
29th
36d (lower better, Efficiency)
Startup Duration
39th
5.0d (lower better, Discipline)
Scrams (5-year)
48th
0.4/yr (lower better, Discipline)
Each dimension's percentile is computed across the active US fleet (94 units with sufficient history). Sub-score = average of its component percentiles. Composite = average of the three sub-scores. 5-year window. View full leaderboard →
Methodology
NukeWorker's Operational Excellence Score is a composite ranking that combines 7 publicly observable performance metrics into a single 0-100 number per US nuclear unit.
How it's computed: Each unit's raw value is converted to a percentile (0-100) within the 94 active US units that have at least 2 completed refueling cycles. The 7 percentiles are averaged into 3 sub-scores (Reliability, Efficiency, Discipline), and those are averaged into the final composite.
Active window — 5-year:
- Reliability — Capacity factor (5yr), forced outage days/yr (5yr), B2B avg streak (lifetime)
- Efficiency — in-cycle fuel utilization (3yr), median refuel duration (5yr)
- Discipline — robust mean startup duration, scrams/yr (5yr, annualised)
Cohort rankings: alongside the fleet rank, each unit gets ranked within its reactor type (PWR/BWR), containment design (Ice Condenser, Mark I, etc.), and cycle length (12/18/24-month). Useful for apples-to-apples comparisons.
What's excluded: subjective community ratings, confidential INPO ratings, financial metrics. We only use publicly available NRC + cycle data.
Why three windows? 5yr (default) is the industry standard. 3yr captures recent operational changes and post-pandemic recovery. Lifetime gives newer units a fair comparison and reveals long-term consistency.
Edge cases: units with fewer than 2 cycles (e.g., Vogtle 4) show "Provisional". Decommissioned units excluded.
Refresh cadence: recomputed daily. Each window cached separately.
A data-derived proxy for operational performance; not affiliated with INPO. INPO ratings are confidential and qualitative — ours is public and quantitative.
5-yr trend:
Stable vs 2025
Compare Sequoyah 2 head-to-head with up to 3 other units.
Compare now
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Duration of each outage in days, shown chronologically. Green bars are scheduled refueling outages, red bars are forced/unscheduled. The orange dashed line marks the average duration. Extended outages (>180 days) and D&D periods are excluded.
Outage Duration Trend
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Days between consecutive scheduled refueling outage starts, showing operating cycle regularity. The purple dashed line marks the average cycle length. Most U.S. reactors operate on 18-month (547 day) or 24-month (730 day) cycles.
Cycle Length History
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Time in days from first power generation (>0%) to sustained full power (≥95% for 2+ consecutive days) after each scheduled refueling outage. The dashed line marks the average. Includes startup testing holds and power dips.
Startup Duration Trend
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Estimated fuel remaining in the current cycle, expressed as a percentage of the unit's typical cycle. Starts at 100% when the unit returns to power post-refuel and drops as full-power-days are burned. Days at reduced power burn fuel proportionally — so a unit with significant downtime (high burn deficit) drops slower and ends up with MORE fuel left than its calendar position would suggest. Coastdown threshold around 15%. Toggle to overlay past cycles on a normalized "days into cycle" axis to see how aggressively this unit historically burns down before refuel.
Fuel Burn Down Cycle since May 26, 2025
37.3% remaining
347 / 492 days
38.5 FPD margin
Avg refuel: 1.6%
Avg refuel (3yr): 6.4%
Deepest burn: 0.0% (1999-05 → 2000-10)
Most margin: 6.4% (2023-04 → 2024-07)
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Monthly capacity factor with outage events overlaid as red bands. Green bars show average power level per month. Toggle to Daily view for raw daily data.
Power History
| Type ⇅ | Actual Start ⇅ | Actual End ⇅ | Duration ⇅ | Days Online ⇅ | Scheduled | Delta |
|---|---|---|---|---|---|---|
|
Unscheduled
|
2025-11-02 | 2025-11-08 | 7 | 128d | - | - |
|
Scram
# 57779
|
2025-06-24 | 2025-06-27 | 4 | 5d | - | - |
|
Unscheduled
|
2025-05-30 | 2025-06-19 | 21 | 6d | - | - |
|
Unscheduled
|
2025-05-20 | 2025-05-24 | 5 | 3d | - | - |
|
Scheduled
SGR/Major
|
2024-07-31 | 2025-05-17 | 291 | 4d | 2024-08-07 | -7d |
|
Unscheduled
|
2024-07-21 | 2024-07-27 | 7 | 465d | - | - |
|
Scheduled
|
2023-03-18 | 2023-04-13 | 27 | 496d | 2023-03-18 | 0d |
|
Scheduled
|
2021-10-02 | 2021-11-07 | 37 | 516d | 2021-10-21 | -19d |
|
Scheduled
|
2020-04-11 | 2020-05-04 | 24 | 120d | 2020-04-18 | -7d |
|
Scram
# 54438
|
2019-12-13 | 2019-12-13 | 1 | 371d | - | - |
|
Scheduled
|
2018-11-03 | 2018-12-07 | 35 | 516d | 2018-09-29 | +35d |
|
Unscheduled
|
2017-06-05 | 2017-06-05 | 1 | 2d | - | - |
|
Unscheduled
|
2017-06-03 | 2017-06-03 | 1 | 4d | - | - |
|
Scheduled
|
2017-04-28 | 2017-05-30 | 33 | 355d | 2017-04-22 | +6d |
|
Unscheduled
|
2016-05-07 | 2016-05-08 | 2 | 146d | - | - |
|
Scheduled
|
2015-11-14 | 2015-12-13 | 30 | 253d | 2015-11-16 | -2d |
|
Scram
# 50856
|
2015-03-03 | 2015-03-06 | 4 | 263d | - | - |
|
Scheduled
|
2014-05-12 | 2014-06-13 | 33 | 440d | 2014-05-12 | 0d |
|
Scram
# 48778
|
2013-02-25 | 2013-02-26 | 2 | 54d | - | - |
|
Scheduled
SGR/Major
|
2012-10-15 | 2013-01-02 | 80 | 58d | 2012-10-15 | 0d |
|
Scram
# 48198
|
2012-08-17 | 2012-08-18 | 2 | 422d | - | - |
|
Scheduled
|
2011-05-23 | 2011-06-22 | 31 | 352d | 2011-04-24 | +29d |
|
Unscheduled
|
2010-05-29 | 2010-06-05 | 8 | 184d | - | - |
|
Unscheduled
|
2009-11-26 | 2009-11-26 | 1 | 2d | - | - |
|
Scheduled
|
2009-10-26 | 2009-11-24 | 30 | 149d | 2009-10-25 | +1d |
|
Unscheduled
|
2009-05-28 | 2009-05-30 | 3 | 61d | - | - |
|
Unscheduled
|
2009-03-27 | 2009-03-28 | 2 | 135d | - | - |
|
Unscheduled
|
2008-11-04 | 2008-11-12 | 9 | 64d | - | - |
|
Unscheduled
|
2008-09-01 | 2008-09-01 | 1 | 89d | - | - |
|
Scheduled
|
2008-05-05 | 2008-06-04 | 31 | 418d | 2008-04-27 | +8d |
|
Unscheduled
|
2007-03-14 | 2007-03-14 | 1 | 49d | - | - |
|
Unscheduled
|
2007-01-24 | 2007-01-24 | 1 | 30d | - | - |
|
Scheduled
|
2006-11-27 | 2006-12-25 | 29 | 247d | 2006-11-26 | +1d |
|
Unscheduled
|
2006-03-23 | 2006-03-25 | 3 | 300d | - | - |
|
Scheduled
|
2005-04-25 | 2005-05-27 | 33 | 59d | 2005-04-24 | +1d |
|
Unscheduled
|
2005-02-24 | 2005-02-25 | 2 | 396d | - | - |
|
Unscheduled
|
2004-01-16 | 2004-01-25 | 10 | 9d | - | - |
|
Unscheduled
|
2003-12-28 | 2004-01-07 | 11 | 18d | - | - |
|
Scheduled
|
2003-11-10 | 2003-12-10 | 31 | 211d | 2003-11-10 | 0d |
|
Unscheduled
|
2003-04-13 | 2003-04-13 | 1 | 15d | - | - |
|
Unscheduled
|
2003-03-25 | 2003-03-29 | 5 | 9d | - | - |
|
Unscheduled
|
2003-03-11 | 2003-03-16 | 6 | 64d | - | - |
|
Unscheduled
|
2002-12-27 | 2003-01-06 | 11 | 166d | - | - |
|
Unscheduled
|
2002-07-13 | 2002-07-14 | 2 | 42d | - | - |
|
Unscheduled
|
2002-05-31 | 2002-06-01 | 2 | 11d | - | - |
|
Scheduled
|
2002-04-15 | 2002-05-20 | 36 | 517d | 2002-04-15 | 0d |
|
Scheduled
|
2000-10-23 | 2000-11-14 | 23 | 277d | 2000-10-23 | 0d |
|
Unscheduled
|
2000-01-19 | 2000-01-20 | 2 | 254d | - | - |
|
Scheduled
|
1999-04-18 | 1999-05-10 | 23 | - | 1999-04-18 | 0d |
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