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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.
26
Excellence
#84 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).
164
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2012-03-30 to 2013-10-14).
563
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (434 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).
89.4%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data.
18
Outages
since 2000
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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.
4.3
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.
92.7%
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
26/100
Bottom Quartile · #84/94
5-year window
Sequoyah 1 ranks #84 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Startup Duration (56th percentile). Weakest: B2B Avg Streak (13th percentile).
Reliability
24
Capacity factor + Forced outages + B2B streaks
Efficiency
19
Fuel utilization + Refuel duration
Discipline
36
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#58 of 61
PWR
Containment:
#9 of 10
Ice Condenser
Cycle length:
#50 of 54
18-month cycle
Fleet rank above (84 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
36th
89.4% (higher better, Reliability)
Forced Outage Days/yr
21th
8.4d (lower better, Reliability)
B2B Avg Streak
13th
497d (higher better, Reliability)
Fuel Utilization
16th
95.7% (higher better, Efficiency)
Refuel Duration
23th
38d (lower better, Efficiency)
Startup Duration
56th
4.1d (lower better, Discipline)
Scrams (5-year)
16th
0.8/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 1 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 Dec 4, 2025
70.3% remaining
160 / 520 days
5.7 FPD margin
Avg refuel: 6.0%
Avg refuel (3yr): 7.3%
Deepest burn: 0.0% (2000-03 → 2001-10)
Most margin: 16.2% (2017-01 → 2018-04)
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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 |
|---|---|---|---|---|---|---|
|
Scheduled
|
2025-10-04 | 2025-12-01 | 59 | 100d | 2025-10-03 | +1d |
|
Scram
# 57778
|
2025-06-24 | 2025-06-26 | 3 | 248d | - | - |
|
Scram
# 57351
|
2024-09-30 | 2024-10-19 | 20 | 30d | - | - |
|
Scram
# 57285
|
2024-08-24 | 2024-08-31 | 8 | 116d | - | - |
|
Scheduled
|
2024-03-23 | 2024-04-30 | 39 | 486d | 2024-03-29 | -6d |
|
Scheduled
|
2022-10-22 | 2022-11-23 | 33 | 440d | 2022-10-22 | 0d |
|
Unscheduled
|
2021-08-06 | 2021-08-08 | 3 | 69d | - | - |
|
Scram
# 55272
|
2021-05-25 | 2021-05-29 | 5 | 15d | - | - |
|
Scheduled
|
2021-04-10 | 2021-05-10 | 31 | 331d | 2021-04-10 | 0d |
|
Scram
# 54708
|
2020-05-13 | 2020-05-14 | 2 | 169d | - | - |
|
Scheduled
|
2019-10-12 | 2019-11-26 | 46 | 45d | 2019-09-29 | +13d |
|
Scram
# 54242
|
2019-08-27 | 2019-08-28 | 2 | 133d | - | - |
|
Scram
# 53999
|
2019-04-14 | 2019-04-16 | 3 | 122d | - | - |
|
Unscheduled
|
2018-12-10 | 2018-12-13 | 4 | 218d | - | - |
|
Scheduled
|
2018-04-07 | 2018-05-06 | 30 | 180d | 2018-04-07 | 0d |
|
Unscheduled
|
2017-10-02 | 2017-10-09 | 8 | 275d | - | - |
|
Scheduled
|
2016-11-26 | 2016-12-31 | 36 | 286d | 2016-11-05 | +21d |
|
Unscheduled
|
2015-12-27 | 2016-02-14 | 50 | 33d | - | - |
|
Scram
# 51559
|
2015-11-24 | 2015-11-24 | 1 | 66d | - | - |
|
Scram
# 51392
|
2015-09-14 | 2015-09-19 | 6 | 31d | - | - |
|
Unscheduled
|
2015-08-09 | 2015-08-14 | 6 | 9d | - | - |
|
Unscheduled
|
2015-07-31 | 2015-07-31 | 1 | 2d | - | - |
|
Scram
# 51265
|
2015-07-28 | 2015-07-29 | 2 | 2d | - | - |
|
Scram
# 51265
|
2015-07-25 | 2015-07-26 | 2 | 71d | - | - |
|
Scheduled
|
2015-04-11 | 2015-05-15 | 35 | 28d | 2015-04-13 | -2d |
|
Scram
# 50878
|
2015-03-12 | 2015-03-14 | 3 | 477d | - | - |
|
Scheduled
|
2013-10-14 | 2013-11-20 | 38 | 563d | 2013-10-14 | 0d |
|
Scheduled
|
2012-02-27 | 2012-03-30 | 33 | 191d | 2012-02-27 | 0d |
|
Scram
# 47169
|
2011-08-19 | 2011-08-20 | 2 | 29d | - | - |
|
Scram
# 47081
|
2011-07-21 | 2011-07-21 | 1 | 24d | - | - |
|
Scram
# 46991
|
2011-06-27 | 2011-06-27 | 1 | 186d | - | - |
|
Unscheduled
|
2010-12-20 | 2010-12-23 | 4 | 33d | - | - |
|
Unscheduled
|
2010-11-17 | 2010-11-17 | 1 | 2d | - | - |
|
Scheduled
|
2010-10-02 | 2010-11-15 | 45 | 512d | 2010-10-01 | +1d |
|
Unscheduled
|
2009-05-07 | 2009-05-08 | 2 | 7d | - | - |
|
Unscheduled
|
2009-04-29 | 2009-04-30 | 2 | 2d | - | - |
|
Scheduled
|
2009-03-27 | 2009-04-27 | 32 | 434d | 2009-03-29 | -2d |
|
Unscheduled
|
2008-01-17 | 2008-01-18 | 2 | 63d | - | - |
|
Scheduled
|
2007-10-04 | 2007-11-15 | 43 | 508d | 2007-09-30 | +4d |
|
Scheduled
|
2006-04-10 | 2006-05-14 | 35 | 364d | 2006-04-09 | +1d |
|
Unscheduled
|
2005-04-10 | 2005-04-11 | 2 | 142d | - | - |
|
Scheduled
|
2004-10-25 | 2004-11-19 | 26 | 220d | 2004-10-25 | 0d |
|
Unscheduled
|
2004-03-15 | 2004-03-19 | 5 | 197d | - | - |
|
Unscheduled
|
2003-08-29 | 2003-08-31 | 3 | 76d | - | - |
|
Scheduled
SGR/Major
|
2003-03-17 | 2003-06-14 | 90 | 481d | 2003-03-17 | 0d |
|
Scheduled
|
2001-10-22 | 2001-11-21 | 31 | 343d | 2001-10-22 | 0d |
|
Unscheduled
|
2000-10-07 | 2000-11-13 | 38 | 2d | - | - |
|
Unscheduled
|
2000-09-26 | 2000-10-05 | 10 | 189d | - | - |
|
Unscheduled
Startup Hold
|
2000-03-21 | 2000-03-21 | 1 | 4d | - | - |
|
Scheduled
|
2000-02-23 | 2000-03-17 | 24 | - | 2000-02-23 | 0d |
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