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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.
33
Excellence
#76 of 94 ↓22
Bottom Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
87
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2019-06-17 to 2021-05-09).
692
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (614 days for this 24-month cycle unit) with no trips to 0% power.
3
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
86.2%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data.
14
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.
8.3
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.
94.5%
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
33/100
Bottom Quartile · #76/94
5-year window
Columbia Generating Station ranks #76 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: B2B Avg Streak (73th percentile). Weakest: Startup Duration (3th percentile).
Reliability
42
Capacity factor + Forced outages + B2B streaks
Efficiency
21
Fuel utilization + Refuel duration
Discipline
36
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#23 of 31
BWR
Containment:
#7 of 8
Mark II (BWR)
Cycle length:
#33 of 40
24-month cycle
Fleet rank above (76 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
38th
89.7% (higher better, Reliability)
Forced Outage Days/yr
14th
10.6d (lower better, Reliability)
B2B Avg Streak
73th
680d (higher better, Reliability)
Fuel Utilization
38th
97.5% (higher better, Efficiency)
Refuel Duration
3th
62d (lower better, Efficiency)
Startup Duration
3th
11.5d (lower better, Discipline)
Scrams (5-year)
70th
0.2/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:
↓ -12.3 pts vs 2025
Compare Columbia Generating Station 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 Jun 17, 2025
54.3% remaining
330 / 685 days
17.0 FPD margin
Avg refuel: 8.0%
Avg refuel (3yr): 5.5%
Deepest burn: 2.7% (2013-06 → 2015-05)
Most margin: 17.2% (2011-09 → 2013-05)
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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 |
|---|---|---|---|---|---|---|
|
Scram
# 58163
|
2026-02-13 | 2026-02-16 | 4 | 230d | - | - |
|
Unscheduled
|
2025-06-24 | 2025-06-28 | 5 | 11d | - | - |
|
Scheduled
|
2025-04-12 | 2025-06-13 | 63 | 664d | 2025-05-11 | -29d |
|
Scheduled
|
2023-05-06 | 2023-06-18 | 44 | 510d | 2023-05-05 | +1d |
|
Unscheduled
|
2021-12-07 | 2021-12-12 | 6 | 173d | - | - |
|
Scheduled
|
2021-05-09 | 2021-06-17 | 40 | 692d | 2021-05-07 | +2d |
|
Scheduled
|
2019-05-12 | 2019-06-17 | 37 | 354d | 2019-05-15 | -3d |
|
Scram
# 53410
|
2018-05-19 | 2018-05-23 | 5 | 261d | - | - |
|
Scram
# 52918
|
2017-08-21 | 2017-08-31 | 11 | 67d | - | - |
|
Scheduled
|
2017-05-14 | 2017-06-15 | 33 | 141d | 2017-05-13 | +1d |
|
Scram
# 52442
|
2016-12-19 | 2016-12-24 | 6 | 264d | - | - |
|
Scram
# 51826
|
2016-03-29 | 2016-03-30 | 2 | 278d | - | - |
|
Scheduled
|
2015-05-10 | 2015-06-25 | 47 | 687d | 2015-05-06 | +4d |
|
Scheduled
|
2013-05-12 | 2013-06-22 | 42 | 349d | 2013-05-09 | +3d |
|
Unscheduled
|
2012-05-21 | 2012-05-28 | 8 | 245d | - | - |
|
Scheduled
SGR/Major
|
2011-04-03 | 2011-09-19 | 170 | 507d | 2011-04-06 | -3d |
|
Unscheduled
|
2009-11-08 | 2009-11-12 | 5 | 38d | - | - |
|
Unscheduled
|
2009-09-29 | 2009-10-01 | 3 | 29d | - | - |
|
Unscheduled
|
2009-08-06 | 2009-08-31 | 26 | 37d | - | - |
|
Unscheduled
|
2009-06-27 | 2009-06-30 | 4 | 7d | - | - |
|
Scheduled
|
2009-05-09 | 2009-06-20 | 43 | 86d | 2009-05-10 | -1d |
|
Unscheduled
|
2009-02-09 | 2009-02-12 | 4 | 82d | - | - |
|
Unscheduled
|
2008-11-16 | 2008-11-19 | 4 | 85d | - | - |
|
Unscheduled
|
2008-08-22 | 2008-08-23 | 2 | 419d | - | - |
|
Unscheduled
|
2007-06-29 | 2007-06-30 | 2 | 6d | - | - |
|
Scheduled
|
2007-05-13 | 2007-06-23 | 42 | 31d | 2007-05-12 | +1d |
|
Unscheduled
|
2007-04-10 | 2007-04-12 | 3 | 155d | - | - |
|
Unscheduled
|
2006-11-01 | 2006-11-06 | 6 | 489d | - | - |
|
Unscheduled
|
2005-06-24 | 2005-06-30 | 7 | 3d | - | - |
|
Unscheduled
|
2005-06-16 | 2005-06-21 | 6 | 7d | - | - |
|
Scheduled
|
2005-05-07 | 2005-06-09 | 34 | 260d | 2005-05-06 | +1d |
|
Unscheduled
|
2004-08-18 | 2004-08-20 | 3 | 2d | - | - |
|
Unscheduled
|
2004-08-16 | 2004-08-16 | 1 | 2d | - | - |
|
Unscheduled
|
2004-07-31 | 2004-08-14 | 15 | 395d | - | - |
|
Unscheduled
|
2003-07-01 | 2003-07-02 | 2 | 7d | - | - |
|
Scheduled
|
2003-05-04 | 2003-06-24 | 52 | 52d | 2003-05-20 (Enhanced) | -16d (Enhanced) |
|
Unscheduled
|
2003-03-01 | 2003-03-13 | 13 | 371d | - | - |
|
Unscheduled
|
2002-02-15 | 2002-02-23 | 9 | 198d | - | - |
|
Unscheduled
|
2001-07-27 | 2001-08-01 | 6 | 26d | - | - |
|
Unscheduled
|
2001-06-29 | 2001-07-01 | 3 | 5d | - | - |
|
Scheduled
|
2001-05-20 | 2001-06-24 | 36 | 241d | 2001-04-17 (Enhanced) | +33d (Enhanced) |
|
Unscheduled
|
2000-09-19 | 2000-09-21 | 3 | 14d | - | - |
|
Unscheduled
|
2000-09-02 | 2000-09-05 | 4 | 61d | - | - |
|
Unscheduled
|
2000-06-27 | 2000-07-03 | 7 | 249d | - | - |
|
Unscheduled
|
1999-09-19 | 1999-10-22 | 34 | 80d | - | - |
|
Scheduled
|
1999-04-18 | 1999-07-01 | 75 | - | - | - |
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