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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.
78
Excellence
#8 of 94 →
Top Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
61
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2022-02-27 to 2024-02-12).
715
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (619 days for this 24-month cycle unit) with no trips to 0% power.
4
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
93.1%
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.
3.3
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.
98.1%
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
78/100
Top Quartile · #8/94
5-year window
Calvert Cliffs 1 ranks #8 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Scrams (5-year) (90th percentile). Weakest: Forced Outage Days/yr (59th percentile).
Reliability
69
Capacity factor + Forced outages + B2B streaks
Efficiency
77
Fuel utilization + Refuel duration
Discipline
87
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#5 of 61
PWR
Containment:
#5 of 48
Dry Ambient (PWR)
Cycle length:
#6 of 40
24-month cycle
Fleet rank above (8 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
71th
93.6% (higher better, Reliability)
Forced Outage Days/yr
59th
2.8d (lower better, Reliability)
B2B Avg Streak
76th
685d (higher better, Reliability)
Fuel Utilization
66th
98.3% (higher better, Efficiency)
Refuel Duration
88th
20d (lower better, Efficiency)
Startup Duration
83th
3.3d (lower better, Discipline)
Scrams (5-year)
90th
0.0/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:
↓ -2.2 pts vs 2025
Compare Calvert Cliffs 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 Mar 15, 2026
91.8% remaining
59 / 713 days
0.3 FPD margin
Avg refuel: 4.8%
Avg refuel (3yr): 1.9%
Deepest burn: 0.8% (2022-02 → 2024-02)
Most margin: 10.3% (2002-06 → 2004-04)
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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
|
2026-02-16 | 2026-03-14 | 27 | 263d | 2026-02-16 | 0d |
|
Unscheduled
|
2025-05-19 | 2025-05-29 | 11 | 443d | - | - |
|
Scheduled
|
2024-02-12 | 2024-03-02 | 20 | 715d | 2024-02-21 | -9d |
|
Scheduled
|
2022-02-07 | 2022-02-27 | 21 | 697d | 2022-02-21 | -14d |
|
Scheduled
|
2020-02-17 | 2020-03-12 | 25 | 703d | 2020-02-17 | 0d |
|
Scheduled
|
2018-02-19 | 2018-03-16 | 26 | 628d | 2018-02-19 | 0d |
|
Scram
# 51967
|
2016-06-01 | 2016-06-01 | 1 | 83d | - | - |
|
Scheduled
|
2016-02-15 | 2016-03-10 | 25 | 21d | 2016-02-15 | 0d |
|
Scram
# 51683
|
2016-01-25 | 2016-01-25 | 1 | 292d | - | - |
|
Scram
# 50961
|
2015-04-08 | 2015-04-08 | 1 | 341d | - | - |
|
Scram
# 50961
|
2015-04-08 | 2015-04-08 | 1 | 0d | - | - |
|
Scram
# 50078
|
2014-05-02 | 2014-05-02 | 1 | 44d | - | - |
|
Unscheduled
Startup Hold
|
2014-03-17 | 2014-03-19 | 3 | 3d | - | - |
|
Scheduled
|
2014-02-17 | 2014-03-14 | 26 | 24d | 2014-02-16 | +1d |
|
Scram
# 49754
|
2014-01-22 | 2014-01-24 | 3 | 418d | - | - |
|
Scram
# 49754
|
2014-01-22 | 2014-01-24 | 3 | 2d | - | - |
|
Unscheduled
|
2012-11-28 | 2012-11-30 | 3 | 104d | - | - |
|
Unscheduled
|
2012-08-13 | 2012-08-16 | 4 | 20d | - | - |
|
Unscheduled
|
2012-07-22 | 2012-07-24 | 3 | 104d | - | - |
|
Scheduled
SGR/Major
|
2012-02-06 | 2012-04-09 | 64 | 160d | 2012-02-05 | +1d |
|
Scram
# 47208
|
2011-08-28 | 2011-08-30 | 3 | 467d | - | - |
|
Unscheduled
|
2010-05-13 | 2010-05-18 | 6 | 52d | - | - |
|
Scheduled
|
2010-02-19 | 2010-03-22 | 32 | 215d | 2010-02-21 | -2d |
|
Unscheduled
|
2009-07-16 | 2009-07-19 | 4 | 473d | - | - |
|
Unscheduled
|
2008-03-29 | 2008-03-30 | 2 | 17d | - | - |
|
Scheduled
|
2008-02-23 | 2008-03-12 | 19 | 429d | 2008-02-18 | +5d |
|
Unscheduled
|
2006-12-19 | 2006-12-21 | 3 | 5d | - | - |
|
Unscheduled
|
2006-12-13 | 2006-12-14 | 2 | 247d | - | - |
|
Scheduled
|
2006-02-21 | 2006-04-10 | 49 | 357d | 2006-02-20 | +1d |
|
Unscheduled
|
2005-03-01 | 2005-03-01 | 1 | 297d | - | - |
|
Scheduled
|
2004-04-10 | 2004-05-08 | 29 | 20d | 2004-04-09 | +1d |
|
Unscheduled
|
2004-03-21 | 2004-03-21 | 1 | 491d | - | - |
|
Unscheduled
|
2002-11-09 | 2002-11-16 | 8 | 104d | - | - |
|
Unscheduled
|
2002-07-25 | 2002-07-28 | 4 | 38d | - | - |
|
Scheduled
SGR/Major
|
2002-02-16 | 2002-06-17 | 122 | 272d | 2002-02-16 | 0d |
|
Unscheduled
|
2001-05-19 | 2001-05-20 | 2 | 250d | - | - |
|
Unscheduled
|
2000-09-11 | 2000-09-11 | 1 | 141d | - | - |
|
Scheduled
|
2000-03-11 | 2000-04-23 | 44 | 56d | 2000-03-11 | 0d |
|
Unscheduled
|
2000-01-15 | 2000-01-15 | 1 | 114d | - | - |
|
Unscheduled
|
1999-09-23 | 1999-09-23 | 1 | 52d | - | - |
|
Unscheduled
|
1999-07-25 | 1999-08-02 | 9 | 69d | - | - |
|
Unscheduled
|
1999-05-10 | 1999-05-17 | 8 | - | - | - |
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