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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.
80
Excellence
#5 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).
363
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2023-05-18 to 2025-04-28).
711
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (632 days for this 24-month cycle unit) with no trips to 0% power.
2
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
94.2%
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.
4
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.
98.3%
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
80/100
Top Quartile · #5/94
5-year window
Limerick 2 ranks #5 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Refuel Duration (93th percentile). Weakest: Startup Duration (51th percentile).
Reliability
82
Capacity factor + Forced outages + B2B streaks
Efficiency
89
Fuel utilization + Refuel duration
Discipline
71
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#2 of 31
BWR
Containment:
#1 of 8
Mark II (BWR)
Cycle length:
#3 of 40
24-month cycle
Fleet rank above (5 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
91th
95.6% (higher better, Reliability)
Forced Outage Days/yr
68th
2.2d (lower better, Reliability)
B2B Avg Streak
85th
700d (higher better, Reliability)
Fuel Utilization
84th
98.8% (higher better, Efficiency)
Refuel Duration
93th
18d (lower better, Efficiency)
Startup Duration
51th
4.2d (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:
Stable vs 2025
Compare Limerick 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 18, 2025
49.7% remaining
360 / 714 days
1.0 FPD margin
Avg refuel: 3.7%
Avg refuel (3yr): 1.7%
Deepest burn: 1.0% (2013-04 → 2015-04)
Most margin: 9.4% (1999-05 → 2001-04)
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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
|
2025-04-28 | 2025-05-16 | 19 | 711d | 2025-04-29 | -1d |
|
Scheduled
|
2023-05-01 | 2023-05-18 | 18 | 39d | 2023-05-01 | 0d |
|
Unscheduled
|
2023-03-19 | 2023-03-23 | 5 | 380d | - | - |
|
Unscheduled
|
2022-03-03 | 2022-03-04 | 2 | 293d | - | - |
|
Scheduled
|
2021-04-26 | 2021-05-14 | 19 | 690d | 2021-04-26 | 0d |
|
Scram
# 54098
|
2019-06-04 | 2019-06-06 | 3 | 33d | - | - |
|
Scheduled
|
2019-04-15 | 2019-05-02 | 18 | 544d | 2019-04-15 | 0d |
|
Unscheduled
|
2017-10-09 | 2017-10-18 | 10 | 137d | - | - |
|
Scheduled
|
2017-04-17 | 2017-05-25 | 39 | 319d | 2017-04-17 | 0d |
|
Scram
# 51968
|
2016-06-02 | 2016-06-02 | 1 | 165d | - | - |
|
Scram
# 51614
|
2015-12-20 | 2015-12-20 | 1 | 2d | - | - |
|
Unscheduled
|
2015-12-14 | 2015-12-18 | 5 | 223d | - | - |
|
Scheduled
|
2015-04-13 | 2015-05-05 | 23 | 349d | 2015-04-13 | 0d |
|
Unscheduled
|
2014-04-25 | 2014-04-29 | 5 | 373d | - | - |
|
Scheduled
|
2013-03-25 | 2013-04-17 | 24 | 239d | 2013-03-25 | 0d |
|
Unscheduled
|
2012-07-28 | 2012-07-29 | 2 | 56d | - | - |
|
Unscheduled
|
2012-06-01 | 2012-06-02 | 2 | 7d | - | - |
|
Unscheduled
|
2012-05-18 | 2012-05-25 | 8 | 353d | - | - |
|
Scram
# 46903
|
2011-05-30 | 2011-05-31 | 2 | 38d | - | - |
|
Scheduled
|
2011-03-28 | 2011-04-22 | 26 | 30d | 2011-03-28 | 0d |
|
Scram
# 46641
|
2011-02-26 | 2011-02-26 | 1 | 686d | - | - |
|
Scheduled
|
2009-03-23 | 2009-04-11 | 20 | 404d | 2009-03-23 | 0d |
|
Unscheduled
|
2008-02-11 | 2008-02-13 | 3 | 4d | - | - |
|
Unscheduled
|
2008-02-02 | 2008-02-07 | 6 | 283d | - | - |
|
Unscheduled
|
2007-04-24 | 2007-04-25 | 2 | 14d | - | - |
|
Unscheduled
Startup Hold
|
2007-04-09 | 2007-04-10 | 2 | 6d | - | - |
|
Scheduled
|
2007-03-10 | 2007-04-03 | 25 | 379d | 2007-03-09 | +1d |
|
Unscheduled
|
2006-02-23 | 2006-02-24 | 2 | 129d | - | - |
|
Unscheduled
|
2005-10-17 | 2005-10-17 | 1 | 3d | - | - |
|
Unscheduled
|
2005-10-13 | 2005-10-14 | 2 | 202d | - | - |
|
Unscheduled
Startup Hold
|
2005-03-21 | 2005-03-25 | 5 | 4d | - | - |
|
Scheduled
|
2005-03-01 | 2005-03-17 | 17 | 251d | 2005-02-28 | +1d |
|
Unscheduled
|
2004-06-23 | 2004-06-23 | 1 | 459d | - | - |
|
Scheduled
|
2003-03-04 | 2003-03-22 | 19 | 221d | 2003-03-04 | 0d |
|
Unscheduled
|
2002-07-24 | 2002-07-26 | 3 | 391d | - | - |
|
Unscheduled
|
2001-06-27 | 2001-06-28 | 2 | 69d | - | - |
|
Scheduled
|
2001-04-05 | 2001-04-19 | 15 | 38d | 2001-04-05 | 0d |
|
Unscheduled
|
2001-02-24 | 2001-02-26 | 3 | 411d | - | - |
|
Unscheduled
|
2000-01-09 | 2000-01-10 | 2 | 8d | - | - |
|
Unscheduled
|
1999-12-31 | 2000-01-01 | 2 | 222d | - | - |
|
Scheduled
|
1999-04-17 | 1999-05-23 | 37 | - | 1999-04-17 | 0d |
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