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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.
54
Excellence
#38 of 94 ↓18
Mid Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
14
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2005-04-10 to 2006-09-20).
528
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (444 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).
87.6%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data.
19
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.
98.2%
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
54/100
Mid Quartile · #38/94
5-year window
Arkansas Nuclear 2 ranks #38 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Forced Outage Days/yr (91th percentile). Weakest: Refuel Duration (10th percentile).
Reliability
43
Capacity factor + Forced outages + B2B streaks
Efficiency
43
Fuel utilization + Refuel duration
Discipline
77
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#26 of 61
PWR
Containment:
#21 of 48
Dry Ambient (PWR)
Cycle length:
#20 of 54
18-month cycle
Fleet rank above (38 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
18th
86.4% (higher better, Reliability)
Forced Outage Days/yr
91th
0.8d (lower better, Reliability)
B2B Avg Streak
19th
500d (higher better, Reliability)
Fuel Utilization
75th
98.6% (higher better, Efficiency)
Refuel Duration
10th
47d (lower better, Efficiency)
Startup Duration
63th
3.9d (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:
↓ -7.9 pts vs 2025
Compare Arkansas Nuclear 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 1, 2026
97.7% remaining
12 / 500 days
0.6 FPD margin
Avg refuel: 3.9%
Avg refuel (3yr): 1.8%
Deepest burn: 0.0% (1999-02 → 2000-09)
Most margin: 18.3% (2018-11 → 2020-03)
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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
|
2026-03-14 | 2026-04-30 | 48 | 502d | 2026-03-07 | +7d |
|
Scheduled
|
2024-09-28 | 2024-10-28 | 31 | 495d | 2024-10-06 | -8d |
|
Scheduled
|
2023-04-15 | 2023-05-22 | 38 | 504d | 2023-04-15 | 0d |
|
Scheduled
|
2021-09-25 | 2021-11-27 | 64 | 286d | 2021-09-25 | 0d |
|
Scram
# 55028
|
2020-12-11 | 2020-12-13 | 3 | 38d | - | - |
|
Unscheduled
|
2020-11-02 | 2020-11-03 | 2 | 196d | - | - |
|
Scheduled
|
2020-03-13 | 2020-04-20 | 39 | 228d | 2020-03-14 | -1d |
|
Scram
# 54091
|
2019-05-27 | 2019-07-29 | 64 | 189d | - | - |
|
Scheduled
|
2018-09-17 | 2018-11-19 | 64 | 437d | 2018-09-15 | +2d |
|
Scheduled
SGR/Major
|
2017-03-29 | 2017-07-07 | 101 | 153d | 2017-04-01 | -3d |
|
Unscheduled
|
2016-09-29 | 2016-10-27 | 29 | 211d | - | - |
|
Unscheduled
|
2016-02-24 | 2016-03-02 | 8 | 103d | - | - |
|
Scheduled
|
2015-09-21 | 2015-11-13 | 54 | 467d | 2015-09-20 | +1d |
|
Scheduled
|
2014-04-28 | 2014-06-11 | 45 | 24d | 2014-03-09 | +50d |
|
Scram
# 49995
|
2014-04-04 | 2014-04-04 | 1 | 84d | - | - |
|
Scram
# 49618
|
2013-12-10 | 2014-01-10 | 32 | 226d | - | - |
|
Scram
# 48869
|
2013-04-01 | 2013-04-28 | 28 | 173d | - | - |
|
Scheduled
|
2012-09-14 | 2012-10-10 | 27 | 36d | 2012-09-13 | +1d |
|
Scram
# 48169
|
2012-08-09 | 2012-08-09 | 1 | 503d | - | - |
|
Scheduled
|
2011-02-21 | 2011-03-25 | 33 | 171d | 2011-02-20 | +1d |
|
Unscheduled
|
2010-08-24 | 2010-09-03 | 11 | 258d | - | - |
|
Unscheduled
|
2009-12-09 | 2009-12-09 | 1 | 76d | - | - |
|
Scheduled
|
2009-09-02 | 2009-09-24 | 23 | 170d | 2009-09-22 | -20d |
|
Unscheduled
|
2009-03-14 | 2009-03-16 | 3 | 58d | - | - |
|
Unscheduled
|
2009-01-15 | 2009-01-15 | 1 | 280d | - | - |
|
Scheduled
|
2008-03-17 | 2008-04-10 | 25 | 410d | 2008-03-16 | +1d |
|
Unscheduled
|
2007-01-26 | 2007-02-01 | 7 | 87d | - | - |
|
Unscheduled
|
2006-10-31 | 2006-10-31 | 1 | 4d | - | - |
|
Scheduled
|
2006-09-20 | 2006-10-27 | 38 | 528d | 2006-09-19 | +1d |
|
Scheduled
|
2005-03-09 | 2005-04-10 | 33 | 158d | 2005-03-08 | +1d |
|
Unscheduled
|
2004-09-28 | 2004-10-02 | 5 | 233d | - | - |
|
Unscheduled
|
2004-02-07 | 2004-02-08 | 2 | 40d | - | - |
|
Unscheduled
|
2003-12-26 | 2003-12-29 | 4 | 73d | - | - |
|
Scheduled
|
2003-09-24 | 2003-10-14 | 21 | 508d | 2003-09-24 | 0d |
|
Scheduled
|
2002-04-13 | 2002-05-04 | 22 | 162d | 2002-04-13 | 0d |
|
Unscheduled
|
2001-11-02 | 2001-11-02 | 1 | 284d | - | - |
|
Unscheduled
|
2001-01-18 | 2001-01-22 | 5 | 41d | - | - |
|
Scheduled
SGR/Major
|
2000-09-16 | 2000-12-08 | 84 | 31d | 2000-09-16 | 0d |
| 2000-07-22 | 2000-08-16 | 26 | 242d | - | - | |
|
Unscheduled
|
1999-11-07 | 1999-11-23 | 17 | 255d | - | - |
|
Scheduled
|
1999-01-09 | 1999-02-25 | 48 | - | 1999-01-09 | 0d |
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