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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.
46
Excellence
#56 of 94 ↑12
Mid Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
404
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2014-10-10 to 2016-03-06).
513
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (450 days for this 18-month cycle unit) with no trips to 0% power.
3
B2B Runs
88% toward B2B (396/450d)
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
89.2%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data.
18
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.
2.7
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.
97.8%
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
46/100
Mid Quartile · #56/94
5-year window
North Anna 2 ranks #56 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Startup Duration (90th percentile). Weakest: B2B Avg Streak (8th percentile).
Reliability
31
Capacity factor + Forced outages + B2B streaks
Efficiency
28
Fuel utilization + Refuel duration
Discipline
80
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#39 of 61
PWR
Containment:
#3 of 5
Dry Subatmospheric (PWR)
Cycle length:
#32 of 54
18-month cycle
Fleet rank above (56 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
65th
92.8% (higher better, Reliability)
Forced Outage Days/yr
20th
8.6d (lower better, Reliability)
B2B Avg Streak
8th
490d (higher better, Reliability)
Fuel Utilization
13th
95.1% (higher better, Efficiency)
Refuel Duration
42th
34d (lower better, Efficiency)
Startup Duration
90th
3.1d (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:
↑ +3.8 pts vs 2025
Compare North Anna 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 Apr 6, 2025
20.4% remaining
402 / 504 days
1.0 FPD margin
Avg refuel: 3.9%
Avg refuel (3yr): 2.2%
Deepest burn: 0.0% (2014-10 → 2016-03)
Most margin: 11.5% (2010-04 → 2011-08)
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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
|
2025-03-02 | 2025-04-05 | 35 | 434d | 2025-03-02 | 0d |
|
Unscheduled
|
2023-12-19 | 2023-12-24 | 6 | 67d | - | - |
|
Scheduled
|
2023-09-10 | 2023-10-13 | 34 | 358d | 2023-09-09 | +1d |
|
Scram
# 56073
|
2022-08-28 | 2022-09-17 | 21 | 2d | - | - |
|
Unscheduled
|
2022-08-14 | 2022-08-26 | 13 | 126d | - | - |
|
Scheduled
|
2022-03-06 | 2022-04-10 | 36 | 504d | 2022-03-05 | +1d |
|
Scheduled
|
2020-09-13 | 2020-10-18 | 36 | 149d | 2020-09-07 | +6d |
|
Unscheduled
|
2020-04-10 | 2020-04-17 | 8 | 368d | - | - |
|
Scheduled
|
2019-03-03 | 2019-04-08 | 37 | 446d | 2019-03-03 | 0d |
|
Unscheduled
|
2017-12-11 | 2017-12-12 | 2 | 63d | - | - |
|
Scheduled
|
2017-09-10 | 2017-10-09 | 30 | 403d | 2017-09-10 | 0d |
|
Unscheduled
|
2016-07-31 | 2016-08-03 | 4 | 112d | - | - |
|
Scheduled
|
2016-03-06 | 2016-04-10 | 36 | 513d | 2016-03-06 | 0d |
|
Scheduled
|
2014-09-07 | 2014-10-10 | 34 | 216d | 2014-09-07 | 0d |
|
Scram
# 49784
|
2014-02-03 | 2014-02-03 | 1 | 249d | - | - |
|
Scram
# 49075
|
2013-05-29 | 2013-05-30 | 2 | 8d | - | - |
|
Scram
# 49020
|
2013-05-11 | 2013-05-21 | 11 | 3d | - | - |
|
Scheduled
|
2013-04-07 | 2013-05-08 | 32 | 164d | 2013-04-07 | 0d |
|
Scram
# 48436
|
2012-10-24 | 2012-10-25 | 2 | 5d | - | - |
|
Unscheduled
|
2012-10-09 | 2012-10-19 | 11 | 324d | - | - |
|
Scheduled
SGR/Major
|
2011-08-24 | 2011-11-20 | 89 | 290d | 2011-09-25 | -32d |
|
Unscheduled
|
2010-11-07 | 2010-11-07 | 1 | 20d | - | - |
|
Unscheduled
|
2010-09-29 | 2010-10-18 | 20 | 103d | - | - |
|
Unscheduled
|
2010-06-17 | 2010-06-18 | 2 | 15d | - | - |
|
Unscheduled
|
2010-05-28 | 2010-06-02 | 6 | 30d | - | - |
|
Unscheduled
|
2010-04-28 | 2010-04-28 | 1 | 4d | - | - |
|
Scheduled
|
2010-03-21 | 2010-04-24 | 35 | 99d | 2010-03-21 | 0d |
|
Unscheduled
|
2009-12-10 | 2009-12-12 | 3 | 393d | - | - |
|
Unscheduled
|
2008-10-30 | 2008-11-12 | 14 | 4d | - | - |
|
Scheduled
|
2008-09-14 | 2008-10-26 | 43 | 219d | 2008-09-14 | 0d |
|
Unscheduled
|
2008-02-02 | 2008-02-08 | 7 | 31d | - | - |
|
Unscheduled
|
2007-12-26 | 2008-01-02 | 8 | 171d | - | - |
|
Unscheduled
|
2007-06-30 | 2007-07-08 | 9 | 70d | - | - |
|
Scheduled
|
2007-03-18 | 2007-04-21 | 35 | 122d | 2007-03-17 | +1d |
|
Unscheduled
|
2006-11-16 | 2006-11-16 | 1 | 382d | - | - |
|
Scheduled
|
2005-10-02 | 2005-10-30 | 29 | 56d | 2005-10-01 | +1d |
|
Unscheduled
|
2005-08-06 | 2005-08-07 | 2 | 421d | - | - |
|
Unscheduled
|
2004-06-11 | 2004-06-11 | 1 | 12d | - | - |
|
Scheduled
|
2004-05-02 | 2004-05-30 | 29 | 457d | 2004-05-01 | +1d |
|
Scheduled
SGR/Major
|
2002-09-08 | 2003-01-31 | 146 | 259d | 2002-09-08 | 0d |
|
Unscheduled
|
2001-12-23 | 2001-12-23 | 1 | 8d | - | - |
|
Unscheduled
|
2001-10-29 | 2001-12-15 | 48 | 203d | - | - |
|
Scheduled
|
2001-03-11 | 2001-04-09 | 30 | 50d | 2001-03-11 | 0d |
|
Unscheduled
|
2001-01-20 | 2001-01-20 | 1 | 291d | - | - |
|
Unscheduled
|
2000-04-04 | 2000-04-04 | 1 | 123d | - | - |
|
Unscheduled
|
1999-12-03 | 1999-12-03 | 1 | 55d | - | - |
|
Scheduled
|
1999-09-12 | 1999-10-09 | 28 | - | 1999-09-12 | 0d |
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