North Anna 1 - Status & History

Comprehensive reactor performance metrics, cycle analysis, and historical outage data.

Plant Info Outage History Daily Power Log
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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.
47
Excellence
#54 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).
202
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2019-09-30 to 2021-03-14).
531
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (449 days for this 18-month cycle unit) with no trips to 0% power.
9
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
91.1%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data.
18
Outages
since 2000
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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.
5
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.
99.7%
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.
Time window — change how far back we look
NukeWorker's
Operational
Excellence Score
47/100
Mid Quartile · #54/94
5-year window

North Anna 1 ranks #54 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Fuel Utilization (87th percentile). Weakest: B2B Avg Streak (27th percentile).

Reliability
39
Capacity factor + Forced outages + B2B streaks
Efficiency
61
Fuel utilization + Refuel duration
Discipline
41
Startup duration + Scram count
Cohort Rankings apples-to-apples comparison within each peer group
Reactor type: #38 of 61 PWR
Containment: #2 of 5 Dry Subatmospheric (PWR)
Cycle length: #31 of 54 18-month cycle
Fleet rank above (54 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor 49th
90.9% (higher better, Reliability)
Forced Outage Days/yr 39th
5.0d (lower better, Reliability)
B2B Avg Streak 27th
504d (higher better, Reliability)
Fuel Utilization 87th
98.9% (higher better, Efficiency)
Refuel Duration 35th
35d (lower better, Efficiency)
Startup Duration 51th
4.2d (lower better, Discipline)
Scrams (5-year) 30th
0.6/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: 2021: 48/100 (#53/93)2022: 39/100 (#63/92)2023: 40/100 (#63/92)2024: 34/100 (#73/93)2025: 22/100 (#84/94)2026: 34/100 (#72/94) ↑ +11.5 pts vs 2025
Compare North Anna 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 Oct 19, 2025

60.7% remaining 206 / 513 days 4.5 FPD margin
Avg refuel: 3.3% Avg refuel (3yr): 0.3% Deepest burn: 0.0% (2009-04 → 2010-09) Most margin: 20.3% (2010-10 → 2012-03)
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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
Scram # 57997
2025-10-22 2025-10-24 3 4d - -
Scheduled
2025-09-07 2025-10-18 42 464d 2025-09-01 +6d
Scram # 57148
2024-05-30 2024-05-31 2 54d - -
Scheduled
2024-03-03 2024-04-06 35 159d 2024-03-02 +1d
Unscheduled
2023-09-25 2023-09-26 2 334d - -
Scheduled
2022-09-21 2022-10-26 36 158d 2022-09-11 +10d
Scram # 55843
2022-04-15 2022-04-16 2 208d - -
Unscheduled
2021-09-12 2021-09-19 8 118d - -
Scram # 55239
2021-05-07 2021-05-17 11 15d - -
Scheduled
2021-03-14 2021-04-22 40 531d 2021-03-06 +8d
Scheduled
2019-09-08 2019-09-30 23 511d 2019-09-02 +6d
Scheduled
2018-03-11 2018-04-15 36 512d 2018-03-11 0d
Scheduled
2016-09-11 2016-10-15 35 526d 2016-09-11 0d
Scram # 50946
2015-04-02 2015-04-04 3 5d - -
Scheduled
2015-03-08 2015-03-28 21 8d 2015-03-08 0d
Scram # 50851
2015-02-27 2015-02-28 2 57d - -
Unscheduled
2014-12-23 2015-01-01 10 436d - -
Scram # 49429
2013-10-12 2013-10-13 2 2d - -
Scheduled
2013-09-08 2013-10-10 33 496d 2013-09-08 0d
Scheduled
2012-03-11 2012-04-30 51 119d 2012-03-11 0d
Scram # 47181
2011-08-24 2011-11-13 82 307d - -
Scram # 47181
2011-08-24 2011-11-13 82 81d - -
Scheduled
2010-09-12 2010-10-21 40 56d 2010-09-12 0d
Unscheduled
2010-07-15 2010-07-18 4 259d - -
Unscheduled
2009-10-24 2009-10-29 6 205d - -
Scheduled
2009-03-08 2009-04-02 26 511d 2009-03-08 0d
Scheduled
2007-09-09 2007-10-14 36 248d 2007-09-09 0d
Unscheduled
2007-01-04 2007-01-04 1 49d - -
Unscheduled
2006-11-13 2006-11-16 4 218d - -
Scheduled
2006-03-12 2006-04-09 29 24d 2006-03-11 +1d
Unscheduled
2006-02-14 2006-02-16 3 496d - -
Scheduled
2004-09-12 2004-10-06 25 199d 2004-09-12 0d
Unscheduled
2004-02-21 2004-02-26 6 246d - -
Unscheduled
2003-06-12 2003-06-20 9 53d - -
Unscheduled
2003-04-20 2003-04-20 1 2d - -
Scheduled
2003-02-23 2003-04-18 55 502d 2003-02-23 0d
Scheduled
2001-09-09 2001-10-09 31 488d 2001-09-09 0d
Unscheduled
2000-05-08 2000-05-09 2 31d - -
Scheduled
2000-03-12 2000-04-07 27 - 2000-03-12 0d
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