Byron 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.
77
Excellence
#9 of 94 ↓2
Top Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
43
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2020-03-26 to 2021-09-13).
536
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (459 days for this 18-month cycle unit) with no trips to 0% power.
14
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.
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.
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.
99.2%
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.
Time window — change how far back we look
NukeWorker's
Operational
Excellence Score
77/100
Top Quartile · #9/94
5-year window

Byron 1 ranks #9 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Fuel Utilization (92th percentile). Weakest: B2B Avg Streak (54th percentile).

Reliability
69
Capacity factor + Forced outages + B2B streaks
Efficiency
90
Fuel utilization + Refuel duration
Discipline
73
Startup duration + Scram count
Cohort Rankings apples-to-apples comparison within each peer group
Reactor type: #6 of 61 PWR
Containment: #6 of 48 Dry Ambient (PWR)
Cycle length: #3 of 54 18-month cycle
Fleet rank above (9 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor 61th
92.4% (higher better, Reliability)
Forced Outage Days/yr 91th
0.8d (lower better, Reliability)
B2B Avg Streak 54th
521d (higher better, Reliability)
Fuel Utilization 92th
99.1% (higher better, Efficiency)
Refuel Duration 88th
20d (lower better, Efficiency)
Startup Duration 56th
4.1d (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: 2021: 88/100 (#3/93)2022: 90/100 (#2/92)2023: 90/100 (#2/92)2024: 87/100 (#8/93)2025: 88/100 (#7/94)2026: 82/100 (#9/94) ↓ -5.9 pts vs 2025
Compare Byron 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 Apr 3, 2026

92.4% remaining 40 / 520 days 0.5 FPD margin
Avg refuel: 1.6% Avg refuel (3yr): 0.8% Deepest burn: 0.0% (2002-03 → 2003-09) Most margin: 6.0% (2011-04 → 2012-09)
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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
2026-03-02 2026-04-01 31 519d 2026-03-02 0d
Scheduled
2024-09-09 2024-09-29 21 535d 2024-09-09 0d
Scheduled
2023-03-06 2023-03-24 19 522d 2023-03-06 0d
Scheduled
2021-09-13 2021-09-30 18 536d 2021-09-03 +10d
Scheduled
2020-03-09 2020-03-26 18 532d 2020-03-09 0d
Scheduled
2018-09-10 2018-09-24 15 533d 2018-09-10 0d
Scheduled
2017-02-27 2017-03-26 28 514d 2017-02-27 0d
Scheduled
2015-09-14 2015-10-02 19 190d 2015-09-07 +7d
Scram # 50859
2015-03-04 2015-03-08 5 342d - -
Scheduled
2014-03-10 2014-03-27 18 519d 2014-03-10 0d
Scheduled
2012-09-10 2012-10-07 28 179d 2012-09-09 +1d
Unscheduled
2012-03-12 2012-03-15 4 324d - -
Scheduled
2011-03-14 2011-04-23 41 522d 2011-03-14 0d
Scheduled
2009-09-14 2009-10-08 25 518d 2009-09-14 0d
Scheduled
2008-03-24 2008-04-14 22 146d 2008-03-24 0d
Unscheduled
2007-10-20 2007-10-30 11 370d - -
Scheduled
2006-09-11 2006-10-15 35 535d 2006-09-10 +1d
Scheduled
2005-02-28 2005-03-25 26 504d 2005-02-27 +1d
Scheduled
2003-09-23 2003-10-13 21 319d 2003-09-23 0d
Unscheduled
2002-11-08 2002-11-08 1 23d - -
Unscheduled
2002-10-16 2002-10-16 1 201d - -
Scheduled
2002-03-12 2002-03-29 18 518d 2002-03-12 0d
Scheduled
2000-09-23 2000-10-10 18 495d 2000-09-23 0d
Unscheduled
1999-05-14 1999-05-17 4 20d - -
Scheduled
1999-03-27 1999-04-24 29 - 1999-03-27 0d
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