Byron 1 - Status & History

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

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Reactor Status Timeline

Online NRC data, Mon to Fri ? Actual daily reactor status from NRC reports (Mon to Fri) and the current state. What is coming -- the utility's published Scheduled outage and NukeWorker's model Projection -- is part of a subscription. Colored by status. How far ahead you can see depends on your plan.
Oct2025NovDecJan2026FebMarAprMayJunJulAugSepOnline: Sep 12, 2025 to Feb 16, 2026Coastdown: Feb 17, 2026 to Mar 1, 2026Refueling Outage (B1R27): Mar 2, 2026 to Apr 1, 2026B1R27Power Ascension: Apr 2, 2026 to Apr 5, 2026Online: Apr 6, 2026 to Aug 11, 2026Reduced Power: Aug 12, 2026Online: Aug 13, 2026 to Sep 12, 2026Today
OnlineReduced PowerCoastdownPower AscensionRefueling Outage
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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.
   
Excellence
ranked of 93
Subscribers
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
164
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 set for this 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).
94.3%
Capacity Factor
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Net electricity actually generated over the most recent 12 months reported by the U.S. EIA (Form EIA-923), summed across every unit at this plant. Authoritative actuals, not an estimate.
19.62 TWh
Net Generation
EIA-923 · 12 mo to 2026-06 · plant total
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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 measured 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
5-yr trend: 2021: 88/100 (#3/93)2022: 90/100 (#2/92)2023: 90/100 (#2/92)2024: 87/100 (#8/92)2025: 88/100 (#7/92)2026: 84/100 (#7/93) ↓ -4.3 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

Byron 1 has 25 outages plotted here, averaging 19 days each. The most recent, in Mar 2026, was a scheduled refueling outage lasting 31 days.
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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

After a refueling outage, Byron 1 takes about 4 days to climb from first power back to full power. That average is drawn from 19 startups on record, and the most recent took 4 days.
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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

69.2% remaining 0.9 FPD margin
Byron 1 has an estimated 69.2% of its fuel left. Across its last 18 cycles, it has refueled with an average of 1.6% remaining.
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

Over its operating life, Byron 1 has run at about 94.3% of its rated capacity. Across the last 12 reported months it averaged 90.6%. On the chart, flat stretches near the top are full-power running and drops to zero are outages.
This table logs every recorded outage for Byron 1, 25 in all since 1999. Of those, 19 were scheduled refueling outages and 6 were unplanned or forced. The typical outage lasted about 19 days. Where the Scheduled column shows (Model), the date is a NukeWorker projection because the utility had not published one.
Type ⇅ Actual Start ⇅ Actual End ⇅ Duration ⇅ Days Online ⇅ Scheduled Delta
Scheduled B1R27
2026-03-02 2026-04-01 31 519d 2026-03-02 0d
Scheduled B1R26
2024-09-09 2024-09-29 21 535d 2024-09-09 0d
Scheduled B1R25
2023-03-06 2023-03-24 19 522d 2023-03-06 0d
Scheduled B1R24
2021-09-13 2021-09-30 18 536d 2021-09-03 +10d
Scheduled B1R23
2020-03-09 2020-03-26 18 532d 2020-03-09 0d
Scheduled B1R22
2018-09-10 2018-09-24 15 533d 2018-09-10 0d
Scheduled B1R21
2017-02-27 2017-03-26 28 514d 2017-02-27 0d
Scheduled B1R20
2015-09-14 2015-10-02 19 190d 2015-09-07 +7d
Scram # 50859
2015-03-04 2015-03-08 5 342d - -
Scheduled B1R19
2014-03-10 2014-03-27 18 519d 2014-03-10 0d
Scheduled B1R18
2012-09-10 2012-10-07 28 179d 2012-09-09 +1d
Unscheduled
2012-03-12 2012-03-15 4 324d - -
Scheduled B1R17
2011-03-14 2011-04-23 41 522d 2011-03-14 0d
Scheduled B1R16
2009-09-14 2009-10-08 25 518d 2009-09-14 0d
Scheduled B1R15
2008-03-24 2008-04-14 22 146d 2008-03-24 0d
Unscheduled
2007-10-20 2007-10-30 11 370d - -
Scheduled B1R14
2006-09-11 2006-10-15 35 535d 2006-09-10 +1d
Scheduled B1R13
2005-02-28 2005-03-25 26 504d 2005-02-27 +1d
Scheduled B1R12
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 B1R11
2002-03-12 2002-03-29 18 518d 2002-03-12 0d
Scheduled B1R10
2000-09-23 2000-10-10 18 495d 2000-09-23 0d
Unscheduled
1999-05-14 1999-05-17 4 20d - -
Scheduled B1R9
1999-03-27 1999-04-24 29 - 1999-03-27 0d
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