Reactor Status Timeline
Online NRC data, Mon to Fri ? Actual daily reactor status from NRC reports (Mon to Fri), the current state, and what is coming: the utility's published Scheduled outage plus, for subscribers, NukeWorker's model Projection. Colored by status. How far ahead you can see depends on your plan.OnlineReduced PowerPower AscensionForced OutageScheduled (published)
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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.
35
Excellence
#70 of 93 ↑8
Mid Quartile
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Days of continuous operation since the last outage ended (Started 2025-10-26). Clean run (no forced outages since last refueling).
255
Current Run
days ✔
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Longest recorded period of continuous operation between outages (1999-06-27 to 2001-02-03).
587
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (452 days for this 18-month cycle unit) with no trips to 0% power.
7
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
90.2%
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.
16.92 TWh
Net Generation
EIA-923 · 12 mo to 2026-04 · plant total
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Total number of scheduled refueling outages detected in the historical data.
17
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.
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.
91.7%
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.
• 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
35/100
Mid Quartile · #70/93
5-year window
Millstone 3 ranks #70 of 93 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Scrams (5-year) (70th percentile). Weakest: Fuel Utilization (5th percentile).
Reliability
28
Capacity factor + Forced outages + B2B streaks
Efficiency
10
Fuel utilization + Refuel duration
Discipline
67
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#49 of 61
PWR
Containment:
#5 of 5
Dry Subatmospheric (PWR)
Cycle length:
#41 of 53
18-month cycle
Fleet rank above (70 of 93) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
30th
89.1% (higher better, Reliability)
Forced Outage Days/yr
11th
14.6d (lower better, Reliability)
B2B Avg Streak
43th
512d (higher better, Reliability)
Fuel Utilization
5th
92.8% (higher better, Efficiency)
Refuel Duration
15th
41d (lower better, Efficiency)
Startup Duration
63th
3.9d (lower better, Discipline)
Scrams (5-year)
70th
0.2/yr (lower better, Discipline)
Each dimension's percentile is computed across the active US fleet (93 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 93 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:
↑ +2.8 pts vs 2025
Compare Millstone 3 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
Millstone 3 has 41 outages plotted here, averaging 21 days each. The most recent, in Oct 2025, was a unplanned outage lasting 10 days.
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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
Between refueling outages, Millstone 3 runs about 552 days, or roughly 18 months, per cycle. That average comes from 16 completed cycles, the most recent lasting 539 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, Millstone 3 takes about 4 days to climb from first power back to full power. That average is drawn from 17 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 May 19, 2025
20.8% remaining
415 / 502 days
17.2 FPD margin
Millstone 3 is 415 days into its current fuel cycle with an estimated 20.8% of its fuel left. This cycle is set up to run about 502 days. Across its last 16 cycles, it has refueled with an average of 1.8% remaining.
Avg refuel: 1.8%
Avg refuel (3yr): 8.3%
Deepest burn: 0.0% (2001-03 → 2002-09)
Most margin: 8.3% (2023-12 → 2025-04)
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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, Millstone 3 has run at about 90.2% of its rated capacity. Across the last 12 reported months it averaged 95.5%. 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 Millstone 3, 41 in all since 1999. Of those, 17 were scheduled refueling outages and 24 were unplanned or forced. The typical outage lasted about 21 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 |
|---|---|---|---|---|---|---|
|
Unscheduled
|
2025-10-17 | 2025-10-26 | 10 | 75d | - | - |
|
Unscheduled
|
2025-08-01 | 2025-08-03 | 3 | 76d | - | - |
|
Scheduled
|
2025-04-11 | 2025-05-17 | 37 | 207d | 2025-04-13 | -2d |
|
Unscheduled
|
2024-09-04 | 2024-09-16 | 13 | 231d | - | - |
|
Unscheduled
|
2024-01-09 | 2024-01-17 | 9 | 32d | - | - |
|
Unscheduled
|
2023-12-03 | 2023-12-08 | 6 | 3d | - | - |
|
Scheduled
|
2023-10-20 | 2023-11-30 | 42 | 114d | 2023-10-14 | +6d |
|
Scram
# 56544
|
2023-05-31 | 2023-06-28 | 29 | 363d | - | - |
|
Scheduled
|
2022-04-08 | 2022-06-02 | 56 | 295d | 2022-04-07 | +1d |
|
Unscheduled
|
2021-06-11 | 2021-06-17 | 7 | 159d | - | - |
|
Unscheduled
|
2020-12-31 | 2021-01-03 | 4 | 50d | - | - |
|
Scheduled
|
2020-10-02 | 2020-11-11 | 41 | 171d | 2020-10-19 | -17d |
|
Scram
# 54663
|
2020-04-14 | 2020-04-14 | 1 | 4d | - | - |
|
Scram
# 54631
|
2020-04-02 | 2020-04-10 | 9 | 102d | - | - |
|
Unscheduled
|
2019-12-18 | 2019-12-22 | 5 | 218d | - | - |
|
Scheduled
|
2019-04-12 | 2019-05-14 | 33 | 515d | 2019-04-13 | -1d |
|
Scheduled
|
2017-10-13 | 2017-11-13 | 32 | 477d | 2017-10-08 | +5d |
|
Scram
# 52000
|
2016-06-13 | 2016-06-23 | 11 | 27d | - | - |
|
Scram
# 51929
|
2016-05-16 | 2016-05-17 | 2 | 4d | - | - |
|
Scheduled
|
2016-04-10 | 2016-05-12 | 33 | 73d | 2016-04-10 | 0d |
|
Scram
# 51682
|
2016-01-25 | 2016-01-28 | 4 | 435d | - | - |
|
Scheduled
|
2014-10-12 | 2014-11-16 | 36 | 132d | 2014-10-12 | 0d |
|
Scram
# 50141
|
2014-05-26 | 2014-06-02 | 8 | 286d | - | - |
|
Scram
# 49260
|
2013-08-10 | 2013-08-13 | 4 | 85d | - | - |
|
Scheduled
|
2013-04-14 | 2013-05-17 | 34 | 509d | 2013-04-14 | 0d |
|
Scheduled
|
2011-10-09 | 2011-11-22 | 45 | 419d | 2011-10-09 | 0d |
|
Unscheduled
|
2010-08-15 | 2010-08-16 | 2 | 89d | - | - |
|
Unscheduled
|
2010-05-18 | 2010-05-18 | 1 | 2d | - | - |
|
Scheduled
|
2010-04-11 | 2010-05-16 | 36 | 96d | 2010-04-04 | +7d |
|
Unscheduled
|
2009-12-20 | 2010-01-05 | 17 | 392d | - | - |
|
Scheduled
|
2008-10-12 | 2008-11-23 | 43 | 513d | 2008-10-12 | 0d |
|
Scheduled
|
2007-04-07 | 2007-05-18 | 42 | 68d | 2007-04-07 | 0d |
|
Unscheduled
|
2007-01-29 | 2007-01-29 | 1 | 421d | - | - |
|
Unscheduled
|
2005-12-02 | 2005-12-04 | 3 | 36d | - | - |
|
Scheduled
|
2005-09-30 | 2005-10-27 | 28 | 153d | 2005-09-29 | +1d |
|
Unscheduled
|
2005-04-18 | 2005-04-30 | 13 | 347d | - | - |
|
Scheduled
|
2004-04-03 | 2004-05-06 | 34 | 461d | 2004-04-02 | +1d |
|
Unscheduled
|
2002-12-23 | 2002-12-29 | 7 | 80d | - | - |
|
Scheduled
|
2002-09-07 | 2002-10-04 | 28 | 527d | 2002-09-07 | 0d |
|
Scheduled
|
2001-02-03 | 2001-03-29 | 55 | 587d | 2001-02-03 | 0d |
|
Unscheduled
|
1999-05-02 | 1999-06-27 | 57 | - | - | - |
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