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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.
42
Excellence
#63 of 94 ↑8
Mid Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
22
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2005-04-14 to 2006-10-01).
535
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (448 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).
89.7%
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.
5.3
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.
• 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
42/100
Mid Quartile · #63/94
5-year window
South Texas 1 ranks #63 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Scrams (5-year) (70th percentile). Weakest: Startup Duration (26th percentile).
Reliability
39
Capacity factor + Forced outages + B2B streaks
Efficiency
41
Fuel utilization + Refuel duration
Discipline
48
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#44 of 61
PWR
Containment:
#37 of 48
Dry Ambient (PWR)
Cycle length:
#37 of 54
18-month cycle
Fleet rank above (63 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
35th
89.3% (higher better, Reliability)
Forced Outage Days/yr
35th
5.4d (lower better, Reliability)
B2B Avg Streak
46th
513d (higher better, Reliability)
Fuel Utilization
28th
97.0% (higher better, Efficiency)
Refuel Duration
53th
32d (lower better, Efficiency)
Startup Duration
26th
5.8d (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:
↑ +3.3 pts vs 2025
Compare South Texas 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 23, 2026
96.1% remaining
20 / 494 days
0.7 FPD margin
Avg refuel: 1.5%
Avg refuel (3yr): 0.3%
Deepest burn: 0.0% (2000-05 → 2001-10)
Most margin: 11.4% (2015-12 → 2017-03)
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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 |
|---|---|---|---|---|---|---|
|
Scheduled
|
2026-03-21 | 2026-04-22 | 33 | 498d | 2026-03-20 | +1d |
|
Scheduled
|
2024-10-05 | 2024-11-08 | 35 | 66d | 2024-10-04 | +1d |
|
Scram
# 57237
|
2024-07-25 | 2024-07-31 | 7 | 143d | - | - |
|
Unscheduled
|
2024-03-01 | 2024-03-04 | 4 | 31d | - | - |
|
Unscheduled
|
2024-01-22 | 2024-01-30 | 9 | 278d | - | - |
|
Scheduled
|
2023-03-18 | 2023-04-19 | 33 | 497d | 2023-03-17 | +1d |
|
Scheduled
|
2021-10-09 | 2021-11-06 | 29 | 105d | 2021-09-11 | +28d |
|
Unscheduled
|
2021-06-24 | 2021-06-26 | 3 | 127d | - | - |
|
Scram
# 55104
|
2021-02-16 | 2021-02-17 | 2 | 306d | - | - |
|
Scheduled
|
2020-03-14 | 2020-04-16 | 34 | 491d | 2020-03-13 | +1d |
|
Scheduled
|
2018-10-06 | 2018-11-09 | 35 | 528d | 2018-10-06 | 0d |
|
Scheduled
|
2017-03-18 | 2017-04-26 | 40 | 317d | 2017-03-18 | 0d |
|
Scram
# 51897
|
2016-05-02 | 2016-05-05 | 4 | 94d | - | - |
|
Scram
# 51687
|
2016-01-27 | 2016-01-29 | 3 | 34d | - | - |
|
Scram
# 51615
|
2015-12-22 | 2015-12-24 | 3 | 3d | - | - |
|
Scheduled
|
2015-10-18 | 2015-12-19 | 63 | 505d | 2015-10-03 | +15d |
|
Unscheduled
|
2014-05-30 | 2014-05-31 | 2 | 5d | - | - |
|
Scheduled
SGR/Major
|
2014-03-16 | 2014-05-25 | 71 | 152d | 2014-03-15 | +1d |
|
Unscheduled
|
2013-10-02 | 2013-10-15 | 14 | 140d | - | - |
|
Unscheduled
|
2013-05-12 | 2013-05-15 | 4 | 167d | - | - |
|
Scheduled
|
2012-10-21 | 2012-11-26 | 37 | 534d | 2012-10-20 | +1d |
|
Scheduled
|
2011-04-03 | 2011-05-06 | 34 | 225d | 2011-04-03 | 0d |
|
Unscheduled
|
2010-08-21 | 2010-08-21 | 1 | 194d | - | - |
|
Unscheduled
|
2010-02-04 | 2010-02-08 | 5 | 78d | - | - |
|
Scheduled
|
2009-10-01 | 2009-11-18 | 49 | 524d | 2009-10-04 | -3d |
|
Scheduled
|
2008-03-30 | 2008-04-25 | 27 | 513d | 2008-03-30 | 0d |
|
Scheduled
|
2006-10-01 | 2006-11-03 | 34 | 535d | 2006-09-30 | +1d |
|
Scheduled
|
2005-03-09 | 2005-04-14 | 37 | 409d | 2005-03-08 | +1d |
|
Unscheduled
|
2004-01-24 | 2004-01-25 | 2 | 170d | - | - |
|
Scheduled
SGR/Major
|
2003-03-26 | 2003-08-07 | 135 | 24d | 2003-03-26 | 0d |
|
Unscheduled
|
2003-03-01 | 2003-03-02 | 2 | 97d | - | - |
|
Unscheduled
|
2002-11-17 | 2002-11-24 | 8 | 390d | - | - |
|
Scheduled
|
2001-10-03 | 2001-10-23 | 21 | 288d | 2001-10-03 | 0d |
|
Unscheduled
|
2000-12-17 | 2000-12-19 | 3 | 218d | - | - |
|
Unscheduled
|
2000-05-13 | 2000-05-13 | 1 | 2d | - | - |
|
Scheduled
SGR/Major
|
2000-03-01 | 2000-05-11 | 72 | 170d | 2000-03-01 | 0d |
|
Unscheduled
|
1999-09-12 | 1999-09-13 | 2 | 76d | - | - |
|
Unscheduled
|
1999-06-28 | 1999-06-28 | 1 | 43d | - | - |
|
Unscheduled
|
1999-05-16 | 1999-05-16 | 1 | 18d | - | - |
|
Unscheduled
|
1999-03-27 | 1999-04-28 | 33 | - | - | - |
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