South Texas 1
Online · 100% powerSTP Nuclear Operating·Palacios, TX·PWR·1,300 MWe
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.OnlineReduced PowerPower 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
Rank locked · 93 units
Subscribers
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Days of continuous operation since the last outage ended (Started 2026-04-22). Clean run (no forced outages since last refueling).
180
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 set for this 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).
89.8%
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.
20.23 TWh
Net Generation
EIA-923 · 12 mo to 2026-07 · plant total
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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
Reactor Status
Capacity Factor (365-Day)
100%
Current
90.1%
365-Day Avg
#49
of 94 plants
Min: 0%
Max: 100%
38 days <80%
Outage Days by Year
?Total days spent in outage each year, split by scheduled refueling (blue) and forced/unplanned (red). Lower totals indicate better reliability and outage execution. Hover for details.
Across its recorded history, South Texas 1 has spent 819 days in scheduled refueling outages and 114 days in forced or unplanned outages. Taller bars mark the years with the most downtime.
Performance Trends
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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
South Texas 1 has 40 outages plotted here, averaging 23 days each. The most recent, in Mar 2026, was a scheduled refueling outage lasting 33 days.
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Scheduled refueling outage durations over time. Green bars are at or below this unit's average, amber up to 30% above it, red beyond that. The dashed line is the average. Shorter outages mean better execution.
Refueling Duration Trend
South Texas 1 has completed 18 scheduled refueling outages on record, averaging 46 days each. The most recent, in Mar 2026, ran 33 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, South Texas 1 takes about 5 days to climb from first power back to full power. That average is drawn from 18 startups on record, and the most recent took 3 days.
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Daily reactor power over the 120 days before each scheduled refueling outage, one line per refueling, lined up on the day the outage began. A coastdown is the slow decline as the fuel runs out near the end of a cycle. The highlighted line is the most recent refueling and fainter lines are older. Counts and medians cover coastdowns of a week or longer. A shutdown straight from full power, with no decline ahead of it, is what a forced outage looks like.
Coastdown Before Refueling
10 of 18 refuelings
13 days median
88% power at shutdown
0.6% per day
South Texas 1 coasted down for a week or longer before 10 of its 18 refuelings on record. Those coastdowns ran a median of 13 days and ended near 88% power. The most recent refueling, in Mar 2026, began with no extended coastdown.
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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
63.9% remaining
0.7 FPD margin
South Texas 1 has an estimated 63.9% of its fuel left. Across its last 17 cycles, it has refueled with an average of 1.5% remaining.
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
Over its operating life, South Texas 1 has run at about 89.8% of its rated capacity. Across the last 12 reported months it averaged 90.0%. On the chart, green stretches near the top are full-power running, amber marks reduced power (50 to 89%), and red drops toward zero are outages.
Estimated reactivity remaining in South Texas 1's current fuel cycle, shown as a stylized fuel rod that drains as the cycle progresses. The cycle starts when the unit returns to power after its most recent refueling outage, and the gauge represents the fraction of that cycle's typical effective full-power days (EFPD) still available. Days at less than 100% power burn fuel proportionally — so a unit with significant downtime (high burn deficit) drains slower and ends with MORE reactivity left, giving operators margin to coast down (extend the cycle by reducing power) instead of refueling on the calendar. The dashed red line near the bottom marks the rough industry coastdown threshold (~15% remaining). Cycle target is the unit's median recent cycle length. Source: NRC daily reactor status reports cross-referenced against scheduled refuel outage history.
Fuel Burn Down Cycle since Apr 23, 2026
South Texas 1 is 179 days into its current fuel cycle with an estimated 63.9% of its fuel left. Its typical cycle runs about 494 days.
Fresh — 100%
Refuel — 0%
63.9% remaining
Fresh fuel
Cycle progress
179 / 494 days
EFPD remaining
316 days
Effective burn
178 EFPD
Burn deficit
0.7 FPD
South Texas 1 is early in its fuel cycle with 316 EFPD of reactivity remaining. Refuel is not expected for many months.
Outage History & Daily Power Log
This table logs every recorded outage for South Texas 1, 40 in all since 1999. Of those, 18 were scheduled refueling outages and 22 were unplanned or forced. The typical outage lasted about 23 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 |
|---|---|---|---|---|---|---|
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Scheduled
1RE26
|
2026-03-21 | 2026-04-22 | 33 | 498d | 2026-03-20 | +1d |
|
Scheduled
1RE25
|
2024-10-05 | 2024-11-08 | 35 | 66d | 2024-10-04 | +1d |
| 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
1RE24
|
2023-03-18 | 2023-04-19 | 33 | 497d | 2023-03-17 | +1d |
|
Scheduled
1RE23
|
2021-10-09 | 2021-11-06 | 29 | 105d | 2021-09-11 | +28d |
|
Unscheduled
|
2021-06-24 | 2021-06-26 | 3 | 127d | - | - |
| 2021-02-16 | 2021-02-17 | 2 | 306d | - | - | |
|
Scheduled
1RE22
|
2020-03-14 | 2020-04-16 | 34 | 491d | 2020-03-13 | +1d |
|
Scheduled
1RE21
|
2018-10-06 | 2018-11-09 | 35 | 528d | 2018-10-06 | 0d |
|
Scheduled
1RE20
|
2017-03-18 | 2017-04-26 | 40 | 317d | 2017-03-18 | 0d |
| 2016-05-02 | 2016-05-05 | 4 | 94d | - | - | |
| 2016-01-27 | 2016-01-29 | 3 | 34d | - | - | |
| 2015-12-22 | 2015-12-24 | 3 | 3d | - | - | |
|
Scheduled
1RE19
|
2015-10-18 | 2015-12-19 | 63 | 505d | 2015-10-03 | +15d |
|
Unscheduled
|
2014-05-30 | 2014-05-31 | 2 | 5d | - | - |
|
Scheduled
1RE18SGR/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
1RE17
|
2012-10-21 | 2012-11-26 | 37 | 534d | 2012-10-20 | +1d |
|
Scheduled
1RE16
|
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
1RE15
|
2009-10-01 | 2009-11-18 | 49 | 524d | 2009-10-04 | -3d |
|
Scheduled
1RE14
|
2008-03-30 | 2008-04-25 | 27 | 513d | 2008-03-30 | 0d |
|
Scheduled
1RE13
|
2006-10-01 | 2006-11-03 | 34 | 535d | 2006-09-30 | +1d |
|
Scheduled
1RE12
|
2005-03-09 | 2005-04-14 | 37 | 409d | 2005-03-08 | +1d |
|
Unscheduled
|
2004-01-24 | 2004-01-25 | 2 | 170d | - | - |
|
Scheduled
1RE11SGR/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
1RE10
|
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
1RE9SGR/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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