?
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.
55
Excellence
#31 of 93
Mid Quartile
?
Current reactor power level from the most recent NRC daily report.
100%
Power
ONLINE
?
Days of continuous operation since the last outage ended. Ranked against all operating units.
136
Current Run
days
#63 of 95
Mid Quartile
?
Longest recorded period of continuous operation between outages.
580
Record Run
days
#51 of 95
Mid Quartile
?
Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (454 days for this 18-month cycle unit) with no trips to 0% power.
9
B2B Runs
#19 of 87
Top Quartile
?
Lifetime capacity factor: average power level across all recorded days (100% = always at full power). Ranked against all NRC-tracked units.
89.8%
Capacity Factor
#52 of 95
Mid Quartile
?
Net electricity actually generated over the most recent 12 months reported by the U.S. Energy Information Administration (Form EIA-923), summed across every unit at this plant. These are authoritative actuals, not an estimate.
20.25 TWh
Net Generation
EIA-923 · 12 mo to 2026-06 · plant total
?
Community rating score (Bayesian-adjusted). Based on 40 votes. Ranked against all rated facilities.
54.3
Rating
40 votes
#38 of 97
Mid Quartile
?
Total NRC-reported scram events (emergency reactor shutdowns). Ranked fleet-wide — fewer scrams = better rank.
5
Scrams
#25 of 94
Mid Quartile
?
Years since commercial operation began. License remaining: 21 years.
38
Operating Age
years
21 yrs remaining
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.OnlineCoastdownPower AscensionRefueling Outage
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 134 days into its current fuel cycle with an estimated 73.0% of its fuel left. Its typical cycle runs about 494 days.
Fresh — 100%
Refuel — 0%
73.0% remaining
Fresh fuel
Cycle progress
134 / 494 days
EFPD remaining
361 days
Effective burn
133 EFPD
Burn deficit
0.7 FPD
South Texas 1 is early in its fuel cycle with 361 EFPD of reactivity remaining. Refuel is not expected for many months.
Historical Burn-Down (17 completed cycles)
Avg refuel point
1.5% remaining
Avg refuel (3yr)
0.3% remaining
Deepest burn
0.0% (2000-05 → 2001-10)
Most margin
11.4% (2015-12 → 2017-03)
Last 5 cycles at refuel
2%
2018-11
0%
2020-04
0%
2021-11
0%
2023-04
1%
2024-11
~0% coastdown (this unit)
Composite Operational Excellence Score for South Texas 1 — average percentile rank across 7 publicly observable metrics in three sub-scores: Reliability (capacity factor, forced outage days, B2B avg streak), Efficiency (fuel utilization, refuel duration), and Discipline (startup duration, scram count). Toggle the time window (3yr / 5yr / Lifetime) to see how this unit's standing shifts. Each dimension percentile-ranked across the active US fleet. Sub-score = average of components. Composite = average of the three sub-scores.
NukeWorker's Operational Excellence Score 5-yr composite · ranks 31 of 93 ↑12
NukeWorker scores South Texas 1's operational excellence at 55 out of 100 over the past five years, ranking it 31 of 93 reactors in the active US fleet. The score blends reliability, efficiency, and operating discipline drawn from public performance data.
Time window
5-yr trend:
↑ +5.2 pts vs 2025
Compare South Texas 1 head-to-head with up to 3 other units.
Compare now
Capacity Factor (365-Day)
100%
Current
90.1%
365-Day Avg
#47
of 94 plants
Min: 0%
Max: 100%
38 days <80%
B2B CHAMPION
766 days without a trip
·
9 Career Runs · 1 since last trip
Champion since Feb 6, 2026
Breaker-to-Breaker Runs 9 runs
Breaker-to-breaker runs measure continuous operation between refueling outages using a cycle-adjusted threshold (90% of cycle length minus RFO duration). An active streak means the unit has been running continuously since the last refueling with no trips to 0% power.
South Texas 1 has logged 9 breaker-to-breaker runs, continuous stretches from one refueling to the next with no trip to zero power. Its longest ran 534 days, and its runs average 513 days.
534
Best Run (days)
1RE12 (2005-04-15) → 1RE13 (2006-10-01)
513
Avg Run (days)
★ Triple breaker-to-breaker
1RE12 → 1RE13 → 1RE14 → 1RE15
All Runs
| 2024-11-09 | 2026-03-21 | 497 days | 1RE25 → 1RE26 |
| 2021-11-07 | 2023-03-18 | 496 days | 1RE23 → 1RE24 |
| 2018-11-10 | 2020-03-14 | 490 days | 1RE21 → 1RE22 |
| 2017-04-27 | 2018-10-06 | 527 days | 1RE20 → 1RE21 |
| 2014-06-01 | 2015-10-18 | 504 days | 1RE18 → 1RE19 |
| 2011-05-07 | 2012-10-21 | 533 days | 1RE16 → 1RE17 |
| 2008-04-26 | 2009-10-01 | 523 days | 1RE14 → 1RE15 |
| 2006-11-04 | 2008-03-30 | 512 days | 1RE13 → 1RE14 |
| 2005-04-15 | 2006-10-01 | 534 days | 1RE12 → 1RE13 |
Scram History 5 events since 2011
Automatic and manual reactor scram (emergency shutdown) events reported to the NRC since 2011. Includes event dates, trip type, and average recovery time. Click the title to view the full fleet scram dashboard.
South Texas 1 has recorded 5 reactor scrams, or emergency shutdowns, since 2011 (3 automatic, 2 manual). On average the unit was back to full power about 6.4 days after each trip.
Outage Duration Trend
?Scheduled refueling outage durations over time. Green bars are below average, yellow near average, red above. Dashed line shows the plant's historical average. Shorter outages mean better execution.
South Texas 1 has completed 18 scheduled refueling outages on record, averaging 46 days each. The most recent, in Mar 2026, ran 33 days.
Power History (12-Month)
?Daily power output as a percentage of rated capacity over the past 365 days. Green segments indicate full power (90%+), yellow shows reduced output, and red indicates significant power reductions or shutdowns.
Over the past 12 months South Texas 1 has run at an average of 90.1% of rated power. On the chart, green stretches are full-power running and dips toward zero mark reduced output or outages.
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.
Facility Statistics
Key performance and lifecycle metrics calculated from NRC operational data. Includes operating age, construction timeline, capacity factor, efficiency, generation totals, and reliability records.
South Texas 1 has operated for about 38 years and averaged a 89.8% lifetime capacity factor, generating roughly 280.7 TWh of electricity. Its longest unbroken run reached 580 days.
Lifecycle & Tenure
Operating Age: 38 Yrs
Build Time: 12.7 Yrs
Lic. Remaining: 21 Yrs
Production & Power
Lifetime CF: 89.8%
Efficiency: 33.7%
Generated: 280.7 TWh
Reliability & Outages
Record Run: 580 Days
Refuelings: 18
Avg Startup: 5.2 Days
NukeWorker Member Ratings 40 votes
Community ratings from NukeWorker members. Vote to share your experience working at this facility. Score uses a Bayesian average that accounts for vote count — facilities with few votes are pulled toward the fleet average, so rankings reflect confidence, not just raw percentages.
Above Average
19 (47%)
Average
7 (17%)
Below Average
14 (35%)
Facility Map
Interactive satellite map showing the facility's geographic location. Marker color indicates current status: green for online, red for offline, orange for reduced power. Click the header to open in Google Maps satellite view.
28.7961, -96.0562
Location & Contact
Physical address, phone number, and website for this facility. Use the directions link to get driving directions via Google Maps.
Phone:
(512) 972-3611
Website:
http://www.nrgenergy.com/
Per Diem Rates FY 2026
Per diem covers lodging and meals & incidental expenses (M&IE) for government and contractor travel near this facility. Rates are from GSA for FY 2026.
$110
Lodging/Night
$68
M&IE/Day
$178
Total/Day
Standard Rate, TX
Unemployment Benefits TX
Maximum state unemployment insurance benefits for TX. Actual benefits depend on your earnings history and may be lower than the maximum. Data as of Jan 2026.
$605
Max Weekly
26
Max Weeks
$15,730
Max Total
7-day waiting period before benefits begin
Jobs at South Texas Project (STP) 10 active
Active job listings posted for this specific facility on the NukeWorker job board. Click a job title for details, or the header to see them all.
More Jobs in TX 62 active
Active nuclear industry job listings in TX from the NukeWorker job board. Click a job title for full details, or click the header to search all jobs in this state.
Photos
Photos of this facility from the NukeWorker photo gallery. Click the header or any photo to browse the full album.
Ownership & Construction
The utility or company that owns and operates the facility, the architect-engineer responsible for plant design, and the primary construction contractor. Click names to view all facilities by that entity on the map.
CEG
Constellation Energy Corporation
NasdaqGS
$298.96
▲ +13.91 (+4.88%)
Previous Close
285.05
Day's Range
284.04 – 299.73
52-Week Range
228.63 – 412.70
Volume
2,798,083
Delayed quote as of Sep 4, 2026 4:00 PM ET.
Source: Yahoo Finance.
Full quote on Yahoo Finance
South Texas Project is co-owned by Constellation (44%), CPS Energy (40%) and Austin Energy (16%), and operated by STP Nuclear Operating Company. Constellation is the only publicly traded co-owner; it bought the stake from NRG Energy in 2023.
Technical Specs
Reactor design specifications including type (PWR/BWR), containment design, nuclear steam supply system manufacturer, thermal and electrical power ratings, and current operational status.
Reactor Type:
PWR
Containment:
PWR-DRYAMB
NSS Supplier:
WEST 4LP
Thermal Power:
3853 MWt
Net Capacity:
1300 MWe
Efficiency:
33.7%
Status:
Operating
Licensing
NRC licensing history including docket number, license type and number, construction permit date, operating license issuance, commercial operation date, license renewal, and expiration date.
Docket #:
05000498
License #:
NPF-76
License Type:
OL-FP
Const. Permit:
1975-12-22
Operating Lic:
1988-03-22
Commercial Op:
1988-08-25
License Renewed:
2017-09-28
License Exp:
2047-08-20
Market & Region
EIA market and grid-region classifications: NERC reliability region, U.S. Census region, balancing authority responsible for grid operations, and whether the unit operates as a rate-regulated utility or a competitive merchant generator. Hover any value for the full name.
NERC Region:
TRE
— Texas Regional Entity
Census Region:
WSC
— West South Central
Balancing Authority:
ERCO
— Electric Reliability Council of Texas (ERCOT) (ISO/RTO)
Market Structure:
Merchant
— Competitive generator selling into wholesale markets