Watts Bar 1
Online · 100% powerTennessee Valley Authority·Spring City, TN·PWR·1,123 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.OnlinePower 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 2026-05-15). Clean run (no forced outages since last refueling).
162
Current Run
days ✔
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Longest recorded period of continuous operation between outages (1999-04-14 to 2000-09-10).
515
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.
4
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
88.4%
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.
19.81 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.
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.
5.3
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.
88.0%
Fuel Utilization
3yr avg
Reactor Status
Capacity Factor (365-Day)
100%
Current
91.2%
365-Day Avg
#59
of 94 plants
Min: 0%
Max: 100%
33 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, Watts Bar 1 has spent 737 days in scheduled refueling outages and 291 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
Watts Bar 1 has 53 outages plotted here, averaging 19 days each. The most recent, in Apr 2026, was a scheduled refueling outage lasting 28 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
Watts Bar 1 has completed 19 scheduled refueling outages on record, averaging 39 days each. The most recent, in Apr 2026, ran 28 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, Watts Bar 1 takes about 6 days to climb from first power back to full power. That average is drawn from 19 startups on record, and the most recent took 5 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
5 of 19 refuelings
28 days median
81% power at shutdown
0.6% per day
Watts Bar 1 coasted down for a week or longer before 5 of its 19 refuelings on record. Those coastdowns ran a median of 28 days and ended near 81% power. The most recent refueling, in Apr 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 May 19, 2026
68.4% remaining
0.5 FPD margin
Watts Bar 1 has an estimated 68.4% of its fuel left. Across its last 18 cycles, it has refueled with an average of 3.0% remaining.
Avg refuel: 3.0%
Avg refuel (3yr): 12.0%
Deepest burn: 0.0% (1999-04 → 2000-09)
Most margin: 24.0% (2024-12 → 2026-04)
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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, Watts Bar 1 has run at about 88.4% of its rated capacity. Across the last 12 reported months it averaged 91.2%. 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 Watts Bar 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 May 19, 2026
Watts Bar 1 is 157 days into its current fuel cycle with an estimated 68.4% of its fuel left. Its typical cycle runs about 495 days.
Fresh — 100%
Refuel — 0%
68.4% remaining
Fresh fuel
Cycle progress
157 / 495 days
EFPD remaining
339 days
Effective burn
156 EFPD
Burn deficit
0.5 FPD
Watts Bar 1 is early in its fuel cycle with 339 EFPD of reactivity remaining. Refuel is not expected for many months.
Outage History & Daily Power Log
This table logs every recorded outage for Watts Bar 1, 53 in all since 1999. Of those, 19 were scheduled refueling outages and 34 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
U1R20
|
2026-04-18 | 2026-05-15 | 28 | 348d | 2026-04-17 | +1d |
| 2025-01-17 | 2025-05-05 | 109 | 39d | - | - | |
|
Scheduled
U1R19
|
2024-11-02 | 2024-12-09 | 38 | 106d | 2024-10-12 | +21d |
| 2024-07-09 | 2024-07-19 | 11 | 43d | - | - | |
|
Unscheduled
|
2024-05-25 | 2024-05-27 | 3 | 380d | - | - |
|
Scheduled
U1R18
|
2023-04-15 | 2023-05-11 | 27 | 498d | 2023-04-14 | +1d |
|
Scheduled
U1R17
|
2021-10-30 | 2021-12-03 | 35 | 514d | 2021-10-29 | +1d |
|
Scheduled
U1R16
|
2020-05-09 | 2020-06-03 | 26 | 79d | 2020-03-10 | +60d |
| 2020-02-20 | 2020-02-20 | 1 | 121d | - | - | |
|
Unscheduled
|
2019-09-16 | 2019-10-22 | 37 | 5d | - | - |
|
Unscheduled
|
2019-09-05 | 2019-09-11 | 7 | 3d | - | - |
| 2019-09-01 | 2019-09-02 | 2 | 306d | - | - | |
| 2018-10-28 | 2018-10-30 | 3 | 2d | - | - | |
|
Scheduled
U1R15
|
2018-09-15 | 2018-10-26 | 42 | 495d | 2018-09-08 | +7d |
| 2017-05-05 | 2017-05-08 | 4 | 2d | - | - | |
| 2017-05-03 | 2017-05-03 | 1 | 3d | - | - | |
|
Scheduled
U1R14
|
2017-03-19 | 2017-04-30 | 43 | 359d | 2017-03-20 | -1d |
| 2016-03-23 | 2016-03-25 | 3 | 131d | - | - | |
|
Unscheduled
|
2015-11-07 | 2015-11-13 | 7 | 17d | - | - |
|
Scheduled
U1R13
|
2015-09-21 | 2015-10-21 | 31 | 204d | 2015-09-14 | +7d |
| 2015-02-22 | 2015-03-01 | 8 | 222d | - | - | |
| 2014-07-14 | 2014-07-15 | 2 | 74d | - | - | |
|
Scheduled
U1R12
|
2014-03-24 | 2014-05-01 | 39 | 267d | 2014-04-07 | -14d |
| 2013-06-29 | 2013-06-30 | 2 | 244d | - | - | |
|
Scheduled
U1R11
|
2012-09-10 | 2012-10-28 | 49 | 12d | 2012-09-10 | 0d |
| 2012-08-28 | 2012-08-29 | 2 | 319d | - | - | |
|
Unscheduled
|
2011-10-08 | 2011-10-14 | 7 | 132d | - | - |
| 2011-05-29 | 2011-05-29 | 1 | 9d | - | - | |
|
Scheduled
U1R10
|
2011-04-04 | 2011-05-20 | 47 | 138d | 2011-03-20 | +15d |
|
Unscheduled
|
2010-11-15 | 2010-11-17 | 3 | 175d | - | - |
|
Unscheduled
|
2010-05-22 | 2010-05-24 | 3 | 214d | - | - |
|
Scheduled
U1R9
|
2009-09-21 | 2009-10-20 | 30 | 362d | 2009-09-20 | +1d |
|
Unscheduled
|
2008-09-21 | 2008-09-24 | 4 | 38d | - | - |
|
Unscheduled
|
2008-08-07 | 2008-08-14 | 8 | 75d | - | - |
|
Unscheduled
|
2008-05-18 | 2008-05-24 | 7 | 55d | - | - |
|
Scheduled
U1R8
|
2008-02-11 | 2008-03-24 | 43 | 438d | 2008-02-10 | +1d |
|
Scheduled
U1R7SGR/Major
|
2006-09-11 | 2006-11-30 | 81 | 38d | 2006-09-10 | +1d |
|
Unscheduled
|
2006-08-01 | 2006-08-04 | 4 | 38d | - | - |
|
Unscheduled
|
2006-05-31 | 2006-06-24 | 25 | 426d | - | - |
|
Scheduled
U1R6
|
2005-02-22 | 2005-03-31 | 38 | 155d | 2005-02-21 | +1d |
|
Unscheduled
|
2004-09-20 | 2004-09-20 | 1 | 247d | - | - |
|
Unscheduled
|
2004-01-17 | 2004-01-17 | 1 | 89d | - | - |
|
Scheduled
U1R5
|
2003-09-08 | 2003-10-20 | 43 | 13d | 2003-09-08 | 0d |
|
Unscheduled
|
2003-08-26 | 2003-08-26 | 1 | 164d | - | - |
|
Unscheduled
|
2003-03-10 | 2003-03-15 | 6 | 239d | - | - |
|
Unscheduled
|
2002-07-14 | 2002-07-14 | 1 | 67d | - | - |
|
Unscheduled
|
2002-05-04 | 2002-05-08 | 5 | 46d | - | - |
|
Scheduled
U1R4
|
2002-02-25 | 2002-03-19 | 23 | 67d | 2002-02-25 | 0d |
|
Unscheduled
|
2001-12-20 | 2001-12-20 | 1 | 106d | - | - |
|
Unscheduled
|
2001-09-05 | 2001-09-05 | 1 | 58d | - | - |
|
Unscheduled
|
2001-06-30 | 2001-07-09 | 10 | 267d | - | - |
|
Scheduled
U1R3
|
2000-09-10 | 2000-10-06 | 27 | 515d | 2000-09-10 | 0d |
|
Scheduled
U1R2
|
1999-02-27 | 1999-04-14 | 47 | - | 1999-02-27 | 0d |
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