Diablo Canyon 1 - Status & History

Comprehensive reactor performance metrics, cycle analysis, and historical outage data.

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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.
Oct2025NovDecJan2026FebMarAprMayJunJulAugSepOnline: Sep 6, 2025 to Dec 16, 2025Forced Outage: Dec 17, 2025 to Dec 18, 2025Reduced Power: Dec 19, 2025Online: Dec 20, 2025 to Feb 20, 2026Reduced Power: Feb 21, 2026 to Feb 23, 2026Online: Feb 24, 2026 to Feb 27, 2026Reduced Power: Feb 28, 2026 to Mar 1, 2026Online: Mar 2, 2026 to Sep 6, 2026Today
OnlineReduced PowerForced 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
ranked of 93
Subscribers
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
262
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2017-06-21 to 2019-02-10).
599
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.
12
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.
18.38 TWh
Net Generation
EIA-923 · 12 mo to 2026-06 · 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.
6.3
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.
96.9%
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 measured 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.
Time window — change how far back we look
5-yr trend: 2021: 65/100 (#27/93)2022: 73/100 (#16/92)2023: 55/100 (#35/92)2024: 62/100 (#24/92)2025: 55/100 (#30/92)2026: 57/100 (#28/93) Stable vs 2025
Compare Diablo Canyon 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

Diablo Canyon 1 has 33 outages plotted here, averaging 24 days each. The most recent, in Dec 2025, was a unplanned outage lasting 2 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, Diablo Canyon 1 takes about 8 days to climb from first power back to full power. That average is drawn from 17 startups on record, and the most recent took 5 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

9.2% remaining 6.2 FPD margin
Diablo Canyon 1 has an estimated 9.2% of its fuel left. Across its last 16 cycles, it has refueled with an average of 0.8% remaining.
Avg refuel: 0.8% Avg refuel (3yr): 3.1% Deepest burn: 0.0% (1999-03 → 2000-10) Most margin: 5.2% (2004-06 → 2005-10)
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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, Diablo Canyon 1 has run at about 90.2% of its rated capacity. Across the last 12 reported months it averaged 98.6%. 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 Diablo Canyon 1, 33 in all since 1999. Of those, 17 were scheduled refueling outages, 1 was planned maintenance and 15 were unplanned or forced. The typical outage lasted about 24 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
2025-12-17 2025-12-18 2 214d - -
Scheduled 1R25
2025-04-13 2025-05-17 35 484d 2025-04-13 0d
Unscheduled
2023-12-09 2023-12-16 8 27d - -
Scheduled # 56769 1R24
2023-10-01 2023-11-12 43 528d 2023-10-04 -3d
Scheduled 1R23
2022-03-27 2022-04-21 26 511d 2022-03-27 0d
Scheduled 1R22
2020-10-04 2020-11-01 29 568d 2020-10-04 0d
Scheduled 1R21
2019-02-10 2019-03-16 35 599d 2019-02-10 0d
Unscheduled
2017-06-21 2017-06-21 1 2d - -
Scheduled 1R20
2017-04-23 2017-06-19 58 533d 2017-04-30 -7d
Scheduled 1R19
2015-10-04 2015-11-07 35 273d 2015-09-27 +7d
Unscheduled
2015-01-01 2015-01-04 4 281d - -
Unscheduled
2014-03-17 2014-03-26 10 5d - -
Scheduled 1R18
2014-02-09 2014-03-12 32 223d 2014-02-09 0d
Unscheduled
2013-06-27 2013-07-01 5 377d - -
Scheduled 1R17
2012-04-23 2012-06-15 54 530d 2012-04-22 +1d
Scheduled 1R16
2010-10-03 2010-11-10 39 377d 2010-10-04 -1d
Unscheduled
2009-09-20 2009-09-21 2 181d - -
Scheduled 1R15
2009-01-26 2009-03-23 57 530d 2009-01-26 0d
Unscheduled
2007-08-11 2007-08-15 5 75d - -
Scheduled 1R14
2007-05-01 2007-05-28 28 518d 2007-04-30 +1d
Scheduled 1R13
2005-10-24 2005-11-29 37 458d 2005-10-23 +1d
Unscheduled
2004-07-22 2004-07-23 2 49d - -
Scheduled 1R12SGR/Major
2004-03-23 2004-06-03 73 468d 2004-04-23 -31d
Planned Mid-Cycle Planned
2002-10-21 2002-12-11 52 139d - -
Unscheduled
2002-06-04 2002-06-04 1 9d - -
Scheduled 1R11
2002-04-29 2002-05-26 28 524d 2002-04-08 (Model) +21d (Model)
Unscheduled
2000-11-21 2000-11-21 1 8d - -
Scheduled 1R10
2000-10-08 2000-11-13 37 135d 2000-10-08 0d
Unscheduled
2000-05-15 2000-05-26 12 177d - -
Unscheduled
1999-11-20 1999-11-20 1 21d - -
Unscheduled
1999-10-29 1999-10-30 2 36d - -
Unscheduled
1999-09-23 1999-09-23 1 193d - -
Scheduled 1R9
1999-02-08 1999-03-14 35 - 1999-02-08 0d
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