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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.
43
Excellence
#61 of 94 ↑10
Mid Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
191
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2016-06-01 to 2018-02-11).
620
Record Run
days
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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.
6
B2B Runs
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power).
88.5%
Capacity Factor
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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.
4.3
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.
97.5%
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
43/100
Mid Quartile · #61/94
5-year window
Diablo Canyon 2 ranks #61 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Scrams (5-year) (70th percentile). Weakest: Refuel Duration (20th percentile).
Reliability
44
Capacity factor + Forced outages + B2B streaks
Efficiency
31
Fuel utilization + Refuel duration
Discipline
52
Startup duration + Scram count
Cohort Rankings
apples-to-apples comparison within each peer group
Reactor type:
#43 of 61
PWR
Containment:
#36 of 48
Dry Ambient (PWR)
Cycle length:
#36 of 54
18-month cycle
Fleet rank above (61 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor
26th
88.3% (higher better, Reliability)
Forced Outage Days/yr
49th
3.8d (lower better, Reliability)
B2B Avg Streak
58th
536d (higher better, Reliability)
Fuel Utilization
42th
97.7% (higher better, Efficiency)
Refuel Duration
20th
39d (lower better, Efficiency)
Startup Duration
35th
5.2d (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:
↑ +7.4 pts vs 2025
Compare Diablo Canyon 2 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 Nov 5, 2025
62.5% remaining
189 / 502 days
0.6 FPD margin
Avg refuel: 3.2%
Avg refuel (3yr): 2.5%
Deepest burn: 0.0% (1999-10 → 2001-04)
Most margin: 39.3% (2019-12 → 2021-02)
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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
|
2025-10-05 | 2025-11-04 | 31 | 504d | 2025-10-05 | 0d |
|
Scheduled
|
2024-04-07 | 2024-05-19 | 43 | 500d | 2024-04-06 | +1d |
|
Scheduled
|
2022-10-16 | 2022-11-24 | 40 | 348d | 2022-10-16 | 0d |
|
Unscheduled
|
2021-10-26 | 2021-11-02 | 8 | 3d | - | - |
|
Scram
# 55526
|
2021-10-16 | 2021-10-23 | 8 | 174d | - | - |
|
Unscheduled
|
2021-04-20 | 2021-04-25 | 6 | 5d | - | - |
|
Scheduled
|
2021-02-04 | 2021-04-15 | 71 | 25d | 2021-02-04 | 0d |
|
Unscheduled
|
2020-12-03 | 2021-01-10 | 39 | 8d | - | - |
|
Unscheduled
|
2020-10-16 | 2020-11-25 | 41 | 76d | - | - |
|
Scram
# 54789
|
2020-07-18 | 2020-08-01 | 15 | 153d | - | - |
|
Unscheduled
|
2020-02-14 | 2020-02-16 | 3 | 64d | - | - |
|
Scheduled
SGR/Major
|
2019-09-22 | 2019-12-12 | 82 | 294d | 2019-09-22 | 0d |
|
Scram
# 53764
|
2018-12-02 | 2018-12-02 | 1 | 256d | - | - |
|
Scheduled
|
2018-02-11 | 2018-03-21 | 39 | 620d | 2018-02-04 | +7d |
|
Scheduled
|
2016-05-01 | 2016-06-01 | 32 | 542d | 2016-05-01 | 0d |
|
Scheduled
|
2014-10-05 | 2014-11-06 | 33 | 49d | 2014-09-28 | +7d |
|
Unscheduled
|
2014-08-15 | 2014-08-17 | 3 | 189d | - | - |
|
Scram
# 49786
|
2014-02-03 | 2014-02-07 | 5 | 205d | - | - |
|
Scram
# 49184
|
2013-07-11 | 2013-07-13 | 3 | 111d | - | - |
|
Scheduled
|
2013-02-03 | 2013-03-22 | 48 | 111d | 2013-02-03 | 0d |
|
Scram
# 48400
|
2012-10-12 | 2012-10-15 | 4 | 167d | - | - |
|
Unscheduled
|
2012-04-26 | 2012-04-28 | 3 | 326d | - | - |
|
Scheduled
|
2011-05-01 | 2011-06-05 | 36 | 31d | 2011-05-02 | -1d |
|
Scram
# 46701
|
2011-03-27 | 2011-03-31 | 5 | 502d | - | - |
|
Scheduled
|
2009-10-04 | 2009-11-10 | 38 | 43d | 2009-10-04 | 0d |
|
Unscheduled
|
2009-08-14 | 2009-08-22 | 9 | 43d | - | - |
|
Unscheduled
|
2009-07-01 | 2009-07-02 | 2 | 251d | - | - |
|
Unscheduled
|
2008-10-22 | 2008-10-23 | 2 | 47d | - | - |
|
Unscheduled
|
2008-08-17 | 2008-09-05 | 20 | 128d | - | - |
|
Scheduled
|
2008-02-04 | 2008-04-11 | 68 | 417d | 2008-02-04 | 0d |
|
Unscheduled
|
2006-12-11 | 2006-12-14 | 4 | 201d | - | - |
|
Scheduled
|
2006-04-18 | 2006-05-24 | 37 | 494d | 2006-04-17 | +1d |
|
Scheduled
|
2004-10-26 | 2004-12-10 | 46 | 560d | 2004-10-25 | +1d |
|
Unscheduled
|
2003-04-05 | 2003-04-15 | 11 | 7d | - | - |
|
Unscheduled
|
2003-03-29 | 2003-03-29 | 1 | 5d | - | - |
|
Scheduled
|
2003-02-04 | 2003-03-24 | 49 | 86d | 2003-02-04 | 0d |
|
Unscheduled
|
2002-11-09 | 2002-11-10 | 2 | 272d | - | - |
|
Unscheduled
|
2002-02-10 | 2002-02-10 | 1 | 260d | - | - |
|
Scheduled
|
2001-04-29 | 2001-05-26 | 28 | 227d | 2001-04-29 | 0d |
|
Unscheduled
|
2000-09-06 | 2000-09-14 | 9 | 291d | - | - |
|
Unscheduled
|
1999-11-20 | 1999-11-20 | 1 | 21d | - | - |
|
Unscheduled
|
1999-10-29 | 1999-10-30 | 2 | 2d | - | - |
|
Scheduled
|
1999-09-26 | 1999-10-27 | 32 | - | 1999-09-26 | 0d |
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