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Count of currently-Operating US nuclear units with at least 2 completed refueling cycles of historical data. Newer units (e.g., Vogtle 4, which started commercial operation in 2024) need a second refuel before they can be ranked — they appear in the count once they have data.
92
Units Ranked
Active operating fleet
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Fleet-wide average fuel utilization = 100% minus the average refuel-point fuel %. Measures the fraction of each unit's typical cycle (calendar days from refuel to refuel) that produced full-power generation, after accounting for startup, derates, forced outages, and coastdown. Higher is more efficient. The fleet median is shown below the average for distribution context.
97.2%
Fleet Avg Utilization
median 98.1%
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Highest fuel utilization in the fleet — the operator that consistently burns the most of each fuel cycle before refueling, leaving the smallest reactivity margin at refuel. A 100% utilization is essentially impossible (every unit has some derate or startup ramp), so this number indicates the practical ceiling for US operators.
99.8%
Top Utilization
Oconee 1
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Fleet-wide average startup duration — typical days from first power generation (>0%) post-refuel to sustained full power (≥95% for 2+ consecutive days). Computed as a robust mean per unit (drops outliers like post-major-outage startups), then averaged across the fleet. Lower is faster restart.
5.0d
Fleet Avg Startup
median 4.2d
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Fastest typical startup duration in the fleet — the operator with the shortest median-time from first power back to sustained full power after refueling. Reflects operating discipline and post-refuel testing efficiency. Outlier startups (like post-major-outage cycles) are excluded so this is the unit's repeatable performance, not its best-ever single restart.
2.1d
Fastest Startup
Oconee 1
Operational Excellence Score Subscribers
Every operating US reactor rated 0 to 100 on how well it actually runs, built from its own operating record rather than from anything a utility publishes about itself. 92 units are ranked on seven measured inputs, rescored every day.
- Fuel utilization leaderboard, all ranked units
- Startup duration leaderboard, all ranked units
- Operational Excellence composite, ranked
- Reliability, Efficiency and Discipline sub-scores
- Year-over-year trend per unit
- Efficiency map: fuel use against restart speed
Included with every outage subscription and with NukeWorker Gold membership. Trading the outage rather than working it? The same record, cut by power market, is on NukeGryd.