Prairie Island 1 - Status & History

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

Plant Info Outage History Daily Power Log
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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.
39
Excellence
#68 of 94 →
Mid Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
296
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2020-10-13 to 2022-10-15).
732
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (543 days for this 24-month cycle 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).
88.6%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data.
15
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.
3.3
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.
85.1%
Fuel Utilization
lifetime 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.
Time window — change how far back we look
NukeWorker's
Operational
Excellence Score
39/100
Mid Quartile · #68/94
5-year window

Prairie Island 1 ranks #68 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: Refuel Duration (75th percentile). Weakest: Fuel Utilization (1th percentile).

Reliability
32
Capacity factor + Forced outages + B2B streaks
Efficiency
38
Fuel utilization + Refuel duration
Discipline
46
Startup duration + Scram count
Cohort Rankings apples-to-apples comparison within each peer group
Reactor type: #47 of 61 PWR
Containment: #39 of 48 Dry Ambient (PWR)
Cycle length: #29 of 40 24-month cycle
Fleet rank above (68 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor 24th
87.5% (higher better, Reliability)
Forced Outage Days/yr 6th
21.6d (lower better, Reliability)
B2B Avg Streak 67th
650d (higher better, Reliability)
Fuel Utilization 1th
83.3% (higher better, Efficiency)
Refuel Duration 75th
25d (lower better, Efficiency)
Startup Duration 43th
4.8d (lower better, Discipline)
Scrams (5-year) 48th
0.4/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: 2021: 59/100 (#35/93)2022: 75/100 (#14/92)2023: 55/100 (#35/92)2024: 51/100 (#45/93)2025: 51/100 (#41/94)2026: 52/100 (#40/94) Stable vs 2025
Compare Prairie Island 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

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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 Jan 18, 2025

32.2% remaining 480 / 691 days 11.3 FPD margin
Avg refuel: 14.9% Deepest burn: 0.0% (2020-10 → 2022-10) Most margin: 29.7% (2011-06 → 2012-10)
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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

Type ⇅ Actual Start ⇅ Actual End ⇅ Duration ⇅ Days Online ⇅ Scheduled Delta
Scram # 57813
2025-07-17 2025-07-22 6 182d - -
Scheduled SGR/Major
2024-09-21 2025-01-16 118 223d 2024-09-15 +6d
Unscheduled
2024-02-09 2024-02-11 3 16d - -
Scram # 56803
2023-10-20 2024-01-24 97 345d - -
Scheduled
2022-10-15 2022-11-09 26 732d 2022-10-14 +1d
Scheduled
2020-09-19 2020-10-13 25 20d 2020-09-18 +1d
Scram # 54859
2020-08-27 2020-08-30 4 672d - -
Scheduled
2018-09-22 2018-10-25 34 671d 2018-09-21 +1d
Scheduled
2016-10-16 2016-11-20 36 502d 2016-10-14 +2d
Scram # 51107
2015-06-01 2015-06-02 2 24d - -
Unscheduled
2015-04-08 2015-05-08 31 56d - -
Unscheduled
2015-01-27 2015-02-11 16 32d - -
Unscheduled
2014-12-11 2014-12-26 16 20d - -
Scheduled
2014-10-08 2014-11-21 45 645d 2014-10-08 0d
Scheduled
2012-10-23 2013-01-01 71 66d 2012-10-27 -4d
Unscheduled
2012-08-15 2012-08-18 4 410d - -
Scram # 47017
2011-07-02 2011-07-02 1 22d - -
Scheduled
2011-04-30 2011-06-10 42 525d 2011-04-30 0d
Scheduled
2009-09-12 2009-11-21 71 114d 2009-09-11 +1d
Unscheduled
2009-05-19 2009-05-21 3 290d - -
Unscheduled
2008-08-01 2008-08-02 2 133d - -
Scheduled
2008-02-13 2008-03-21 38 51d 2008-02-28 -15d
Unscheduled
2007-12-22 2007-12-24 3 218d - -
Unscheduled
2007-05-18 2007-05-18 1 3d - -
Unscheduled
2007-05-12 2007-05-15 4 341d - -
Scheduled
2006-04-29 2006-06-05 38 14d 2006-04-28 +1d
Unscheduled
2006-04-15 2006-04-15 1 408d - -
Unscheduled
2005-03-03 2005-03-03 1 5d - -
Unscheduled
2005-02-19 2005-02-26 8 89d - -
Scheduled
2004-09-11 2004-11-22 73 515d 2004-09-10 +1d
Unscheduled
2003-04-15 2003-04-15 1 131d - -
Scheduled
2002-11-16 2002-12-05 20 432d 2002-11-16 0d
Unscheduled
2001-08-02 2001-09-10 40 158d - -
Scheduled
2001-01-20 2001-02-25 37 38d 2001-01-20 0d
Unscheduled
2000-12-02 2000-12-13 12 556d - -
Scheduled
1999-04-17 1999-05-26 40 96d 1999-04-17 0d
Unscheduled
1999-01-06 1999-01-11 6 - - -
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