Prairie Island 2 - 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.
33
Excellence
#75 of 94 →
Bottom Quartile
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Days of continuous operation since the last outage ended. Clean run (no forced outages since last refueling).
181
Current Run
days ✔
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Longest recorded period of continuous operation between outages (2019-10-27 to 2021-10-02).
706
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (605 days for this 24-month cycle unit) with no trips to 0% power.
2
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.
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.
9
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.
79.3%
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.
Time window — change how far back we look
NukeWorker's
Operational
Excellence Score
33/100
Bottom Quartile · #75/94
5-year window

Prairie Island 2 ranks #75 of 94 active US units on NukeWorker's Operational Excellence Score over the 5-year window. Strongest area: B2B Avg Streak (81th percentile). Weakest: Fuel Utilization (18th percentile).

Reliability
44
Capacity factor + Forced outages + B2B streaks
Efficiency
30
Fuel utilization + Refuel duration
Discipline
25
Startup duration + Scram count
Cohort Rankings apples-to-apples comparison within each peer group
Reactor type: #52 of 61 PWR
Containment: #42 of 48 Dry Ambient (PWR)
Cycle length: #32 of 40 24-month cycle
Fleet rank above (75 of 94) compares all active US units; cohort ranks compare only against units sharing this property.
Per-dimension breakdown (7 metrics)
Capacity Factor 21th
87.1% (higher better, Reliability)
Forced Outage Days/yr 30th
6.4d (lower better, Reliability)
B2B Avg Streak 81th
695d (higher better, Reliability)
Fuel Utilization 18th
95.8% (higher better, Efficiency)
Refuel Duration 42th
34d (lower better, Efficiency)
Startup Duration 21th
6.3d (lower better, Discipline)
Scrams (5-year) 30th
0.6/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: 80/100 (#9/93)2022: 83/100 (#7/92)2023: 69/100 (#20/92)2024: 48/100 (#50/93)2025: 38/100 (#66/94)2026: 39/100 (#65/94) Stable vs 2025
Compare Prairie Island 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 18, 2025

75.5% remaining 176 / 703 days 4.1 FPD margin
Avg refuel: 16.9% Avg refuel (3yr): 20.7% Deepest burn: 2.1% (2019-10 → 2021-10) Most margin: 35.6% (2012-05 → 2013-09)
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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
2025-10-11 2025-11-14 35 336d 2025-10-02 +9d
Scram # 57404
2024-10-30 2024-11-09 11 237d - -
Scram # 57003
2024-03-04 2024-03-07 4 3d - -
Scheduled SGR/Major
2023-10-07 2024-03-01 147 113d 2023-10-06 +1d
Unscheduled
2023-06-08 2023-06-16 9 7d - -
Scram # 56543
2023-05-28 2023-06-01 5 577d - -
Scheduled
2021-10-02 2021-10-28 27 706d 2021-10-01 +1d
Scheduled
2019-10-05 2019-10-27 23 685d 2019-10-04 +1d
Scheduled
2017-10-14 2017-11-19 37 600d 2017-10-13 +1d
Scram # 51609
2015-12-18 2016-02-22 67 15d - -
Scheduled
2015-10-17 2015-12-03 48 128d 2015-10-16 +1d
Scram # 51136
2015-06-08 2015-06-11 4 65d - -
Scram # 50950
2015-04-04 2015-04-04 1 10d - -
Unscheduled
2015-03-06 2015-03-25 20 287d - -
Unscheduled
2014-05-18 2014-05-23 6 136d - -
Scheduled SGR/Major
2013-09-21 2014-01-02 104 482d 2013-09-21 0d
Scheduled SGR/Major
2012-02-22 2012-05-27 96 126d 2012-02-18 +4d
Unscheduled
2011-10-05 2011-10-19 15 148d - -
Scram # 46830
2011-05-10 2011-05-10 1 350d - -
Unscheduled
2010-05-25 2010-05-25 1 2d - -
Scheduled
2010-04-17 2010-05-23 37 532d 2010-04-15 +2d
Scheduled
2008-09-20 2008-11-01 43 532d 2008-09-17 +3d
Unscheduled
2007-04-06 2007-04-07 2 30d - -
Unscheduled
2007-03-01 2007-03-07 7 78d - -
Scheduled
2006-11-15 2006-12-13 29 268d 2006-11-14 +1d
Unscheduled
2006-02-06 2006-02-20 15 241d - -
Scheduled
2005-04-16 2005-06-10 56 13d 2005-04-15 +1d
Unscheduled
2005-03-31 2005-04-03 4 132d - -
Unscheduled
2004-11-18 2004-11-19 2 406d - -
Scheduled
2003-09-13 2003-10-09 27 561d 2003-09-13 0d
Scheduled
2002-02-02 2002-03-01 28 92d 2002-02-02 0d
Unscheduled
2001-11-01 2001-11-02 2 150d - -
Unscheduled
2001-05-10 2001-06-04 26 338d - -
Scheduled
2000-04-29 2000-06-06 39 447d 2000-04-29 0d
Unscheduled
1999-02-07 1999-02-07 1 - - -
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