Three Mile Island 1 - Status & History

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

Plant Info Outage History Daily Power Log

Decommissioned

Permanently shut down on 2019-09-20. Outage statistics below reflect only the operating period. The final shutdown is not counted as an outage.
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This unit is permanently shut down (shutdown date: 2019-09-20).
Shut Down
2019-09-20
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Longest recorded period of continuous operation between outages (2007-11-20 to 2009-10-26).
706
Record Run
days
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (400 days for this 24-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).
87%
Capacity Factor
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Total number of scheduled refueling outages detected in the historical data. D&D shutdown period excluded.
10
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.
3.7
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.
96.6%
Fuel Utilization
lifetime avg
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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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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 Ext. Shutdown
2019-09-21 Decommissioned 1 (D&D) 710d 2019-09-18 +3d
Unscheduled Startup Hold
2017-10-11 2017-10-11 1 4d - -
Scheduled
2017-09-19 2017-10-07 19 282d 2017-09-18 +1d
Unscheduled
2016-12-01 2016-12-11 11 373d - -
Scheduled
2015-10-30 2015-11-24 26 175d 2015-10-19 +11d
Unscheduled
2015-05-06 2015-05-08 3 527d - -
Scheduled
2013-10-28 2013-11-25 29 401d 2013-10-21 +7d
Scram # 48325
2012-09-21 2012-09-22 2 18d - -
Scram # 48221
2012-08-23 2012-09-03 12 273d - -
Scheduled
2011-10-25 2011-11-24 31 513d 2011-10-24 +1d
Unscheduled
2010-05-29 2010-05-30 2 85d - -
Unscheduled
2010-03-05 2010-03-05 1 41d - -
Scheduled SGR/Major
2009-10-26 2010-01-23 90 706d 2009-10-26 0d
Scheduled
2007-10-22 2007-11-20 30 312d 2007-10-22 0d
Unscheduled
2006-12-14 2006-12-14 1 40d - -
Unscheduled
2006-11-03 2006-11-04 2 351d - -
Scheduled
2005-10-24 2005-11-17 25 690d 2005-10-23 +1d
Scheduled
2003-10-19 2003-12-04 47 684d 2003-10-19 0d
Scheduled
2001-10-09 2001-12-04 57 149d 2001-10-09 0d
Unscheduled
2001-05-12 2001-05-13 2 571d - -
Scheduled
1999-09-11 1999-10-19 39 - 1999-09-11 0d
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