Three Mile Island

  • TMI Reactor Unit 1 begins commercial operation

    TMI Reactor Unit 1 begins commercial operation

    • Construction cost: $2.37B adjusted for inflation
    • Initially licensed to operate for 40 years
    • Generates 819 MWatts of electricity
  • TMI Reactor Unit 2 begins commercial operation

    TMI Reactor Unit 2 begins commercial operation

    • Began operation over four years following Unit 1
    • Slightly larger than Unit 1
    • Greater output by 87 MWatts electrical capacity
  • "The China Syndrome" theatrical release date

    "The China Syndrome" theatrical release date

    • Film showing fictional nuclear power plant meltdown and cover-up
    • Theatrical release twelve days prior to TMI event
    • Well received publicly, though experts deemed unrealistic
  • 0400: Reactor 2 cooling system malfunction

    0400: Reactor 2 cooling system malfunction

    • Malfunction in secondary coolant circuit causes temp in primary to rise
    • Reactor automatically shuts down
    • Relief valve fails to close
    • Core suffers severe damage due to loss of primary coolant
  • 0520: Pumps around reactor core shut off

    0520: Pumps around reactor core shut off

    • High pressure injections pumps automatically turned on to replace the lost coolant
    • Operators misinterpret the rising water levels to be increased pressure building and shut down pumps
    • This contributes to a rise in hydrogen levels
    • The continued lack of coolant contributes to rising heat levels at the reactor core and damages fuel rods
    • Damage releases radioactive materials into the remaining coolant waters
  • 0622: Block valve manually closed between relief valve and pressurizer

    0622: Block valve manually closed between relief valve and pressurizer

    • An operator arriving for their shift notices the irregular temperature of one of the valves
    • Initiates a manual block valve to prevent further loss of coolant
    • By this point 100,000 liters of coolant had been lost
  • 0645: Alarms detect radiation levels in leaking coolant waters

    0645: Alarms detect radiation levels in leaking coolant waters

    • Radiation alarms begin signalling detection of radioactive materials
    • A site-wide emergency is declared
    • Metropolitan Edison, the site operator, in notified of the incident
  • 0825: First on-air news report of incident

    0825: First on-air news report of incident

    • Mike Pintek, local WKBO's news director, is alerted by a local traffic reporter of emergency vehicles entering and leaving TMI facilities
    • Pintek calls TMI directly, operators answer with alarms blaring and state they cannot speak
    • Pintek goes on air to confirm an incident is ongoing at the reactor site
    • FEMA briefly considers an evacuation declaration but quickly calls it off
  • 1030: Metropolitan Edison release first statement

    1030: Metropolitan Edison release first statement

    • MetEd release statement insisting that no radiation levels have been detected off-site
    • Conflicting information from the site operators, local news and government officials causes public unease and panic
    • MetEd VP John Herbein makes public press conference appearance to state that misinformation is preventing workers from "doing their jobs"
  • Cooldown continues; Gov Thornburgh says no need to evacuate

    Cooldown continues; Gov Thornburgh says no need to evacuate

    • Further cooldown efforts seem to stabilize the reactor core to prevent total meltdown
    • Staff for Gov. Thornburgh assures residents that there is no need to evacuate at this time
    • Recommendations are made to remain indoors and close windows
  • 1145: Discovery of two new dangers

    1145: Discovery of two new dangers

    • Release of gasses to continue cooling reactor results in the release of radiation into atmosphere
    • Helicopters monitoring the site detect 12 mSv of radiation in air, the first off-site detection of radiation
    • Risk of hydrogen bubble developing from increased reactor pressure adds to worry of a hydrogen explosion
    • Gov. Thornburgh consults with NRC about potentially evacuating residents
  • 1230: Press conference to recommend special groups evacuation

    1230: Press conference to recommend special groups evacuation

    • Gov. Thornburgh appears publicly to address the new developments
    • Pregnant women and preschool-aged children are recommended to evacuate within five miles of the plant
    • Mistrust and lack of communication results in the eventual evacuation of 100,000 people
    • Thornburgh asks President Carter to send Harold Denton, director of NRC, to provide reliable information on risks and assessments going forward
  • Pres. Carter visit; hydrogen bubble update

    Pres. Carter visit; hydrogen bubble update

    • Pres. and Mrs. Carter visit the site and control rooms in an effort to abate the public's fears
    • Experts determine the lack of oxygen present in the pressure vessel made the possibility of a hydrogen explosion not feasible
    • Hundreds of environmental samples taken at this time determined almost no iodine levels and only slightly elevated levels of noble gasses in the surrounding areas
  • Carter appoints 12 member commission to investigate

    Carter appoints 12 member commission to investigate

    • Pres. Carter appoints commission to investigate the events that lead to the incident and potential public health risks
    • Studies found average radiation dose to residents within 10 miles to be 0.08 mSv, with the highest possible dose at 1 mSv
    • Over the course of several years, it was officially determined that no adverse health events came of the incident
  • Period: to

    TMI Reactor 2 Cleanup Effort

    • TMI-2 cleanup plan took nearly twelve years
    • Total cost was $973 million
    • 100 tons of damaged uranium fuel were safely removed
    • 10.6 MLiters were processed, stored and evaporated