Three Mile Island

By missy.murphy

  • 4 AM - Start of Event

    4 AM - Start of Event
    • Unit 2 pressurized water reactor operating at 97% power
    • Minor malfunction in secondary cooling circuit
    • Ultimately lead to reactor core partial melting and radioactive material released

  • 6:45 AM

    6:45 AM
    • 165 minutes after start of problem, radiation alarms activated
    • 6:56 AM plant supervisor declared site area emergency
    • Less than 30 minutes later, station manager announced general emergency

  • Reactor Shutdown

    Reactor Shutdown
    • Control room operators needed to ensure integrity of reactor vessel
    • Boron concentration sample needed to approve shutdown of reactor entirely
    • Sample looked like "Alka-Seltzer" and highly radioactive

  • Evacuation

    Evacuation
    • Trying to relieve pressure on primary system, significant radiation released from plant's auxiliary building
    • Citizens most vulnerable to radiation evacuated within 5 mile radius- pregnant women and pre-school-aged children
    • Residents returned within 3 weeks

  • Hydrogen Bubble

    Hydrogen Bubble
    • Hydrogen bubble discovered in pressure vessel
    • Concern for hydrogen explosion
    • Determined no oxygen was present for hydrogen to burn/explode- hydrogen bubble reduced

  • Clean Up. August 1979- December 1993

    Clean Up. August 1979- December 1993
    • Damaged reactor permanently closed and entombed in concrete
    • Cost approximately $1 billion
    • About 100 tons of damaged uranium fuel removed from reactor vessel and taken to Idaho National Lab
    • The radioactive waste decays in steel and concrete containers

  • Investigatiion

    Investigatiion
    • President Jimmy Carter commissioned 12 people to investigate the TMI crisis and study was released 10/31/1979
    • Criticized agencies for lapses in quality assurance and maintenance, inadequate operator training, lack of communication of important safety information, poor management, and complacency.
    • "Fundamental changes will be necessary in the organization, procedures, and practices—and above all—in the attitudes" of the NRC and the nuclear industry."

  • Released Radioactivity Amount

    Released Radioactivity Amount
    • Approximately 2.5 megacuries of radioactive gases and approximately 15 curies of iodine-131 released into environment
    • Average radiation dose to people living within 10 miles of plant: 8 mrem (0.08 Sv) and no more than 100 mrem (1 mSv)
    • 8 mrem equivalent to 1 chest x-ray; 100 mrem equivalent to 1/3 average background level of radiation
    • Detection of excess cancer deaths in the population as a consequence of the radiation dose it received is not expected

  • Effects on Nuclear Power Plants

    Effects on Nuclear Power Plants
    • Post TMI: The number of reactors under construction in the U.S. declined from 1980-1998
    • At the time of the TMI accident 129 power plants were approved for construction, only 53 were completed
    • 2012 saw the first authorized nuclear power plant in Georgia since TMI

  • TMI 1 Shutdown

    TMI 1 Shutdown
    • In October 2009, TMI 1 license extended from April 2014- 2034
    • September 2019: TMI 1 announced to be closed
    • September 20, 2019 TMI 1 shutdown at noon