INTRODUCTION
• Middletown, Pennsylvania
• May 1968 Three Mile Island (TMI) Unit 1 Construction began
• November 1969 TMI Unit 2 Construction began
• Unit 1 began operation in September 1974
• Unit 2 started up in December 1978
• Within 90 days, on March 28, 1979, a nuclear meltdown
occurred in TMI 2
• A non-nuclear failure led to a nuclear meltdown
• Worst accident at a nuclear power plant in the history of U.S.
commercial power plants
NUCLEAR REACTOR MAIN COMPONENTS
• Fuel Source: Uranium
• Moderator to slow the release of neutrons of the Uranium
• Typically water
• Control rods to absorb neutrons and control the rate of reaction
• Coolant to transfer heat from the reactor core
• Steam generator that is part of the coolant system
• Containment to protect outside from radiation and core from
foreign particles
PROCESS DESCRIPTION
• Reactor splits atoms of elements to release heat
• Splits the Uranium atoms
• Moderator slows the release of neutrons and control rods
absorb neutrons
• Heat is captured in gas or water (the coolant)
• Transfer from the reactor to steam generator
• This is used to create steam
• The steam is used to drive a turbine and create electricity
TMI UNIT 2 DIAGRAM
TIMELINE
•
Video
•
4:00 AM March 28, 1979
•
Initial Problem - Secondary cooling circuit stopped flowing
• Valves closed due to water leak into air line
• Secondary pipes boiled dry
• Prevented primary coolant from removing heat from core
• Automatic shutdown occurred
•
Relief valve in primary loop failed to close
•
Two valves manually closed two weeks prior for maintenance so water unable to
flow
• Loss of coolant occurred and relief valve opened
• Plant experienced: uncovered core, hydrogen gas generation, radioactive
primary coolant on reactant-building floor
TIMELINE (CONTINUED)
•
Pressure in primary unit was high
• Operators over-rode emergency core-coolant system and shut off pumps
•
Valves closed for cleaning were opened to move cooling water into boiling region,
but water turned to steam
• Pumps began to vibrate
• Operators shut down pumps and ended forced cleaning to prevent damage
to pumps
•
Temperatures failed to decrease due to gas and hydrogen pockets in system
• Operators had gas transferred to hold-up tanks in another building
• Pipe transferring gas leaked to atmosphere
•
Sudden build-up in pressure indicated hydrogen burn occurred
• Operators periodically opened vent in the reactor to cool slowly (one month)
• Cooled by natural movement of water, no mechanical movement
EVACUATION
• Inadequate evacuation plans in place
• At first, no evacuation was called for
• Public confusion
• On Friday, March 30, Governor called for a limited evacuation
ULTIMATE RESULTS
• No fatalities or injuries
• Radiation exposure ~ 0.3 - 0.6 rem
• No conclusive evidence for an increase in cancer cases
• Unit 2 not allowed to resume operation
• Unit 1 not allowed to resume operations until 1985
• General Public Utilities paid $82 million as compensation
• Negative media coverage
• Property values dropped
• Mistrust of Nuclear Industry
• Loss of income for surrounding farms
CLEAN-UP
• Lasted 14 years
• Vented 44,000 curies of radioactive gases
• Water decontamination
• Removal of solid waste
• Cost ~ $1 billion
LESSONS LEARNED
• New Regulations
• Inherently Safer Design and Operation
• Emphasis on Training and Transparency
• Creation of INPO
• Expect the Unexpected
SUMMARY
• Worst Nuclear Industry accident in U.S. history
• No injuries or fatalities
• Major changes to the industry
• New research into what causes a core meltdown
• Fed public mistrust of nuclear industry
REFERENCES
1
2
Kemeny, John G. The Accident at Three Mile Island. Rep.
Washington D.C., 1979. The Accident at Three Mile Island.
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"Backgrounder on the Three Mile Island Accident." NRC:. Web. 23
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3
"Three Mile Island Accident." Three Mile Island. Web. 01 Mar.
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4
Del, Tredici Robert. The People of Three Mile Island. San
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5
Flynn, Cynthia B. The Social and Economic Effects of the Accident
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TMI 25 Years Later: The Three Mile Island Nuclear Power
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"Backgrounder on the Three Mile Island Accident." NRC:. Web. 01
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8
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Walker, J. Samuel. Three Mile Island: A Nuclear Crisis in Historical
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"News." Three Mile Island: 30 Years of What If ... Web. 01 Mar.
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<http://www.pittsburghlive.com/x/pittsburghtrib/news/multi
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Toth, L. M. The Three Mile Island Accident: Diagnosis and
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12
Hargreaves, Steve. "First New Nuclear Reactors OK'd in over 30
Years." CNNMoney. Cable News Network, 09 Feb. 2012. Web.
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<http://money.cnn.com/2012/02/09/news/economy/nucle
ar_reactors/index.htm>.
13
Greenwire, PETER BEHR,. "Three Mile Island Still Haunts U.S.
Nuclear Industry." The New York Times. The New York Times,
27 Mar. 2009. Web. 01 Mar. 2012.
<http://www.nytimes.com/gwire/2009/03/27/27greenwirethree-mile-island-still-haunts-us-reactor-indu10327.html?pagewanted=all>.
QUESTIONS?