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Nuclear Power Generation In The United States. 103 Nuclear Power Reactors. Steam Engines. Outline. Electric Power Generation What About Accidents? Safety By Design and Operation. Waste Contained in Used Fuel Assemblies, Cooling-off In Pools. - PowerPoint PPT Presentation
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Nuclear Power GenerationIn The United States
103 Nuclear Power Reactors
Steam Engines
HOW A NUCLEAR REACTOR WORKS
Outline
Electric Power Generation
What About Accidents?
Safety By Design and Operation
Waste Contained in Used Fuel Assemblies, Cooling-off In Pools
Loaded into Steel Containers, Stored in Concrete Casks
Steel Containers Buried Deep Underground WHEN?/WHERE?
Three Mile Island (TMI)
March 28th 1979, Unit 2 reactor trips at 4 AM.(The movie “China Syndrome” is playing in theaters)
Pressurer relief value sticks open, lose of cooling accident (LOCA) begins.
Hampered by inadequate training and instrumentation, operators shut off emergency core cooling.
By 6:30 AM, blocking value is closed, shutting off the loss of coolant but …
The water level has fallen below the top of the reactor core. The fuel rods containing the uranium fuel pellets melt and release radioactive gas into the Containment Building.
TMI: Hydrogen “Bubble” When the fuel rods melt, hydrogen gas is generated.
A “bubble” of hydrogen gas collects in the reactor head.
Fear that the hydrogen could explode result in confusion, panic. About 150,000 people evacuate.
However, the hydrogen explosion was never possible (not enough oxygen)
Major lessons: Better operator training Better emergency planning
TMI: Consequences Public confidence is severely damaged.
Many health effects studies have been conducted. In 1996, a U.S. District Court dismisses all lawsuits finding no evidence of harm.
Improvements to operator training, instrumentation, and emergency plans are now required.
Chernobyl
Chernobyl April 1986 disaster at Chernobyl in the Ukraine was a
result of a dangerous reactor design and weak operational controls.
Weak Operational Control:
Poorly trained operators were performing a dangerous and unauthorized “test”.
Dangerous Reactor Design: A “positive” temperature coefficient of “reactivity”
resulted in a huge power surge that cause water to flash to steam, blowing the cover plate off the top of the reactor…
Broken pipes spilled water onto the hot “graphite” moderator, which bursts into flames.
Flawed Reactor Design
graphite core & unstable reactor
Environmental Pathways
82% of the iodine exposure was avoidable
Chernobyl: Consequences
Huge release of radioactive material, distributed around Europe.
World confidence is severely damaged.
Fuel RodsTypical values:
The uranium fuel is made of solid ceramic pellets.
The fuel pellets are sealed inside 13’ long zirconium alloy rods.
236 rods in each assembly
217 assemblies in the reactor core
Reactor Vessel
Typical values:
Weight: 400 tons
Thickness: 8 inches
Fuel Assemblies (Core)
PWR Containment
Initial Construction
Completed Concrete Dome
Regulatory Control
Nuclear Regulatory Commission Headquarters
Rockville, Maryland
(www.nrc.gov)