Nuclear Power GenerationIn The United States
103 Nuclear Power Reactors
HOW A NUCLEAR REACTOR WORKS
OutlineElectric Power GenerationWhat 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 BubbleWhen 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: ConsequencesPublic 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.
ChernobylApril 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: ConsequencesHuge 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 assembly217 assemblies in the reactor core
Reactor VesselTypical values:Weight: 400 tonsThickness: 8 inchesFuel Assemblies (Core)
PWR ContainmentInitial Construction
Completed Concrete Dome
Regulatory ControlNuclear Regulatory Commission Headquarters Rockville, Maryland(www.nrc.gov)
**The United States has 103 nuclear power reactors in 31 states.
Nuclear energy is the second largest source providing electricity for one of every five homes and business in the country and in California.
Some states clearly are more dependent on nuclear energy than others. Vermont gets 76 percent of its electricity from nuclear reactors New Hampshire and South Carolina well over 50 percent.
*About 90% of all electric power is generated by boiling water. The only with nuclear power is the heat source. **When a reactor is refueled, the removed fuel assemblies are immediately placed in used fuel pools, where they cool under water for many years and become less radioactive. But used fuel pools were not intended as permanent storage. The Department of Energy is supposed to build a permanent underground storage facility for used fuel from nuclear power plants and high-level radioactive waste from defense programs. **Over the past two years, we have seen evidence of strong political support in the series of decisions to move forward with the Yucca Mountain project. The president reached a formal determination that the Yucca Mountain site in Nevada was suitable for used fuel disposal, and both houses of Congress affirmed that determination.
Having made that decision to move forward with the Yucca Mountain project, we saw a determined commitment during 2003 to implement that decision.
The Department of Energy is developing the transportation infrastructure necessary to move used fuel from plant sites to a central disposal facility.
And at the end of this year, we expect DOE to submit its license application to the NRC. The NRC will review that application over the next three years. If the schedule holds, we should see NRC issue a construction authorization in 2007. The repository is expected to begin accepting waste in 2010.