Nuclear Power Generation

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Nuclear Power Generation Emergency Preparedness

• Health Physics Society
• Power Reactor Section

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103 Nuclear Power Reactors
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Steam Engines
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Outline

• Electric Power Generation
• Why Nuclear?
• What About Accidents?
• Safety By Design and Operation
• What About Drill Scenarios?

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Electricity A Vital Resource
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Sources of Power
(2002)
Source EIA - Updated 11/03
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Pros Cons

• cheap and abundant
• but source of greenhouse gases
• clean
• but seasonal and no new sources
• cleaner than coal
• but limited supply
• renewable
• but expensive, low energy density, and
  intermittent

• COAL
• HYDRO
• NATURAL GAS
• SOLAR WIND

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Why Nuclear?

• high energy density
• no air pollution
• small, contained waste
• But what about
• safety, security, and waste disposal ?

• NUCLEAR

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High Energy Density

• Each person in the United States uses either
• 4 tons of coal or
• a few ounces of uranium
• 1 pellet 150 gallons gasoline
• 1780 pounds coal
• 16,000 ft3 natural gas
• 2.5 tons wood

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No Air Pollution
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Waste Contained in Used Fuel Assemblies,
Cooling-off In Pools
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Loaded into Steel Containers, Stored in Concrete
Casks
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Steel Containers Buried Deep Underground
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Waste Hazard Decreases Over Time
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Nuclear Safety Record

• 440 civil nuclear reactors in 30 countries
  sharing operating experiences (http//www.world-n
  uclear.org/index.htm)
• Impressive safety record covering 12,000
  reactor-years of operating experience
• Two nuclear accidents
• TMI (1979)
• Chernobyl (1986)

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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 630 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.

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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

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TMI Consequences

• No one killed, no one injured.
• Offsite radiation is minimal, a small fraction of
  natural background radiation.
• 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.

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Chernobyl
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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.

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Flawed Reactor Design

• graphite core unstable reactor

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Environmental Pathways

• 82 of the iodine exposure was avoidable

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Chernobyl Consequences

• 31 workers, mostly fire fighters are killed
  largely due to acute radiation exposure.
• Huge release of radioactive material, distributed
  around Europe.
• World confidence is severely damaged.
• The Whole Health Organization has linked hundreds
  of child thyroid cancers to the accident (10
  deaths), but no detectable increase in other
  cancers.
• The greatest damage was from fear
  (psychological), NOT radiation.

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Can Chernobyl Happen Here?

• Reactor Design Apples Oranges
• Positive temperature coefficients of reactivity
• Graphite core that catches fire and burns for
  days
• No containment building
• Institutional Controls Apples Oranges
• No strict operating license
• No strict regulatory oversight
• Lesson Never Take Safety For Granted

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Nuclear Safety

• Design and Construction
• Operation and Training

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Safety By Design Low Enrichment

• Fission chain reaction E m c2
• U-235 atoms fission. 5 in fuel, 95 in bombs.

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Safety By Design Fuel Rods

• Typical 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

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Safety By Design Reactor Vessel

• Typical values
• Weight 400 tons
• Thickness 8 inches

Fuel Assemblies (Core)
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Safety By Design PWR Containment
Initial Construction
Completed Concrete Dome
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Layers of Protection Against 9/11
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Safety By Design Reactor Control

• Automatic shutdown system relies on gravity
• Negative temperature pressure coefficients of
  reactivity
• Controls rods maintain maximum shutdown potential

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Safety By DesignRedundant Safety Systems

• Reactivity Control
• Core Heat Removal
• RCS Inventory Control
• RCS Heat Removal
• Containment Isolation

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Regulatory Control

• Nuclear Regulatory Commission Headquarters in
  Rockville, Maryland
• (www.nrc.gov)

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NRC Regulatory Functions
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This IS Rocket Science

• Final Safety Analysis Report (FSAR)
• Volume 15 Accident Analysis
• Design Basis Accidents (Worst Case Scenarios)
• Loss of Cooling Accident (LOCA)
• Steam Generator Tube Rupture (SGTR)

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What Can Get Released?

• Noble gas fission products
• Chemically inert (xenon)
• Volatile fission products
• Chemically reactive (iodine)
• All other fission products
• Remain in solid form

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Beyond Worst Case Scenarios

• EP drills must exercise the emergency plan,
  requiring an unbelievable sequence of events.
• Nuclear Engineering uses the science of
• Probabilistic Risk Assessment
• Probability of an typical EP Scenario
• 1 in 10 billion

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Summary

• Benefits of nuclear power include no air
  pollution and low volume of contained waste.
• Were here today because of the lessons-learned
  at TMI.
• Because of differences in design, the Chernobyl
  disaster has little relevance to the safety of
  U.S. nuclear power plants.
• U.S. nuclear plants are safe through design,
  operation, and strict regulatory control.
• EP Drills must use unrealistic scenarios to
  exercise our Emergency Plan.

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Thanks

• for your interest and patience !