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Nuclear Power Generation

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Title: Nuclear Power Generation


1
Nuclear Power Generation Emergency Preparedness
  • Health Physics Society
  • Power Reactor Section

2
103 Nuclear Power Reactors
3
Steam Engines
4
Outline
  • Electric Power Generation
  • Why Nuclear?
  • What About Accidents?
  • Safety By Design and Operation
  • What About Drill Scenarios?

5
Electricity A Vital Resource
6
Sources of Power
(2002)
Source EIA - Updated 11/03
7
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

8
Why Nuclear?
  • high energy density
  • no air pollution
  • small, contained waste
  • But what about
  • safety, security, and waste disposal ?
  • NUCLEAR

9
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

10
No Air Pollution
11
Waste Contained in Used Fuel Assemblies,
Cooling-off In Pools
12
Loaded into Steel Containers, Stored in Concrete
Casks
13
Steel Containers Buried Deep Underground
14
Waste Hazard Decreases Over Time
15
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)

16
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.

17
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

18
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.

19
Chernobyl
20
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.

21
Flawed Reactor Design
  • graphite core unstable reactor

22
Environmental Pathways
  • 82 of the iodine exposure was avoidable

23
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.

24
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

25
Nuclear Safety
  • Design and Construction
  • Operation and Training

26
Safety By Design Low Enrichment
  • Fission chain reaction E m c2
  • U-235 atoms fission. 5 in fuel, 95 in bombs.

27
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

28
Safety By Design Reactor Vessel
  • Typical values
  • Weight 400 tons
  • Thickness 8 inches

Fuel Assemblies (Core)
29
Safety By Design PWR Containment
Initial Construction
Completed Concrete Dome
30
Layers of Protection Against 9/11
31
Safety By Design Reactor Control
  • Automatic shutdown system relies on gravity
  • Negative temperature pressure coefficients of
    reactivity
  • Controls rods maintain maximum shutdown potential

32
Safety By DesignRedundant Safety Systems
  • Reactivity Control
  • Core Heat Removal
  • RCS Inventory Control
  • RCS Heat Removal
  • Containment Isolation

33
Regulatory Control
  • Nuclear Regulatory Commission Headquarters in
    Rockville, Maryland
  • (www.nrc.gov)

34
NRC Regulatory Functions
35
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)

36
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

37
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

38
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.

39
Thanks
  • for your interest and patience !
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