Environmental Science: Toward a Sustainable Future Richard T' Wright

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Environmental Science Toward a Sustainable
Future Richard T. Wright
Chapter 13

• Energy from Nuclear Power PPT by Clark E.
  Adams

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Energy from Nuclear Power

• Nuclear energy in perspective
• How nuclear power works
• The hazards and costs of nuclear power facilities
• More advanced reactors
• The future of nuclear power

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Nuclear Energy in Perspective
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Nuclear Energy in Perspective
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Nuclear Energy in Perspective
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How Nuclear Power Works

• From mass to energy
• Comparing nuclear power to coal power

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From Mass to Energy
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Terms and Definitions

• Fission a large atom of one element is split to
  produce two different smaller elements
• Fusion two small atoms combine to form a larger
  atom of a different element
• Isotope different (mass number) forms of the
  same element

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Two Forms of Uranium

• 238U 92 protons 146 neutrons
• 235U 92 protons 143 neutrons

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Fission, Fusion, or Both?

• Energy is released
• Begins with 235U
• Produces radioactive by-products
• Produces free neutrons

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Fission, Fusion, or Both?

• Splits a larger atom into smaller atoms
• Fuses smaller atoms in one larger atom
• Begins with 2H and 3H
• Produces helium

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Terms and Definitions

• Fuel rods rods full of 235U pellets
• Moderator fluid (water) coolant that slows down
  neutrons
• Control rods moderate rate of the chain reaction
  by absorbing neutrons

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A Nuclear Reactor
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A Nuclear Reactor Is Designed to

• Sustain a continuous chain reaction
• Prevent amplification into a nuclear explosion
• Consist of an array of fuel and control rods
• Make some material intensely hot

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A Nuclear Power Plant
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A Nuclear Power Plant Designed to

• Use steam to drive turbogenerators
• Convert steam into electricity
• Produce superheated water in a reactor vessel
• Prevent meltdown

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Comparing Nuclear Power with Coal Power
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Comparing Nuclear Power with Coal Power

• Requires 3.5 million tons of raw fuel
• Requires 30 tons of raw material
• Emits over 7 million tons of CO2 into the
  atmosphere
• Emits no CO2 into the atmosphere

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Comparing Nuclear Power with Coal Power

• Emits over 300 thousand tons of SO2 into the
  atmosphere
• Emits no acid-forming pollutants
• Produces about 100 thousand tons of ash
• Produces 250 tons of radioactive waste
• Possible meltdown

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Comparing Nuclear Power with Coal Power

• Produces 250 tons of radioactive waste
• Possible meltdown

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Terms and Definitions

• Radioisotopes unstable isotopes of the elements
  resulting from the fission process

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Terms and Definitions

• Radioactive emissions subatomic particles
  (neutrons) and high-energy radiation (alpha,
  beta, and gamma rays)
• Radioactive wastes materials that become
  radioactive by absorbing neutrons from the
  fission process

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The Hazards and Costs of Nuclear Power Facilities

• Radioactive emissions
• Radioactive wastes
• Disposal of radioactive wastes
• Nuclear power accidents
• Safety and nuclear power
• Economic problems with nuclear power

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Radioactive Emissions and Wastes
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Radioactive Decay
Half life the time for half the amount of a
radioactive isotope to decay
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Half-life

• Molybdenum-99 (half-life 2.8 days)
• Xenon-133 (half-life 5.3 days)
• Krypton-85 (half-life 10.7 years)
• Cesium-137 (half-life 30.0 years)
• Plutonium-239 (half-life 24,000 years)

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Disposal of Radioactive Wastes (200 Thousand
Tons)

• Finding long-term containment sites
• Transport of highly toxic radioactive wastes
  across the United States
• The lack of any resolution to the radioactive
  waste problem
• Environmental racism
• Cost (60 billion to 1.5 trillion)

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Disposal of Radioactive Wastes

• To be safe, plutonium-239 would require 240,000
  years (10 half-lives) of containment!
• Discuss the implications of this in terms of
  disposal of radioactive wastes.
• Yucca Mountain in southwestern Nevada the
  nations nuclear waste repository

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Nuclear Power Accidents

• Three-mile Island
• 1979
• Harrisburg, PA
• Loss of coolant in reactor vessel
• Damage so bad, reactor shut down permanently
• Unknown amount of radioactive waste released into
  atmosphere

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How Chernobyl Blew Up

• Loss of water coolant perhaps triggered the
  accident. When the water-circulation system
  failed, the temperature in the reactor core
  increased to over 5,000 oF, causing the uranium
  fuel to begin melting and producing steam that
  reacted with the zirconium alloy cladding of the
  fuel rods to produce hydrogen gas.

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How Chernobyl Blew Up

• A second reaction between steam and graphite
  produced free hydrogen and carbon oxides. When
  this gas combined with oxygen, a blast blew off
  the top of the building, igniting the graphite.
  The burning graphite threw a dense cloud of
  radioactive fission products into the air.

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Consequences of Radiation Exposure

• Block cell division
• Damage biological tissues and DNA
• Death
• Cancer
• Birth defects

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Safety and Nuclear Power

• Passive rather than active safety features
• New generations of reactors (ALWRs, see Fig.
  13-15)
• Terrorism and nuclear power dirty bombs or
  outright attacks

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Economic Problems with Nuclear Power

• Energy demand estimates were unrealistic.
• Costs increases (5x) to comply with new safety
  standards.
• Withdrawal of government subsidies to nuclear
  industry.
• Public protests delayed construction.
• Any accident financially ruins the utility.

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More Advanced Reactors

• Breeder reactors
• Fusion reactors

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Breeder, Fusion, or Both

• Creates more fuel than it consumes
• Raw material is 238U
• Splits atoms

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Breeder, Fusion, or Both

• Fuses atoms
• Releases energy
• Raw material is deuterium and tritium
• Source of unprecedented thermal pollution

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The Future of Nuclear Power Opposition

• General distrust of technology
• Skepticism of management
• Doubt overall safety claims about nuclear power
  plants
• Nuclear power plants are prime targets for
  terrorist attacks
• Nuclear waste disposal problems

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The Future of Nuclear Power Rebirth?

• Need to address public concerns listed in the
  opposition section.
• Waste dilemma must be resolved.
• Strong political leadership capable of analyzing
  the full spectrum of problems associated with the
  future of nuclear power is needed.

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End of Chapter 13