Geologic Resources: Nonrenewable Mineral and Energy Resources

1
Geologic Resources Nonrenewable Mineral and
Energy Resources
Chapter 15 G. Tyler Millers Living in the
Environment 13th Edition
2
NUCLEAR POWER

• President Dwight Eisenhower, 1953, Atoms for
  Peacespeech.
• Nuclear-powered electrical generators would
  provide power too cheap to meter.
• Between 1970 and 1974, American utilities ordered
  140 new reactors for power plants.

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Nuclear Power

• After 1975, only 13 orders were placed for new
  nuclear reactors, and all of those were
  subsequently cancelled.
• In all, 100 of 140 reactors on order in 1975 were
  cancelled.
• Construction costs, declining demand for
  electrical power, safety fears
• Electricity from nuclear power plants was about
  half the price of coal in 1970, but twice as much
  in 1990.

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How Do Nuclear Reactors Work

• Most commonly used fuel is U235, a naturally
  occurring radioactive isotope of uranium.
• Occurs naturally at 0.7 of uranium, but must be
  enriched to about of 3.
• Formed in cylindrical pellets (1.5 cm long) and
  stacked in hollow metal rods (4 m long).
• About 100 rods and bundled together to make a
  fuel assembly.
• Thousands of fuel assemblies bundled in reactor
  core.

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How Do Nuclear Reactors Work

• When struck by neutrons, radioactive uranium
  atoms undergo nuclear fission (splitting)
  releasing energy and more neutrons.
• Triggers nuclear chain reaction.

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Nuclear Fission
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How Do Nuclear Reactors Work

• Reaction is moderated in a power plant by
  neutron-absorbing solution (Moderator).
• In addition, Control Rods composed of
  neutron-absorbing material are inserted into
  spaces between fuel assemblies to control
  reaction rate.
• Cadmium or boron
• Water or other coolant is circulated between the
  fuel rods to remove excess heat.

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PWR
9
Small amounts of radioactive gases
Waste heat
Electrical power
Steam
Useful energy 25 to 30
Generator
Turbine
Hot water output
Condenser
Pump
Pump
Cool water input
Waste heat
Black
Pump
Water
Waste heat
Water source (river, lake, ocean)
Periodic removal and storage of radioactive
wastes and spent fuel assemblies
Periodic removal and storage of radioactive
liquid wastes
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RADIOACTIVE WASTE MANAGEMENT

• Until 1970, the US, Britain, France, and Japan
  disposed of radioactive waste in the ocean.
• Production of 1,000 tons of uranium fuel
  typically generates 100,000 tons of tailings and
  3.5 million liters of liquid waste.
• Now approximately 200 million tons of radioactive
  waste in piles around mines and processing plants
  in the US.

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Radioactive Waste Management

• About 100,000 tons of low-level waste (clothing)
  and about 15,000 tons of high-level (spent-fuel)
  waste in the US.
• For past 20 years, spent fuel assemblies have
  been stored in deep water-filled pools at the
  power plants. (Designed to be temporary.)
• Many internal pools are now filled and a number
  plants are storing nuclear waste in metal dry
  casks outside.

12
Radioactive Waste Management

• US Department of Energy announced plans to build
  a high-level waste repository near Yucca Mountain
  Nevada in 1987.
• Facility may cost between 10 and 35 billion, and
  will not open until at least 2015.

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Decommissioning Old Nuclear Plants

• Most plants are designed for a 30 year operating
  life.
• Only a few plants have thus far been
  decommissioned.
• General estimates are costs will be 2-10 times
  more than original construction costs.

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CHANGING FORTUNES

• Public opinion has fluctuated over the years.
• When Chernobyl exploded in 1985, less than
  one-third of Americans favored nuclear power.
• Now, half of all Americans support
  nuclear-energy.
• Currently, 103 nuclear reactors produce about 20
  of all electricity consumed in the US.

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NUCLEAR FUSION

• Nuclear Fusion - Energy released when two smaller
  atomic nuclei fuse into one large nucleus. (Sun)
• Duterium and tritium, two heavy isotopes of H
• Temperatures must be raised to 100,000,000o C and
  pressure must reach several billion atmospheres.
• Advantages
• Production of few radioactive wastes
• Elimination of products that could be made into
  bombs
• Fuel supply that is larger and less hazardous
  than uranium.

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NUCLEAR FUSION

• Despite 50 years and 25 billion, fusion reactors
  have never produced more energy than they
  consume!

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Nuclear Energy

• Fission reactors

Fig. 15-35 p. 366

• Uranium-235

• Potentially dangerous

• Radioactive wastes

Refer to Introductory Essay p. 338
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Dealing with Nuclear Waste

• Low-level waste
• High-level waste
• Underground burial
• Disposal in space
• Burial in ice sheets
• Dumping into subduction zones
• Burial in ocean mud
• Conversion into harmless materials

Fig. 15-40 p. 370
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Nuclear Alternatives

• Breeder nuclear fission reactors

• Nuclear fusion

• New reactor designs

Storage Containers
Fuel rod
Primary canister
Ground Level
Overpack container sealed
Unloaded from train
Personnal elevator
Air shaft
Nuclear waste shaft
Underground
Buried and capped
Lowered down shaft
Fig. 15-42 p. 376