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Geologic Resources: Nonrenewable Mineral and Energy Resources

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Title: 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.

3
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.

4
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.

5
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.

6
Nuclear Fission
7
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.

8
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
10
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.

11
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.

13
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.

14
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.

15
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.

16
NUCLEAR FUSION
  • Despite 50 years and 25 billion, fusion reactors
    have never produced more energy than they
    consume!

17
Nuclear Energy
  • Fission reactors

Fig. 15-35 p. 366
  • Uranium-235
  • Potentially dangerous
  • Radioactive wastes

Refer to Introductory Essay p. 338
18
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
19
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
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