Nuclear Energy - PowerPoint by 4qZ843

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									      BI 105A
Environmental Biology
    Professor Jill Nissen
    Montgomery College
          Fall 2006
Chapter 12
Nuclear Energy
          Chemical Energy
• Chemical energy is the energy stored in the
  bonds of molecules
• Chemical reactions involve the
forming and breaking of bonds
between atoms, but
• atoms of one element do not change to atoms
of another element, nor does any of their mass
change to energy
           Nuclear Energy
• Nuclear energy is the energy released by
  nuclear fission or fusion
• Nuclear reactions involve
changes in the nuclei of atoms,
and
• small amounts of mass are converted to
large amounts of energy:
                 E = mc2
           Nuclear Energy
• Nuclear reactions produce 100,000 times
  more energy per atom than do chemical
  reactions such as combustion
Nuclear Energy Comes
From Fission


                         Split atoms
Neutrons




           Uranium-235
Splitting Atoms Releases
Neutrons, Making Heat
                 Heat




                        Neutrons
Heat Produces Steam,
Generating Electricity
           Steam



                                  Generator
Steam
produced    Turbine


                                      Electricity
   Heat
                      Condenser
 Nuclear Power Plant
Turbine and Generator

                Steam




                        Spinning
                        turbine blades
                        and generator
Boiling water
              Uranium-235
• Uranium ore consists of 3 isotopes: U-238,
  U-235, and U-234
• Uranium is naturally radioactive
  – the emission of energetic particles or rays
    from unstable atomic nuclei
• Only U-235 is a fissionable material that can
  be used for nuclear power
 Uranium Ore Is
Mined and Refined
Enrichment Concentrates the
       U-235 Isotope
Uranium Is Encased in
Solid Ceramic Pellets
Fuel Rods Filled With Pellets
   Are Grouped Into Fuel
        Assemblies
 Controlling the Chain
       Reaction


                  Fuel
                  Assemblies

                  Control rods




Withdraw control rods,      Insert control rods,
reaction increases          reaction decreases
Pressurized Water
     Reactor

       Steam




               Condenser
          U.S. Emission-Free Electricity
                                                     (2003)

    80%


    70%


    60%


    50%


    40%


    30%


    20%


    10%


     0%
                Nuclear               Hydro      Geothermal   Wind   Solar
                  71%                  24%          1.2%      1.0%   0.1%


Source: U.S. Energy Information Administration
                              Nuclear Energy Limits Carbon
                          Dioxide Emissions in Power Sector
                       3640                       (2002)


                       3140

                                                                 3,104
                       2640
                                            29% Greater
 Million Metric Tons




                       2140       2,410

                       1640



                       1140



                        640



                        140
                                 Electric Power            Estimated Electric Power
                                  Industry CO2             Industry CO2 Emissions
Source: EPA                        Emissions                Without Nuclear Power
  Nuclear Energy Limits Sulfur Dioxide
      Emissions in Power Sector
                                            (2002)
                       14                                    13.5

                       12             33% Greater
                            10.1
                       10
  Million Short Tons




                       8


                       6


                       4


                       2


                       0
                  Electric Power Industry            Without Nuclear Power
Sources: EPA, EIA     SO2 Emissions
    International Programs
• Finland and China are adding reactors to meet
  energy demand and enhance air quality
• Germany and Sweden committed to phasing out
  nuclear power, then
  – Germany later launched a pilot program that includes
    allowances for nuclear plants
  – In 2002 Sweden removed the deadline for shut down
• Canada approved tax incentives for nuclear
  capacity
• France obtains 77% of its electricity from
  nuclear power
         U.S. Programs
U.S. phasing out
 U.S. currently ~7% of energy nuclear;
 no new U.S. power plants ordered since
  1976
 40% of 105 commercial nuclear power
  expected to be retired by 2015 & all by
  2030;
            What Happened?

   crippled by high & uncertain costs;
   frequent malfunctions (Three Mile Island,
    Chornobyl);
   false assurances and cover–ups;
   overproduction of energy in some areas;
   poor management;
   lack of public acceptance.
          Three Mile Island
• What happened,
  step by step
• http://www.pbs.org/
  wgbh/amex/three/sf
  eature/index.html
History’s Worst Nuclear Accident

• April 26, 1986 - During a test at the
  Chornobyl plant, the No. 4 reactor exploded
• April 27, 1986 – The secret was out!
• 203 hospitalized, 31 died
• Evacuation zone 30km over a month
• Thyroid cancer among children increased
• Still waiting for long-term effects
  History’s Worst Nuclear Accident

• The sum of [Chornobyl] and exposures to
  people all over the world," writes Bernard
  Cohen, "will eventually, after about fifty
  years, reach 60 billion millirems, enough to
  cause about 16,000 deaths.“ He puts
  Chornobyl's danger in context by pointing out
  that 16,000 deaths are caused every year by
  air pollution from coal-burning power plants
  in the United States alone.
  Pros and Cons of Nuclear Energy
Impact          Coal             Nuclear
Land use        17,000 ac        1,900 ac
Daily fuel
                9,000 tons/day   3 kg/day
requirement
                Moderate to
Air pollution                    Low
                severe
Radioactive
                1 curie          28,000 curies
emissions
Risk from                        Long-term risk
                Short-term       over large area
catastrophic
                local risk
accidents
Radioactive Wastes
       • Low level radioactive wastes are
         items contaminated by
         radioactivity that give off small
         amounts of ionizing radiation
       • High level radioactive wastes are
         produced by nuclear power
         plants and give off large amounts
         of ionizing radiation
          – Dangerous levels of radioactivity
            require special handling and secure
            storage
          – Case-in-Point: Yucca Mountain
          – http://msnbc.msn.com/id/3042216/
   Fuel for Nuclear Weapons

• The Link Between Nuclear Energy and
  Nuclear Weapons
                Can be
Spent fuel from reprocessed        Fuel for
 conventional for . . .        breeder reactor
 nuclear plant

                          OR     Nuclear
                                 weapons
 The Future of Nuclear Power
• The safe disposal of radioactive wastes is
  one of the main difficulties to be overcome if
  nuclear energy is to realize its potential in the
  21st centure
                  Review Objectives
Introduction to Nuclear Processes
    • Distinguish between nuclear energy and chemical energy.
    • Contrast fission and fusion.
    • Define radioactive decay.
Nuclear Fission
    • Describe the nuclear fuel cycle, including the process of enrichment.
    • Define nuclear reactor and describe a typical nuclear power reactor.
Pros and Cons of Nuclear Energy
    • Discuss the pros and cons of electric power produced by nuclear energy versus coal.
Safety Issues in Nuclear Power Plants
    • Describe the nuclear power plant accidents at Three Mile Island and Chornobyl.
    • Discuss the link between nuclear energy and nuclear weapons.
Radioactive Wastes
    • Distinguish between low-level and high-level radioactive wastes.
    • Relate the pros and cons of permanent storage of high-level radioactive wastes at Yucca
    Mountain
The Future of Nuclear Power
    • Briefly summarize the issues that must be addressed if nuclear power is to become a
    major energy source in the future.

								
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