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Nuclear Reactions


Nuclear Reactions: AN INTRODUCTION TO FISSION, FUSION, AND NUCLEAR POWER * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Nuclear reactions deal with ... – PowerPoint PPT presentation

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Title: Nuclear Reactions

Nuclear Reactions
  • Nuclear reactions deal with interactions between
    the nuclei of atoms
  • The focus of this presentation are the processes
    of nuclear fission and nuclear fusion
  • Both fission and fusion processes deal with
    matter and energy

Matter and Energy
  • Previous studies have taught us that matter and
    energy cannot be created nor destroyed
  • We now need to understand that Matter and Energy
    are two forms of the same thing

E mc2
  • Matter can be changed into Energy
  • Einsteins formula above tells us how the change
  • In the equation above
  • E Energy
  • m Mass
  • c Speed of Light (Universal Constant)

E mc2
  • The equation may be read as follows
  • Energy (E) is equal to Mass (m) multiplied by
    the Speed of Light (c) squared
  • This tells us that a small amount of mass can be
    converted into a very large amount of energy
    because the speed of light (c) is an extremely
    large number

Fission notes
  • Fission may be defined as the process of
    splitting an atomic nucleus into fission
  • The fission fragments are generally in the form
    of smaller atomic nuclei and neutrons
  • Large amounts of energy are produced by the
    fission process

Fission notes
  • Fissile nuclei are generally heavy atoms with
    large numbers of nucleons
  • The nuclei of such heavy atoms are struck by
    neutrons initiating the fission process
  • Fission occurs due to electrostatic repulsion
    created by large numbers of protons within the
    nuclei of heavy atoms

Fission notes
  • A classic example of a fission reaction is that
    of U-235
  • U-235 1 Neutron
  • 2 Neutrons Kr-92 Ba-142 Energy
  • In this example, a stray neutron strikes an atom
    of U-235. It absorbs the neutron and becomes an
    unstable atom of U-236. It then undergoes
    fission. Notice that more neutrons are released
    in the reaction. These neutrons can strike other
    U-235 atoms to initiate their fission.

Fission notes
  • The fission process is a natural one. A French
    researcher found a natural uranium reactor in
    Gabon, West Africa it has been estimated to be
    over 2 billion years old
  • Fission produces large amounts of heat energy and
    it is this heat that is captured by nuclear power
    plants to produce electricity

Fusion notes
  • Fusion is a nuclear reaction whereby two light
    atomic nuclei fuse or combine to form a single
    larger, heavier nucleus
  • The fusion process generates tremendous amounts
    of energy refer back to Einsteins equation
  • For fusion to occur, a large amount of energy is
    needed to overcome the electrical charges of the
    nuclei and fuse them together

Fusion notes
  • Fusion reactions do not occur naturally on our
    planet but are the principal type of reaction
    found in stars
  • The large masses, densities, and high
    temperatures of stars provide the initial
    energies needed to fuel fusion reactions
  • The sun fuses hydrogen atoms to produce helium,
    subatomic particles, and vast amounts of energy

Review notes
  • Mass and Energy are two forms of the same thing
    neither can be created nor destroyed but mass can
    be converted into energy (E mc2)
  • Fission is a nuclear reaction in which a heavy
    atomic nucleus is split into lighter atomic
  • Fusion is a nuclear reaction in which 2 light
    atomic nuclei are combined into a single, heavier
    atomic nucleus

Nuclear reaction notes
  • Chain reaction occurs when a Uranium atom splits
  • Different reactions
  • Atomic Bomb in a split second
  • Nuclear Power Reactor more controlled, cannot
    explode like a bomb

History of nuclear power
  • 1938 Scientists study Uranium nucleus
  • 1941 Manhattan Project begins
  • 1942 Controlled nuclear chain reaction
  • 1945 U.S. uses two atomic bombs on Japan
  • 1949 Soviets develop atomic bomb
  • 1952 U.S. tests hydrogen bomb
  • 1955 First U.S. nuclear submarine

Atoms for Peace
  • Program to justify nuclear technology
  • Proposals for power, canal-building, exports
  • First commercial power plant, England 1956

Economic advantages notes
  • The energy in one pound of highly enriched
    Uranium is comparable to that of one million
    gallons of gasoline.
  • One million times as much energy in one pound of
    Uranium as in one pound of coal.

Emissions Free notes
  • Nuclear energy annually prevents
  • 5.1 million tons of sulfur
  • 2.4 million tons of nitrogen oxide
  • 164 metric tons of carbon
  • Nuclear often pitted against fossil fuels
  • Some coal contains radioactivity
  • Nuclear plants have released low-level radiation

Nuclear Power Plants
Nuclear power around the globe
  • 17 of worlds electricity from nuclear power
  • U.S. about 20 (2nd largest source)
  • 431 nuclear plants in 31 countries
  • 103 of them in the U.S.
  • Built none since 1970s (Wisconsin as leader).
  • U.S. firms have exported nukes.
  • Push from Bush/Cheney for new nukes.

Countries Generating Nuclear Power
Technology depends on operators
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Nuclear Reactor Process
  • 3 enriched Uranium pellets formed into rods,
    which are formed into bundles
  • Bundles submerged in water coolant inside
    pressure vessel, with control rods.
  • Bundles must be SUPERCRITICAL will overheat and
    melt if no control rods. Reaction converts water
    to steam, which powers steam turbine

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Nuclear Reactor Structure
  • Reactors pressure vessel typically housed in 8
    of steel
  • 36 concrete shielding
  • 45 steel reinforced concrete

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Back end Radioactive waste
  • Low-level wastes in commercial facilities
  • Spent fuel in pools or dry casks by plants
  • Nuclear lab wastes
  • Hanford wastes leaked radiation into Columbia
  • High-level underground repository
  • Yucca Mountain in Nevada to 2037
  • Wolf River Batholith in Wisconsin after 2037?
  • Risks of cracks in bedrock, water seepage

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Yucca Mountain
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Radioactive Waste Recycling
  • Disposal of radioactive waste from nuclear power
    plants and weapons facilities by recycling it
    into household products.
  • In 1996, 15,000 tons of metal were received by
    the Association of Radioactive Metal Recyclers .
    Much was recycled into products without consumer
  • Depleted Uranium munitions for military.

Summary notes
  • Nuclear energy has no typical pollutants or
    greenhouse gasses
  • Nuclear waste contains high levels of radioactive
    waste, which are active for hundreds of thousands
    of years.
  • The controversy around nuclear energy stems from
    all parts of the nuclear chain.