HONR228Q Notes section j:

  • The Water Drop Model of the Nucleus

    1. Basic features of the water drop model

      1. Protons and neutrons combine randomly to form nucleus
      2. All equal, like molecules in drop of water
      3. Average binding energy per nucleon
        1. Binding energy low for very large nuclei
          1. Large nuclei break up to form more stable configuration
          2. Process called fission
        2. Binding energy very low for very small nuclei
          1. Small nuclei combine to form more stable configuration
          2. Process called fusion
        3. Binding energy maximum near A=60
          1. Nuclei with A~60 are most stable
          2. Iron is most common element on the earth
          3. Very large elements and very small elements less common
        4. The neutron excess for large nuclei
          1. Neutrons experience no repulsive electrostatic force (Coulomb force)
          2. Neutron more tightly bound, protons less tightly bound
          3. Heavier nucleus means greater neutron excess (more neutrons than protons)

    2. Models of Nuclear Fission

      1. FILM LOOP: OSCILLATING SOAP BUBBLES
        1. Model of fission
        2. Waves in a Large Free Sphere of Water: See vibrations of a water drop as analog to nuclear vibrations in fission.
      2. Features of fission
        1. Heavy nucleus "fissions," or breaks apart
        2. Produces smaller nuclei and energy
        3. Controlled fission = nuclear reactor
        4. Uncontrolled fission = "atomic bomb"
      3. Models of nuclear chain reaction
        1. FILM LOOP: CHAIN REACTION - CRITICAL MASS
          1. Describes critical mass effect
          2. Illustrates chain reaction
        2. DEMO P4-61: CHAIN REACTION - DOMINOES MODEL
        3. DEMO P4-62: CHAIN REACTION - MOUSE TRAP MODEL
          1. Models of nuclear chain reaction
          2. Each event causes more events to occur
          3. Chain reaction requires enough individuals in group

    3. Fission reactors

      1. Nuclear fission
        1. Fission process
          1. U235 used as fuel in reactor
          2. Started by slow-moving (thermal) neutrons
          3. Slow neutrons are absorbed by U235, adding energy to nucleus
          4. Adding energy causes Uranium atom to vibrate and break apart (water drop)
          5. Each fission produces more neutrons to keep chain reaction going
          6. Must have a minimum amount of U235, the critical mass, to produce chain reaction
        2. Products of fission
          1. Produces variety of fission products, some are radioactive
          2. Energy from rapidly moving fission fragments and neutrons produces heat
        3. Production of electricity
          1. Some energy removed as heat, used to boil water to run turbines
          2. Turbines same as those in a fossil fuel reactor
        4. The Virtual Nuclear Tourist ! Nuclear Power Plants Around the World
          1. Excellent web site!!
          2. Covers all areas of nuclear power
      2. Uses for reactors
        1. Production of electricity
        2. Production of fuel for atomic (fission) bombs
        3. Research on fission and reactor technology
        4. Materials research on radiation damage effects
        5. Research on interaction of neutrons with matter
        6. Research and application of neutrons in medical radiation treatment
        7. Production of neutron-rich radioisotopes for spectroscopy research
        8. Production of neutron-rich radioisotopes for commercial use
        9. Production of neutron-rich radioisotopes for medical use
      3. World-wide use of reactors for electrical energy
        1. Fission reactors contribute ~20% of US power
        2. More in some developed countries, ~75% in France and ~35% in Japan and growing
        3. Less in some developed countries, ~30% in Germany
      4. Advantages of fission reactor over fossil fuel
        1. See Bernard L. Cohen: The Nuclear Power Advantage
        2. See Coal Combustion: Nuclear Resource or Danger, by Alex Gabbard
        3. Clean "burning"
        4. No greenhouse gases
        5. Economical
      5. Disadvantages of fission reactor
        1. Uses U235, ~1% of uranium, fuel must be "enriched" to increase percentage U235
        2. Produces nuclear waste
        3. Only about 100 year supply available
      6. Breeder reactors
        1. Fuel is U238
        2. Fission process the same as U235 reactor
        3. Breeder process
          1. U238 absorbs fast neutron to become U239
          2. U239 sometimes beta decays twice to form Pu239, which fissions
          3. U239 sometimes absorbs another neutron to become U240
          4. U240 beta decays twice to form Pu240, which fissions
      7. Advantages of breeder over conventional reactor
        1. U238 is most abundant isotope, ~99% of all uranium
        2. Fuel needs much less processing
        3. Virtually indefinite supply available
        4. Can be "mined" from oceans
      8. Disadvantages of breeder reactor
        1. Pu239 can be used in nuclear bomb
        2. Pu is highly toxic and radioactive
        3. Creates nuclear waste as does U235 fission reactor

  • Present state of reactor technology

    1. Types of reactors in common use
      1. World Nuclear Association: Nuclear Power Reactors, Information Paper # 32, April 2001
      2. Listing of types of fission power reactors now in use world-wide
      3. Most common are Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR)
    2. Nuclear Chemistry 10. Nuclear Reactors
      1. Kennesaw State University nuclear chemistry web class
      2. Elementary discussion of Pressurized Water Reactor and the Hanford Weapons Reactor
    3. New reactor technology
      1. World Nuclear Association: New Reactor Technology
      2. Technical and general papers on new reactor technologies
      3. Increase efficiency and safety over previous reactor designs
    4. World Nuclear Association: US Nuclear Power Industry, Information Paper # 41 May 2001
      1. Summary description of United States nuclear power industry
      2. Industry based views
      3. Covers many areas, including performance, safety, advanced designs, and nuclear waste

  • Nuclear Fusion

    1. Features of fusion
      1. Very small nuclei "fuse," or combine
      2. Produces larger nucleus and energy
      3. Controlled fusion = fusion reactor
      4. Uncontrolled fusion = "hydrogen bomb"

  • Fusion reactor

    1. Reactor mechanism
      1. Diagram of a Hypothetical Fusion Power Plant
      2. Use H, D, T, He3 as fuel
      3. Fusion produces He4 and energy
      4. Fusion process description
        1. Plasma of light gases confined by magnetic field
        2. Plasma formed of small nuclei, electrons, and gas ions
        3. Plasma squeezed by increasing magnetic field; process called "theta pinch"
        4. Fusion occurs when nuclei get within nuclear force range
      5. Electricity production from heat same as other generators
      6. Fusion process reaction summary
        1. Start with deuterium plasma
        2. d + d à He3 + n + 3.27 MeV (produces He3)
        3. d + d à t + p + 4.03 MeV (produces tritium)
        4. d + He3 à alpha + p + 18.3 MeV (heats coolant)
        5. d + t à alpha + n + 17.6 MeV
        6. Ealpha = 3.54 MeV (feeds reaction); En = 14.1 MeV (heats coolant)
      7. DEMO K2-62: CAN SMASHER - ELECTROMAGNETIC
        1. Demonstrates squeezing by "Theta Pinch"
        2. Alternative explanation involves several laws of electromagnetism
    2. Advantages of fusion reactor
      1. Produces very large amount of energy per event
      2. Infinite supply of fuel (hydrogen and deuterium)
      3. Relatively clean - very little nuclear waste
      4. Inherently safer than fission reactors
    3. Disadvantages of fusion reactor
      1. They evoke even more fear than fission reactors
      2. They seem to be a long way off
      3. There may be inherent problems with their development
    4. Future of nuclear fusion
      1. Subject for contemporary research
      2. Research recently cut back due to lack of rapid progress
      3. Best efficiency yet attained: energy out ~ energy in
      4. Not viewed hopefully in near term
      5. May be very important in long term

  • Cold fusion

    1. Method 1: D2O and palladium electrodes
      1. Theory
        1. Paladium electrodes immersed in heavy water (D2O)
        2. Deuterium absorbed by paladium electrodes
        3. Two deuterons pulled close enough to cause fusion into He4
        4. Resulting energy would be harnessed to create steam for turbine
      2. Critical comments
        1. Generally accepted as false conclusion
        2. Lack of nuclear physics expertise by experimenters
        3. No peer review - published in popular magazine
      3. Minimal research still continuing
    2. Method 2: Sonoluminescence with neutron seeding
      1. Container of heavy water
      2. Neutrons injected to cause bubbles
        1. Bubbles expand rapidly
        2. Bubbles then implode creating sonoluminescence
        3. Inward pressure pushes deuterons together, initiating fusion process
      3. More plausible scenario
      4. Submitted to legitimate journals
      5. Rejected virtually unanimously by referees
      6. Published anyway
      7. Active research continuing in several laboratories
    3. Which of these might you believe, if either?

  • Nuclear bombs

    1. "Atomic" bomb
      1. Fuel
        1. U235
        2. Pu239
      2. Fission process in bombs
        1. "Uncontrolled" fission
        2. Critical mass of Uranium forced into close proximity by explosion
        3. Exposed to source of slow neutrons to start process
        4. Moderator in material slows down neutrons so they will continue the chain reaction
        5. Neutrons not absorbed so fission will occur rapidly
      3. Nuclear Chemistry 9. The First Atomic Bombs
        1. Kennesaw State University nuclear chemistry web class
        2. Elementary discussion of technical aspects of first atomic bombs
    2. "Hydrogen" bomb
      1. Fuel is Lithium deuteride
        1. Description of hydrogen bomb from Encyclopedia.com
        2. LiD layer squeezed between two layers of fissionable material to induce fusion
        3. Lithium breaks up
        4. Lithium nuclides and deuterium create fusion as described above
      2. Fusion process in bomb
        1. Fission explosion used to squeeze fusion fuel
        2. Uncontrolled fusion explosion occurs
        3. More powerful than fission bomb
        4. Less radioactive residue than with atomic bomb
        5. Sometimes called the "thermonuclear bomb"
      3. Variations on the thermonuclear bomb
        1. Neutron bomb
        2. Cobalt bomb
    3. Use of reactor fuel to produce Pu239 bomb
      1. U238 breeds Pu: first Pu239 then Pu240
      2. Pu240 too unstable to use in bombs (might go off spontaneously)
      3. Must change fuel rods often to remove Pu239 for bombs
      4. "Commercial" nuclear power reactor used for too long to produce weapons grade Pu
      5. "Research" reactor core changed more often so Pu may be weapons grade
    4. Radiological bomb
      1. Uses conventional (non-nuclear) explosive device
      2. Contains radioactive material
      3. Explosion scatters radioactive material
      4. Damage not extensive
      5. Fear factor more important

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