The Nucleus by wanghonghx

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Seated
 The Nucleus
   Physics is Phun
October/November 2008
Topics:
Nuclear structure
Nuclear reactors
Nuclear radiation
Useful radiation effects
Nu-cle-ar
    good 


Nu-cu-lar
 not so good 
The Electromagnetic Spectrum

    ―Waves‖                  ―Photons‖

    c=fλ                    E=hf
c = the speed of light    E = photon energy
    f = frequency        h = Planck’s constant
   λ = wavelength            f = frequency
  Infrared

Visible light

Ultraviolet
  ―Members‖
     of the
Electromagnetic
   Spectrum
     Atomic models:
1. the ―plum-pudding‖ model
    2. the ―nuclear‖ model
 (tiny nucleus with electrons
     in much larger orbits)
Beryllium
atom
(without
neutrons!!)
The Hydrogen
Balmer Series
       The Nucleus
 1. Protons (positive charge)
 2. Neutrons (neutral charge)
3. Nuclear Diameter ~10   -15 m

 (atomic diameter ~10  -10 m)

 The term ―nucleon‖ refers to either a
 proton or a neutron in the nucleus.
The term ―nuclide‖ refers to a nucleus with
a specific number of protons and neutrons.
The Chart of Nuclides
Stable Nuclides   All Known Nuclides
Nuclear models:
1. the ―water-drop‖ model
    2. the ―shell‖ model
   Models describe aspects
   of the structure of nuclei
   and how they behave.
The water-drop model
  all nucleons ―undifferentiated‖
binding energy is equally distributed
  Binding Energy
BE = M(Z protons) + M(N neutrons) –
M(Nucleus)
      Atomic Number: A = Z + N
BE is the energy required to separate
       the full nucleus into its
  individual protons and neutrons
             E = mc     2
Average Binding energy per nucleon
 Applications of the
 water-drop model
       1. Nuclear fission
  (very large nuclei break up)
       2. Nuclear fusion
(very small nuclei fuse together)
Nuclear fission
235U + n –—> small nuclei
       + neutrons
       + ENERGY!!
 n + 235U –—> another fission
creating a ―chain reaction‖
Vibrating
water drop
 Click title above to see video
Critical Mass
   Click title above to see video
    Nuclear
 Chain Reaction
Mousetrap Model
   Click title above to see video
Uncontrolled fission:
     Atomic bomb
 (235U or 239Pu bomb)

 Controlled fission:
   Nuclear reactor
Pressurized Water Reactor




From: Joseph Gonyeau, P.E., Virtual Nuclear Tourist
           http://www.nucleartourist.com/
Advantages of Nuclear Power:
1. Clean (no air pollution, including
     greenhouse gases)
2. Safe compared with other fuels
3. Price competitive with fossil fuels
4. 100 year supply of 235U
5. Infinite supply (>10,000 years) of
     238U (if we use breeder reactors)
Patrick Moore*: Going Nuclear
A Green Makes the Case
(for Nuclear Power)
OUTLOOK, Washington Post,
April 16, 2006

*Co-founder of Greenpeace (ca. 1970)
In the early 1970s when I helped
found Greenpeace, I believed that
nuclear energy was synonymous
with nuclear holocaust, as did
most of my compatriots. ….
…. Thirty years on, my views
have changed, and the rest of the
environmental movement needs
to update its views, too, because
nuclear energy may just be the
energy source that can save our
planet from another possible
disaster: climate change.
"It doesn’t matter what is
true; what matters is what
people think is true."
   Founder, Greenpeace (2000)
UM Reactor Core




        Blue Cerenkov radiation
UM Reactor Core




        Blue Cerenkov radiation
             Not green, Homer!
Nuclear fusion
 2D   +   2D –—>   larger nuclei
           + LOTS OF ENERGY        !!
Average Binding energy per nucleon
   “Theta Pinch”
electromagnetic squeezing
     to produce fusion
Nuclear Shell Model
      Discrete energy levels
    for protons and neutrons
               and
 discrete energies for radiation
   when energy levels change
 or following radioactive decay
     Radiation types:
Alpha particle (2 Ps + 2 Ns: 4He nucleus)
     Beta particle (- or + electron)
  Gamma ray (photon energy packet)

               Neutrons

             Cosmic Rays
Radiation Exposure
Sources of radiation exposure:
1. Natural Exposure
2. Man-made Exposure
Natural Exposure:
1. Radon gas
2. Cosmic Rays
3. External Environment
4. Internal: The Body
238U   Decay Chain
Cosmic Rays:
1. Cosmic ray muons
2. Other particles
Cosmic Radiation
Man-made radiation:
1. X-rays and γ-rays
2. Nuclear medicine
3. Consumer products (food, etc.)
Sources of Radiation Exposure




   From: National Institutes of Health
Useful Radiation Effects I
Nuclear Power
Medical:
   Diagnostic scans, tracers
   Magnetic resonance imaging
   Cancer radiation treatment
   Plutonium powered pacemaker
   Medical, dental sterilization
Useful Radiation Effects II
Polymer cross-linking
    Shrink tubing (eg., turkey wrapping)
    Ultra-strong materials (eg Kevlar)
    Tires (replaces vulcanization)
    Flooring
Food irradiation
    Sterilization of meat
    Disinfestation of grain and spices
    Increase shelf life (eg, fruits, veggies)
The ―radura.‖
Useful Radiation Effects III
Absolute sterilization of food:
    hospitals and space travel
Radioactive dating
Insect control
Semiconductor doping
Testing of space computer technology
Environmental studies:
    air purity, global warming, ozone
  The
Nuclear
 Waste
 Test
      Test Question #1
 Suppose that all of the electrical
 energy for the world for the next
  500 years were obtained from
nuclear reactors. Further suppose
that all of the nuclear waste from
these reactors were dissolved and
 spread uniformly throughout the
       oceans of the world.
Which statement is true:
1. The oceans would be a vast wasteland,
   unable to support life.
2. Much death and damage to ocean life
   would be caused.
3. Any effect would be so small that it
   would be virtually impossible to see
Which statement is true:
1. The oceans would be a vast wasteland,
   unable to support life.
2. Much death and damage to ocean life
   would be caused.
3. Any effect would be so small that it
   would be virtually impossible to see
      Test Question #2
     Consider all of the people
throughout history who have been
   exposed to man-made nuclear
 radiation, such as Hiroshima and
Nagasaki, Chernobyl, Three Mile
    Island, nuclear bomb tests,
       accidental spills, etc.
   Which number most nearly
 approximates how many children
 conceived and born later to these
people suffered genetic damage due
 to a parent’s exposure, excluding
    exposure during pregnancy?
          1. ~ millions
         2. ~ thousands
              3. zero
   Which number most nearly
 approximates how many children
 conceived and born later to these
people suffered genetic damage due
 to a parent’s exposure, excluding
    exposure during pregnancy?
          1. ~ millions
         2. ~ thousands
              3. zero
        Reference materials:

Nuclear Physics and Society web site

Joseph Gonyeau's Virtual Nuclear Tourist!
    Nuclear Plants Around the World

          Albert B. Reynolds:
     Bluebells and Nuclear Energy;
Cogito Books, Madison, Wisconsin (1996)
A Nuclear Sunset
          The End
    See you in January!
―ELECTRICITY AND MAGNETISM‖
         We are on the web at
  http://www.physics.umd.edu/lecdem/



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