Nuclear PoweR

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Nuclear PoweR
The discovery of nuclear reactions need not
bring about the destruction of mankind any more
than the discovery of matches -Albert
Einstein
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I. Using Nuclear Reactions to Generate Power

• A. Nuclear Fission the splitting of a nucleus
  into smaller fragments (the splitting is caused
  by bombarding the nucleus with neutrons). This
  process releases enormous amounts of energy.

A nuclear chain reaction is a reaction in which
the material that starts the reaction (neutron)
is also one of the products and can be used to
start another reaction.
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• B. Nuclear Reactors use controlled fission
  chain reactions to produce energy.

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I. Using Nuclear Reactions to Generate Power

• C. A radioisotope is a radioactive isotope
  (remember different number of neutrons).
  Uranium-235 is the radioisotope used in nuclear
  reactors to produce energy.
• D. Nuclear fission produces much more energy than
  coal or natural gas. 2.2 pounds of uranium
  produces the same amount of heat energy as 16
  tons of coal.

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I. Using Nuclear Reactions to Generate Power

• E. A nuclear reactor is just a complex device
  used to boil water, generate steam, and use that
  steam to turn a turbine.
• F. Four critical components to any nuclear
  reactor are shielding, fuel, control rods, and
  coolant.

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I. Using Nuclear Reactions to Generate Power

• 1) shielding radiation absorbing material that
  is used to decrease exposure to radiation.

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I. Using Nuclear Reactions to Generate Power

• 2) fuel uranium is most often used

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I. Using Nuclear Reactions to Generate Power

• 3) control rods neutron absorbing rods that
  help control the reaction by limiting the number
  of free neutrons

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I. Using Nuclear Reactions to Generate Power

• 4) coolant water acts as a coolant and
  transports heat between the reaction and the
  steam turbines to produce electric current

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• G. A light water reactor is the type of reactor
  used most in the world (85 worldwide, 100 in
  the U.S.).
• H. Light-water reactors are very inefficient,
  losing about 83 of the energy in their nuclear
  fuel as waste heat to the environment. Nuclear
  reactors cause huge amounts of thermal pollution
  in the lake or river with which they are
  associated.

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Coal vs. Nuclear
Coal Nuclear
Ample Supply Ample supply of uranium
High net energy yield Low net energy yield
Very high air pollution No air pollution
High carbon dioxide emissions No carbon dioxide emissions
High land disruption from surface mining Much lower land disruption from surface mining
High land use Moderate land use
Low cost (with huge subsidies) High cost (even with huge subsidies)
Long term waste storage issues
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II. Radioactive Waste

• A. Radioactive waste is the huge long-term
  problem with nuclear reactors.
• B. There are two types of radioactive wastes,
  low-level and high-level wastes.
• C. Low-level wastes contains low levels of
  radiation, and remains dangerous for a relatively
  short period (has a half-life of a few hundred
  years or less).

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II. Radioactive Waste

• D. Low level wastes includes most medical and
  university research.
• E. Low level waste can be stored on-site, for a
  few hundred years at most, and just needs to be
  stored in barrels, with shielding not required.

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F. Applications that Produce Low-Level Waste

• Carbon-14 dating
• Used to determine the age of historical artifacts
• 2) Radioactive Tracers
• In medicine
• absorbed by specific organs and used to diagnose
  disease (Iodine-131)

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• 3. Nuclear Medicine
• Radiation Treatment
• larger doses are used to kill cancerous cells
  in targeted organs
• internal or external radiation source,
• usually Cobalt-60

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II. Radioactive Waste

• G. High level nuclear waste is produced from
  spent nuclear fuel and wastes from producing
  nuclear weapons.
• H. High-level waste has high levels of
  radioactivity, is hard to store, and has very
  long half-lives (thousands to millions of years).

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II. Radioactive Waste

• I. High-level nuclear waste often stays on-site
  until it can be shipped to a permanent repository
  (if one is available). Storage must be stable for
  thousands of years, and waste must be stored in
  specially shielded containers (casks) or in water
  pools.

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III. Half-life

1. Knowing how to calculate half-life is very
   important in determining how long things will
   stay radioactive, and how long materials need to
   be safely stored.
2. Half-life means the amount of time it takes half
   of the original material to decay to a stable,
   non-radioactive form.

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C. Half-Life Equations

• Fraction remaining 1/2n
• n number of half-lives elapsed
• Amount remaining (g)
• Original amount x 1/2n
• Nt No x (1/2)n

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IV. Storing Nuclear Waste

• A. Containment on-site storage and off-site
  disposal (Remember that every radioactive
  substance has a half-life, some only a few
  months, others hundreds of thousands of years.)
• 1) On-Site Storage most common nuclear waste
  is spent fuel rods from nuclear power plants
• -water pools
• -dry casks (concrete or steel)
• 2) Off-Site Disposal disposal of nuclear waste
  is done with the intention of never retrieving
  the materials.
• -77 disposal sites around the United States
• -new site near Las Vegas, Nevada Yucca Mountain

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IV. Storing Nuclear Waste

• C. Any long term storage site needs to be very
  geologically stable, and sites are evaluated for
  the following
• Volcanic activity
• Earthquake activity
• Characterization of groundwater flow
• Estimation of changes in storage environment over
  long periods of time
• Depth of at least 2,000 ft underground
• Away from major cities/population centers

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IV. Storing Nuclear Waste

• D. All High-level nuclear waste must be stored
  for a minimum of 10,000 years, and up to 240,000
  years before it decays to stable radioactive
  levels.
• E. Most scientists and engineers agree that deep
  burial is the safest and cheapest way to store
  high-level nuclear waste.

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IV. Storing Nuclear Waste

• F. Yucca Mountain 160 miles northwest of Las
  Vegas. Process to evaluate and open a long-term
  storage facility began in 1985, may start
  accepting waste by 2017. Controversial due to
  concerns about flooding and moving waste to be
  stored there.
• G. WIPP near Carlsbad, NM. Storage facility in
  salt band 2,150 feet underground. Opened in 1999
  for long-term storage of nuclear weapons waste.

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IV. Storing Nuclear Waste

• H. Some other suggestions for long term nuclear
  storage include paying to ship to other
  countries, permanently entombing old reactors in
  layers of steel and concrete, storing under the
  deep ocean, storing under large ice sheets
  (Antarctic, Greenland), shipping off on a rocket
  to space, or storing on the moon. As of yet,
  none of these have been deemed acceptable in
  terms of risk and ethics.

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V. Effects of Radiation

• A. Radiation is so harmful for living tissue
  because it can cause DNA damage and mutation,
  cell/tissue damage, and cell death.
• B. Radiation at high enough doses is lethal, and
  at low doses can cause any of the following
  problems

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V. Effects of Radiation

• - Cancer/tumors
• Brain damage
• Eye damage or cataracts
• GI damage from nausea and vomiting
• Damage and birth defects to fetuses
• Burns
• Damage to bone marrow
• Impairment of the immune system

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VI. Nuclear Disasters

• A. The worst nuclear accident in U.S. history
  took place at Three Mile Island nuclear power
  plant in 1979. A valve malfunctioned and human
  errors led to a partial core meltdown. High
  levels of radiation were released into a
  containment structure, but only a small amount of
  radiation was released into the environment.

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VI. Nuclear Disasters

• B. Although radiation release was small, the
  state of Pennsylvania was unprepared to deal with
  a nuclear problem, and the evacuation and
  aftermath was poorly organized and led to a huge
  public mistrust in nuclear power in the U.S.

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VI. Nuclear Disasters

• C. Chernobyl, in 1986, was the worlds worst
  nuclear disaster. An explosion blew the top off a
  containment building, a reactor melted down, and
  a fire burned for 10 days, releasing more than
  100 times the radiation released by the atomic
  bombs dropped by the U.S. in WWII.
• D. A poor reactor design, combined with human
  error, caused the explosion.

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VI. Nuclear Disasters

• E. In 2008, after 22 years, areas of the Ukraine
  and Europe are still dangerously contaminated
  with radioactive materials as a result of
  Chernobyl.
• F. Eventual death estimates range from 9,000 to
  212,000 from the accident, and in contaminated
  areas rates of birth defects, thyroid cancer,
  leukemia, and immune system abnormalities are
  very common.

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VI. Nuclear Disasters

• G. Japan has come close to having a
  Chernobyl-type disaster. It is an
  earthquake-prone country that gets 39 of its
  power from nuclear reactors. In 2007 a huge
  earthquake caused severe damage to the worlds
  largest nuclear reactor.

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