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Nuclear Energy

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Nuclear Energy SI A. What does radioactive mean? Radioactive materials have unstable nuclei, which go through changes by emitting particles or releasing energy to ... – PowerPoint PPT presentation

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Title: Nuclear Energy


1
Nuclear Energy
  • SI

2
A. What does radioactive mean?
  • Radioactive materials have unstable nuclei, which
    go through changes by emitting particles or
    releasing energy to become stable
  • Call this nuclear decay

3
B. Types of Radiation
  1. Background Radiation radiation that the general
    population is exposed to (ex. the sun, water,
    plants)
  2. Nuclear Radiation the particles that are
    released from the nucleus during radioactive decay

4
Background Radiation
5
  • 3. Alpha Particle a positively charged atom that
    consists of two protons and two neutrons
  • Do not travel far through materials (cannot pass
    through a piece of paper)
  • Symbol 42He

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7
  • 4. Beta Particle a negatively charged electron
    emitted during radioactive decay
  • Fast-moving
  • Can penetrate sheet of paper, but stopped by
    piece of aluminum
  • Symbol 0-1e

8
d. A neutron turns into a proton and an electron.
The electron gets emitted from the nucleus.
9
  • 5. Gamma Rays high-energy radiation emitted
    during radioactive decay and nuclear fission
  • Gamma rays are a form of electromagnetic energy
  • Not stopped by clothing or most building
    materials, so are much more dangerous
  • Symbol ?

10
d) Atom goes from an excited state to a less
excited state. The nucleus does not change and a
gamma ray (unit of energy) is emitted from the
nucleus.
11
C. Decay Rates
  • Half-life time required for half of a sample of
    radioactive substance to decay
  • Use these decay rates to tell the age of rocks
    and fossils (radiometric dating)
  • Carbon-14 is common isotope used in radiometric
    dating

12
D. What makes a substance radioactive?
  • Substances with too many or too few neutrons
  • Substances with equal amounts of protons and
    neutrons are stable
  • Which isotope is more stable?
  • C-14 or C-12

13
E. What happens during nuclear decay?
  • The parent element (starting substance) decays
    into the daughter element (new substance) and
    emits radiation
  • The daughter element can be an entirely new
    element or an isotope of the parent element

14
II.) Nuclear Reactions
  • A) Nuclear Fission the process by which a
    nucleus splits into two or more smaller atoms and
    releases neutrons and energy
  • In nuclear fission, tremendous amounts of energy
    can be produced from very small amounts of mass

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16
  • Converting Mass into Energy
  • Albert Einstein introduced the mass-energy
    equation
  • E mc2
  • According to the law of conservation of mass and
    energy, the total amount of mass and energy
    remains constant

17
  • Triggering a Chain Reaction
  • Nuclear fission follows a pattern of a chain
    reaction
  • Chain reaction a continuous series of nuclear
    fission reactions Fig 8 p.296

18
  • Nuclear weapons are designed to have an
    uncontrolled chain reactions
  • In controlled chain reactions, heat from the
    reaction can be used to generate electrical
    energy
  • Critical Mass the minimum amount of a substance
    that can undergo a fission reaction and can also
    sustain a chain reaction.

19
  • Nuclear Energy From Fission
  • Nuclear power plants generate about 20 of
    electricity in the U.S.
  • Controlled fission of uranium-235 in a fission
    reactor
  • Dont emit air pollutants, but have other safety
    concerns
  • 1986 meltdown of reactor at Chernobyl nuclear
    power plant in Ukraine

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22
  • Fusion the process in which smaller nuclei fuse
    together at high temperatures and release energy
  • In nuclear fusion, tremendous amounts of energy
    can be produced from very small amounts of mass
  • Releases more energy than nuclear fission

23
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24
  1. Requires extremely high temperaturesi.e. Sun
    reaches temp of 10,000,000oC
  2. Fusion may someday provide clean and efficient
    source of electricity

25
  • Two problems creating a fusion reactor
  • Need very high temperatures to start reaction
  • Must contain plasma
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