Nuclear Energy

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Nuclear Energy

• SI

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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

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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

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Background Radiation
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• 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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• 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

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d. A neutron turns into a proton and an electron.
The electron gets emitted from the nucleus.
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• 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 ?

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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.
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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

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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

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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

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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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• 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

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• 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

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• 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.

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• 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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• 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

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

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