Atomic Energy

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Atomic Energy

• 3U Physics

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Mass-Energy Equivalence

• All matter is a form of stored energy.

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Mass-Energy Equivalence

• All matter is a form of stored energy.
• If matter of mass m is converted to energy, the
  amount of energy E that can be released is equal
  to

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Mass-Energy Equivalence

• All matter is a form of stored energy.
• If matter of mass m is converted to energy, the
  amount of energy E that can be released is equal
  to
• E mc2

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Mass-Energy Equivalence

• All matter is a form of stored energy.
• If matter of mass m is converted to energy, the
  amount of energy E that can be released is equal
  to
• E mc2
• c 3.0 x 108 m/s

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Mass-Energy Equivalence Example

• What is the energy equivalent of a 52 kg person?

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Mass-Energy Equivalence Example

• What is the energy equivalent of a 52 kg person?

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Mass-Energy Equivalence Example

• What is the energy equivalent of a 52 kg person?

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The Mass Defect

• More practically, we look at the energy
  equivalent of the mass defect.

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The Mass Defect

• More practically, we look at the energy
  equivalent of the mass defect.

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The Mass Defect

• Consider a Carbon 12 nucleus

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The Mass Defect

• Consider a Carbon 12 nucleus
• 6 protons, 1.007276 amu each
• 6 neutrons, 1.008665 amu each
• 12.095646 amu

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The Mass Defect

• Consider a Carbon 12 nucleus
• 6 protons, 1.007276 amu each
• 6 neutrons, 1.008665 amu each
• 12.095646 amu
• Actual mass of Carbon 12 nucleus
• 11.996709 amu

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The Mass Defect

• The 0.098937 amu mass defect is the binding
  energy of the nucleus.
• E mc2
• E (0.098937)(1.66 x 10-27 kg)(3.0 x 108 m/s)2
• E 1.5 x 10-11 J

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The Mass Defect

• Energy stored in the nucleus can be released in
  nuclear reactions such as radioactive decay

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The Mass Defect

• Energy stored in the nucleus can be released in
  nuclear reactions such as radioactive decay
• The energy is released in the form of kinetic
  energy (of the resulting particles).

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Nuclear Fission

• However, in a nuclear reactor, we dont sit
  around waiting for a radioactive decay.

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Nuclear Fission

• However, in a nuclear reactor, we dont sit
  around waiting for a radioactive decay. We
  trigger them by bombarding nuclei with neutrons

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Nuclear Fission

• Notice that the reaction produces more neutrons,
  which can then bombard more nuclei in a chain
  reaction

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Nuclear Fusion

• Energy can also be obtained by fusing together
  light elements, e.g. hydrogen into helium

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Nuclear Fusion

• However, fusing nuclei requires overcoming the
  electrostatic repulsion between the nuclei.

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Nuclear Fusion

• However, fusing nuclei requires overcoming the
  electrostatic repulsion between the nuclei.
• This requires enormous temperatures and pressures
  such as those produced in the core of the Sun.

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Nuclear Power

• The ejected neutron has too much energy to start
  another nuclear reaction on its own

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CANDU Reactor

• Fuel rods are surrounded by heavy water
• Deuterium istotope of hydrogen with one neutron
• Makes water 11 more dense

• Heavy water heats up free neutrons slow down
• Chain reaction continues
• EK of neutron becomes Eth of water
• Steam turns turbine, generates power

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CANDU Reactor

• http//www.youtube.com/watch?vjNOzh4Kwgpw
• Is it environmentally friendly?

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Radioactive Waste

• Unstable atoms are called radioactive
• They have the ability to decay into another
  substance and emit radiation
• The rate of decay is predictable

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Half-Life

• The average length of time it takes a radioactive
  material to decay to half its original mass
• Ex. If a 10 kg sample of radioactive material has
  a half-life of 5 years, how much will be left
  after 5 years? 10 years?

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Types of Decay
Type of Decay Radiation Emitted Particle Penetrating Power
alpha alpha particle helium nucleus skin or paper (slow moving)
beta negative beta particle electron a few sheets of aluminum foil
gamma gamma rays photon a few centimetres of lead