Radioactivity and Nuclear Energy

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Chapter 19
Radioactivity and Nuclear Energy
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• Strong Nuclear Force is the interaction that
  binds protons and neutrons together in a nucleus.
  These forces are greater than the electric
  repulsion among the protons.
• Facts About the Nucleus
• Very small volume compared to volume of atom
• Essentially entire mass of atom and very dense
• Composed of nucleons( protons and neutrons) that
  are tightly held together
• Every atom of an element has the same number of
  protons ( Atomic Number)
• Isotopes are atoms of the same elements that have
  different masses and Different numbers of
  neutrons
• Mass Number number of protons neutrons

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Facts About the Nucleus

• The number of neutrons is calculated by
  subtracting the atomic number from the mass
  number
• The nucleus of an isotope is called a nuclide
• less than 10 of the known nuclides are
  nonradioactive, most are radionuclides
• Each nuclide is identified by a symbol

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19.1 Radioactive Decay

• Radioactive nuclei spontaneously decompose
  forming a different nucleus and producing one or
  more particles.
• We say that radioactive nuclei are unstable
• During radioactive decay, atoms of one element
  are changed into atoms of a different element
• In order for one element to change into another,
  the number of protons in the nucleus must change
• All nuclides with 84 or more protons are
  radioactive
• We describe nuclear changes with using nuclear
  equations
• atomic numbers and mass numbers are conserved

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Types of Nuclear Radiation
Changes Resulting From Nuclear Decay
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Types of Radioactive Decay

• Alpha Decay
• 226 88Ra ? 42He 22286Rn
• Radium-226 Alpha particle Radon-222
• Beta Decay
• 21082Pb ? 21083Bi 0-1e
• Lead-210 Bismuth-210 Beta
  particle(electron)
• Gamma Ray (00? ray)
• Is a high energy photon of light.
• A nuclide in an excited nuclear energy state can
  release excess energy by producing a gamma ray.
• 238 92U ? 42He 23490Th 2 00?

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Figure 19.2 A representation of a Geiger-Müller
counter.
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• 19.7 Nuclear Fission
• Nuclear Fission is the splitting of an atom into
  two smaller atoms releasing neutrons and energy.
• One of the fission reactions that produced barium
  is
• 1 0n 23592U ? 14156 Ba 9236Kr 3 1 0n
  Energy
• The fission of 1 mol of 23592U produces about 26
  million times as much energy as the combustion of
  1 mol of methane.

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• The energy produced by nuclear fission is huge,
  and this is what makes nuclear explosions so
  devastating.
• Energy mass ? (speed of light)2
• E mc2
• c 3.0 ? 108 m/s
• If m1kg of matter
• E 1 ? (3.0 ? 108)2 9 ? 1016 J. This is more
  than the chemical energy of 8 million tons of
  TNT.

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Figure 19.5 Representation of a fission process.
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Figure 19.4 Unstable nucleus.
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Figure 19.1 The decay series.
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Nuclear Fission Reaction
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• 19.9 Nuclear Fusion
• Nuclear Fusion Involves forcing two small
  nuclei to combine into a new, heavier atom.
• The energy released by nuclear fusion is due to
  the conversion of mass to energy and it is three
  to ten times more than the energy released by
  nuclear fission.
• Nuclear fusion power the Sun and other planets.
• The nuclear fusion reactions that occur in the
  Sun are summarized by this equation
• 4 11H ? 42He 2
  01e
• Hydrogen-1 Helium-4 positrons
• Nuclear fusion has been used in hydrogen bomb.

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How a Nuclear Power Plant Works?

• Nuclear power plants run on uranium fuel. In the
  reactor, uranium atoms are split through a
  process known as fission. When atoms are spilt,
  they produce a large amount of energy that is
  then converted to heat. The heat boils water,
  creating steam that is used to turn turbines,
  which spins the shaft of a generator. Inside the
  generator, coils of wire spin in a magnetic field
  and electricity is produced.

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• Nuclear power plants in the United States use two
  types of reactors to achieve this process
  boiling water reactors and pressurized water
  reactors.
• Pressurized Water Reactors (PWR) keep water under
  pressure, so the water heats but does not boil.
  The heated pressurized water is run through
  pipes, which heat a separate water line to create
  steam. The water to generate steam is never
  mixed with the pressurized water used to heat it.
  

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The Pressurized Water Reactor (PWR) 
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• Boiling Water Reactors (BWR) heat water by
  generating heat from fission in the reactor
  vessel to boil water and create steam, which
  turns the generator. In both types of plants, the
  steam is turned back into water and can be used
  again in the process.

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Boiling Water Reactor (BWR) 
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19.10 Effects of Radiation

• The biological effects of radiation depend on
• The more energy the radiation has the more damage
  it can cause.
• The penetrating ability of the radiation in human
  tissue.
• Gamma gtgt Beta gt Alpha
• The more ionizing the radiation, the more effect
  the radiation has
• Alpha gt Beta gt Gamma

Causes serious damage
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Figure 19.8 Radioactive particles and rays vary
greatly in penetrating power.
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Dangers and Benefits of Nuclear Radiation

• Background radiation nuclear radiation that
  arises naturally from cosmic rays and from
  radioactive isotopes in the soil and air. It is
  the most common source of radiation that we are
  exposed to.
• Radioactive tracer is a radioactive material
  added to a substance so that the substances
  location can be detected later.
• Nuclear radiation can damage living cells,
  causing radiation sickness and birth defects,
  even death.
• Nuclear radiation is used in medicine to diagnose
  and treat diseases. Gamma rays can target brain
  tumors.
• Nuclear fission is an alternative to fossil fuels
  as a source of energy

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Figure 19.6 Diagram of a nuclear power plant.
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Figure 19.9 Diagram for the tentative plan for
deep underground isolation of nuclear waste.