Module 11: Radioecology in the North

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Module 11 Radioecology in the North

• The three types of radiation
• Identify radiation as a normal part of the
  environment
• Define the concept of half-life and nuclear
  fission
• Man-made radionuclides and their effects on the
  environment

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Overview

• Awesome energies are locked in the nuclei of
  atoms (e.g. explosion of first atomic bomb in
  1945)
• All humankind shares the benefits and danger of
  atomic energy (a dilemma in itself)
• Chernobyl and Amchitka events have left a legacy
  that the circumpolar North has to deal with
• Nuclear energy represents both opportunities
  (e.g. economic benefit of uranium mining) and
  challenges (e.g. high radio-activity)

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Concepts

• Chemical Energy
• Energy produced (exothermic) or absorbed
  (endothermic) in the process of a chemical
  reaction. In such a reaction, energy losses or
  gains usually involve only the outermost
  electrons of the atoms (or ions) of the system
  undergoing change.
• Note A chemical bond is established or broken
  without disrupting the original atomic or ionic
  identities of the constituents.

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Concepts

• Nuclear energy
• Energy stored in the bonds of the sub-atomic
  particles in the nuclei of atoms. Such energy can
  be released through nuclear reaction such as (1)
  emission of radioactivity, (2) nuclear fission,
  and (3) nuclear fusion.

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Nuclear Fission
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Concepts

• Radioactivity
• The phenomenon of an unstable nucleus breaking
  down and giving off energy-loaded radiation
  (electromagnetic radiation and sub-atomic
  particles)
• Note X-rays is a form of radioactivity used in
  medical imaging (invented by Marie Curie)

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Nuclear Chemistry and Radioactivity

• Basic building block of matter is the atom
• The atom is composed of three basic particles a
  proton with a positive charge, an electron with a
  negative charge, and a neutron with no charge
• The protons and neutrons in an atom are located
  in a very small volume called the nucleus
• Each atomic element is characterized by the
  number of its electrons, its protons, and its
  neutrons
• Many atoms bonded together is called a molecule

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Nuclear Chemistry and Radioactivity (contd)

• Each element has an atomic number equal to its
  number of protons
• Hydrogen, H has atomic number 1 (1 proton in the
  nucleus)
• Radon, Rn has atomic number 86 (86 protons in
  the nucleus)
• Atoms of a given element contain the same number
  of protons, but may contain different numbers of
  neutrons in the nucleus (i.e. isotopes)
• protium (0 neutron)
• H deuterium (1 neutron)
• tritium (2 neutrons)

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Nuclear Chemistry and Radioactivity (contd)

• Protons and neutrons are held together by forces
  that are very strong
• There are limits to the stability of nuclear
  forces
• Changes of the nucleus from a less stable to a
  more stable condition always release radioactive
  emission
• Energies of nuclear reactions are 100,000 times
  as much as those associated with molecular
  re-arrangements

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Radioactivity

• Spontaneous disintegration of certain unstable
  nuclei
• Many of these unstable nuclei occur naturally
  (e.g. each of you is emitting radioactivity right
  now, due to K isotopes in your body!)
• Living organisms receive a normal dose of
  radioactivity from cosmic and terrestrial sources
• Primary terrestrial sources include carbon-14,
  strontium-90, and cesium-37 from uranium and
  thorium ores

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Alpha Decay Reaction
(Uranium) (Thorium) (Helium)
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Radioactivity (contd)

• There are 3 types of transformation by which a
  naturally occurring radioactive nuclei can decay
  
• Alpha particle (He nuclei)
• Beta particle (electrons)
• Gamma rays (photons)

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Radioactivity (contd)

• Different nuclei disintegrate, or decay, at
  different rates
• The rate of decay is reflected by the half life
  of the nuclei (13Cs 30 years half life, 14C is
  5770 years)

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Half life
2 x Half life
4 x Half life
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Sources of Radioactivity
Chernobyl (nuclear accident)
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Chernobyl Global Radiation Patterns
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Chernobyl Radiation Fallout
Released one hundred times more radiation than
the atom bombs dropped over Hiroshima and
Nagasaki
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Chernobyl Radiation Fallout
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Sources of Radioactivity Nuclear TestingAmchitka
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Amchitka
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Physics of Radioactivity

• Radioactivity emits energy-loaded particles (He
  nuclei, protons, electrons, neutrons, and
  photons)
• Damages to living tissues relate to how the
  energy of particles are dissipated
• Water, when irradiated, contains H and OH- (free
  radical) ions that are very reactive

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Radioactivity Damages to Tissues

• Radiation creates ions in our cells and these
  ions disrupt cell processes
• Radiation may alter bio-molecules like DNA (most
  important), proteins, and lipid cell membranes
• Radiation, through DNA dysfunctions, may result
  in cells becoming tumors

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Radioactivity Biological Effects
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Radioactivity the Good Parts

• The body has the ability to repair radiation
  damage
• Protection against source-radiation can be
  achieved through the use of barriers (lead,
  concrete)
• Natural sources of radiation are about 300
  mrem/year, mostly from radon-222 (a by-product of
  uranium-238 decay)

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Radioactive Contamination(due to man-made
radionuclides)
(Finland)
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Radioactive Contamination
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Radioactive Contamination
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Iodine-129 (a new issue)
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Radionuclide Behaviour in Marine Systems

• Transport pathways
• Water movements
• Precipitation
• Sediments from rivers
• Marine ecosystems are less vulnerable to
  atmospheric radiocesium than freshwater and
  terrestrial systems

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Radionuclides in Rivers
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Radionuclides in Rivers