Nuclear Chemistry

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Nuclear Chemistry

• What is it?
• What are our options?
• Is it safe?

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How many times did I say it, Harold? How many
times? Make sure that bomb shelters got a can
opener--aint much good without a can opener, I
said.
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Energy and Atoms

• Becquerels Experiment
• The Alchemists Dream
• Radioactive Decay--the spontaneous breakdown of
  unstable nuclei by emission of particles and/or
  energy
• Electromagnetic Radiation

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Properties of Electromagnetic Radiation

• Form of energy has no mass
• Speed of light
• Can travel through vacuum
• Emitted by excited or decaying atoms
• Moves as photons, each with characteristic
  frequency
• Higher frequency higher energy

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Electromagnetic Spectrum
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Ionizing v. Nonionizing Radiation

• Ionizing radiation--highest energy high energy
  EMR (X-rays ?-rays) or high energy electrons,
  ions or other emitted particles
• Can cause electrons to be ejected from chemical
  bonds, thus disrupting those bonds can cause
  serious damage
• All nuclear radiation

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Non-Ionizing Radiation

• Lower energy
• UV, Visible, Lower end of spectrum
• Can excite atoms
• Microwaves
• Can still be harmful--(sunburn)
• Baseball v. bullet

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Roentgens Discovery

• 1895, Wilhem Roentgen discovers X-rays
• Bequerels Experiment
• Pierre and Marie Curie--Ra, Po

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3 Types of Nuclear Radiation

• Rutherford again!
• 1899--Radioactivity consisted of two different
  rays, ? and ?
• Later ? rays were also found

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Properties of Radiation Types
00g
0-1 ?
a 42He
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Isotopes and Radioisotopes

• Isotopes--same number of protons, different
  numbers of neutrons, and therefore different
  masses
• Radioisotopes--radioactive isotopes
• Isotope notation

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Radioactive Decay

• Geiger counter
• Intensity--cpm
• Background radiation
• Pre-lab
• Which type of radiation is the most penetrating?
  What material shields best?
• What effect does distance have on exposure?
• How much material is needed for shielding?

See handout!
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Natural Radioactive Decay

• Alpha Decay
• 42He2 (helium nucleus)
• Masses on top and bottom must remain same
• Net effect Mass decreases by 4 and atomic
  number decreases by 2

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Alpha Decay

• 23892U --gt 42He ____
• 21084Po--gt 42He ____

a
a
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Alpha Decay

• 23892U --gt 42He 23490Th
• 21084Po --gt 42He ____

a
a
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Alpha Decay

• 23892U --gt 42He 23490Th
• 21084Po--gt42He 20682Pb

a
a
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Radioactive Decay (Contd.)

• Beta Decay
• 0-1 ? (fast moving electrons emitted from
  nucleus)
• Net effect Mass stays same, atomic number
  increases by 1

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Beta Decay

• 9038Sr --gt 0-1b ____
• 3617Cl--gt 0-1e ____

b
b
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Beta Decay

• 9038Sr --gt 0-1b 9039Y
• 3617Cl--gt 0-1e ____

b
b
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Beta Decay

• 9038Sr --gt 0-1b 9039Y
• 3617Cl--gt 0-1e 3618Ar

b
b
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Radioactive Decay (Contd.)

• Gamma Decay
• Only energy is released
• Symbol m for metastable sometimes used

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Gamma Decay

• 9943Tcm --gt 00g _____

g
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Gamma Decay

• 9943Tcm --gt 00g 9943Tc
• Notice the gamma carries away energy leaving a
  more stable atom behind.

g
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Half-Life

• One half-life is the time it takes for one-half
  of the atoms in a sample to decay
• Half-lives vary greatly
• Remaining (Initial amt.)(.5)n
• Amount
• n total time /length of one half-life number of
  half-lives

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Radiation Detectors

• Scintillation Counters
• Solid-state Detectors
• Cloud chambers

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Artificial Radioactivity

• Nuclear Transmutation
• Target nucleus-stable isotope being bombarded
• Projectile-bullet
• Product--heavy nucleus produced
• Ejected particle--light nucleus
• Equations very similar to Decay Equations

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Nuclear Energy

• Hahn and Strassman--1938--bombarded U with
  neutrons didnt understand results
• Lise Mietner--explained results neutron had
  split atom into two nearly equal parts
• Worlds first nuclear fission reaction

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Nuclear Fission

• Fission releases at least a million times as much
  energy as that produced by any chemical reaction
• Strong force--holds protons and neutrons together
  in nucleus source of nuclear energy 1000 x
  stronger than electrical forces holding
  atoms/ions together in chemical bonds

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Nuclear Fission (contd)

• E mc2
• Complete conversion of one gram of matter to
  energy would release energy equivalent to burning
  700,000 gallons of gasoline
• Chain reactions
• Critical mass

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Nuclear Power Plants

• First reactors designed during WWII solely to
  produce Pu-239 for atomic bombs
• Today about 80 commercial reactors produce
  electricity.
• In 1984, nuclear power met 4.85 of our total
  energy needs and 13.56 of our electrical energy
  needs

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Nuclear Power Plants

• Both nuclear and coal-fired plants generate
  electricity by boiling water to make steam-turned
  turbines
• Fuel Rods--Most is U-238 only 3 is U-235
  (fissionable) about 1/3 replaced yearly
• Control Rods--Absorb neutrons B or Cd

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Nuclear Power Plants

• Moderator
• Slows down neutrons to enhance fission
• Made of heavy water, light water, or graphite
• Generator
• Steam-turned turbines, just like coal-fired plants

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Nuclear Power Plants

• Cooling System--Core surrounded by concrete 2-4 m
  thick
• Water used as coolant
• Reactor housed in steel-reinforced concrete
  designed to withstand chemical explosion or
  earthquake

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Nuclear Fusion

• Energy released from fusing two light nuclei
  together
• Powers sun and stars
• Hydrogen bomb
• Extremely high temps needed
• Confinement very expensive
• Not currently feasible

Deuterium-tritium fuel pellet in the path of a
laser, used for laser fusion
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Benefits of Radioisotopes

• Tracers and Irradiators
• Tracers--radioisotopes with short half-lives used
  to find out what is happening in a chemical
  reaction, locate tumors, locate damaged areas,
  locate bone cancers, etc...
• Thyroid treatment with I-131 Co-60 used in many
  caner treatments

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Benefits of Radioisotopes

• Irradiators--radioisotopes used to put radiation
  in specific place
• Sterilization of medical equipment
• Destroy microorganisms in food
• Seal plastic containers
• Used frequently in other countries US just
  getting around to approving more currently about
  35 irradiators operating in US

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Measuring Radiation

• Rad (radiation absorbed dose)
• Rem (roentgen equivalent man)
• SI Units gray, sievert
• Curies

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Rem Advantage

• Measures tissue damage regardless of radiation
  type

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Factors Affecting Biological Damage From Radiation

• Dose
• Length of time of exposure
• Area of body exposed
• Tissue type exposed

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Natural Sources of Exposure

• Cosmic rays
• Radioisotopes in rocks, soil, groundwater
• Radioisotopes in atmosphere

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Human Sources of Exposure

• Fallout from nuclear weapons testing
• Air travel
• X-rays
• Radioisotopes released into environment by
  nuclear power generation and other used of
  nuclear technology

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Radon in Homes

• Better insulated homes allow Rn to build up
• Produced when U in soil decays
• Inhaled as gas decays in lungs to produce solid
  Po

http//www.epa.gov/radon/zonemap/georgia.htm
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Sources of Ionizing Rad. in US
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Nuclear Waste

• Federal law requires spent fuel rods from nuclear
  power plants to be stored at each reactor site
  space is limited
• Military waste is greater than commercial waste
• Illegal for military to use rods from civilian
  reactors
• 1980 NRC declared technology for disposal
  available, but acceptable sites must be found

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Nuclear Waste

• Vitrification after cooling 7-10 years
• Pu buried in KY WA
• We have to do something with it!!!!

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2 Nuclear Accidents

• Chernobyl, Ukraine, USSR, April 26,1986
• Reactor 4 Explosion
• 30 people died
• 400 x more radioactivity than Hiroshima,
• About 300,000 evacuated
• Epidemic of thyroid cancer in children (4000
  children and teenagers to date)
• Psychological effects depression, fear,
  alcoholism,
• Cataracts, heart disease, leukemia, other
  cancers, estimate 4000 will die
• Government aid recipients ostracized
• Shelter (Sarcophagus) needs repair to begin
  late 2006

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Three Mile Island

• Harrisburg, Pennsylvania, 1979
• Partial meltdown of one reactor
• No one died
• Mechanical failure caused a valve to stay open,
  releasing too much water reactor overheated and
  partially melted.
• About 1mrem to the 2 million people exposed

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Nuclear Power Near You!

• Plant Hatch, Near Baxley, GA, not too far from
  Savannah, about 243 mi. from here
• Plant Vogtle, Near Waynesboro, GA, about half-way
  between Atlanta and Savannah, NE of Macon, about
  192 mi.
• Link to Southern Co.s web site