Nuclear

1
Chapter 11

• Nuclear

2
PGE Bill

• PGE Website

3
Definitions

• Combustion- chemical reaction
• Nuclear- changes w/in the nuclei of atoms
• Fission- large atoms split into 2 smaller atoms
  of different elements
• Fusion- 2 smaller atoms combine to make 1 larger
  atom of a different elements

4

• Nuclear reactions produce 100,000x more than
  energy per atom than chemical reaction
• The atom
• Atomic Mass- sum of protons neutrons in nucleus
• Atomic Number- of protons per atom

5
More Definitions

• Isotopes- forms of a single element that differ
  in atomic mass (due to different of neutrons)
• Radioisotopes- unstable isotope that
  spontaneously emit a form of energy consisting of
  particles (radiation)
• Radioactive Decay- process of a radioisotope
  emitting radiation whose nucleus changes into the
  nucleus changes into the nucleus of a different
  element as a result of the radiation
• Radioactive half-life- period of time required
  for one half of the total amount of a radioactive
  substances to change into different material
  (daughter product)
• Nuclear power plants use fission.

6
Nuclear Fission

• Uses uranium as fuel
• Non-renewable resources
• Found predominantly in Australia, Africa, North
  America (Winnowing, Texas, Colorado, New Mexico
  Utah)

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• 3 main uranium isotopes
• U-238 99 of ores, not fissionable, waste
  product of conventional nuclear fission
• U-235 0.71 of ore, used in conventional nuclear
  fission but must be refined to 3 (enrichment)
  (Bomb grade is 20)
• U-234 lt0.01 of ore

8
Fission Process

• Enriched uranium (U-235) ore formed into pellets
  placed in fuel rods
• Fuel rods put into fuel assemblies placed in
  reactor vessel
• Reaction controlled by control rod
• In fission process, U-235 is bombarded w/
  neutrons which splits the atom releasing energy
  daughter product

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• Energy is in form of heat gt used to form steam
  generate electricity (steam turns turbine which
  turns generator which makes electricity)
• Fission occurs in reactor core
• Condenser used to cool steam

10

• http//reactor.engr.wisc.edu/pics/reactor2.gif

11
Water cooling

• 3 water circuits
• Primary (closed)- pulls heat from reactor core
• Secondary (closed)- moves heat from primary
  circuit and turn turbine
• Tertiary- cooling water to cool secondary circuit
• Reactor vessel and generator/water system are in
  containment building

12
Breeder Nuclear Fission

• Alternate type of nuclear fission
• Uses U-238 and changes it into Pu (plutonium)
  -239 to use as a fuel in the reactor
• Breeder reactors use have many safety problems.
  Main one is use of liquid sodium as coolant (a
  highly reactive metal that explodes when in
  contact with water and burns spontaneously in air
  at high temperature)
• Plutonium also used in nuclear weapons

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What are the advantages and disadvantages of
Nuclear Power?

• Advantage of nuclear- less environmental impact
  than fossil fuels
• Disadvantage- radioactive waste spent fuel gt
  storage problems

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Nuclear Power in US

• 104 nuclear power plants in US (434 world wide)
  supply 19 of nations electricity
• Nuclear plants regulated by US Department of
  Energy, Nuclear Regulator Agency

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• Internationally- Intl Atomic Energy Agency
  (IAEA)
• Effects of ionizing radiation (contains enough
  energy to eject electrons from atoms) damages DNA
  (mutations) resulting in birth defects, mental
  retardation or genetic disease
• Mutations in genes controlling cellular growth
  may convert them oncogenes (genes that cause
  cancer)

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What do we do with the waste?

• 1 problem with plants dealing with wastes
• 2 types of waste
• Low-level radioactive wastes- radioactive solids,
  liquids and gases that give off small amounts of
  ionizing radiation and include glassware, food,
  paper, clothing, etc.
• High-level radioactive wastes- radioactive
  solids, liquids and gases that initially give off
  large amounts of ionizing radiation and include
  reactive metals, coolants fluids and reactor gases

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• 1980 Low-level Radioactive Policy Act
• Specified all states are responsible for the
  wastes they generate and encourage states to
  develop faculties to handle low-level wastes
• No permanent facility for high-level wastes
  (Yucca Mountain is proposed location)
• 72 temporary sites in US
• 1982 Nuclear Waste Policy Act- requires federal
  government to find permanent disposal site and be
  operational by 1998

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Pros/Cons of Yucca Mountain

• Near volcano and earthquake fault line
• Transportation of high level wastes is a problem
• Dry areagtdeep ground water

19
Decommissioning (closing) Nuclear Power Plants

• Storage- simply guard the plant for 50-100 years
  during which some radioactive material will decay
  and is safer to handle
• Entombment- permanently encast plant in concrete
  (problem tomb will have to remain intact for at
  least 1000years) Chernobyl- heat of radiation
  caused concrete to crack
• Decommission- dismantle plant after it closes.
  All materials taken to permanent storage sites
  after torn down

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Radioactive Waste Disposal

• Liquid wastes- highly unstable and difficult to
  monitor must be converted to solid form via
  vitrification (conversion to solid glass or
  ceramic logs)
• Solid Waste- Consolidation and storage/monitoring
  underground

21
Fusion

• Combining 2 lighter atoms into one large one
  producing very large amounts of energy
• Animation
• Isotopes of hydrogen (heavily hydrogen or
  deuterium) used for the process
• Radioactive Tritium is formed by fusion
  (man-made not found in nature)
• Tritium and deuterium formed together to create
  energy and Helium-4

22
Fusion

• Advantage- no high-level radioactive wastes
  (low-level wastes produced)
• 1 problem- requires very high temperature
• 2 problem- confining fuel
• Super heated ionizing gas (plasma) has tendency
  to expand and nuclei arent close together and
  will lose energy when hit container wall (looking
  _at_ magnetic fields for containment)