Physics 362

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Physics 362 week 7

• Modern Physics Seminars

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The energy challenge
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The energy challenge
HDI longevity (life expectancy), educational
attainment, and standard of living (gross
domestic product per capita)
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How to produce electricity?

• Conversion of mechanical energy into electricity
  (dynamo)
• Conversion of chemical energy into electricity
• Conversion of nuclear energy into electricity
• Conversion of solar energy into electricity

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Energy sources

• Oil, Natural Gas, and Coal
• Nuclear
• Solar
• Solar Cells
• Water Power plants
• Windmills
• Biomass
• Hydrogen

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Energy sources
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Cost of energy production
Photovoltaic cells 0.2-0.3 per kW h Wind
turbines 0.04-0.05 per kW h Gas
0.02 per kW h
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Carbon reduction
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Carbon Reduction
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World and U.S. reserves
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Nuclear Energy Production
E m c2
?
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Chronology
1905 Emc2 Einstein 1939 First nuclear fission
Hahn and Strassmann 1942 First nuclear reactor
Fermi 1951 First reactor to generate electricity
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Nuclear Forces

• EM repulsion between protons
• Nuclear attraction

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Binding Energy

• BE gt 0
• Higher Binding energy means more stable nuclei
• ltBE/Agt 8 MeV/nucleon
• BE/A constant for Agt20

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Energy production
If BE/A initial lt BE/A final ? Einitial S Mjc2
S (ZjmpNjmn)c2-BEj/AjAj Efinal S Mic2
S (ZimpNimn)c2-BEi/AiAi ? Efinal - Einitial
S BEi/AiAi - S BEj/AjAj gt 0
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Energy production
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Uranium Isotopes
Isotope Percent Half-life (years)
238U 99.284 4.46 billions
235U 0.711 704 millions
234U 0.0055 245,000
239Pu 93/57 24,110
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Nuclear Fission
Heavy nucleus is bombarded with neutrons ? It
decays into two smaller nuclei neutrons
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Uranium Fission
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Uranium Fission
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Chain reaction
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Self sustained chain reaction
K Reproduction Constant
K lt 1 ? The reactor is sub-critical ? it dies
out K 1 ? The reactor is critical ? self
sustained chain Kgtgt1 ? The reactor becomes
unstable
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Energy Production
K 1

• Neutron leakage ? area/volume ratio
• Neutron Energy
• Neutron capture by non-fission elements
• Control of power level
• Safety

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Nuclear Reactor
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Nuclear Power Plants
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Generation I reactors
Fuel 235U 238U/239Pu 232Th/233U Oxides Carbides
Metal alloys
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Generation I reactors
Fuel 235U 238U/239Pu 232Th/233U Oxides Carbides
Metal alloys
Coolants Light water Gases Heavy water Organic
liquid Liquid metal Molten salts
System configuration Pressurized water Boiling
water
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Pressurized Water Reactor
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Next Generation
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Solar cells
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Solar cells
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Satellites
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Solar Cells
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Water Power plants
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Windmills
Up to 72 m in rotor diameter
Estimated 3-22 Q of energy
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Biomass
Wood burning Fermentation and distillation to
produce ethanol Steam-powered generators
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Hydrogen fuel cells
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Hydrogen fuel cells
Gemini and Apollo spacecrafts
2H2O2?2H2Oelectricityheat
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Hydrogen fuel cells

• Open issues
• Production
• Distribution
• Storage
• Burning