Issues with petroleum. Announcements. Problems with coal. Natural gas. Projected Energy Consumption. Natural gas

Transcription

1 Announcements Ecological Footprint assignment starts this afternoon to be completed by 10 AM Thursday Today: Alternatives to fossil fuels? Issues with petroleum Limited reserves (near peak in Hubbert curve?) Trade deficit currently $44.3 billion (largely due to imports of oil) Externalities (military costs, environmental impacts) Environmental pollution (persistent combustion products, toxic components of oil, greenhouse gases, etc) Transportation system depends upon it Problems with coal Dirtiest of fossil fuels Strip mining degrades land, watersheds Many pollutants emitted from coal-fired power plants: sulfur dioxide, nitrogen oxides, carbon dioxide, mercury, and others But, the most important fuel for producing electricity in the world And, it won t fit into your gas tank Quadrillion BTU Natural gas 30 US Natural Gas Production Year Data from US EIA, 2014 Natural gas Projected Energy Consumption Production increasing Cleaner than coal (no Hg, SO x, NO x, and ~50% less CO 2 per unit energy produced) But, methane released during extraction Can be used in vehicles, even trucks All fossil fuels release greenhouse gases And, what about fracking? 1

2 Energy outlook Petroleum: Limitation today? Natural Gas: Maybe 100 y of reserves in the U.S. Coal: Perhaps 200 y of reserves What can we do about transportation? Short term: Increase fuel efficiency of vehicles Longer term: Alternative fuels for transportation Increased efficiency and alternative sources for electricity Is there another cheap reliable power source that does not pollute air and water or release greenhouse gases? "The most important responsibility of this atomic energy agency would be to devise methods whereby this fissionable material would be allocated to serve the peaceful pursuits of mankind. Experts would be mobilized to apply atomic energy to the needs of agriculture, medicine and other peaceful activities. A special purpose would be to provide abundant electrical energy in the power-starved areas of the world" Dwight D. Eisenhower on the International Atomic Energy Agency (1953) 3 Mile Island March 1979, Middletown PA Partial meltdown of Unit 2 due to loss of coolant water, ambiguous warning indicators, and inadequate operator training. Chernobyl: Чорнобильська катастрофа 1000s of miles of fallout Radiation leaked into atmosphere and into Susquehanna River Timing coincided with release of the movie The China Syndrome. Unit 2 permanently shut down. Unit 1 still producing electricity Chernobyl (1986) A major nuclear accident anywhere is a nuclear accident everywhere. 31 deaths according to Soviet Union official statements Union of Concerned Scientists estimate 27,000 deaths (including cancer) Other estimates of deaths are higher Exposed 0.5 million people to potentially dangerous levels of radioactivity 400,000 people relocated 19-mile exclusion zone Area the size of Florida is still contaminated Other reactors remained running until December 2000 Fukushima Daiichi nuclear disaster After 9.0 magnitude Tohoku earthquake units 1-3 shut down (4-6 already shut down for maintenance) and emergency generators began pumping coolant Tsunami flooded and destroyed generators so that coolant could not longer be pumped into reactors. Units 1-3 experienced full meltdown An explosion in unit 4 occurred near spent fuel pool Hydrogen produced by heat and chemical reactions exploded, emitting radiation into atmosphere. Seawater was used to flood the reactors, sending radioactive waste into the ocean Two months later, tuna off California had measureable levels of radioactivity from the Fukushima plant 2

3 U92Nuclear Power ATOMIC NUMBER: number of protons MASS NUMBER: number of protons + neutrons ATOMIC MASS: mass of atom in atomic units ISOTOPES: forms of an element with different mass numbers EXAMPLES: 238 U, 235 U, 236 U are isotopes of uranium RADIOACTIVITY: Spontaneous conversion of one element to another through the emission of radiation Radioactivity (decays per unit time) Half life Time (half lives) Spontaneous Fission Nuclear Fission 1n U 236 U (fission) 140 Ba + 93 Kr + 3n (slow) (or 140 Cs + 93 Rb + 3n) E = mc 2 Mass of 235 U + 1n is greater than the mass of 140 Ba + 93 Kr + 3 n 3

4 Nuclear Power Step-by-step Refine uranium from uranium-bearing rock Controlling the nuclear reaction Enrich the uranium in 235 U (~ 0.7% of total U) (4% 235 U), very difficult to separate 235 U from 238 U Methods: Diffusion of UF 6 through a membrane, centrifugation Create a fuel geometry that can be controlled Fuel rods: contains the uranium ore Moderator: slows neutrons Control rods: absorbs neutrons to stop the nuclear reaction Connect the nuclear vessel to a steam generator and turbine for producing electricity Control rods absorb neutrons stopping reaction (cadmium) Moderator (H 2 O) slows neutrons to allow fission Heat released generates steam, which turns a turbine, which turns a generator to make electricity Nuclear disasters Loss of coolant Reactor cores and spent fuel rods remain hot for many years after fission stops Causes of coolant loss: human error, design flaws, natural disasters Controlling a nuclear power plant Types of reactors Boiled water reactor Fast-neutron reactor Gas cooled reactor Light water cooled Pressurized heavywater reactor Pressurized-water reactor 4

5 Nuclear Power around the world Ages of 435 nuclear power plants Nuclear power plants in operation today Number of reactors Belarus Armenia Iran Netherlands Slovenia Bulgaria Japan Mexico Romania South Africa Argentina Brazil Pakistan Hungary Finland Slovakia Switzerland Czech Republic Taiwan Belgium Spain Germany Sweden Ukraine United Kingdom China Canada India South Korea Russia France United States Data from the IAEA Nuclear reactor age (y) Data from the IAEA Number of nuclear power plants has not grown since mid-1980s Why not? Nuclear power in the U.S. Hanford, WA Why no new nuclear power plants in US for > 25y? High up-front costs (~7 billion) Long construction times Difficult to finance Public concerns Nuclear Power Hazards Uranium mining and purification is not clean (e.g., Hanford, WA) Spent fuel is toxic for tens of thousands of years 239 Pu made (24,000y half life) in nuclear plants from 238 U Storage sites: At nuclear power plants Yucca mountain, Nevada Waste Isolation Pilot Plant (New Mexico) Potential for accidents (e.g., Chernobyl, Fukushima) Potential for theft of fissionable material - during storage, transport 5

6 What to do with ~ 60,000 metric tons of spent fuel? Spent nuclear fuel contamination with neutron absorbers and radioactive by-products Reprocess? On-site storage Transmutation (under development) Long-term storage Vitrification (add sugar and heat to make glass) Geologic disposal (requires ~ 1 million years) Yucca Mtn, NV rejected, WIPP near Carlsbad, NM? DOE Nuclear Waste Sites 239 Pu production for WWII Manhattan project 40 billion gallons of waste dumped into soil 177 huge underground tanks, ⅓ leaking in 2001 Contaminated groundwater moving toward Columbia R. 60 billion spent on cleanup so far, 200 billion more estimated World s largest cleanup site Hanford Site U.S. Options for Electricity Coal Nuclear Nuclear power Should the U.S. invest in more nuclear power plants to meet rising demands for energy? How much should we invest in other, potentially safer, types of nuclear power (Thorium fission? Fusion?) Film clip 6