2 I. Mining Law of 1872 – encouraged mineral exploration and mining. 1. First declare your belief that minerals on the land. Then spend $500 in improvements, pay $100 per year and the land is yours2. Domestic and foreign companies take out $2-$3 billion/ year3. Allows corporations and individuals to claim ownership of U.S. public lands.4. Leads to exploitation of land and mineral resources.
3 "This archaic, 132-year-old law permits mining companies to gouge billions of dollars worth of minerals from public lands, without paying one red cent to the real owners, the American people. And, these same companies often leave the unsuspecting taxpayers with the bill for the billions of dollars required to clean up the environmental mess left behind."-- Senator Dale Bumpers (D-AR, retired)
4 Nature and Formation of Mineral Resources A. Nonrenewable Resources – a concentration of naturally occurring material in or on the earth’s crust that can be extracted and processed at an affordable cost. Non-renewable resources are mineral and energy resources such as coal, oil, gold, and copper that take a long period of time to produce.
5 Nature and Formation of Mineral Resources 1. Metallic Mineral Resources – iron, copper, aluminum2. Nonmetallic Mineral Resources – salt, gypsum, clay, sand, phosphates, water and soil.3. Energy resource: coal, oil, natural gas and uranium
6 Nature and Formation of Mineral Resources B. Identified Resources – deposits of a nonrenewable mineral resource that have a known location, quantity and quality based on direct geological evidence and measurementsC. Undiscovered Resources– potential supplies of nonrenewable mineral resources that are assumed to exist on the basis of geologic knowledge and theory (specific locations, quantity and quality are not known)D. Reserves – identified resources of minerals that can be extracted profitably at current prices.Other Resources – resources that are not classified as reserves.
7 Ore Formation1. Magma (molten rock) – magma cools and crystallizes into various layers of mineral containing igneous rock.
8 Ore FormationHydrothermal Processes: most common way of mineral formationA. Gaps in sea floor are formed by retreating tectonic platesB. Water enters gaps and comes in contact with magmaC. Superheated water dissolves minerals from rock or magmaD. Metal bearing solutions cool to form hydrothermal ore deposits.E. Black Smokers – upwelling magma solidifies. Miniature volcanoes shoot hot, black, mineral rich water through vents of solidified magma on the seafloor. Support chemosynthetic organisms.
9 Ore FormationManganese Nodules (pacific ocean)– ore nodules crystallized from hot solutions arising from volcanic activity. Contain manganese, iron copper and nickel.
10 Ore Formation3. Sedimentary Processes – sediments settle and form ore deposits.A. Placer Deposits – site of sediment deposition near bedrock or course gravel in streamsB. Precipitation: Water evaporates in the desert to form evaporite mineral deposits. (salt, borax, sodium carbonate)C. Weathering – water dissolves soluble metal ions from soil and rock near earth’s surface. Ions of insoluble compounds are left in the soil to form residual deposits of metal ores such as iron and aluminum (bauxite ore).
11 Methods For Finding Mineral Deposits A. Photos and Satellite ImagesB. Airplanes fly with radiation equipment and magnetometersC. Gravimeter (density)D. DrillingE. Electric Resistance MeasurementF. Seismic SurveysG. Chemical analysis of water and plants
12 Mineral ExtractionSurface Mining: overburden (soil and rock on top of ore) is removed and becomes spoil. 1. open pit mining – digging holes2. Dredging – scraping up underwater mineral deposits3. Area Strip Mining – on a flat area an earthmover strips overburden4. Contour Strip Mining – scraping ore from hilly areas
13 Subsurface Mining: 1. dig a deep vertical shaft, blast underground tunnels to get mineral deposit, remove ore or coal and transport to surface 2. disturbs less land and produces less waste3. less resource recovered, more dangerous and expensive4. Dangers: collapse, explosions (natural gas), and lung disease
14 Environmental Impacts of Mineral Resources A. Scarring and disruption of land,B. Collapse or subsidenceC. Wind and water erosion of toxic laced mine wasteD. Air pollution – toxic chemicalsE. Exposure of animals to toxic wasteF. Acid mine drainage: seeping rainwater carries sulfuric acid ( acid comes from bacteria breaking down iron sulfides) from the mine to local waterwayGoogle earth
15 Environmental Effects StepsEnvironmental EffectsDisturbed land; mining accidents;health hazards; mine waste dumping;oil spills and blowouts; noise;ugliness; heatMiningexploration, extractionProcessingSolid wastes; radioactive material;air, water, and soil pollution;noise; safety and healthhazards; ugliness; heattransportation, purification,manufacturingUseNoise; uglinessthermal water pollution;pollution of air, water, and soil;solid and radioactive wastes;safety and health hazards; heattransportation or transmissionto individual user,eventual use, and discardingFig. 14.6, p. 326
16 Percolation to groundwater Leaching of toxic metals SubsurfaceMine OpeningSurface MineRunoff ofsedimentAcid drainage fromreaction of mineralor ore with waterSpoil banksPercolation to groundwaterLeaching of toxic metalsand other compoundsfrom mine spoilLeaching may carryacids into soil andgroundwater suppliesFig. 14.7, p. 326
17 Scattered in environment SmeltingSeparationof ore fromgangueMeltingmetalConversionto productMetal oreRecyclingSurfaceminingDiscardingof productFig. 14.8, p. 327Scattered in environment
18 A. Life Cycle of Metal Resources (fig. 14-8) Mining OreA. Ore has two components: gangue(waste) and desired metalB. Separation of ore and gangue which leaves tailingsC. Smelting (air and water pollution and hazardous waste which contaminates the soil around the smelter for decades)D. Melting MetalE. Conversion to product and discarding product
19 Economic Impact on Mineral Supplies A. Mineral prices are low because of subsidies: depletion allowances and deduct cost of finding moreB. Mineral scarcity does not raise the market pricesC. Mining Low Grade Ore: Some analysts say all we need to do is mine more low grade ores to meet our need1. We are able to mine low grade ore due to improved technology2. The problem is cost of mining and processing, availability of fresh water, environmental impact
20 Recycle; increase reserves by improved mining Mine, use, throw away;no new discoveries;rising pricesRecycle; increase reservesby improved miningtechnology, higher prices,and new discoveriesBProductionRecycle, reuse, reduceconsumption; increasereserves by improvedmining technology,higher prices, andnew discoveriesCPresentDepletiontime ADepletiontime BDepletiontime CFig. 14.9, p. 329Time
22 A. Mining Oceans1. Minerals are found in seawater, but occur in too low of a concentration2. Continental shelf can be mined3. Deep Ocean are extremely expensive to extract (not currently viable)
23 A. Substitutes for metals 1. Materials Revolution2. Ceramics and Plastics3. Some substitutes are inferior (aluminum for copper in wire)4. Will be difficult to find substitutes for helium, manganese, phosphorus and copper
24 Evaluating Energy Sources What types of energy do we use?1. 99% of our heat energy comes directly from the sun (renewable fusion of hydrogen atoms)2. Indirect forms of solar energy (renewable)windhydrobiomass
25 Oil and Natural Gas Coal Geothermal Energy Contour strip mining Hot waterstorageFloating oil drillingplatformOil storageGeothermalpower plantOil drillingplatformon legsPipelineArea stripminingOil wellPipelineMined coalDrillingtowerGas wellValvesPumpWaterpenetratesdownthroughtherockUndergroundcoal mineWater is heatedand brought upas dry steam orwet steamImpervious rockNatural gasCoal seamOilHot rockWaterWaterMagmaFig , p. 332
26 Kilocalories per Person per Day SocietyKilocalories per Person per DayModern industrial(United States)260,000Modern industrial(other developednations)130,000Earlyindustrial60,000Advancedagricultural20,000Earlyagricultural12,000Hunter–gatherer5,000Primitive2,000Fig , p. 333
27 Hydropower, geothermal, Nuclear power6%Hydropower, geothermal,Solar, wind7%NaturalGas23%Biomass12%Coal22%Oil30%Fig a, p. 333World
28 Nuclear power 7% Hydropower geothermal, solar, wind 5% Natural Gas 22% Coal22%Biomass4%Oil40%Fig b, p. 333United States
29 20th Century Trends1. Coal use decreases from 55% to 22%2. Oil increased from 2% to 30%3. Natural Gas increased from 0% to 25%4. Nuclear increased from 0% to 6%
30 100 Wood Coal 80 60 Natural gas Oil 40 Hydrogen Solar 20 Nuclear 1800 Contribution to total energyconsumption (percent)Oil40HydrogenSolar20Nuclear18001875195020252100YearFig , p. 334
31 Evaluating Energy Sources Evaluating Energy Resources; Take into consideration the following:Availabilitynet energy yieldCostenvironmental impact
32 Electric resistance heating (coal-fired plant) 0.4 Space HeatingPassive solar5.8Natural gas4.9Oil4.5Active solar1.9Coal gasification1.5Electric resistance heating(coal-fired plant)0.4Electric resistance heating(natural-gas-fired plant)0.4Electric resistance heating(nuclear plant)0.3Fig a, p. 335
33 High-Temperature Industrial Heat 28.2Surface-mined coalUnderground-mined coal25.8Natural gas4.9Oil4.7Coal gasification1.5Direct solar (highlyconcentrated by mirrors,heliostats, or other devices)0.9Fig b, p. 335
35 Net EnergyNet Energy – total amount of energy available from a given source minus the amount of energy used to get the energy to consumers (locate, remove, process and transport)G. Net Energy Ratio - ratio of useful energy produced to the useful energy used to produce it.
36 OilA. Petroleum/Crude Oil – thick liquid consisting of hundreds of combustible hydrocarbons and small concentrations of nitrogen, sulfur, and oxygen impurities.B. Produced by the decomposition of dead plankton that were buried under ancient lakes and oceans. It is found dispersed in rocks.
37 Oil Life Cycle 1:14 1. Primary Oil Recovery a. drill well b. pump out light crude oil1:14
38 Secondary Oil Recovery a. pump water under pressure into a well to force heavy crude oil toward the wellb. pump oil and water mixture to the surfacec. separate oil and waterd. reuse water to get more oil
39 Tertiary Oil Recoverya. inject detergent to dissolve the remaining heavy oilb. pump mixture to the surfacec. separate out the oild. reuse detergent
40 Transport oil to the refinery (pipeline, truck, boat)
41 Oil refining– heating and distilling based on boiling points of the various petrochemicals found in the crude oil. (fractional distillation in a cracking tower)
44 . Location of World Oil Supplies 1. 64% Middle East (67% OPEC – 11 countries)a. Saudi Arabia (26%)b. Iraq, Kuwait, Iran, (9-10% each)2. Latin America (14%) (Venezuela and Mexico)3. Africa (7%)4. Former Soviet Union (6%)5. Asia (4%) (China 3%)6. United States (2.3%) we import 52% of the oil we use7. Europe (2%)
45 ALASKA CANADA UNITED STATES MEXICO ArcticOceanPrudhoe BayCoalBeaufortSeaALASKAGasTrans Alaskaoil pipelineArctic NationalWildlife RefugeOilPrince WilliamSoundHigh potentialareasGulf ofAlaskaValdezCANADAGrandBanksPacificOceanUNITEDSTATESAtlanticOceanFig , p. 338MEXICO
46 Oil price per barrel ($) 70605040Oil price per barrel ($)3020(1997 dollars)101950196019701980199020002010YearFig , p. 339
47 40 2,000 x 109 barrels total 30 (x 109 barrels per year) Annual production2010190019251950197520002025205020752100YearWorldFig a, p. 339
48 4 200 x 109 barrels total 1975 3 Undiscovered: 32 x 109 barrels (x 109 barrels per year)Annual productionProvenreserves:34 x 109barrels2119001920194019602080200020202040YearUnited StatesFig b, p. 339
49 286% Coal-fired electricity Synthetic oil and 150% gas produced from coal150%100%Coal86%Oil58%Natural gas17%Nuclear powerFig , p. 339
51 How long will the oil last 1. Identified Reserve will last 53 years at current usage rates2. Known and projected supplies are likely to be 80% depleted within 42 to 93 years depending on usage rateUS oil supplies are expected to be depleted within 15 to 48 years depending on the annual usage rate
52 Heavy OilsOil Shale – fine grained sedimentary rock containing solid organic combustible material called kerogenShale Oil – kerogen distilled from oil shale.a. could meet U.S. crude oil demand for 40 years at current usage rates (Colorado, Utah and Wyoming public lands)Tar Sand – mixture of clay sand and water containing bitumen (high sulfur heavy oil)
54 Shale oil pumped to surface Mined oil shaleRetortConveyorSpent shaleAbove GroundConveyorPipelineShale oilstorageImpuritiesremovedHydrogenaddedCrude oilRefineryAircompressorsSulfur and nitrogencompoundsAirinjectionShale layerShale oil pumped to surfaceUndergroundShale heated to vaporized kerogen, which is condensed to provide shale oilFig , p. 341
55 Tar sand is mined. Tar sand is heated until bitumen floats to the top. Bitumen vaporIs cooled andcondensed.PipelineImpuritiesremovedHydrogenaddedSyntheticcrude oilRefineryFig , p. 341
58 XI. Natural GasNatural Gas is a mixture of 50-90% methane (CH4) by volume; contains smaller amounts of ethane, propane, butane and toxic hydrogen sulfide.B. Conventional natural gas - lies above most reservoirs of crude oilC. Unconventional deposits - include coal beds, shale rock, deep deposits of tight sands and deep zones that contain natural gas dissolved in hot hot water
59 Oil and Natural Gas Coal Geothermal Energy Contour strip mining Hot waterstorageFloating oil drillingplatformOil storageGeothermalpower plantOil drillingplatformon legsPipelineArea stripminingOil wellPipelineMined coalDrillingtowerGas wellValvesPumpWaterpenetratesdownthroughtherockUndergroundcoal mineWater is heatedand brought upas dry steam orwet steamImpervious rockNatural gasCoal seamOilHot rockWaterWaterMagmaFig , p. 332
60 XI. Natural GasGas Hydrates - an ice-like material that occurs in underground deposits (globally) Liquefied Petroleum Gas (LPG) - propane and butane are liquefied and removed from natural gas fields. Stored in pressurized tanks.Liquefied Natural Gas (LNG) - natural gas is converted at a very low temperature (-184oC)
61 Where is the world’s natural gas? Russia and Kazakhstan - 40% Iran - 15% Qatar - 5% Saudi Arabia - 4% Algeria - 4% United States - 3% Nigeria - 3% Venezuela - 3%
62 Advantages: 1. Cheaper than Oil 2. World reserves - >125 years 3. Easily transported over land (pipeline)4. High net energy yield5. Produces less air pollution than other fossil fuels6. Produces less CO2 than coal or oil7. Extracting natural gas damages the environment much less that either coal or uranium ore8. Easier to process than oil9. Can be used to transport vehicles10. Can be used in highly efficient fuel cells
63 Advantages Disadvantages Ample supplies(125 years)Releases CO2when burnedHigh net energyyieldMethane(a greenhousegas) can leakfrom pipelinesLow cost (withhuge subsidies)Shipped acrossocean as highlyexplosive LNGLess air pollutionthan otherfossil fuelsSometimesburned off andwasted at wellsbecause of lowpriceLower CO2emissions thanother fossil fuelsModerate environ-mental impactEasily transportedby pipelineLow land useGood fuel forfuel cells andgas turbinesFig , p. 342
64 Disadvantages:1. When processed, H2S and SO2 are released into the atmosphere2. Must be converted to LNG before it can be shipped (expensive and dangerous)3. Conversion to LNG reduces net energy yield by one-fourth4. Can leak into the atmosphere; methane is a greenhouse gas that is more potent than CO2.
65 XII. CoalCoal is a solid, rocklike fossil fuel; formed in several stages as the buried remains of ancient swamp plants that died during the Carboniferous period (ended 286 million years ago); subjected to intense pressure and heat over millions of years.Coal is mostly carbon (40-98%); small amount of water, sulfur and other materials
66 Three types of coallignite (brown coal)bituminous coal (soft coal)anthracite (hard coal)Carbon content increases as coal ages; heat content increases with carbon content
67 Increasing heat and carbon content Increasing moisture content Peat(not a coal)Lignite(brown coal)Bituminous Coal(soft coal)Anthracite(hard coal)HeatHeatHeatPressurePressurePressurePartially decayedplant matter in swampsand bogs; low heatcontentLow heat content;low sulfur content;limited supplies inmost areasExtensively usedas a fuel becauseof its high heat contentand large supplies;normally has ahigh sulfur contentHighly desirable fuelbecause of its highheat content andlow sulfur content;supplies are limitedin most areasFig , p. 344
68 Coal ExtractionSubsurface Mining - labor intensive; world’s most dangerous occupation (accidents and black lung disease Surface Mining - three types1. Area strip mining 2. contour strip mining 3. open-pit mining
69 Oil and Natural Gas Coal Geothermal Energy Contour strip mining Hot waterstorageFloating oil drillingplatformOil storageGeothermalpower plantOil drillingplatformon legsPipelineArea stripminingOil wellPipelineMined coalDrillingtowerGas wellValvesPumpWaterpenetratesdownthroughtherockUndergroundcoal mineWater is heatedand brought upas dry steam orwet steamImpervious rockNatural gasCoal seamOilHot rockWaterWaterMagmaFig , p. 332
70 Why we need coalCoal provides 25% of world’s commercial energy (22% in US).Used to make 75% of world’s steelGenerates 64% of world’s electricity
71 Coal-Fired Electric Power Plant Coal is pulverized to a fine dust and burned at a high temperature in a huge boiler. Purified water in the heat exchanger is converted to high-pressure steam that spins the shaft of the turbine. The shaft turns the rotor of the generator (a large electromagnet) to produce electricity.
72 . Coal-Fired Electric Power Plant Air pollutants are removed using electrostatic precipitators (particulate matter) and scrubbers (gases). Ash is disposed of in landfills. Sulfur dioxide emissions can be reduced by using low-sulfur coal.
73 I. World’s Coal Supplies US - 66% of worlds proven reserves Identified reserves should last 220 years at current usage rates. Unidentified reserves could last about 900 years
74 . Pros and Cons of Solid Coal AdvantagesWorld’s most abundant and dirtiest fossil fuel, High net energy yield
75 Advantages Disadvantages Ample supplies(225–900 years)Very highenvironmentalimpactHigh net energyyieldSevere landdisturbance, airpollution, andwater pollutionLow cost (withhuge subsidies)High land use(including mining)Severe threat tohuman healthHigh CO2emissionswhen burnedReleasesradioactiveparticles andmercury into airFig , p. 344
76 Disadvantages:harmful environmental effects -mining is dangerous (accidents and -black lung disease) -harms the land and causes water pollution -Causes land subsidence -Surface mining causes severe land disturbance and soil erosion -Surface mined land can be restored - involves burying toxic materials, returning land to its original contour, and planting vegetation (Expensive and not often done) -Acids and toxic metals drain from piles of water materials -Coal is expensive to transport -Cannot be used in sold form in cars (must be converted to liquid or gaseous form) -Dirtiest fossil fuel to burn releases CO, CO2, SO2, NO, NO2, particulate matter (flyash), toxic metals and some radioactive elements. -Burning Coal releases thousands of times more radioactive particles into the atmosphere per unit of energy than does a nuclear power plant -Produces more CO2 per unit of energy than other fossil fuels and accelerates global warming. -A severe threat to human health (respiratory disease)
77 Clean Coal Technology. Fluidized-bed combustion - developed to burn coal more cleanly and efficiently.Use of low sulfur coal - reduces SO2 emissionCoal gasification – uses coal to produce synthetic natural gas (SNG). Coal liquefaction - produce a liquid fuel - methanol or synthetic gasoline
78 Flue gases Coal Limestone Steam Fluidized bed Water Air nozzles Air Calcium sulfateand ashFig , p. 345
79 Raw coal Remove dust, tar, water, sulfur Recover sulfur Air or oxygen SteamRaw gasesCleanMethane gas2CCoal+O22COPulverizerRecycle unreactedcarbon (char)CO+3H2CH4+H2OMethane(natural gas)Slag removalPulverized coalFig , p. 345
80 Advantages Disadvantages Large potentialsupplyLow to moderatenet energy yieldHigher cost thancoalVehicle fuelHighenvironmentalimpactIncreased surfacemining of coalHigh water useHigher CO2emissions thancoalFig , p. 346
81 Clean Coal TechnologySynfuels - can be transported by pipeline inexpensively; burned to produce electricity; burned to heat houses and water; used to propel vehicles.
82 XIII. Nuclear EnergyA. Three reasons why nuclear power plants were developed in the late 1950s:1. Atomic Energy Commission promised electricity at a much lower cost than coal2. US Gov’t paid ~1/4 the cost of building the first reactors3. Price Anderson Act protected nuclear industry from liability in case of accidents
83 Gigawatts of electricity 375300225Gigawatts of electricity150751960197019801990200020102020YearFig a, p. 348
84 Gigawatts of electricity 35302520Gigawatts of electricity15105196019701980199020002010YearFig b, p. 348
85 Why is nuclear power on the decline? B. Globally, nuclear energy produces only 17% of world’s electricity (6% of commercial energy)-huge construction overruns -high operating costs -frequent malfunctions -false assurances -cover-ups by government and industry -inflated estimates of electricity use -poor management -Chernobyl -Three Mile Island -public concerns about safety, cost and disposal of radioactive wastes
86 C. How a Nuclear Reactor Works Nuclear fission of Uranium-235 and Plutonium-239 releases energy that is converted into high-temperature heat. This rate of conversion is controlled. The heat generated can produce high-pressure steam that spins turbines that generate electricity.
87 Small amounts of Radioactive gases Uranium fuel input (reactor core) Containment shellWaste heatElectrical powerEmergency coreCooling systemSteamControlrodsUseful energy25 to 30%TurbineGeneratorHeatexchangerHot coolantHot water outputCondenserPumpPumpCoolantCoolantpassageModeratorCool water inputBlackPumpWasteheatPressurevesselWaterShieldingWasteheatWater source(river, lake, ocean)Periodic removaland storage ofradioactive wastesand spent fuel assembliesPeriodic removaland storage ofradioactive liquid wastesFig , p. 346
88 Front end Back end Fuel assemblies Spent fuel assemblies Reactor (conversion of enriched UF6 to UO2and fabrication of fuel assemblies)Open fuel cycle todayProspective “closed” end fuel cycleFuel fabricationInterim storageUnder waterEnrichedUF6Plutonium-239as PuO2Spent fuelassembliesEnrichmentUF6Spent fuelreprocessingDecommissioningof reactorUranium-235 as UF6High-levelradioactivewaste orspent fuelassembliesConversion of U3O8to UF6Uranium tailings(low level butlong half-life)Processeduranium oreGeologic disposalof moderate-and high-levelradioactive wastesUranium mines and millsOre and ore concentrate (U3O8)Fig , p. 347Front endBack end
89 D. Light-water reactors (LWR) 1. Core containing 35,000-40,000 fuel rods containing pellets of uranium oxide fuel. Pellet is 97% uranium-238 (nonfissionable isotope) and 3% uranium-235 (fissionable).2. Control rods - move in and out of the reactor to regulate the rate of fission3. Moderator - slows down the neutrons so the chain reaction can be kept going [ liquid water in pressurized water reactors; solid graphite or heavy water (D2O) ].4. Coolant - water to remove heat from the reactor core and produce steam
90 Decommissioning Power Plants 1/3 of fuel rod assemblies must be replaced every 3-4 years. They are placed in concrete lined pools of water (radiation shield and coolant).A. Nuclear wastes must be stored for 10,000 yearsB. After years of operation, the plant must be decommissioned by1. dismantling it2. putting up a physical barrier, or3. enclosing the entire plant in a tomb (to last several thousand years)
91 Advantages Disadvantages Large fuelsupplyHigh cost (evenwith largesubsidies)Lowenvironmentalimpact (withoutaccidents)Low netenergy yieldHighenvironmentalimpact (with majoraccidents)Emits 1/6 asmuch CO2 as coalModerate landdisruption andwater pollution(withoutaccidents)Catastrophicaccidents canhappen(Chernobyl)Moderate land useNo acceptablesolution forlong-term storageof radioactivewastes anddecommissioningworn-out plantsLow risk ofaccidentsbecause ofmultiplesafety systems(except in 35poorly designedand run reactorsin former SovietUnion andEastern Europe)Spreadsknowledge andtechnology forbuilding nuclearweaponsFig , p. 349
92 Coal Nuclear Ample supply Ample supply of uranium High net energy yieldLow net energyyieldLow air pollution(mostly from fuelreprocessing)Very high airpollutionHigh CO2emissionsLow CO2emissions(mostly from fuelreprocessing)65,000 to 200,000deaths per yearin U.S.About 6,000deaths peryear in U.S.High landdisruption fromsurface miningMuch lower landdisruption fromsurface miningHigh land useModerate landuseLow cost (withhuge subsidies)High cost (withhuge subsidies)Fig , p. 349
93 F. Advantages of Nuclear Power: 1. Don’t emit air pollutants2. Water pollution and land disruption are low
94 G. Nuclear Power Plant Safety 1. Very low risk of exposure to radioactivity2. Three Mile Island - March 29, 1979; No. 2 reactor lost coolant water due to a series of mechanical failures and human error. Core was partially uncovered3. Nuclear Regulatory Commission estimates there is a 15-45% chance of a complete core meltdown at a US reactor during the next 20 years.4. US National Academy of Sciences estimates that US nuclear power plants cause 6000 premature deaths and 3700 serious genetic defects each year.
95 Chernobyl Crane for moving fuel rods Steam generator Cooling pond Almost all control rodswere removed from thecore during experiment.Automatic safety devicesthat shut down the reactorwhen water and steam levelsfall below normal and turbinestops were shut off becauseengineers didn’t want systemsto “spoil” experiment.Crane formoving fuel rodsEmergency coolingsystem was turnedoff to conduct anexperiment.SteamgeneratorCoolingpondTurbinesRadiation shieldsReactorWaterpumpsReactor power output was lowered toomuch, making it too difficult to control.Additional water pump to cool reactorwas turned on. But with low power outputand extra drain on system, water didn’tactually reach reactor.ChernobylFig , p. 350
96 H. Low-Level Radioactive Waste 1. Low-level waste gives off small amounts of ionizing radiation; must be stored for years before decaying to levels that don’t pose an unacceptable risk to public health and safety: low-level waste was put into drums and dumped into the oceans. This is still done by UK and Pakistan3. Since 1970, waste is buried in commercial, government-run landfills.4. Above-ground storage is proposed by a number of environmentalists.: the NRC proposed redefining low-level radioactive waste as essentially nonradioactive. That policy was never implemented (as of early 1999).
97 I. High-Level Radioactive Waste 1. Emit large amounts of ionizing radiation for a short time and small amounts for a long time. Must be stored for about 240,0002. Spent fuel rods; wastes from plants that produce plutonium and tritium for nuclear weapons.
98 J. Possible Methods of Disposal and their Drawbacks 1. Bury it deep in the ground2. Shoot it into space or into the sun3. Bury it under the Antarctic ice sheet or the Greenland ice cap4. Dump it into descending subduction zones in the deep ocean5. Bury it in thick deposits of muck on the deep ocean floor6. Change it into harmless (or less harmful) isotopes7. Currently high-level waste is stored in the DOE $2 billion Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. (supposed to be put into operation in 1999)
99 Up to 60 deep trenches dug into clay. As many as 20 flatbed trucks deliver wastecontainers daily.Barrels are stackedand surroundedwith sand. Coveringis mounded to aidrain runoff.Clay bottomFig b, p. 351
100 What covers waste Grass Topsoil Gravel Soil Compacted clay Sand Gravel Fig c, p. 351
101 Waste container 2 meters wide 2–5 meters high Several steel drums holding wasteSteel wallSteel wallLead shieldingFig a, p. 351
102 Storage Containers Fuel rod Primary canister Overpack container sealed Fig c, p. 352
104 Ground Level Unloaded from train Lowered down shaft Fig a, p. 352
105 2,500 ft. (760 m) deep Personnel elevator Air shaft Nuclear waste shaftFig b, p. 352
106 K. Worn-Out Nuclear Plants 1. Walls of the reactor’s pressure vessel become brittle and thus are more likely to crack.2. Corrosion of pipes and valves
107 3. Decommissioning a power plant (3 methods have been proposed) A. immediate dismantlingB. mothballing for yearsC. entombment (several thousand years)4. Each method involves shutting down the plant, removing the spent fuel, draining all liquids, flushing all pipes, sending all radioactive materials to an approved waste storage site yet to be built.
108 Connection between Nuclear Reactors and the Spread of Nuclear Weapons 1. Components, materials and information to build and operate reactors can be used to produce fissionable isotopes for use in nuclear weapons.Los Alamos Muon Detector CouldThwart Nuclear Smugglers
109 M. Can We Afford Nuclear Power? 1. Main reason utilities, the government and investors are shying away from nuclear power is the extremely high cost of making it a safe technology.2. All methods of producing electricity have average costs well below the costs of nuclear power plants.
110 N. Breeder Reactors1. Convert nonfissionable uranium-238 into fissionable plutonium-2392. Safety: liquid sodium coolant could cause a runaway fission chain reaction and a nuclear explosion powerful enough to blast open the containment building.3. Breeders produce plutonium fuel too slowly; it would take years to produce enough plutonium to fuel a significant number of other breeder reactors.
111 O. Nuclear Fusion1. D-T nuclear fusion reaction; Deuterium and Tritium fuse at about 100 million degrees2. Uses more energy than it produces