mrs. sealy apes i.mining law of 1872 – encouraged mineral exploration and mining. 1. first declare...
TRANSCRIPT
Mrs. Sealy
APES
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 yours
• 2. Domestic and foreign companies take out $2-$3 billion/ year
• 3. Allows corporations and individuals to claim ownership of U.S. public lands.
• 4. Leads to exploitation of land and mineral resources.
http://seattlepi.nwsource.com/specials/mining/26875_mine11.shtml
• "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)
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.
Nature and Formation of Mineral Resources
• 1. Metallic Mineral Resources – iron, copper, aluminum
• 2. Nonmetallic Mineral Resources – salt, gypsum, clay, sand, phosphates, water and soil.
• 3. Energy resource: coal, oil, natural gas and uranium
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 measurements
• C. 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.
Ore Formation
1.Magma (molten rock) – magma cools and crystallizes into various layers of mineral containing igneous rock.
Ore Formation
• Hydrothermal Processes: most common way of mineral formation
• A. Gaps in sea floor are formed by retreating tectonic plates• B. Water enters gaps and comes in contact with magma• C. Superheated water dissolves minerals from rock or
magma• D. 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.
Ore Formation
• Manganese Nodules (pacific ocean)– ore nodules crystallized from hot solutions arising from volcanic activity. Contain manganese, iron copper and nickel.
Ore Formation
• 3. Sedimentary Processes – sediments settle and form ore deposits.
• A. Placer Deposits – site of sediment deposition near bedrock or course gravel in streams
• B. 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).
Methods For Finding Mineral Deposits
• A. Photos and Satellite Images • B. Airplanes fly with radiation equipment
and magnetometers• C. Gravimeter (density)• D. Drilling• E. Electric Resistance Measurement• F. Seismic Surveys• G. Chemical analysis of water and plants
Mineral Extraction
• Surface Mining: overburden (soil and rock on top of ore) is removed and becomes spoil.
• 1. open pit mining – digging holes• 2. Dredging – scraping up underwater
mineral deposits• 3. Area Strip Mining – on a flat area an
earthmover strips overburden• 4. Contour Strip Mining – scraping ore
from hilly areas
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 waste
• 3. less resource recovered, more dangerous and expensive
• 4. Dangers: collapse, explosions (natural gas), and lung disease
Environmental Impacts of Mineral Resources
• A. Scarring and disruption of land, • B. Collapse or subsidence• C. Wind and water erosion of toxic laced
mine waste• D. Air pollution – toxic chemicals• E. Exposure of animals to toxic waste• F. Acid mine drainage: seeping rainwater
carries sulfuric acid ( acid comes from bacteria breaking down iron sulfides) from the mine to local waterway
Google earth
Steps Environmental Effects
exploration, extraction
MiningDisturbed land; mining accidents;health hazards; mine waste dumping;oil spills and blowouts; noise;ugliness; heat
Solid wastes; radioactive material;air, water, and soil pollution;
noise; safety and healthhazards; ugliness; heat
Processing
transportation, purification,manufacturing
Use
transportation or transmissionto individual user,
eventual use, and discarding
Noise; uglinessthermal water pollution;
pollution of air, water, and soil;solid and radioactive wastes;
safety and health hazards; heat
Fig. 14.6, p. 326
Percolation to groundwater
Leaching of toxic metalsand other compounds
from mine spoil
Acid drainage fromreaction of mineralor ore with water
Spoil banks
Runoff ofsediment
Surface MineSubsurfaceMine Opening
Leaching may carryacids into soil andgroundwater
supplies
Fig. 14.7, p. 326
Surface mining
Metal ore
Separationof ore fromgangue
Scattered in environment
Recycling
Discarding of product
Conversion to product
Melting metal
Smelting
Fig. 14.8, p. 327
A. Life Cycle of Metal Resources (fig. 14-8)
• Mining Ore• A. Ore has two components: gangue(waste) and
desired metal• B. Separation of ore and gangue which leaves
tailings• C. Smelting (air and water pollution and
hazardous waste which contaminates the soil around the smelter for decades)
• D. Melting Metal• E. Conversion to product and discarding
product
Economic Impact on Mineral Supplies
• A. Mineral prices are low because of subsidies: depletion allowances and deduct cost of finding more
• B. Mineral scarcity does not raise the market prices
• C. Mining Low Grade Ore: Some analysts say all we need to do is mine more low grade ores to meet our need
1. We are able to mine low grade ore due to improved technology
– 2. The problem is cost of mining and processing, availability of fresh water, environmental impact
Present Depletiontime A
Depletiontime B
Depletiontime C
Time
Pro
du
ctio
n
C
B
A
Recycle, reuse, reduceconsumption; increasereserves by improvedmining technology,higher prices, andnew discoveries
Recycle; increase reservesby improved miningtechnology, higher prices,and new discoveries
Mine, use, throw away;no new discoveries;rising prices
Fig. 14.9, p. 329
Fig. 14.10, p. 329
A. Mining Oceans
• 1. Minerals are found in seawater, but occur in too low of a concentration
• 2. Continental shelf can be mined
• 3. Deep Ocean are extremely expensive to extract (not currently viable)
A. Substitutes for metals
1. Materials Revolution
• 2. Ceramics and Plastics
• 3. Some substitutes are inferior (aluminum for copper in wire)
• 4. Will be difficult to find substitutes for helium, manganese, phosphorus and copper
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)
– wind– hydro– biomass
Mined coal
Pipeline
Pump
Oil well
Gas well
Oil storage
CoalOil and Natural Gas Geothermal Energy
Hot waterstorage
Contourstrip mining
PipelineDrillingtower
Magma
Hot rock
Natural gasOil
Impervious rock
Water Water
Oil drillingplatformon legs
Floating oil drillingplatform
Valves
Undergroundcoal mine
Water is heatedand brought upas dry steam or
wet steam
Waterpenetratesdownthroughtherock
Area stripmining
Geothermalpower plant
Coal seam
Fig. 14.11, p. 332
Primitive
Hunter–gatherer
Earlyagricultural
Advancedagricultural
Earlyindustrial
Modern industrial(other developed
nations)
Modern industrial(United States)
Society Kilocalories per Person per Day
260,000
130,000
60,000
20,000
12,000
5,000
2,000 Fig. 14.12, p. 333
World
NaturalGas23%
Coal22%
Biomass12%
Oil30%
Nuclear power6%
Hydropower, geothermal,Solar, wind
7%
Fig. 14.13a, p. 333
United States
Oil40%
Coal22%
NaturalGas22%
Nuclear power7%
Hydropowergeothermal, solar, wind
5%
Biomass4%
Fig. 14.13b, p. 333
20th Century Trends
• 1. 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%
Year
210020251950187518000
20
40
60
80
100C
ontr
ibut
ion
to t
otal
ene
rgy
cons
umpt
ion
(per
cent
)Wood
Coal
Oil
Nuclear
HydrogenSolar
Natural gas
Fig. 14.14, p. 334
Evaluating Energy Sources
• Evaluating Energy Resources; Take into consideration the following:
– Availability– net energy yield– Cost– environmental impact
Space Heating
Passive solar
Natural gas
Oil
Active solar
Coal gasification
Electric resistance heating(coal-fired plant)
Electric resistance heating (natural-gas-fired plant)
Electric resistance heating(nuclear plant) 0.3
0.4
0.4
1.5
1.9
4.5
4.9
5.8
Fig. 14.15a, p. 335
High-Temperature Industrial Heat
Surface-mined coalUnderground-mined coalNatural gasOilCoal gasification
Direct solar (highlyconcentrated by mirrors, heliostats, or other devices)
0.91.5
4.74.9
25.8
28.2
Fig. 14.15b, p. 335
Transportation
Natural gas
Gasoline (refined crude oil)
Biofuel (ethyl alcohol)
Coal liquefaction
Oil shale 1.2
1.4
1.9
4.1
4.9
Fig. 14.15c, p. 335
Net Energy
• Net 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.
Oil
• A. 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.
http://www.schoolscience.co.uk/content/4/chemistry/petroleum/knowl/4/2index.htm?origin.html
Oil Life Cycle
• 1. Primary Oil Recovery
• a. drill well• b. pump out light
crude oil
http://science.howstuffworks.com/oil-drilling3.htm
• 1:14
Secondary Oil Recovery
• a. pump water under pressure into a well to force heavy crude oil toward the well
• b. pump oil and water mixture to the surface
• c. separate oil and water
• d. reuse water to get more oil
Tertiary Oil Recovery
• a. inject detergent to dissolve the remaining heavy oil
• b. pump mixture to the surface
• c. separate out the oil
• d. reuse detergent
• Transport oil to the refinery (pipeline, truck, boat)
Oil refining
• – heating and distilling based on boiling points of the various petrochemicals found in the crude oil. (fractional distillation in a cracking tower)
Diesel oil
Asphalt
Greaseand wax
Naphtha
Heating oil
Aviation fuel
Gasoline
Gases
FurnaceFig. 14.16, p. 337
Heatedcrude oil
Conversion to product
• a. Industrial organic chemicals
• b. Pesticides
• c. Plastics
• d. Synthetic fibers
• e. Paints
• f. Medicines
• g. Fuel
. 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
use• 7. Europe (2%)
MEXICO
UNITED STATES
CANADA
PacificOcean
AtlanticOcean
GrandBanks
Gulf ofAlaska
Valdez
ALASKABeaufort
Sea
Prudhoe Bay
ArcticOcean
Coal
Gas
Oil
High potentialareas
Prince WilliamSound
Arctic National Wildlife Refuge
Trans Alaskaoil pipeline
Fig. 14.17, p. 338
Year
1950 1960 1970 1980 1990 2000 20100
10
20
30
40
50
60
70O
il pr
ice
per
barr
el (
$)
(1997 dollars)
Fig. 14.18, p. 339
World
Year1900 1925 1950 1975 2000 2025 2050 2075 21000
10
20
30
40A
nnua
l pro
duct
ion
(x 1
09 ba
rrel
s pe
r ye
ar)
2,000 x 109
barrels total
Fig. 14.19a, p. 339
United StatesYear
1900 1920 1940 1960 2080 2000 2020 20400
1
2
3
4A
nnua
l pro
duct
ion
(x 1
09 ba
rrel
s pe
r ye
ar)
Proven reserves:34 x 109
barrels
200 x 109
barrels total 1975
Undiscovered:32 x 109
barrels
Fig. 14.19b, p. 339
Nuclear power
Natural gas
Oil
Coal
Synthetic oil andgas produced
from coal
Coal-firedelectricity
17%
58%
86%
100%
150%
286%
Fig. 14.20, p. 339
Low land use
Easily transportedwithin and between countries
High netenergy yield
Low cost (withhuge subsidies)
Ample supply for42–93 years
Advantages
Moderate waterpollution
Releases CO2 when burned
Air pollutionwhen burned
Artificially low price encourageswaste and discourages search for alternatives
Need to findsubstitute within50 years
Disadvantages
Fig. 14.21, p. 340
How long will the oil last
• 1. Identified Reserve will last 53 years at current usage rates
• 2. Known and projected supplies are likely to be 80% depleted within 42 to 93 years depending on usage rate– US oil supplies are expected to be depleted
within 15 to 48 years depending on the annual usage rate
Heavy Oils
• Oil 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)
Fig. 14.22, p. 340
Above Ground
Conveyor
Conveyor
Spent shale
Pipeline
Retort
Mined oil shale
Aircompressors
Shale oilstorage
Impuritiesremoved
Hydrogenadded
Crude oil Refinery
Airinjection
Shale layer
Underground
Shale heated to vaporized kerogen, which is condensed to provide shale oil
Sulfur and nitrogencompounds
Fig. 14.23, p. 341
Shale oil pumped to surface
Hydrogenadded
Impuritiesremoved
Syntheticcrude oil
Refinery
Pipeline
Tar sand is mined. Tar sand is heateduntil bitumen floats
to the top.
Bitumen vaporIs cooled andcondensed.
Fig. 14.24, p. 341
Advantages Disadvantages
Moderate existingsupplies
Large potentialsupplies
High costs
Low net energyyield
Large amount ofwater needed toprocess
Severe land disruption fromsurface mining
Water pollution from mining residues
Air pollution when burned
CO2 emissionswhen burned
Fig. 14.25, p. 342
XI. Natural Gas
• Natural 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 oil
• C. Unconventional deposits - include coal beds, shale rock, deep deposits of tight sands and deep zones that contain natural gas dissolved in hot hot water
Mined coal
Pipeline
Pump
Oil well
Gas well
Oil storage
CoalOil and Natural Gas Geothermal Energy
Hot waterstorage
Contourstrip mining
PipelineDrillingtower
Magma
Hot rock
Natural gasOil
Impervious rock
Water Water
Oil drillingplatformon legs
Floating oil drillingplatform
Valves
Undergroundcoal mine
Water is heatedand brought upas dry steam or
wet steam
Waterpenetratesdownthroughtherock
Area stripmining
Geothermalpower plant
Coal seam
Fig. 14.11, p. 332
XI. Natural Gas
• Gas 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)
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%
Advantages:
1. Cheaper than Oil2. World reserves - >125 years3. 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
Advantages Disadvantages
Good fuel forfuel cells andgas turbines
Low land use
Easily transportedby pipeline
Moderate environ-mental impact
Lower CO2 emissions thanother fossil fuels
Less air pollutionthan otherfossil fuels
Low cost (withhuge subsidies)
High net energyyield
Ample supplies(125 years)
Sometimes burned off andwasted at wellsbecause of lowprice
Shipped acrossocean as highlyexplosive LNG
Methane(a greenhouse gas) can leakfrom pipelines
Releases CO2
when burned
Fig. 14.26, p. 342
Disadvantages:
1. When processed, H2S and SO2 are released into the atmosphere
2. Must be converted to LNG before it can be shipped (expensive and dangerous)
3. Conversion to LNG reduces net energy yield by one-fourth
4. Can leak into the atmosphere; methane is a greenhouse gas that is more potent than CO2.
XII. Coal
– Coal 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
Three types of coal
• lignite (brown coal)• bituminous coal (soft coal)• anthracite (hard coal)
• Carbon content increases as coal ages; heat content increases with carbon content
Increasing moisture content
Increasing heat and carbon content
Peat(not a coal)
Lignite(brown coal)
Bituminous Coal(soft coal)
Anthracite(hard coal)
Heat
Pressure Pressure Pressure
Heat Heat
Partially decayedplant matter in swampsand bogs; low heatcontent
Low heat content;low sulfur content;limited supplies inmost areas
Extensively usedas a fuel becauseof its high heat contentand large supplies;normally has ahigh sulfur content
Highly desirable fuelbecause of its highheat content andlow sulfur content;supplies are limitedin most areas
Fig. 14.27, p. 344
Coal Extraction
• Subsurface Mining - labor intensive; world’s most dangerous occupation (accidents and black lung disease Surface Mining - three types
• 1. Area strip mining2. contour strip mining3. open-pit mining
Mined coal
Pipeline
Pump
Oil well
Gas well
Oil storage
CoalOil and Natural Gas Geothermal Energy
Hot waterstorage
Contourstrip mining
PipelineDrillingtower
Magma
Hot rock
Natural gasOil
Impervious rock
Water Water
Oil drillingplatformon legs
Floating oil drillingplatform
Valves
Undergroundcoal mine
Water is heatedand brought upas dry steam or
wet steam
Waterpenetratesdownthroughtherock
Area stripmining
Geothermalpower plant
Coal seam
Fig. 14.11, p. 332
Why we need coal
• Coal provides 25% of world’s commercial energy (22% in US).
• Used to make 75% of world’s steel
• Generates 64% of world’s electricity
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.
http://www.eas.asu.edu/~holbert/eee463/coal.html
. 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.
I. World’s Coal Supplies
• US - 66% of worlds proven reservesIdentified reserves should last 220 years at current usage rates. Unidentified reserves could last about 900 years
. Pros and Cons of Solid Coal
• Advantages
• World’s most abundant and dirtiest fossil fuel, High net energy yield
Advantages Disadvantages
Low cost (with huge subsidies)
High net energyyield
Ample supplies(225–900 years)
Releases radioactive particles and mercury into air
High CO2 emissionswhen burned
Severe threat tohuman health
High land use (including mining)
Severe land disturbance, air pollution, andwater pollution
Very high environmentalimpact
Fig. 14.28, p. 344
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)
Clean Coal Technology
• . Fluidized-bed combustion - developed to burn coal more cleanly and efficiently.
• Use of low sulfur coal - reduces SO2 emission
• Coal gasification – uses coal to produce synthetic natural gas (SNG)
• . Coal liquefaction - produce a liquid fuel - methanol or synthetic gasoline
Calcium sulfateand ash
Air
Air nozzles
Water
Fluidized bed
Steam
Flue gases
Coal Limestone
Fig. 14.29, p. 345
Raw coal
Pulverizer
Air oroxygen
Steam
Pulverized coalSlag removal
Recycle unreactedcarbon (char)
Raw gases CleanMethane gas
Recoversulfur
Methane(natural gas)
2CCoal
+ O2 2CO
CO + 3H2 CH4 + H2O
Remove dust,tar, water, sulfur
Fig. 14.30, p. 345
Advantages Disadvantages
Large potentialsupply
Vehicle fuel
Low to moderatenet energy yield
Higher cost thancoal
High environmentalimpact
Increased surfacemining of coal
High water use
Higher CO2 emissions than coal
Fig. 14.31, p. 346
Clean Coal Technology
• Synfuels - can be transported by pipeline inexpensively; burned to produce electricity; burned to heat houses and water; used to propel vehicles.
XIII. Nuclear Energy
• A. Three reasons why nuclear power plants were developed in the late 1950s:
• 1. Atomic Energy Commission promised electricity at a much lower cost than coal
• 2. US Gov’t paid ~1/4 the cost of building the first reactors
• 3. Price Anderson Act protected nuclear industry from liability in case of accidents
Gig
awat
ts o
f el
ectr
icity
1960 1970 1980 1990 2000 2010 2020
Year
0
75
150
225
300
375
Fig. 14.34a, p. 348
Gig
awat
ts o
f el
ectr
icity
Year
1960 1970 1980 1990 2000 20100
5
10
15
20
25
30
35
Fig. 14.34b, p. 348
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
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.
Periodic removaland storage of
radioactive wastesand spent fuel assemblies
Periodic removaland storage of
radioactive liquid wastes
Pump
Steam
Small amounts of Radioactive gases
Water
Black
Turbine Generator
Waste heat Electrical power
Hot water output
Condenser
Cool water input
Pump
Pump Wasteheat
Useful energy25 to 30%
WasteheatWater source
(river, lake, ocean)
Heatexchanger
Containment shell
Uranium fuel input(reactor core)
Emergency coreCooling system
Controlrods
Moderator
Pressurevessel
Shielding
Coolantpassage
Fig. 14.32, p. 346
CoolantCoolant
Hot coolantHot coolant
Front end Back end
Uranium mines and millsOre and ore concentrate (U3O8)
Geologic disposalof moderate-and high-levelradioactive wastes
High-levelradioactivewaste orspent fuelassemblies
Uranium tailings(low level but long half-life)
Conversion of U3O8
to UF6
Processeduranium ore
Uranium-235 as UF6
Enrichment UF6
EnrichedUF6
Fuel fabrication
Spent fuelreprocessing
Plutonium-239as PuO2
(conversion of enriched UF6 to UO2
and fabrication of fuel assemblies)
Fuel assemblies Reactor Spent fuel assemblies
Interim storageUnder water
Open fuel cycle today
Prospective “closed” end fuel cycle
Decommissioningof reactor
Decommissioningof reactor
Spent fuelassembliesSpent fuelassemblies
Fig. 14.33, p. 347
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 fission
• 3. 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
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 years
• B. After 15-40 years of operation, the plant must be decommissioned by
• 1. dismantling it• 2. putting up a physical barrier, or• 3. enclosing the entire plant in a tomb (to last
several thousand years)
Low risk of accidents because of multiplesafety systems(except in 35 poorly designed and run reactors in former SovietUnion and Eastern Europe)
Moderate land use
Moderate landdisruption andwater pollution(without accidents)
Emits 1/6 asmuch CO2 as coal
Lowenvironmentalimpact (withoutaccidents)
Large fuelsupply
Spreads knowledge and technology for building nuclear weapons
No acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants
Catastrophic accidents can happen (Chernobyl)
High environmental impact (with major accidents)
Low net energy yield
High cost (even with large subsidies)
Advantages Disadvantages
Fig. 14.35, p. 349
Coal
Ample supply
High net energyyield
Very high airpollution
High CO2emissions
65,000 to 200,000deaths per yearin U.S.
High land disruption fromsurface mining
High land use
Low cost (with huge subsidies)
Nuclear
Ample supplyof uranium
Low net energyyield
Low air pollution(mostly from fuelreprocessing)
Low CO2emissions(mostly from fuelreprocessing)
About 6,000deaths per year in U.S.
Much lower landdisruption fromsurface mining
Moderate land use
High cost (with huge subsidies)
Fig. 14.36, p. 349
F. Advantages of Nuclear Power:
• 1. Don’t emit air pollutants
• 2. Water pollution and land disruption are low
G. Nuclear Power Plant Safety
• 1. Very low risk of exposure to radioactivity• 2. 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 uncovered
• 3. 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.
http://www.angelfire.com/extreme4/kiddofspeed/chapter1.html
Steamgenerator
Waterpumps
Crane formoving fuel rods
TurbinesTurbines
ReactorReactor
Coolingpond
Coolingpond
Reactor power output was lowered too much, making it too difficult to control.
Additional water pump to cool reactor was turned on. But with low power output and extra drain on system, water didn’t actually reach reactor.
Automatic safety devices that shut down the reactor when water and steam levels fall below normal and turbine stops were shut off because engineers didn’t want systems to “spoil” experiment.
Radiation shieldsRadiation shields
Almost all control rods were removed from the core during experiment.
Emergency cooling system was turned off to conduct an experiment.
Fig. 14.37, p. 350Chernobyl
H. Low-Level Radioactive Waste
• 1. Low-level waste gives off small amounts of ionizing radiation; must be stored for 100-500 years before decaying to levels that don’t pose an unacceptable risk to public health and safety
• 2. 1940-1970: low-level waste was put into drums and dumped into the oceans. This is still done by UK and Pakistan
• 3. Since 1970, waste is buried in commercial, government-run landfills.
• 4. Above-ground storage is proposed by a number of environmentalists.
• 5. 1990: the NRC proposed redefining low-level radioactive waste as essentially nonradioactive. That policy was never implemented (as of early 1999).
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 240,000
• 2. Spent fuel rods; wastes from plants that produce plutonium and tritium for nuclear weapons.
J. Possible Methods of Disposal and their Drawbacks
• 1. Bury it deep in the ground• 2. Shoot it into space or into the sun• 3. Bury it under the Antarctic ice sheet or the Greenland
ice cap• 4. Dump it into descending subduction zones in the
deep ocean• 5. Bury it in thick deposits of muck on the deep ocean
floor• 6. Change it into harmless (or less harmful) isotopes• 7. 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)
Clay bottom
Up to 60deep trenchesdug into clay.
As many as 20flatbed trucksdeliver wastecontainers daily.
Barrels are stackedand surroundedwith sand. Coveringis mounded to aidrain runoff.
Fig. 14.38b, p. 351
What covers waste
Clay
Gravel
Sand
Compacted clay
Soil
Topsoil
Grass
Gravel
Fig. 14.38c, p. 351
Waste container
Steel wall
Steel wall
Severalsteel drumsholding waste
Lead shielding
2 meters wide2–5 meters high
Fig. 14.38a, p. 351
Storage Containers
Fuel rod
Primary canister
Overpack container sealed
Fig. 14.39c, p. 352
Underground
Buried and capped
Fig. 14.39d, p. 352
Ground Level
Unloaded from train
Lowered down shaft
Fig. 14.39a, p. 352
Personnel elevator
Air shaft
Nuclear waste shaft
2,500 ft.(760 m)deep
Fig. 14.39b, p. 352
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
3. Decommissioning a power plant (3 methods have been proposed)
• A. immediate dismantling• B. mothballing for 30-100 years• C. 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.
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 Could Thwart Nuclear Smugglers
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.
N. Breeder Reactors
• 1. Convert nonfissionable uranium-238 into fissionable plutonium-239
• 2. 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 1-200 years to produce enough plutonium to fuel a significant number of other breeder reactors.
O. Nuclear Fusion
• 1. D-T nuclear fusion reaction; Deuterium and Tritium fuse at about 100 million degrees
• 2. Uses more energy than it produces