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8/12/2019 Chapter 17 15 New Part 2
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Nonrenewable Energy
Chapter 17 - Nuclear
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Key Concept 5: What Are the Advantages
and Disadvantages o f Nuc lear Energy?
Nuclear power has a low environmental impactand a very low accident risk, but high costs, a
low net energy yield, long-lived radioactive
wastes, vulnerability to sabotage, and the
potential for spreading nuclear weapons
technology have limited its use.
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How Does a Nuclear Fission
Reactor Work?
Controlled nuclear fission reactions occur in areactor
MostlyLight-water reactors
Fueled by uranium ore that is mined from earths
crust
Packed (or concentrated) as uranium dioxide pelletsin fuel rods
One pellet contains the energy of 1 ton of coal Rods grouped intofuel assemblies and placed in
core of reactor
Control rods absorb neutrons regulating rate of
fission
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How Does a Nuclear Fission
Reactor Work?
Water is the usualcoolant that removes heatfrom the reactor to prevent melting
Containment shell (steel and concrete) aroundthe core for protection from radioactive leakage
Water-filled pools or dry casks for storage ofradioactive spent fuel rod assemblies
Remain radioactive for 10,000-240,000 years
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Light-Water-Moderated and -Cooled
Nuclear Power Plant with Water Reactor
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After 3 or 4 Years in a Reactor, Spent Fuel
Rods Are Removed and Stored in Water
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The Nuclear Fuel Cycle
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What Happened to Nuclear Power?
Slowest-growing energy source and expected todecline more
Reactors ordered have since been cancelled
France (77%), Japan & S. Korea (39%)
Why? Economics
Poor management
Low net yield of energy of the nuclear fuel cycle Safety concerns
Need for greater government subsidies
Concerns of transporting uranium
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Worst Commercial Nuclear Power Plant
Accident in the U.S.
Three Mile Island March 29, 1979
Near Harrisburg, PA, U.S.
Nuclear reactor lost its coolant, mechanical failuredue and human error
Led to a partial uncovering and melting of theradioactive core
Unknown amounts of radioactivity escaped 50,000 people fled the area (+50,000 evacuated)
Increased public concerns for safety
Led to improved safety regulations in the U.S.
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Worst Nuclear Power Plant Accident in
the World
Chernobyl
April 26, 1986 in Chernobyl, Ukraine
Series of explosions caused the roof of a reactorbuilding to blow off
Partial meltdown and fire for 10 days Huge radioactive cloud spread over many
countries and eventually the world
100 times more radioactivity released than atomicbombs in WWII
350,000 people left their homes
Effects on human health, water supply, and
agriculture still remain
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Remains of a Nuclear Reactor at the
Chernobyl Nuclear Power Plant
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Nuclear Power Plants Are Vulnerable to
Terrorists Acts
Explosions or meltdowns possible at the powerplants but more seriously are the risks of.
Storage pools and casks are vulnerable tosabotage and terrorist attack
60 countries have or have the ability to build
nuclear weapons
Some believe this is reason enough not to
expand nuclear power use
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Dealing with Radioactive Wastes Produced
by Nuclear Power Is a Difficult Problem
High-level radioactive wastes Must be stored safely for 10,000240,000
(plutonium) years
Where to store it
Deep burial: safest and cheapest option
Would any method of burial last long enough?
There is still no facility
Can the harmful isotopes be changed intoharmless isotopes?
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O
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What Do We Do with Worn-Out Nuclear
Power Plants?
Decommission or retire a power plant withcorrosion and radiation damage
Some options Dismantle the plant and safely store the
radioactive materials
Enclose the plant behind a physical barrier with
full-time security until a storage facility has beenbuilt
Enclose the plant in a tomb
Monitor this for thousands of years
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Can Nuclear Power Lessen Dependence
on Imported Oil, Reduce Global Warming?
Nuclear power plants: no CO2emission, but Nuclear fuel cycle: emits CO2
Opposing views on nuclear power and globalwarming
Nuclear power advocates
2003 study by MIT researchers reports 1000-1500 reactors necessary to help global warming
439 exist today
2007: Oxford Research Groupsimilar study and
results
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Will Nuclear Fusion Save Us?
What is nuclear fusion?
Deuterium and tritium at 100 million degrees
Still in the laboratory phase after 50 years of researchand $34 billion dollarsnone produced more energythan used
2006: U.S., China, Russia, Japan, South Korea, andEuropean Union
Will build a large-scale experimental nuclear fusionreactor by 2040
Nuclear fusion is the power of the future and alwayswill be
A N d S f N l R t th
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Are New and Safer Nuclear Reactors the
Answer?
Advanced light-water reactors (ALWR) Built-in passive safety features
High-temperature-gas-cooled reactors (HTGC)
Removes water cooled problems
Pebble bed modular reactor (PBMR) Pros: no need to shut down for refueling, check
and rotate pebbles
Consstill many mostly safety related
Breeder nuclear fission reactorsexpensive! Converts nonfissionable uranium-238 into fissionable
plutonium-239
Produces more energy than consumed
A N d S f N l R t th
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Are New and Safer Nuclear Reactors the
Answer?
New Generation nuclear reactors must satisfythese five criteria:
Safe-runaway chain reaction is impossible
Fuel can not be used for nuclear weapons Easily disposed of fuel
Nuclear fuel cycle must generate a higher netenergy yield than other alternative fuels, without
huge government subsidies Emit fewer greenhouse gases than other fuels
E t Di b t th F t f
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Experts Disagree about the Future of
Nuclear Power
Proponents of nuclear power Fund more research and development
Pilot-plant testing of potentially cheaper and safer
reactors Test breeder fission and nuclear fusion
Opponents of nuclear power
Fund rapid development of energy efficient andrenewable energy resources