chapter 17 15 new part 2

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

chapter 17 15 new part 2

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