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BI 105A Environmental Biology Professor Jill Nissen Montgomery College Fall 2006 Chapter 12 Nuclear Energy Chemical Energy Chemical reactions involve the forming and breaking of bonds between atoms, but Chemical energy is the energy stored in the bonds of molecules

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bi 105a environmental biology

BI 105AEnvironmental Biology

Professor Jill Nissen

Montgomery College

Fall 2006

chapter 12

Chapter 12

Nuclear Energy

chemical energy
Chemical Energy
  • Chemical reactions involve the forming and breaking of bonds between atoms, but
  • Chemical energy is the energy stored in the bonds of molecules
  • atoms of one element do not change to atoms of another element, nor does any of their mass change to energy
nuclear energy
Nuclear Energy
  • Nuclear energy is the energy released by nuclear fission or fusion
  • Nuclear reactions involve changes in the nuclei of atoms, and
  • small amounts of mass are converted to large amounts of energy:
  • E = mc2
nuclear energy5
Nuclear Energy
  • Nuclear reactions produce 100,000 times more energy per atom than do chemical reactions such as combustion
slide6

Split atoms

Neutrons

Uranium-235

Nuclear Energy Comes From Fission

slide7

Heat

Neutrons

Splitting Atoms Releases Neutrons, Making Heat

slide8

Steam produced

Electricity

Heat

Heat Produces Steam, Generating Electricity

Steam

Generator

Turbine

Condenser

slide9

Nuclear Power PlantTurbine and Generator

Steam

Spinning turbine blades and generator

Boiling water

uranium 235
Uranium-235
  • Uranium ore consists of 3 isotopes: U-238, U-235, and U-234
  • Uranium is naturally radioactive
    • the emission of energetic particles or rays from unstable atomic nuclei
  • Only U-235 is a fissionable material that can be used for nuclear power
slide15

Controlling the Chain Reaction

Fuel Assemblies

Control rods

Withdraw control rods,

reaction increases

Insert control rods,

reaction decreases

slide17

U.S. Emission-Free Electricity(2003)

Source: U.S. Energy Information Administration

slide18

29% Greater

Nuclear Energy Limits Carbon Dioxide Emissions in Power Sector(2002)

Electric Power Industry CO2 Emissions

Estimated Electric Power Industry CO2 Emissions Without Nuclear Power

Source: EPA

slide19

33% Greater

Nuclear Energy Limits Sulfur Dioxide Emissions in Power Sector(2002)

Electric Power Industry SO2 Emissions

Without Nuclear Power

Sources: EPA, EIA

slide20

International Programs

  • Finland and China are adding reactors to meet energy demand and enhance air quality
  • Germany and Sweden committed to phasing out nuclear power, then
    • Germany later launched a pilot program that includes allowances for nuclear plants
    • In 2002 Sweden removed the deadline for shut down
  • Canada approved tax incentives for nuclear capacity
  • France obtains 77% of its electricity from nuclear power
slide21

U.S. Programs

  • U.S. phasing out
  • U.S. currently ~7% of energy nuclear;
  • no new U.S. power plants ordered since 1976
  • 40% of 105 commercial nuclear power expected to be retired by 2015 & all by 2030;
what happened
What Happened?
  • crippled by high & uncertain costs;
  • frequent malfunctions (Three Mile Island, Chornobyl);
  • false assurances and cover–ups;
  • overproduction of energy in some areas;
  • poor management;
  • lack of public acceptance.
three mile island
Three Mile Island
  • What happened, step by step
  • http://www.pbs.org/wgbh/amex/three/sfeature/index.html
history s worst nuclear accident
History’s Worst Nuclear Accident
  • April 26, 1986 - During a test at the Chornobyl plant, the No. 4 reactor exploded
  • April 27, 1986 – The secret was out!
  • 203 hospitalized, 31 died
  • Evacuation zone 30km over a month
  • Thyroid cancer among children increased
  • Still waiting for long-term effects
history s worst nuclear accident25
History’s Worst Nuclear Accident
  • The sum of [Chornobyl] and exposures to people all over the world," writes Bernard Cohen, "will eventually, after about fifty years, reach 60 billion millirems, enough to cause about 16,000 deaths.“ He puts Chornobyl's danger in context by pointing out that 16,000 deaths are caused every year by air pollution from coal-burning power plants in the United States alone.
pros and cons of nuclear energy

Land use

17,000 ac

1,900 ac

Daily fuel requirement

9,000 tons/day

3 kg/day

Moderate to severe

Air pollution

Low

Radioactive emissions

1 curie

28,000 curies

Long-term risk over large area

Risk from catastrophic accidents

Short-term local risk

Pros and Cons of Nuclear Energy

Impact

Coal

Nuclear

radioactive wastes
Radioactive Wastes
  • Low level radioactive wastes are items contaminated by radioactivity that give off small amounts of ionizing radiation
  • High level radioactive wastes are produced by nuclear power plants and give off large amounts of ionizing radiation
    • Dangerous levels of radioactivity require special handling and secure storage
    • Case-in-Point: Yucca Mountain
    • http://msnbc.msn.com/id/3042216/
fuel for nuclear weapons

Can be reprocessed for . . .

OR

Nuclear weapons

Fuel for Nuclear Weapons
  • The Link Between Nuclear Energy and Nuclear Weapons

Spent fuel from conventional nuclear plant

Fuel for breeder reactor

the future of nuclear power
The Future of Nuclear Power
  • The safe disposal of radioactive wastes is one of the main difficulties to be overcome if nuclear energy is to realize its potential in the 21st centure
review objectives
Review Objectives

Introduction to Nuclear Processes• Distinguish between nuclear energy and chemical energy.• Contrast fission and fusion.• Define radioactive decay.

Nuclear Fission• Describe the nuclear fuel cycle, including the process of enrichment.• Define nuclear reactor and describe a typical nuclear power reactor.

Pros and Cons of Nuclear Energy• Discuss the pros and cons of electric power produced by nuclear energy versus coal.

Safety Issues in Nuclear Power Plants• Describe the nuclear power plant accidents at Three Mile Island and Chornobyl.• Discuss the link between nuclear energy and nuclear weapons.

Radioactive Wastes• Distinguish between low-level and high-level radioactive wastes.• Relate the pros and cons of permanent storage of high-level radioactive wastes at Yucca Mountain

The Future of Nuclear Power• Briefly summarize the issues that must be addressed if nuclear power is to become a major energy source in the future.