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Nuclear Energy: Benefits and Risks Chapter 11 The Nature of Nuclear Energy Radioactive - Nuclei of certain atoms are unstable and spontaneously decompose. Neutrons, electrons, protons, and other larger particles are released, along with energy.

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the nature of nuclear energy
The Nature of Nuclear Energy
  • Radioactive - Nuclei of certain atoms are unstable and spontaneously decompose.
    • Neutrons, electrons, protons, and other larger particles are released, along with energy.
      • Radioactive Half-Life - Time it takes for half the radioactive material to spontaneously decompose.
the nature of nuclear energy3
The Nature of Nuclear Energy
  • Only certain kinds of atoms are suitable for development of a nuclear chain reaction.
    • The two most common are uranium-235 and Plutonium-239.
      • Requires certain quantity of nuclear fuel (critical mass).
radiation
Radiation
  • Types:
    • Alpha - Moving particles composed of two neutrons and two protons.
      • Stopped by layer of skin.
    • Beta - Consists of electrons from nucleus.
      • Stopped by layer of clothing.
    • Gamma - Form of electromagnetic radiation.
      • Can pass through several centimeters of concrete.
radiation5
Radiation
  • If the radiation reaches living tissue, equivalent doses of beta and gamma radiation can cause equal amounts of biological damage.
    • Alpha particles are more massive, thus can cause more damage to biological tissues.
the nature of nuclear energy6
The Nature of Nuclear Energy
  • Nuclear Fission - Occurs when neutrons impact and split the nuclei of certain atoms.
    • Nuclear Chain Reaction - Splitting nuclei release neutrons, which themselves strike more nuclei, in turn releasing even more neutrons.
history of nuclear energy development
History of Nuclear Energy Development
  • First controlled fission - Germany 1938.
  • 1945 - U.S. dropped atomic bombs on Hiroshima and Nagasaki.
  • Following WW II, people began exploring other potential uses of nuclear energy.
  • U.S. built world’s first nuclear power plant in 1951.
dwight d eisenhower
Dwight D. Eisenhower
  • “Atoms for Peace” 1953:
    • “Nuclear reactors will produce electricity so cheaply that it will not be necessary to meter it.”
  • Today’s Reality:
    • Accidents have caused worldwide concern.
    • Most new projects have been stopped.
      • Many experts predict rebirth.
nuclear fission reactors
Nuclear Fission Reactors
  • Nuclear Reactor - Device that permits a controlled fission chain reaction.
    • Nucleus of U-235 atom struck by slowly moving neutron from another atom.
      • Nucleus split into smaller particles.
        • More neutrons released.
          • Strike more atoms.
nuclear fission reactors12
Nuclear Fission Reactors
  • Control Rods - Made of a non-fissionable material (boron, graphite) that are lowered into reactor to absorb neutrons.
    • Withdrawn to increase rate of fission.
  • Moderator - A substance that absorbs energy, slowing neutrons, enabling them to split the nuclei of other atoms more efficiently.
workings of a nuclear reactor
Workings of A Nuclear Reactor
  • Nuclear reactor serves same function as fossil-fuel boiler: produces heat - converts water to steam - turns a turbine - generating electricity.
        • Boiling Water Reactors (BWR)
plans for new reactors worldwide
Plans for New Reactors Worldwide
  • Currently 439 nuclear power reactors in 31 countries.
    • Combined capacity of 354 gigawatts.
    • Provide 16% of world’s electricity.
  • Currently 32 reactors under construction in 10 countries.
    • Forecasting becomes uncertain after 2005.
      • Most planned reactors in Asia and parts of former Soviet Union.
plant life extension
Plant Life Extension
  • Most nuclear power plants originally had normal design lifetime up to 40 years.
    • Engineering assessments have established many plants can operate much longer.
      • Economic, regulatory, and political considerations have thus far led to premature closure of some plants.
nuclear power concerns
Nuclear Power Concerns
  • Currently, 17% of electricity consumed worldwide comes from nuclear power.
    • Accidents raised questions about safety.
    • Contamination and disposal problems.
    • Plants may be terrorism targets.
      • Spent fuel storage facilities.
        • More total radioactivity than the reactor.
          • Still not easy, or prime target.
reactor safety
Reactor Safety
  • Three Mile Island - Pennsylvania
    • March 28, 1979 - Partial Core Melt-Down.
      • Pump and valve malfunction.
        • Operator error compounded problem.
      • Crippled reactor was de-fueled in 1990 at a cost of about $1 billion.
        • Placed in monitored storage until its companion reactor reaches the end of its useful life.
reactor safety19
Reactor Safety
  • Chernobyl - Ukraine
    • April 26, 1986
    • Experiments being conducted on reactor.
      • Multiple serious safety violations.
    • Reactor Explodes.
      • 31 deaths.
        • 116,000 people evacuated.
          • 24,000 evacuees received high doses of radiation.
      • Increased thyroid cancer in children.
reactor safety20
Reactor Safety
  • A consequence of both of the accidents has been a deepened public concern over nuclear reactor safety.
    • Since 1980, 10 countries have cancelled nuclear plant orders or mothballed plants under construction.
      • Increased Public Opposition:
        • United Kingdom: 65% - 83%
        • Germany: 46% - 83%
        • United States: 67% - 78%
exposure to radiation
Exposure to Radiation
  • Type and degree of damage vary with radiation form, dosage and duration of exposure, and type of cells irradiated.
    • Because mutations are permanent, radiation effects may build up over years and only appear later in life.
thermal pollution
Thermal Pollution
  • Addition of waste heat to the environment.
    • Especially dangerous in aquatic systems.
      • In a nuclear power plant, 1/3 of heat used to generate electricity while the other 2/3 is waste.
        • Fossil fuel plants are 50:50.
      • To reduce the effects of waste heat, utilities build cooling facilities.
        • Ponds
        • Towers
decommissioning costs
Decommissioning Costs
  • Life expectancy of most electrical generating plants is 30-40 years.
    • Unlike other plants, nuclear plants are decommissioned, not demolished.
      • Involves removing the fuel, cleaning surfaces, and permanently barring access.
        • Over 70 nuclear power plants in the world are awaiting decommissioning.
decommissioning costs24
Decommissioning Costs
  • By 2005, 68/104 U.S. plants will be at least 20 years old.
    • Nuclear Regulatory Commission may extend authorization an additional 20 yrs.
decommissioning uncertainties
Decommissioning Uncertainties
  • Utilities Have (3) Options:
    • Decontaminate and Dismantle plant ASAP.
    • Shut Down plant for 20-100 years, allowing radiation to dissipate, then dismantle.
    • Entomb plant within concrete barrier.
      • Recent experience indicates decommissioning a large plant will cost between $200 and $400 million.
radioactive waste disposal
Radioactive Waste Disposal
  • Today, the U.S. has 380,000 cubic meters of highly radioactive military waste temporarily stored at several sites.
    • Waste Isolation Pilot Plant (WIPP) Carlsbad, NM began accepting waste in March, 1999.
      • Transuranic wastes - High-level radioactive waste consisting primarily of various isotopes of plutonium.
radioactive waste disposal28
Radioactive Waste Disposal
  • In addition to high-level waste from weapons programs, 2 million cubic meters of low-level radioactive military and commercial waste are buried at various sites.
    • About 30,000 metric tons of highly radioactive spent fuel rods are stored in special storage ponds at nuclear reactor sites.
      • Many plants are running out of storage.
radioactive waste disposal29
Radioactive Waste Disposal
  • High Level Radioactive Waste:
    • At this time, no country has a permanent storage solution for the disposal of high-level radioactive waste.
      • Politics of disposal are as crucial as disposal method.
        • Most experts feel the best solution is to bury waste in a stable geologic formation.
high level waste storage in the united states
High-Level Waste Storage in the United States
  • In 1982, Congress called for a high-level radioactive disposal site to be selected by March 1987, and to be completed by 1998.
    • In 2002, the Secretary of Energy indicated the choice of a site at Yucca Mountain in Nevada was based on scientifically sound and suitable science.
      • Current work is primarily exploratory and is seeking to characterize the likelihood of earthquake damage and water movement.
high level waste storage in the united states31
High-Level Waste Storage in the United States
  • If completed, the facility would hold about 70,000 metric tons of spent fuel rods and other highly radioactive material.
    • Not to be completed before 2015.
      • By that time, waste produced by nuclear power plants will exceed the storage capacity of the site.
low level waste
Low - Level Waste
  • Currently, U.S. produces about 800,000 cubic metersof low-level radioactive waste annually.
    • Presently buried in various scattered disposal sites.
      • Political limbo.
exposure to radiation35
Exposure to Radiation
  • Human exposure usually expressed in rems.
    • Measure of biological damage to tissue.
      • The higher the dose, the more observable the results.
        • No human is subject to zero exposure.
          • Average person exposed to 0.2 to 0.3 rems per year from natural and medical sources.
politics of nuclear power
Politics of Nuclear Power
  • Nuclear power projections are subject to considerable uncertainty, both economic and political.
    • In large part, governmental support for nuclear power has waxed and waned with the changing of government regimes.
politics of nuclear power37
Politics of Nuclear Power
  • Nuclear power is projected to represent a shrinking share of the world’s electricity consumption from 2004 through 2025.
    • Most nuclear additions are expected to be in Asia. (China, India, Japan, S. Korea)
      • Life extension and higher capacity factors will play a major role in sustaining the U.S. nuclear industry throughout this period.