Chapter 20 Nuclear Energy and the Environment. Nuclear Energy –The energy of the atomic nucleus...
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Chapter 20 Nuclear Energy and the Environment
Chapter 20 Nuclear Energy and the Environment. Nuclear Energy –The energy of the atomic nucleus Nuclear Fission –The splitting of the atomic nuclei Nuclear
Nuclear Energy The energy of the atomic nucleus Nuclear Fission
The splitting of the atomic nuclei Nuclear Fusion The fusing of
atomic nuclei Nuclear Reactors Devises that produce controlled
nuclear fission
Slide 3
History Enrico Fermi (Italian Physicist) Demonstrated the 1 st
human controlled nuclear fission in 1942. Led to the development of
nuclear energy to produce electricity Nuclear reactors supply power
for Electricity for homes & industry Submarines, aircraft
carriers and icebreaker ships
Slide 4
Uranium Isotopes Three types of uranium isotopes occur in
nature U-238 99.3% U-2350.7% U-2340.005% U-235 & U-238 are two
radioactive isotopes of uranium. U-235 is the only naturally
occurring fissionable material essential for production of nuclear
energy
Slide 5
Fission Reactors Split U-235 by neutron bombardment. Produces:
neutrons, fission fragments and heat. The released neutrons strike
other U-235, releasing more neutrons, fragments and heat. Neutrons
are fast moving, water is used as a MODERATOR to slow them
down
Slide 6
Fission Reactors As fission occurs, energy is released (HEAT)
Major components of a fission reactor: Core, control rods, coolant,
reactor vessel Burner Reactors: 1% of uranium is used, 99% end up
as waste. The heat produced is used to create steam to run turbine
generators that produce electricity. (The reactor has the same
function as a boiler in a coal or oil-burning plant)
Slide 7
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Slide 10
Fission Reactor Reactor Core made up of fuel pins enriched
uranium pellets. A minimum fuel concentration is necessary to keep
the reactor CRITICAL able to achieve a self-sustaining chain
reaction. To control the number of neutrons that cause fission. A
control rod is used. It is suspended fully into the core to STOP
the fission reaction. B-10B-11Ag-105Ag-107Cd-113 In-115Hf-174
Hf-176 High neutron absorption rate.
Slide 11
Reactor and Core
Slide 12
Fission Reactor Coolant is cycled through the reactor to remove
heat. The rate of generation of heat MUST EQUAL the rate at which
the heat is carried away. Major nuclear accidents occur when this
balance is NOT maintained. Meltdown: a nuclear accident in which
the nuclear fuel forms a molten mass that breaches the containment
of the reactor, contaminating the outside environment with
radioactivity
Slide 13
Sustainability and Nuclear Power Nuclear Radiation occurs when
a radioisotope spontaneously undergoes radioactive decay and
changes into another isotope 3 types of nuclear radiation: Alpha,
Beta, Gamma
Slide 14
Breeder Reactor Uses nuclear fission Designed to produce new
nuclear fuel a type of nuclear reactor that utilizes between 40-70%
of its nuclear fuel and converts low level nuclear waste into
fisible nuclear fuel. Highly radioactive, extremely high heat
production.
Slide 15
Fusion Reactor Combining the nuclei of light elements
(hydrogen) to form heavier ones (helium) Two isotopes of hydrogen
deuterium and tritium are used in the fusion reaction to produce
helium Helium 20% of energy released Neutrons 80% of energy
released Temp must be approx. 100 million degrees celcius. Density
of the fuel elements must be high One gram of DT fuel = 45 barrels
of oil
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Nuclear Energy and the Environment Nuclear Fuel Cycle: the
process involved in producing nuclear power from the mining and
processing of uranium to controlled fission, the reprocessing of
spent nuclear fuel, the decommissioning of power plants and the
disposal of radioactive waste Each part of the cycle is associated
with different potential environmental problems
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Slide 19
Problems with Nuclear Power Uranium mines & mills produce
radioactive waste material. U-235 enrichment produces radioactive
waste Environmental review process for the building of nuclear
power plants is very cumbersome. The site on which a plant will be
built is concerning to neighbors (NIMBY) The US does NOT reprocess
spent fuel disposal is a problem Nuclear waste disposal facilities
are extremely controversal (NIMBY) Decommissioning of power plants
is relatively new. The lifetime of a plant is several decades.
Terrorist Activity
Slide 20
Effects of Radioisotopes Effect Environment in 2 Ways Emitting
radiation Entering ecological food chains Biomagnification Ex.
Ce-137 and reindeer moss (Read pg 420 and outline)
Slide 21
Slide 22
Nuclear Power Plant Accidents Three Mile Island, Pa (1979)
Chernobyl (1986)
Slide 23
Three Mile Island March 28, 1979 Harrisburg, Pa Malfunction of
a valve, along with human error Radiation released was contained by
the containment structure as designed. Small amounts of radiation
released into environment On day 3 at the site radiation measured
12 mSv/hour. Comparison Avg. American recieves 2 mSv/yr from
natural radiation mSv = millisievert
Slide 24
Chernobly April 26, 1986 The world found out about the accident
two days later, when in Sweden, a nuclear power plant was measuring
elevated radiation levels Cooling system failed, due to human error
3 billion people in the Northern Hemisphere received varying amts
of radiation Acutely effects the 30-km zone surrounding the
site
Slide 25
Chernobyl Major long term affect Thyroid Cancer Most cancers
associated with radiation exposure have an onset 10 25 yrs later
(this is year 25) Radiation still contaminates soil, vegetation,
surface & groundwaters.
Slide 26
Radioactive Waste Management Low-Level Radioactive Waste Waste
materials that contain sufficiently low concentrations or
quantities of radioactivity so as not to present a significant
environment hazard if properly handled Solutions from chemical
processing, sludges, acids, tools, plastics, glass, etc. US started
with 6 sites 3 have been closed due to leaks 1 closed due to
finances 2 sites remain open in Washington and S. Carolina
Slide 27
Radioactive Waste Management Transuranic Waste Radioactive
waste consisting of human-made radioactive elements heavier than
uranium Contaminated clothing rags, tools, etc. Generated from
production of nuclear weapons and Cleanup of nuclear weapon
facilities Contain plutonium life of 250,000 yrs. Carlsbad,
N.Mexico Isolated at 655m deep in salt beds, geologically
stable
Slide 28
Radioactive Waste Management High-Level Radioactive Waste
Extremely toxic nuclear waste, such as spent fuel elements from
commercial reactors. Extremely toxic Temporary solution Stored at
more than 100 sites in 40 states Nuclear Waste Policy Act of 1982,
1987,1992,2002 Yucca Mountain, Nevada only site evaluation
specified in the 1987 Act.