Transcript Nuclear Energy

Nuclear Energy
What is it?
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Nuclear Energy- splitting of Atoms
Heavy Elements, such as Uranium have their
atoms split. A small amount of mater is
changed into a tremendous amount of
Energy
This energy is NOT used directly, instead it is
used to create heat---to boil water---creates
steam---move turbines—create Electricity
The Atom
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Summary: All matter is made
up of atoms.
All atoms are made up of
Protons and Neutrons, making
up the nucleus ,center of the
atom, while the Electrons fly
around it and is responsible for
all chemical activities.
Atomic Number: Gives the
atom its IDENTITY and
=Number of Protons
Atomic Mass: # P + N
ISOTOPES
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When atoms of the same element, have
different Atomic Masses, because of different
numbers of Neutrons, they are called
ISOTOPES.
Ex.: U-238(92 P, 146 N); U235( 92P, 143N)
C-12 (6P,6N); C-14 (6P, 8P)
RADIOACTIVITY
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Most Isotopes are unstable, and will decay or
break down. This allows for Energy and
particles to be emitted from their nuclei.
Atoms that decay in this way are called
radioactive atoms
Marie Curie, Polish physicist and chemist
was the first to use this term.
After a series of decay changes, a radioactive
element becomes stable and stops decaying.
Alpha, Beta particles and Gamma Rays
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Two types of particles are given off by the
nucleus of a radioactive atom,
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Alpha- made up of 2 P and 2N
Beta- it is a high-speed electron; this decay
converts a neutron into a proton.
Gamma Rays- energy given off as a form of
electromagnetic radiation.
All of the above, given off in the decaying of
unstable nuclei are called RADIATIONS.
HALF-LIFE
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The changes that occur in the decaying of an atom
cause the altering of that atom’s atomic number and
mass. Since the atomic number of an atom determines
the identity of an element, the decay process changes
one element into another.
Uranium’s isotopes eventually change to a stable form
of lead.
The amounts of time it takes for HALF of the atoms in
a sample of a radioactive element to decay is called
the isotope’s HALF-LIFE.
½ life of U-238= 4.5 BILLIONS years
½ life of U-235= 700 million years
Reactions and Reactors
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Nuclear Fission- a
reaction in which the
nucleus of a large atom
is split into smaller
nuclei, releasing
tremendous amounts of
Energy. This is what is
used to generate
Electricity.
Continue:
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Chain Reaction- when a neutron is fired into
the nucleus of an atom like U-235, it splits,
forming 2 new nuclei called daughter nuclei,
releases lots of E and more neutrons. These
other neutrons can hit other U-235 nuclei
splitting them causing more E and more
neutrons to be released. This continuous
action of N splitting nuclei is a CHAIN RxN.
Nuclear Reactors
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Heat is produced through fission of nuclear
material to generate electricity
Nuclear Fuel is about 97% U-238 and 3%
U-235.
The U-238 is NOT fissionable, so it does
NOT take part in the nuclear reaction.
Nuclear reactors use water as a coolant, and
to slow the movement of neutrons released
during the chain reaction.
Cont.
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The control rods, absorb some of the
neutrons released by the fission of U-235
fuel, again slowing the chain reaction.
If the above did not occur, the number of
neutrons in the core of the reactor would
increase, this would make it run faster,
producing more and more heat until the core
melted from the heat of its own reaction.
Remember, you want to create “controlled
amounts” of heat to generate electricity.
Breeder Reactors
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Over 99% of the naturally occurring Uranium
is not fissionable isotope U-238.
BUT, if U-238 absorbs a Neutron it changes
into a fissionable Plutonium-239 or P-239. A
breeder reactor uses this process to produce
new fuel while it generates usable energy.
B. R.- not used in US because of fear of
nuclear terrorism. The plutonium used for
energy can also be used to create Atomic
bombs.
Radioactive Waste
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Two types of radioactive wastes:
1. High Level Wastes- Radioactive wastes that emit
large amounts of radiations.
a. Uranium fuel rods, water used as
coolant,
vessel surrounding fuel rods
2. Medium level and low level wastes- not as
radioactive, but more of it is being produced.
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Clothes of power plant worker, wastes from
hospitals and laboratories.
b. Because the above wastes are more common,
they might actually be more dangerous than
the high level wastes.
a.
Waste Disposal
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The long Half-lives of elements of radioactive
wastes pose a serious disposal problems.
Wastes sealed in containers that will not corrode for
thousands of years. Glass is the preferred
containers
Sites- must be geologically stable, no volcanic or
earthquake activity must be present.
Stored deep underground-very expensive
Most wastes are not permanently disposed of. They
are placed in positions to poison the environment,
since the cost of disposal is too prohibitive.
Safety and Cost
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Most Imp! At Nuclear power plant- safety
must be a priority. Unthinkable damage can be done to
the environment.
Meltdown- the process by which a nuclear chain
reaction goes out of control and melts the reactor core.
Most power plants are built to avoid melt downs,
however in 1986, in Chernobyl, Ukraine, one of their
cores had a melt down.
Today people are still paying fort eh Chernobyl
incident.
IS THE USE OF NUCLEAR POWER WORTH THE
RISK? library.thinkquest.org/
C004218/Homepage.htm
Chernobyl: Before
Chernobyl: After
Trench Disposal Method
Low Level Waste Disposal
Vault Concept
YUCCA MOUNTAIN