Transcript Nuclear Fission

Nuclear Power: Basics
An Alternative to Coal?
Statistics
• Over 16% of the worlds energy is
produced from nuclear reactors
• There are 439 nuclear power stations in
the world, 104 of which are in the USA
Fun Facts
• Nuclear energy is the energy from the
nucleus of a Uranium atom.
• Uranium is made into small pellets, about
the size of your fingertip.
• Each pellet produces the same amount of
energy as 150 gallons of oil.
Atoms and
Radioactivity
Section 16.1
What is an Atom?
• Atoms: protons, neutrons,
electrons
• Nucleus: cluster of protons
and neutrons in the center
of an atom
Atoms and Isotopes
• Atomic number: number of protons in an atom
• Mass number: number of protons plus the
number of neutrons
• Isotopes: atoms of the same element that have
different numbers of neutrons
Isotopes
What is the difference
between U-238 and
U-235?
Examples: Page 429
Element 1. Silver
2. Ca
3. Hydrogen
4. Iron
5. Cu
Atomic Number / Mass Number
Radioactivity
• Radioactive atoms: unstable atoms that decay
and emit particles and energy from their nuclei
– Not all elements are radioactive
• Most cases it is only certain isotopes that are radioactive
– Example:
»H – 1 =
»H – 2 =
»H – 3 =
3 Types of Particles
• Alpha particles: made up of two protons and two
neutrons
– Emitted by uranium – byproduct of Nuclear Energy
• Beta particles: high speed electron
– used to treat health conditions such as eye and bone
cancer
• Gamma particles: form of electromagnetic radiation
– often used to kill living organisms, in a process called
irradiation
• sterilizing medical equipment
Radiation
• Radiation: the alpha particles,
beta particles, and gamma
rays given off in the decaying
of unstable nuclei
HALF-LIFE
• Emitting alpha particles =
– Losing protons and neutrons
• Emitting beta particles =
– Converting neutrons to protons
• ULTIMATELY
– Change alters the atomic number and the mass
number of the atom
– Atomic number = determines identity
• CHANGES ONE ELEMENT INTO ANOTHER
HALF-LIFE
• The amount of time it takes for half of the atoms in
a sample of radioactive element to decay
– Amount of time it takes for half of atom to decay
• Vary from few seconds to billions of years
• U-238 = 4.5 billion years & U-235 = 700
million years
Section 16.2
Reactions
and
Reactors
Nuclear Energy
• Nuclear energy: energy within the
nucleus of an atom
• Advantages:
– Very concentrated
– Doesn’t produce air polluting gases
– Release less radioactivity than coal fired
power plants
• Disadvantages:
– Very expensive
– Difficult to find a safe place to store waste
– High safety concerns
Nuclear Fission
Nuclear fission is the process of splitting a
nucleus into two nuclei with smaller
masses.
• Energy can be released from an
atom by splitting the nucleus of
the atom apart
• Nuclear Fission: a reaction in
which the nucleus of a large atom
is split into smaller nuclei
– Large Energy =
Electricity
Nuclear Fission
• Fissionable: an atom splits when its nucleus is
struck by a neutron
– Only large nuclei with atomic numbers above 90 can
undergo fission.
• CONTINUOUS REACTION CREATES
– Chain reaction: continuous action of neutrons splitting
atomic nuclei
• Mass of atomic nucleus is converted to energy
Nuclear Reactors
• Heat is produced through the
fission of nuclear material
• Nuclear reactor vessel: where
the fission of U-235 takes place
• Control rods: absorbs neutrons
1. Raising and lowering rods
regulates the amount of heat
produced –
2. Sot water moves inside pipes to a
heat exchanger where it heats
water for steam
3. Steam is then used to turn
turbines connected to electric
generators
Nuclear Reactor vs. Breeder Reactor
• Nuclear Reactor
– Uses Uranium – 235 (U-235)
• Breeder Reactor
– 99% of natural occurring Uranium = U-238
• Not Fissionable
• BUT
• Absorbs neutron = Highly fissionable Plutonium-239
– Process forms energy.
Breeder Reactors
• Breeder reactor: process used to
produce new fuel while
generating usable energy
• NOT used in the U.S. because of
concerns about nuclear terrorism
– the plutonium produced by
breeder reactors can be used to
make atomic bombs
Section 16.3
Radioactive
Waste
Nuclear Power Plants
• Produce Radioactive Waste
• Radiation
–Changes in DNA = Cancer & Genetic
Mutations
–Large Doses = Burns, Anemia, & Death
–Amount of Exposure = Extent of
Damage
Radiation Exposure
• Measured in “rems”
–Normally = 0.2-0.5 rems per year
• 88% Natural occurring substances
• TWO TYPES
–High-Level Wastes
–Medium-Level & Low-Level Wastes
High-Level Waste
• Emits large amounts of radiation
• Types
– Used Uranium fuel rods
– Control Rods
– Water used to cool and control chain reaction
– Vessel surrounding the
fuel rods
Medium-Level & Low Level Waste
• Slightly less radioactive, BUT generated in
much larger volume.
• Types of Medium-Level
– Mine waste around uranium mine
– Containment protective clothing
• Low-Level
– Hospitals and laboratories
Waste: Storage
Pools
The spent fuel rod pool inside the Clinton Nuclear Power Plant in Clinton, Ill., is shown on Tuesday, Nov. 19, 1996. The water in the pool
acts as a shield against radiation from the used uranium rods. The reactor was shut down due to an equipment malfunction Sept. 5, 1996.
(AP Photo/Mark Cowan)
Waste: Dry Cask
Storage
In this photo released by Holtec International, dry cask storage units are seen at the James A. Fitzpatrick nuclear power plant in
Scriba, N.Y., in this undated photo. The Vermont Public Service Board approved "dry cask storage," of spent nuclear fuel at
Vermont Yankee, lifting the threat that running out of room in its existing spent fuel storage pool would cause the plant to close
by 2008.(AP Photo/Holtec International)
Waste: Long-Term
Storage
NRC
Nuclear Waste &
Nuclear Accidents
Three Mile Island nuclear power plant is pictured in Jan. 21,
1996. This is the site of the 1979 partial core melt. (AP
Photo/Tim Shaffer, files)
Accidents: Chernobyl
http://blogs.newamericamedia.org/kitchensink/78/nuclear-nightmares-twenty-yearssince-chernobyl
Nuclear Future?