Download 11.3 Nuclear Energy

Chapter 11:
Energy
Resources
Section 3: Nuclear Energy
Nucleus: the central core of an atom that contains the protons and neutrons
1. Nuclear Fission: the splitting of an atom’s nucleus into two smaller nuclei
a. Nuclear reactions convert matter into energy
i. Albert Einstein developed a formula describing the relationship between
energy and matter
1. E=mc2
2. E=energy, m=mass, and c=speed of light
3. States that when matter is changed into energy, an enormous amount
of energy is released
b. Fission Reactions
i. The fuel for nuclear fission is a large atom with an unstable nucleus,
uranium-235
1. A neutron is shot at the U-235 at high speed
2. The nucleus splits apart into two smaller nuclei and two or more
neutrons
3. The small amount of mass that makes up the difference between the
original nucleus and the two new nucleus converts to a lot of energy
4. Three more neutrons are produced and have the potential to strike
another nucleus and the fission reaction is repeated—more neutrons
and more energy are released
c. Energy from Fission
i. If a nuclear chain reaction is not controlled, the released energy causes a
huge explosion
1. Explosion of an atomic bomb is an uncontrolled nuclear fission
reaction
ii. If the chain reaction is controlled, the result is energy released as heat
2. Nuclear Power Plants
a. Controlled nuclear fission reactions
i. The heat released is used to change water into steam, turns a turbine,
generating electricity
b. Reactor Vessel: the part of the nuclear reactor where nuclear fission occurs
i. Fuel Rods: rods of U-235 in the reactor
1. A series of fission reactions occurs when several fuel rods are placed
close together
ii. Control Rods: used to slow down the chain reactions-made of cadmium
metal
1. Inserted between the fuel rods
2. Cadmium absorbs neutrons released during fission and slows chain
reactions
c. Heat Exchanger
i. Heat is removed by water or another fluid that is pumped through the
reactor
ii. Fluid passes through a heat exchanger where the fluid boils water to
produce steam, which runs the electrical generator, the steam is condensed
and pumped back through
d. The Risks of Nuclear Power
i. In 1986, a reactor vessel overheated in Ukraine
ii. The fuel rods generated so much heat that they started to melt, or have a
meltdown
iii.Injured or killed dozens of people
iv.Radioactive materials escaped into the environment
v. A more difficult problem is the disposal of radioactive wastes
1. Remain dangerous for thousands of years
3. Quest to Control Fusion
a. Nuclear Fusion: the combining of two atomic nuclei to produce a single larger
nucleus
i. Two hydrogen nuclei combine to create a helium nucleus, which has slightly
less mass
1. The lost mass is converted to energy
ii. Could produce much more energy than nuclear fission
iii.Should produce less radioactive waste than nuclear fission
iv.The pressure and temperature required make the construction of a fusion
reactor impractical
Review
• What is the difference between nuclear fission and
nuclear fusion?
Review
• Describe the steps that occur in a nuclear fission
reaction.
Review
• What type of nuclear reaction produces electricity
in a nuclear power plant?