Nuclear Energy
Nuclear Reactions
Nuclear Fission / Nuclear Fusion
Harnessing the Power of the Nucleus
Unstable Atomic Nuclei
Shortly after the discovery of
radioactivity by Becquerel, scientists
discovered that the nucleus of an atom
contained huge amounts of potential
energy
WHY?
Unstable Atomic Nuclei
A nucleus becomes unstable when the
strong nuclear force is not strong
enough to overcome the repulsion of
protons
All atoms with atomic numbers greater
than 83 are radioactive
Radioactive: unstable nucleus emits
energy when it breaks into smaller parts
Nuclear Fission
Proposed by Lise Meitner & Otto Frisch
in 1939
Definition: Splitting of a larger atomic
nucleus into smaller nuclei
Tremendous amounts of energy are
released from very small amounts of
mass
Two smaller nuclei that are not radioactive are created
Fast moving neutron
runs into a radioactive
nucleus
Why use a neutron?
Also
Neutrons have no charge – their released: 2 or 3 stray
neutrons and LOTS of
motion will not change as they move
closer to the nucleus energy!!
Mass-Energy Equation
Proposed by Einstein in 1905 (long
before fission or fusion were
discovered)
E = mc2
E: Energy
m: mass
c: speed of light (3.010 m/s)
8
Mass-Energy Equation
What does it mean?
Tremendous amounts of energy are
released from very small amounts of
mass
Chain Reactions
The neutrons released during fission can
be used to split other unstable atoms
Left unchecked, a chain reaction can
produce huge amounts of energy
Atomic Bombs
Nuclear Reactors use a controlled chain
reaction where the number of neutrons
that split other unstable atoms is limited
Chain Reactions
(Nuclear Reactors)
Steam turns generator
Electricity is created
Fission
reaction
occurs
Energy
released
turns
water into
steam
Nuclear Fusion
Two small nuclei are combined to form
a nucleus with a greater atomic number
A small amount of mass is converted to
energy during fusion
Mass-Energy equation says small amounts
of mass produces large amounts of energy
Fusion requires extremely high
temperatures (WHY?)
The only way to get them to stay close
together is to raise the temperature
really high to make them move really
fast
Both small nuclei are
positively charged –
they repel
When they combine,
a small amount of
mass turns to a
HUGE amount of
energy