Nuclear Energy
A. What does “radioactive”
mean?
1.
Radioactive materials have
unstable nuclei, which go
through changes by emitting
particles or releasing energy to
become stable
a. Call this nuclear decay
B. Types of Radiation
1.
Nuclear Radiation: the particles that
are released from the nucleus
during radioactive decay
a. When a radioactive nucleus
decays, the radiation leaves the
nucleus
b. IMPORTANT
This may form
an isotope of the same element
or make a new element
Types of radiation
1.
 2.
 3.
 4.

Alpha particle
Beta particle
Gamma ray
Neutron
2.
Alpha Particle: a positively charged
particle that consists of 2 protons
and 2 neutrons (2P + 2N)
a. + charged
b. Most massive- Do not travel far
through materials (cannot pass
through a piece of paper)
c. Symbol: 42He
d. Ex. Uranium-238 is radioactive
and releases alpha particles

How would emitting an alpha particle
affect the properties of the atom?
 The
atomic number would….
 -Go down by 2!!
 -A new element!!!
 The mass number would….
 -decrease by 4!!!
Alpha Particle
3.
Beta Particle: a negatively (-) charged
electron emitted during radioactive
decay
a. Fast-moving electronb. MADE FROM A NEUTRON THAT
DECAYS & FORMS A PROTON AND
A ec. THE PROTON STAYS AND THE eLEAVES THE ATOM
d. Can penetrate sheet of paper, but
stopped by 3 mm of aluminum
e. Symbol: 0-1e
Beta Particle

How would emitting a beta particle affect
the properties of the atom?

-The atomic number would….
-Increase
by 1!!!
-New element!!!
The mass number would….
-NOT CHANGE
4.
Gamma Rays: high-energy radiation
emitted during radioactive decay and
nuclear fission
-Marie Curie- isolated radium & saw it emitted
gamma rays
a. Gamma rays are a form of
electromagnetic energy so they are “not
charged” and “not made of matter”
b. Not stopped by clothing or most building
materials, (can penetrate up to 60 cm of
Al or 7 cm of Pb) so are much more
dangerous
c. Symbol: γ
Gamma Rays
Neutron Emission


No charge;
Need 15 cm Pb to
stop fast moving
neutrons
Nuclear Decay
When an unstable nucleus emits alpha or
beta particles; # of P & # N changes
 Alpha Decay- lose 2 P + 2 N (same as He
nuclei)- causes the mass number to
decrease by 4 & the atomic number to
decrease by 2
 Example: The process of alpha decay
of radium-226 is written as follows.

226 Ra
88
→ 22286Rn +
4 He
2
Nuclear Decay
Beta Decay- gain 1 P + lose 1 N
(remember a neutron decays to form 1 P &
1 e- (the proton stays and the e- leaves)
 Example: Carbon-14 decays to nitrogen14 by emitting a beta particle

 146C

→ 147N + 0-1e
Gamma Ray decay- no change in # P;
energy content changes in the matter it
hits
C. Decay Rates
Half-life: time required for half of a sample
of radioactive substance to decay
-1st half life = ½ sample remains
-2nd half life = ½ x ½ = ¼ sample remains
-3rd half life= ½ x ½ x ½ = 1/8 sample remains
2. Use these decay rates to tell the age of
rocks and fossils (radiometric dating)
a. Carbon-14 is common isotope used in
radiometric dating
1.
Nuclear Reactions
Strong Nuclear Force- force that causes
protons & neutrons to attract each other in
the nucleus
 Protons are + and repel each other
 Neutrons have no charge so they help
create the strong nuclear force to hold
protons & neutrons together in the nucleus

Nuclear Reactions
Stable Nuclei- strong nuclear force is
stronger than the repulsion force
 Unstable Nuclei- strong nuclear force is
less than the repulsion force
A. Have too many or too few neutrons in
nucleus
B. Have more than 83 protons in nucleus
C. Will decay (and release radiation) into a
more stable nucleus
D. B/C IT IS NOT A 1:1 RATIO OF
PROTONS AND NEUTRONS

II.) Nuclear Reactions
A) Nuclear Fission: the process by
which a nucleus splits into two or
more smaller atoms and releases
neutrons and energy
1. In nuclear fission, tremendous
amounts of energy can be
produced from very small amounts
of mass (Fig. 7 p.295)
Nuclear Fission
 23592 U
+ 10n → 13756 Ba + 8436 Xe + 15 10n + energy
2.
Converting Mass into Energy
a.
Albert Einstein introduced the massenergy equation:
2
E = mc
b.
According to the law of conservation
of mass and energy, the total amount
of mass and energy remains constant
Mass defect- the total mass of any
nucleus measured is less than the
sum of the individual masses of
protons & neutrons that form it; SOME
OF THE MASS HAS TURNED INTO
ENERGY!!
c.
Converting Mass into Energy


The amount of energy released during
nuclear fission is related to the mass that
is turned into energy
E = mc2
3.
Triggering a Nuclear Chain
Reaction
a.
b.
c.
d.
Nuclear fission follows a pattern of a
chain reaction; The speed of a chain
reaction can vary
Chain reaction: a continuous series of
nuclear fission reactions [Fig 8 p.296]
Nuclear fission releases more
neutrons which trigger more
fission reactions
The number of neutrons
released determines the
success of a chain reaction
Nuclear Chain Reaction
c.
d.
c.
Nuclear weapons- ex. Atomic bombs (use
U-235 or Pu-239) are designed to have an
uncontrolled chain reactions
Nuclear Power Plants- A controlled chain
reaction, heat from the reaction can be used
to generate electrical energy
-controls chain reaction with control rods
that absorb neutrons emitted after fission
reaction
Critical Mass: the minimum amount of a
substance that can undergo a fission
reaction and can also sustain a chain
reaction.
4.
Nuclear Energy From Fission
a.
b.
c.
d.
Nuclear power plants generate
about 20% of electricity in the
U.S.
Controlled fission of uranium235 in a fission reactor
Don’t emit air pollutants, but
have other safety concerns
1986: meltdown of reactor at
Chernobyl nuclear power plant
in Ukraine
B.
Fusion: the process in which smaller
nuclei fuse together at extremely high
temperatures and release energy
(occurs in stars like the sun)
C.
Light nuclei combine to form
heavy nuclei
1.
2.
In nuclear fusion, tremendous
amounts of energy can be produced
from very small amounts of mass
THE FUSION OF HYDROGEN
RELEASES MORE ENERGY THAN
THE BURNING OF NATURAL GAS,
BURNING OF COAL, OR THE
Fusion
Nuclear fusion plants using hydrogen may
be a possibility one day
 1 pound of hydrogen in a fusion reactor
may release as much energy as 16
million pounds of burning coal!!

Fusion Reaction
.
2H + 3 H  4He + 1n
1
1
2
0
Requires extremely high
temperatures—i.e. Sun
reaches temp of 10,000,000oC
- need a lot of energy to
overcome repulsion force of
protons
3. Fusion may someday provide
clean and efficient source of
electricity
3.
5.
Two problems creating a
fusion reactor:
a. Need very high
temperatures to start
reaction
b. Must contain plasma
Nuclear Radiation Today




Background Radiation- all around us; comes
from natural sources like the sun, plants, water,
heat, soil, rocks, etc. ( due to the fact that
radioactive isotopes live there)
Exposure varies from one location to another
ex. Living in higher altitudes or around rocks
increases radiation exposure
-Also, things like smoking, getting x-rays
Beneficial Uses of Radiation
1. Smoke detectors- release alpha particles
which are charged & release an electric current,
smoke decreases the flow of current which sets
off the alarm
 2. Used to detect disease A). X-rays
 B). MRI
 C). Radioactive tracers- isotopes that
concentrate in affected areas to locate tumors

Nuclear Radiation is used to treat
cancer





Radiotherapy- is a treatment that uses controlled
doses of nuclear radiation for treating diseases
such as cancer
Ex. A) Brain tumor- uses gamma rays to treat
them
B) iodine isotopes treat thyroid cancer
C) Radiation is used to kill defective bone
marrow of leukemia patients
Agriculture- radioactive tracers move through
crops to see how fast water moves through
them.