WHAT YOU ARE RESPONSIBLE FOR
Quia – PARTS OF NUCLEAR REACTOR – Vocab
from game
 SAT REVIEW BOOK:
 P. 336 Methods of Detection
 P. 335 Nature of Radioactive Emissions
 Writing Nuclear Equations
 Solving Half Life problems
 Differentiating between Decay, fission and fusion
 Benefits and Harm of using Radioactive Isotopes

NUCLEAR CHEMISTRY OVERVIEW
Nuclear Chemistry is the study of reactions
which alter the NUCLEUS of an atom.
 Reactions involving changes to the nucleus
also involve

NUCLEAR REACTIONS HAPPEN IN TWO WAYS

NATURALLY and ARTIFICIALLY
1)Natural Transmutation –
 Alpha, Beta and Positron Decay - also FUSION

Isotopes of elements that have unstable nuclei, (a
ratio of neutron to protons that causes instability),
will undergo decay. This causes them to be
transformed into another element. The time it takes
for half a sample of this isotope to decay and be
transformed into another element is called half life.
NUCLEAR REACTIONS HAPPEN IN TWO WAYS

Fusion as natural transmutation:
In stars, the nuclear reaction fusion results in the
combination of lighter nuclei to form larger
elements.
In most cases fusion cannot occur on earth, the
temperature and pressures required are too
extreme to allow for fusion without it becoming too
destructive.
UNSTABLE ATOMS

If # of neutrons is too
high or too low, the
nucleus becomes
unstable and emits
energy.

Above atomic #83
there are no stable
nuclides.
5
WHAT HAPPENS TO ELEMENTS
WHEN THEY DECAY??

A isotope undergoes transmutation when it
decays. So the portion of the sample that has
decayed, will turn into another element.
If a sample of N-16 will decay to produce another
gas. If the half life of N-16 is 7.13s, and there
are 45 grams present, what other element will
be present after decay occurs for 35.65
seconds? How much of it will be present?
PARTICLE EMISSION & ENERGY
Each particle leaves the nucleus, traveling
through other materials. This is radiation.
 YOU MUST KNOW, the penetrating power of
different particles.
 Some reactions generate gamma radiation- this
is a very high energy emission with no mass or
charge. As a result it has the greatest
penetrating power.

PENETRATING POWER
THESE ARE IN YOUR REGENTS and SAT
REVIEW BOOKS
8
NUCLEAR REACTIONS HAPPEN IN TWO WAYS
2) Artificial Transmutation Fission and Nuclear Bombardment

These are manmade reactions in which the
nucleus of an atom is forced to collide with a
smaller particle.
WE STARTED WITH

1)
2)
3)
Types of nuclear equations which include:
Alpha decay, beta decay and positron decay
Fission
Fusion
WHAT ABOUT EMISSIONS?

Particles given off by reactions are somewhat
similar to subatomic particles or elements you
already know.
Alpha particles = the nucleus of a helium atom.
Since they have 2 protons and NO electrons,
they have a net positive charge of +2
WHAT ABOUT EMISSIONS?
Beta Particles – Are high energy electrons
ejected from the nucleus when a neutron decays
into a proton. They have negligible mass and a
charge of -1.
 Positrons – An anti-particle, basically the
opposite of a beta particle. It also has negligible
mass but the opposite +1 charge.
 Neutrons can be emitted by reactions, neutron
notation will show it has a mass of 1, and the
zero subscript, shows it is alone and has no
protons.

WHAT ABOUT EMISSIONS?

Gamma Radiation- when gamma radiation is
emitted, it does not necessarily mean that
transmutation has occurred. It does often occur
after natural decay. It may also accompany
fission and fusion reactions. It has no charge
and no mass, so balance accordingly.
BALANCING NUCLEAR
REACTIONS
ALPHA DECAY:
MASS DECREASES BY FOUR,
ATOMIC NUMBER DECREASES BY
TWO.
 238U
238U
92
undergoes alpha decay
4He
2
+ 234Th
90
The total mass on the left must equal the total mass on
the right (238 = 4 + 234)
The total charge on the left must equal the total charge
on the right (92 = 2 + 90)
ALPHA DECAY
240
94
236
Pu
92
4
U
+
2
He
16
BETA (MINUS) DECAY:
MASS REMAINS THE SAME,
ATOMIC NUMBER INCREASES BY ONE.
 234Th
234Th
90
undergoes beta decay
0e
-1
+ 234Pa
91
The total mass on the left must equal the total
mass on the right (234 = 0 + 234)
The total charge on the left must equal the total
charge on the right (90 = -1 + 91)
BETA DECAY
137
55
137
Cs
1
0
56
0
Ba +
1
n
1
-1
e
0
p
+
-1
e
(One of Cs’s neutrons converts to a proton and electron.)
18
POSITRON (BETA PLUS) DECAY:
MASS REMAINS THE SAME,
ATOMIC NUMBER DECREASES BY ONE.
 37K
37K
19
undergoes positron decay
0e
+1
+ 37Ar
18
The total of the mass numbers on the left must
equal the total on the right (37 = 0 + 37)
The total charge on the left must equal the
total charge on the right (19 = 1 + 18)
POSITRON DECAY
53

26
53
Fe
25
0
Mn +
+1
e
20
FISSION & TRANSMUTATION

Fission converts a larger element into several
atoms of elements with smaller atomic
numbers.

Therefore, this is a form of TRANSMUTATION,
however, since it is initiated by people…IT IS
ARTIFICIAL TRANSMUTATION
PATTERN
Fission Reactions: A Large nuclei will be shown,
colliding with/absorbing a neutron or small
particle. The product will be several smaller
elements and emissions.
 Nuclear Bombardment, a smaller particle is shown
colliding with an element.
 Fusion Reactions: Smaller elements, (such as
hydrogen), will be shown combining to form larger
elements. Other particles and emissions may be
present.

FISSION PRACTICE

Complete the fission equation and account
for the missing particle:

Use table O for help with particle symbols
FUSION PRACTICE


Complete the following equation by finding the
missing particle.
3
1
H +
2
1
H  4 He+
2
1
0
n
THE HALF-LIFE OF A RADIOACTIVE NUCLIDE IS
THE AMOUNT OF TIME IT TAKES FOR HALF OF
THAT NUCLIDE TO DECAY INTO A STABLE
NUCLIDE.
The half-life of a radioactive
nuclide cannot be changed.
HALF LIFE

The principle behind half life allows radioactive
isotopes to be used to:
1) Determine the age of
organic and inorganic
material.
2) Use selected isotopes for
medical treatment and
imaging
PROBLEM

If a sample of Radon – 222 is allowed to decay
for 15.28 days…

If the amount left is 5 grams, how much was
present in the original sample?

How many half lives did the sample undergo?
PROBLEM
How
much of a 20.g
131
sample of I remains
unchanged after 24 days?
PROBLEM

What is the half life of an isotope that has
decayed for 120 hours, if the original sample
was 40 grams and the sample left weighs 1.25
grams.
DISINTEGRATION SERIES
“Heavy” atoms (greater than Bismuth, #83) naturally decay
to smaller atoms along a consistent path, or series, of
decays.
Radioactive U-238 → Th-234 + a
Th-234 → Pa-234 + b
Pa-234 → U-234 + b
U-234 → Th-230 + a
Th-230 → Ra-226 + a
Ra-226 → Rn-222 + a
Rn-222 → Po-218 + a
Po-218 → Pb-214 + a
Pb-214 → Bi-214 + b
Bi-214 → Po-214 + b
Po-214 → Pb-210 + a
Pb-210 → Bi-210 + b
Bi-210 → Po-210 + b
Po-210 → Stable Pb-206 + a
Atomic Number & Symbol
Mass Number

Source: http://www.frontiernet.net/~jlkeefer/uranium.html
ENERGY RELEASED DURING NUCLEAR
REACTIONS IS MUCH GREATER THAN
THE ENERGY RELEASED DURING
CHEMICAL
REACTIONS.
Fission – used in nuclear reactors and
atomic bombs
 Fusion – used in hydrogen bombs and the
energy that powers the sun.

ENERGY RELEASED IN A NUCLEAR
REACTION (FISSION OR FUSION)
COMES FROM THE FRACTIONAL
AMOUNT OF MASS CONVERTED
INTO ENERGY. NUCLEAR CHANGES
CONVERT MATTER INTO ENERGY.
E=mc2
The energy released is equal to the mass lost (m) times the speed of
light (c) squared. A small amount of mass lost converts to a very large
amount of energy.
NUCLEAR FISSION

Fission: process in which the nucleus of a large, radioactive atom
splits into 2 or more smaller nuclei
 Caused by a collision with an energetic neutron.
1n +
0
•
235U
92
139 Ba + 94 Kr + 3 1 n + energy
0
56
36
*A neutron is absorbed by a U-235 nucleus. The nucleus is now less stable than before.
It then splits into 2 parts and energy is released. Several neutrons are also produced;
they may go on to strike the nuclei of other atoms causing further fissions in a process
called supercriticality.
33
 *The
process of neutron capture and
nucleus splitting happens very quickly
(takes about 1 x 10-12 seconds).
 An
incredible amount of energy is released:
As heat and gamma radiation
Because the product atoms and neutrons
weigh less than the original U-235 atom;
the “missing mass“ has been converted
to energy by E=mc2
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*A FISSION CHAIN REACTION
QUESTION???

Why are neutrons used in this process and
not protons?
Since neutrons are not charged, they can approach the
nucleus. Using a proton would mean having to overcome
the repulsive force of the other positive protons present in
the nuclei.
Additionally, Particle accelerators often manipulate protons
and electrons using enormous magnets. Due to a neutrons
lack of charge, this is not possible.
Basic
Tour of
a
Nuclear
Power
Plant
THE REACTOR

The reactor contains what are known as fuel
rods. Fuel rods contain about 3% of the isotope
U-235, (Uranium).

The Fission reaction, is a chain reaction.

The reactor employs what are known as Control
Rods to help slow the reaction down if
necessary. Control Rods are made of Boron and
Cadmium, (other elements) and these absorb
some of the neutrons.
The reaction produces
a lot of heat, and
water is circulated
around it to transfer
that heat to a place
where it can
produce steam.
Water that
Circulates around
the reactor is
heated to
temperatures of
320 degrees
Celsius
That is a temp of 608 degrees
Fahrenheit.
Water Boils at 212 degrees
Fahrenheit.
www.howstuffworks.com
PRODUCING STEAM
 This
super heated water is piped through
a separate tank where the heat transfers
to water that is heated to produce steam.
 The
steam produced then turns the
turbine of an electrical generator.
www.HowStuffWorks.com
www.HowStuffWorks.com
These structures we all associate with Nuclear Power Plants
are actually the cooling towers. They help cool water down so
it can either be re-circulated into the system, or moved to
cooling reservoirs to be returned to a body of water.
If technicians are able to
drop the control rods into
the reactor, they can stop
the fission reaction…
However a meltdown can
still occur since so much
heat collects in the reactor.
This is also a reason why
shutting a reactor down,
even for temporary service,
is a tricky maneuver.
NUCLEAR POWER

The United States currently imports over 58% of its
oil supply. There is a need to develop alternative
energy sources, such as nuclear, wind,
geothermal, solar, …

By 2020 it is expected to be 67%.

At present about 20% of the electrical energy used
in the U.S. is generated from power plants using
uranium. In France the percentage is 75% .
46
THE ATOMIC BOMB
Uses an unregulated fission reaction in a very fast
chain reaction that releases a tremendous
amount of energy.
*Critical mass: the minimum amount of radioactive,
fissionable material needed to create a
sustainable fission chain reaction
* Site of fission reaches temperatures believed to be
about 10,000,000°C.
 Produces shock waves and a, b, g, x-rays, and UV
radiation.

47
*The classic “mushroom cloud” is a result of dust and
debris lifted into the air as a result of the detonation.
*US Army aerial photograph from 80 km away, taken about 1 hour
after detonation over Nagasaki, Japan, August 9, 1945.
NUCLEAR FUSION
Fusion: process in which 2 nuclei of small elements are united to
form one heavier nucleus

* Requires temperatures on the order of tens of millions of
degrees for initiation.

* The mass difference between the small atoms and the
heavier product atom is liberated in the form of energy.

Responsible for the tremendous energy output of stars (like
our sun) and the devastating power of the hydrogen bomb.
3H
1
+
2H
1
4 He +
2
1n
0
+ energy
49
STARS & THE HYDROGEN BOMB


The first thermonuclear bomb was exploded in 1952 in the
Marshall islands by the United States; the second was exploded
by Russia (then the USSR) in 1953.
“H bombs” utilize a fission bomb to ignite a fusion reaction.
50
ISOTOPES &USES
U-238 and Pb-206 are used to date rocks and
inorganic material – C-14 used for organic
material
 I-131 is used to take images of and to treat
thyroid cancer
 Cobalt-60 and Tc-99 are used in radiation
treatments to destroy cancerous tumors.
 Gamma radiation is used to irradiate food and
kill pathogens. (source Cs-137&Co-60)

*RADIOCARBON (C-14) DATING
• Discovered at University of Chicago in 1949 by Dr. W.F. Libby and his
colleagues.
Basic assumptions:
CO2 in the atmosphere contains about
0.00000000010% C-14; this level is held
constant through the decay of N-14 to form
C-14 which happens in the upper atmosphere.
 Plants consume CO2 during photosynthesis and
animals eat plants, so they contain C-14:C-12 in
the atmoshperic ratio as long as they are alive.

52
- When
an organism dies, the amount of C12 does not change, but the C-14 content
diminishes as it decays. The half-life of C14 is 5730 years.
- By comparing the C-14:C-12 ratio in an
artifact to the same ratio in living plants,
the age of the artifact can be estimated.
Limitations:
 C-14 dating has a limit of about 70,000 years. Beyond that, the % of
C-14 remaining is too small to accurately calculate the age.
Sources:
http://www.geology.sdsu.edu/visualgeology/geology101/lab6time.htm
http://www.dc.peachnet.edu/~pgore/geology/geo102/radio.htm
http://superstringtheory.com/cosmo/cosmo1.html
NUCLEAR MEDICINE: IMAGING
Thyroid imaging using Tc-99m
FOOD
IRRADIATION
•Food can be irradiated with g rays from
60Co or 137Cs.
•Irradiated milk has a shelf life of 3 mo.
without refrigeration.
•USDA has approved irradiation of meats
and eggs.
DANGERS OF RADIATION
Remember that isotopes will have
different masses, but that chemically they
will be the same as other stable forms of
the element.
For example Sr-90 can be taken up in
bone because it is chemically similar to
Calcium. The half life of Sr-90 is 28 years.
Before nuclear weapons and power
plants it was not
Marvel Comics’ “The Incredible Hulk” was created in
found in the
1962 by Stan Lee and artist Jack Kirby. The Hulk’s
Environment.
powers began when nuclear scientist Dr. Bruce Banner
was accidentally bombarded with gamma rays from a
"gamma bomb" he had invented.
BIOLOGICAL EFFECTS OF RADIATION
Acute:



High level radiation (gamma ray & x–ray) can cause death.
Damage is centered in nuclei of cells; cells undergoing rapid cell division
are most susceptible.
Gamma rays from a Co-60 source are often used to treat cancer (since
cancer cells multiply rapidly).
Long term:
• Can weaken organism and lead to onset of malignant tumors, even after fairly
long time delays.
• Largest source: X–rays
• Sr-90 isotopes are present in fallout from atmospheric testing of nuclear
weapons.
• Contaminated foods can increase incidence of leukemia and bone cancers.
57