Nuclear Changes
Nuclear Energy – An introduction
Chapter 9
Radioactivity
Radioactive materials
have an unstable
nucleus that release
one or more particles
or energy
Nuclear radiation refers
to the released energy
and matter.
 Where
does radiation come from?
 Radiation
is generally produced when particles interact
or decay
 A large contribution of the radiation on the earth is
from the sun (solar) or from radioactive isotopes of the
elements (terrestrial)
 Radiation
is going through you at this very moment!
Isotopes (a review)
What’s an isotope?
Two or more varieties of an element
having the same number of protons but
different number of neutrons. Certain
isotopes are “unstable” and decay to
lighter isotopes or elements.
Deuterium and tritium are isotopes of
hydrogen. In addition to the 1 proton,
they have 1 and 2 additional neutrons
in the nucleus respectively*.
Nuclear Radiation
As the radioactive nucleus decays, nuclear
radiation leaves the nucleus and interacts with
other matter.
Types of nuclear radiation: (4)
1. Alpha Particles (a)
2. Beta particles (b)
3. Gamma rays (g)
4. Neutron emission


1. Alpha Particles: a positively charged particle and has
a large mass. (consists of 2 protons and 2 neutrons).
Do not travel far because of its size.
 Can barely travel through a piece of paper.

Radium
Radon
R226
Rn222
88 protons
138 neutrons
86 protons
136 neutrons
+
a (4He)
2 protons
2 neutrons
The alpha-particle (a) is a Helium nucleus.
It’s the same as the element Helium, with the
electrons stripped off !

2. Beta Particles: negatively charged particle that has little
mass
Travels much faster than alpha particles
 Travel through 3mm of aluminum or 10 mm of wood…but are
stopped because they lose energy fairly quickly.

Carbon
C14
6 protons
8 neutrons
Nitrogen
N14
7 protons
7 neutrons
+
eelectron
(beta-particle)
We see that one of the neutrons from the C14 nucleus
“converted” into a proton, and an electron was ejected.
The remaining nucleus contains 7p and 7n, which is a nitrogen
nucleus.
 Gamma
Rays: are not made of matter and do not
have an electric charge
 Gamma Rays consist of electromagnetic energy
called PHOTONS
 Have very high energy…can travel through 60 cm
of aluminum or 7 cm of lead
 Gamma
Rays are more dangerous to living things than
alpha or beta particles.
Gamma particles (g)
In much the same way that electrons in atoms can be in an
excited state, so can a nucleus.
Neon
Ne20
10 protons
10 neutrons
(in excited state)
Neon
Ne20
+
10 protons
10 neutrons
(lowest energy state)
gamma
A gamma is a high energy light particle.
It is NOT visible by your naked eye because it is not in
the visible part of the EM spectrum.
Gamma Rays
Neon
Ne20
Neon
Ne20
+
The gamma from nuclear decay
is in the X-ray/ Gamma ray
part of the EM spectrum
(very energetic!)
Nuclear Radiation
 Neutron
Emission: The release of a neutron from a
nucleus…does not have any charge.
 Can travel much farther because they do not lose
energy very quickly.
 Can
travel through a 15 cm block of lead.
Half-Life
 The “half-life” (h) is the time it takes for half the atoms of a
radioactive substance to decay.
 For example, suppose we had 20,000 atoms of a radioactive
substance. If the half-life is 1 hour, how many atoms of that
substance would be left after:
#atoms
% of atoms
Time
remaining
remaining
1 hour (one lifetime) ?
10,000
(50%)
2 hours (two lifetimes) ?
5,000
(25%)
3 hours (three lifetimes) ?
2,500
(12.5%)
Predicting Age
 Scientists
use the Half-Life of an object to
determine its age.
 For example: Potassium-40 decays to Argon-40, so
the ratio of Potassium-40 to argon-40 is smaller for
older rocks than it is for younger rocks.
 Scientists use Carbon-14 to date more recent
materials like remains of an animal or parts of
ancient clothing.
Practicing Half-Life
 Radium
226 has a half-life of 1599 years. How
long would it take seven-eighths of a radium-226
sample to decay?
 Given:
half-life = 1599 years
 Given: fraction of sample decayed = 7/8
 Unknown: fraction of sample remaining
 Unknown: total time of decay

1. Calculate the fraction of radioactive sample remaining.


Fraction of sample remaining = 1 – 7/8 = 1/8
2. Calculate the number of half-lives
Amount of sample remaining after one half-life = ½
 Amount of sample remaining after 2 half-lives = ¼
 Amount of sample remaining after 3 half-lives = 1/8
 3 Half-lives are needed for one-eighth of the sample to remain
undecayed.


3. Calculate the total time required for the radioactive
decay.

Total time of decay = 3 half-lives x 1599 years = 4797 years
Radioactive Dating Game
 Sign
out a laptop
 Log in and open the Internet
 Go to phet.colorado.edu
 New
Sims - PhET Simulations
Nuclear Energy
Basics of Nuclear
Power Video Clip
Brief History
Nuclear energy was first discovered in 1934 by Enrico
Fermi
 The first nuclear bombs were built in 1945 as a result of
the Manhattan Project
 The first plutonium bomb (Trinity) was detonated on July
16, 1945
 The first uranium bomb was detonated over Hiroshima on
August 6th 1945
 The second plutonium bomb was dropped on Nagasaki on
August 9th 1945
 Electricity was produced with nuclear energy in 1951.

Fission: History and Overview





Discovered 1938 by Otto
Hahn and Frittz Strassmann
Presented in 1939 by Lise
Meitner and Otto Frisch
Research of Nuclear Fission
began U.S. weapons program
1942 first controlled self
sustaining fission reaction by
Enrico Fermi
Nuclear fission creates
Electricity
Fission Overview




Fission is the process of
splitting heavier nuclei into
lighter nuclei
Fission releases Energy
The mass equivalent of 1kg of
matter is more than the
chemical energy of 22 million
tons of TNT
Neutrons released by fission
can start a chain reaction…a
continuous series of nuclear
fission reactions.
Fission Today
435 Nuclear Power
plants worldwide
 1/6 of the worlds
power is nuclear
 World Energy
Consumption
doubled by 2050
 World will turn to
fission energy

World Nuclear Power Plants
How Stuff Works - Nuclear Energy
United States Nuclear Power Plants
Nuclear Power in Northeast U.S.
Japan’s Nuclear Power Problems
Japan’s Power Plant Meltdown
 Japan’s
Nuclear Emergency
 Efforts to cool down the nuclear reactor
 Concerns about Proximity to the Power plant
Fusion: Overview and History
British Physicists in the 1940’s and 50’s housed ina
hangar at Harwell a device called ZETA-Zero Energy
Toroidal Assembly which was the first fusion based
operating system
 Masked in the secrecy of the Cold War
 Fusion is the production of a thermonuclear reaction
in a gas discharge
 Called fusion because it is based on fusing light nuclei
such as hydrogen isotopes to release energy, similar to
that which powers the sun and other stars.

Fast Facts
A
vast, new source of energy
 Fuels are plentiful
 Inherently safe since any malfunction results in a
rapid shutdown
 No atmospheric pollution leading to acid rain or
the greenhouse effect
 Sunlight is energy released from fusion reactions
in the sun.
The Future is Fusion
 The
sun is our greatest source of energy…the sun
uses fusion.
 The source of fusion is vastly abundant in our
oceans (an isotope of hydrogen in water)
 The waste of fusion is helium, and there is no
pollution of long term extent
 The price of fusion is estimated to be equivalent to
that of fossil fuels
 Fusion can give us energy for millions of years
Nuclear Waste
Most used Nuclear Waste Sites
Nuclear Waste
 Nuclear
Waste has been accumulating since the
mid-1940’s and is currently in temporary storage at
131 sites in 39 states
 Nuclear waste remains highly radioactive for
thousands of years.
 It will still be potentially harmful to humans long
after the manmade containers holding the waste
have disintegrated.
Yucca Mountain
Will become the nation's first longterm geologic repository for spent
nuclear fuel and high-level
radioactive waste that is currently
stored at 126 sites around the nation.
 Yucca Mountain is located in a
remote desert on federally
protected land within the secure
boundaries of the Nevada Test Site
in Nye County, Nevada. It is
approximately 100 miles northwest
of Las Vegas, Nevada.

Nuclear Radiation Today
Radiation
 You
are exposed to radiation everyday
 Background Radiation – nuclear radiation that
arises naturally from cosmic rays and from
radioactive isotopes in the soil and air
 We are adapted to survive low levels of this natural
source of radiation
 Radiation is measured in rems or millirems
What are the Possible Effects of
Radiation?
 Inside
Chernobyl - National Geographic Magazine
 Kasakhstan Fallout Video Clip
 Safety
Videos
 Duck
and Cover
 Living Under the Shadow of the Nuclear Umbrella
Video Clip
Radiation Exposure
 There
are many occupations where people are
exposed to higher levels of radiation.
 Nuclear
radiation, health physics, radiology,
radiochemistry, X-ray technology, MRI
 It has been decided that these occupations can be
exposed to 5000 millirems annually plus regular
background radiation.
 Exposure
amounts will also depend on where a
person lives.
 Exposure may increase based on some day-to-day
activities as well
Radiation Exposure







Average annual radiation dose is 360 millirems per person. 300
from natural sources.
Sleeping next to someone for 8 hours: 2 mrems
Exposure comes from the naturally radioactive potassium in the
other person's body
Coal plant, living within 50 miles: .03 mrem There is much
thorium and uranium in coal.
Living within 50 miles of a nuclear power plant adds .009 mrem of
exposure. Both figures are considered extremely low levels.
Living in a masonry home: 7 mrems Stone, brick and adobe have
natural radioisotopes in them.
Living on the Earth: 200 mrems We are living in a sea of radon. It
is made from the natural decay of uranium and thorium in the soil,
left over from the creation of the solar system. Radon is a rare gas
that diffuses out of soil and into the air. It contributes more than half
of our background






Smoking: up to 16,000 mrems The tobacco leaf acts like the
absorbing surface of charcoal in a radon test kit. It collects longlived isotopes of airborne radon, like lead-210 and polonium. Small
portions of the lungs can get relatively whopping doses, compared
to background levels.
Porcelain teeth or crowns: tenths of a rem Uranium is often added
to these dental products to increase whiteness and florescence.
Air Travel: 1 mrem per 1000 miles 30,000 feet above the ground
you're closer to the ionizing radiation (high-energy gammas well as
particles) from the sun.
Grand Central Station, NYC: 120 mrem for employees Its granite
walls have a high uranium content.
Brazil Nuts: This is the world's most radioactive food due to high
radium concentrations 1000-times that of average foods.The US
Capitol Building in
Washington DC: This building is so radioactive, due to the high
uranium content in its granite walls, it could never be licensed as a
nuclear power reactor site.
Radiation Exposure
1500% increase in incidence of testicular and ovarian
cancer in children on Navaho reservation in uranium
mining area
 500% increase in bone cancer in children affected by
uranium
 250% increase in leukemia (all ages) in the Navaho
population
 200% increase in each of the following non-cancer effects:
miscarriage, infant death, congenital defects, genetic
abnormalities, learning disorders.





400% increase in leukemia incidence in the population living
downwind of the Pilgrim nuclear power reactor in Massachusetts in
the first 5 years after fuel was know to have leaked excess
radioactivity.
Baseline: Disease in population before and after Pilgrim radioactive
releases and comparison to upwind population.
300—400% increase in lung cancer in the general population within
the plume of the Three Mile Island accident releases
600—700% increase in leukemia in the general population within
the plume of Three Mile Island accident releases Baseline: Disease
in population upwind (out of the radiation plume path) is compared
to disease in population downwind (in the pollution plume.)
50% increase in childhood cancer incidence in the Three Mile Island
area for each 10 millirem increase in radiation exposure per year.
500% increase in leukemia among Utah nuclear bomb test
Downwinders
 121% increase in thyroid cancer incidence in the same
group
 200% increase in breast cancer
 700% increase in bone cancer
 a greater then 120% increase in thyroid cancer in those
who drank milk laced with Iodine-131 from atmospheric
nuclear weapons tests

200% increase in lung cancer in women who received
radiation treatments for breast cancer
 66—96% increase in early cancer deaths due to
background radiation

Radiation
Exposure in
the U.S.
Benefits of Nuclear Radiation
 Nuclear
radiation is used in a controlled way
 Smoke Detectors use nuclear radiation in small
amounts
 Alpha
particles are charged and produce an electric
current
 Detecting
disease
 Ultrasound,
CT scanning, Radioactive tracers
Benefits in Medicine

Radioactive tracers are short-lived isotopes that tend to
accumulate in specfic cells…help to find tumors.
Benefits in Medicine
 Radiotherapy
is used to treat cancers.
 Controlled doses of nuclear radiation are used to
kill fast growing cells (also damages healthy cells)
Uses in Agriculture


Radioactive tracers are used to identify the flow of water and how it moves
through the crops.
Help to identify biochemical processes
NUCLEAR RADIATION: A REVIEW
Risks of Nuclear Radiation
 Nuclear
radiation reacts with living tissue (alpha,
beta, and gamma particles)
 They change the number of electrons in atoms of
living materials
 Alpha particles – stopped by layer of clothing
 Beta particles – travel through a fraction of an inch
in solids and liquids
 Gamma particles – depends on energy … can
travel through several feet.
Nuclear Radiation
Risk and Amount of Radiation
 Small
amount of nuclear radiation --- changes
cannot be detected.
 Relationship with high levels of nuclear radiation
and cancer
 Cancers
related to radiation levels include: leukemia,
breast cancer, lung cancer, and stomach cancer