ENVIRONMENTAL SCIENCE UNIT 3
MRS. SHARPLESS - TEAM E
MR. CONRAD - TEAM F
Radiation was discovered purely by chance ……….
He put a couple of photographic
plates in a drawer next to a rock.
Days later he discovered that the
plates had patches on them where
they had been developed.
WHAT DO YOU BELIEVE HAPPENED HERE?
The “rock” in his desk contained URANIUM in it.
Becquerel discovered that it gave off invisible rays which
developed the film plates.
All nuclear energy begins in the area of the atom called
the ……
The central “core” of the atom.
Contains PROTONS and
NEUTRONS.
Reactions that produce energy and
involve the nucleus of an atom are
called NUCLEAR REACTIONS,
and produce a tremendous amount
of energy.
Developed a formula to
describe how matter
changes into energy.
When matter is turned
into energy, large
amounts of energy are
released.
E = energy
M = mass
C = speed of light (squared)
WHAT MAKES SOMETHING “RADIOACTIVE”
ANYWAY?
The atoms that make up the substance must be giving
off nuclear particles (protons and neutrons) and energy.
The spontaneous release of
nuclear particles and energy.
Isotopes - Atoms which possess the
same atomic number, but different
mass numbers. (Same number of
protons, different number of neutrons)
1
2
3
1
1
1
Stable Isotopes -Atoms that do not
release protons or neutrons from the
nucleus and ARE NOT
RADIOACTIVE.
Unstable Isotopes - Atoms that
spontaneously release protons and
neutrons from its nucleus. These
isotopes ARE RADIOACTIVE.
THERE ARE THREE TYPES OF PARTICLES AND
ENERGY GIVEN OFF BY RADIOACTIVE ELEMENTS
1.ALPHA PARTICLES Type of radiation where the
particles possess a positive
-
charge, cannot even penetrate
paper, has the most mass, and
moves slowly.
If you could see an alpha particle, it would look just like a helium
nucleus. Two protons, two neutrons.
THERE ARE THREE TYPES OF PARTICLES AND
ENERGY GIVEN OFF BY RADIOACTIVE ELEMENTS
Type of radiation where the
BETA PARTICLES - particles have a negative
charge, penetrates living tissue,
and has less mass but moves
quicker than an alpha particle.
If you could actually see a beta particle it would appear
to be one “free” electron capable of moving anywhere.
THERE ARE THREE TYPES OF PARTICLES AND
ENERGY GIVEN OFF BY RADIOACTIVE ELEMENTS
The only type of radiation which is
GAMMA RAYS - “energy” instead of particles.
Travels at the speed of light, has
no mass, is neutral in charge, and
penetrates just about every
substance. POWERFUL!!!!!!
Since Gamma rays are energy only and travel so
quickly, you would not see them even if you could!
Radiation strips electrons out of atoms. This causes
your cells to malfunction or die. High levels of radiation
exposure causes burns, and lowers your number of
white blood cells, it could also cause cancer and other
health problems.
HOW CAN YOU TELL IF
THERE IS RADIATION
PRESENT AROUND US? ARE
WE IN DANGER!!!
There is radiation all around us, but fear not!!!! Almost
all of it is low-level radiation. We can use radiation
detection devices to tell how much radiation might be
present in a given location.
THERE ARE THREE DEVICES WE WILL DISCUSS
1. Cloud chamber - Contains air
inside which is thick with water
vapor. A radioactive element is
placed inside and forms a vapor
trail. The size of the vapor trail tells
scientists what type of radiation is
given off.
THERE ARE THREE DEVICES WE WILL DISCUSS
2. Geiger counter - Device which
contains a tube of argon gas with a
wire inside. Radiation causes the
gas to get “excited” and electricity
moves through the wire to a speaker
that “clicks”. The louder/faster the
clicks, the more radiation present.
THERE ARE THREE DEVICES WE WILL DISCUSS
3. Film badge - Item worn by
people who work with radiation
daily. Made of photographic film.
Chemicals in the film react to the
radiation, show the level of radiation
the person was exposed to.
So if radioactive elements are losing protons and
neutrons out of the nucleus (causing radiation) what
happens to the element?
THE ELEMENT EXPERIENCES …..
The element changes
form because the
number of protons
and neutrons are now
different.
238
234
-->
92
232
-->
90
88
238
234
232
-->
-->
90
92
230
-->
228
-->
86
88
226
-->
84
82
What did you notice about the elements you ended up
with as you continued this process?
Change from one
element to another
through the
spontaneous release
of nuclear particles
and energy.
The time it takes for 1/2 of a radioactive element
to decay. Every radioactive element has a unique
half-life. (some are in seconds and some are
billions of years.)
On the island of Bikini Atoll, scientists
back in the 1950’s tested nuclear
bombs for the government. Today,
nobody is still allowed to return there
because it is STILL RADIOACTIVE!!
Iodine-137 has a half-life of 23 seconds. Calculate how
much of the 302 grams of iodine-137 remains after 138
seconds.
STEP 1 - CALCULATE HOW MANY HALF-LIVES YOUR
ISOTOPE WILL GO THROUGH. DIVIDE TOTAL TIME
BY HALF-LIFE TIME.
138 sec / 23 sec = 6 half-lives
STEP 2 - DIVIDE YOUR ORIGINAL AMOUNT OF YOUR
ISOTOPE BY TWO AS MANY TIMES AS YOU HAVE
HALF-LIVES (YOUR ANSWER IN STEP 1)
302 g / 2 = 151g / 2 = 75.5 g / 2 = 37.75 g / 2 =18.87 g /
2 = 9.4 g / 2 = 4.72 grams of iodine-137 left.
The splitting of an atom’s
nucleus into two smaller
nuclei.
HOW FISSION WORKS: The fuel for this reaction is a
large radioactive and unstable atom such as Uranium 235, or U-235. A neutron is shot at the U-235 atom at a
high speed, and splits apart the U-235 atom. Tons of
nuclear energy is released as well as three more
neutrons. Nuclear power plants use this fission reaction
to produce electricity.
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WHAT WOULD HAPPEN IF THE 3 RELEASED
NEUTRONS RAN INTO 3 MORE U-235 ATOMS?
A nuclear “chain reaction”
occurs. Nuclear power plants
keep this chain reaction under
control, however an explosion
can occur if this reaction is out
of control. The atomic bomb is
an example of this.
Fission Reaction
Krypton-92
nucleus
neutron
energy
neutron
energy
neutron
Neutron
Uranium-235
nucleus
Barium-141
nucleus
The fusion process occurs
naturally in our sun. This is
how the sun produces it’s
heat and light energy.
In fusion, two hydrogen atoms
collide together at high
temperatures and fuse (melt)
together to form a larger helium
atom.
The combining of two
smaller nuclei to form
one large nucleus. This
reaction produces five
times more energy than
fission.
-->
Fusion Reaction
Neutron and
energy
H-2 nucleus
H-3 nucleus
Helium
nucleus
1. Fuel (Uranium) is in
limited supply.
2. Reaction can be
controlled.
3. High-level radioactive
waste products are
made.
4. Waste products are
large and take years to
decay to safe levels.
1. Fuel (Hydrogen) can be
taken from water, which
we have great supply of.
2. Reaction needs high
temperatures, cannot be
easily controlled.
3. Produces low-level safe
waste products.
4. It takes more energy to get
fusion started than what
you get out of it.
Fission vs. Fusion
Comparing Nuclear Fission and Nuclear Fusion
Type of Reaction
Process
Products
Fission
One nucleus
splits
Two nuclei, neutrons,
energy
Fusion
Two nuclei
fuse
One nucleus, neutrons,
energy
There are two nuclear power plants very close to our
area. Can you tell me where they are?
A nuclear power plant uses the
heat produced by the fission
reaction (breaking uranium
atoms) to produce steam. The
steam turns a large set of
turbine blades which then turns
a generator producing electricity
for us to use.
1. Fuel - Uranium-235 provides the nuclear energy
needed to heat the reactor vessel or core. Made in
pellets the size of your fingernail.
2. Reactor vessel (core) - The section of a nuclear
power plant where the fission reaction occurs.
3. Fuel rods - The uranium-235 pellets are placed in
these. Many rods are bundled together in the reactor
vessel (core).
4. Control rods - These are placed within the fuel rods.
They are usually made of the element Cadmium. They
control the speed of the fission reaction.
5. Cooling water (coolant) - Surrounds the control and
fuel rods inside the core. This water is heated by fission,
and pumped into the heat exchanger.
6. Heat exchanger - Hot radioactive water inside the
pipe makes contact with normal water in the tank. The
normal water is heated up, and turns to steam.
7. Steam turbine - Contains sets of fan blades that turn
when steam is shot through them.
8. Generator - A magnet connected to the turbine spins
inside giant coils of wire producing electricity.
Are we done yet !? Last one - I promise!!
9. Cooling Tower - A holding tank where the heated
water collects to cool down. When the water is cooled, it
is pumped back into the plant to be used again. Steam
rises from the tower - not smoke!!!!
THE NUCLEAR POWER PLANT
Meltdown - When temperatures inside the reactor core
get too hot, the fuel rods melt together causing a
possible explosion/release of radiation.
Chernobyl, Russia (1986)
Three Mile Island, PA (1979?)
Yucca Mountain , Nevada
This proposed site by our
government is where nuclear
power plants will eventually send
their high-level wastes. The
wastes would be put into metal
air-tight containers and placed
into underground caverns dug
under this mountain.