Radioactivity and Nuclear energy

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Radioactivity and Nuclear energy
ENVIRONMENTAL SCIENCE UNIT 3
MRS. SHARPLESS - TEAM E MR. CONRAD - TEAM F
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Radiation was discovered purely by chance .
Henri Becquerel
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.
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All nuclear energy begins in the area of the atom
called the
The central core of the atom. Contains PROTONS
and NEUTRONS.
NUCLEUS
Reactions that produce energy and involve the
nucleus of an atom are called NUCLEAR REACTIONS,
and produce a tremendous amount of energy.
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Developed a formula to describe how matter
changes into energy. When matter is turned into
energy, large amounts of energy are released.
Albert Einstein -
E energy M mass C speed of light (squared)
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WHAT MAKES SOMETHING RADIOACTIVE ANYWAY?
The atoms that make up the substance must be
giving off nuclear particles (protons and
neutrons) and energy.
Radioactivity -
The spontaneous release of nuclear particles and
energy.
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RADIOACTIVE ISOTOPES
Isotopes - Atoms which possess the same atomic
number, but different mass numbers. (Same number
of protons, different number of neutrons)
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1
3
H
H
H
1
1
1
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Radioactive Isotopes
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.
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Radioactive Emissions
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.
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Radioactive Emissions
THERE ARE THREE TYPES OF PARTICLES AND ENERGY
GIVEN OFF BY RADIOACTIVE ELEMENTS
Type of radiation where the particles have a
negative charge, penetrates living tissue, and
has less mass but moves quicker than an alpha
particle.
BETA PARTICLES -
If you could actually see a beta particle it
would appear to be one free electron capable of
moving anywhere.
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Radioactive Emissions
THERE ARE THREE TYPES OF PARTICLES AND ENERGY
GIVEN OFF BY RADIOACTIVE ELEMENTS
The only type of radiation which is energy
instead of particles. Travels at the speed of
light, has no mass, is neutral in charge, and
penetrates just about every substance.
POWERFUL!!!!!!
GAMMA RAYS -
Since Gamma rays are energy only and travel so
quickly, you would not see them even if you could!
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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.
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Radiation detection devices
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.
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Radiation detection devices
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.
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Radiation detection devices
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.
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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.
NUCLEAR CHANGE -
U
Th
238
234
Ra
232
--gt
--gt
92
90
88
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U
238
Th
234
Ra
232
--gt
--gt
88
90
92
Pb
Rn
Po
230
228
226
--gt
--gt
--gt
86
84
82
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What did you notice about the elements you ended
up with as you continued this process?
Radioactive decay -
Change from one element to another through the
spontaneous release of nuclear particles and
energy.
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Half-life
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 1950s tested nuclear bombs for the
government. Today, nobody is still allowed to
return there because it is STILL RADIOACTIVE!!
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Calculating Half-life
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.
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Nuclear fission -
The splitting of an atoms 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.
--gt
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Nuclear fission
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.
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Fission Reaction
Krypton-92 nucleus
neutron
energy
neutron
energy
neutron
Neutron
Uranium-235 nucleus
Barium-141 nucleus
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Nuclear fusion -
The combining of two smaller nuclei to form one
large nucleus. This reaction produces five times
more energy than fission.
The fusion process occurs naturally in our sun.
This is how the sun produces its heat and light
energy.
In fusion, two hydrogen atoms collide together at
high temperatures and fuse (melt) together to
form a larger helium atom.
--gt
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Fusion Reaction
H-2 nucleus
H-3 nucleus
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Fission vs. Fusion

• Fuel (Hydrogen) can be taken from water, which we
  have great supply of.
• Reaction needs high temperatures, cannot be
  easily controlled.
• Produces low-level safe waste products.
• 4. It takes more energy to get fusion started
  than what you get out of it.

• Fuel (Uranium) is in limited supply.
• Reaction can be controlled.
• High-level radioactive waste products are made.
• 4. Waste products are large and take years to
  decay to safe levels.

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Fission vs. Fusion
Comparing Nuclear Fission and Nuclear Fusion
Type of Reaction
Process
Products
Fission Fusion
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Nuclear Power Plants
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.
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Nuclear Power Plant Parts
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.
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Nuclear Power Plant Parts
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.

• 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.
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Nuclear Power Plant Parts
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!!!!
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THE NUCLEAR POWER PLANT
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Nuclear power plant risks ?
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?)
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Nuclear Waste Storage
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.