Module 1
Introduction to
Radiation
1
Introduction to Radiation
Terminal Objective:
DEFINE the fundamentals of
radiation, radioactive material,
ionization, ionizing radiation, and
contamination.
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Enabling Objectives
• LIST the three basic components
of an atom.
• DESCRIBE the differences
between ionizing radiation and
non-ionizing radiation.
• DEFINE radioactivity.
3
Enabling Objectives
• STATE the four basic types of
ionizing radiation.
• DESCRIBE the shielding materials
and biological hazards for each of
the four types of ionizing radiation.
• LIST the three techniques for
minimizing exposure to radiation
and radioactive material (ALARA).
4
Radiation Basics Video
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
5
Parts of an Atom
• Protons
• Neutrons
• Electrons
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Stable and Unstable Atoms
• An atom with too many
or too few neutrons
contains excess
energy and is not
stable.
• Unstable atoms give
off excess energy
(radiation).
• Unstable atoms are
radioactive.
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Ionization
Radiation
Removing electrons from atoms or molecules
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Ionizing Radiation
Excess energy
(from unstable
atoms), capable
of removing
electrons from
an atom
Radiation
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Non-Ionizing Radiation
Non-ionizing
Ionizing
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Radioactivity
Radioactivity is the process of
unstable (radioactive) atoms trying
to become stable by emitting
ionizing energy.
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Radioactive Material
Radioactive Material
Material containing unstable
(radioactive) atoms
Radioactive Contamination
Radioactive material in an
unwanted place
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“Radiological” vs. “Nuclear”
“Radiological” deals with radiation or
material that emits radiation.
Example Radiological WMD: “Dirty Bomb”
“Nuclear” refers to processes that
involve splitting a nucleus (fission) or
combining nuclei of atoms (fusion).
Example Nuclear WMD: atomic bomb
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Measuring Radiation
Radiation Dose
• Radiation energy absorbed by the
human body
• Dose is measured in units of rem.
• A millirem (mrem) is one thousandth of
a rem.
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Measuring Radiation
Radiation Dose Rate
• Radiation energy received over a
period of time
• Radiation dose rate is dose per time
• mrem per hour = mrem/hr
“strength” of radiation at a location
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Types of Ionizing Radiation
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
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Types of Ionizing Radiation
•
Alpha radiation
•
Beta radiation
•
Gamma rays/X-rays
•
Neutron radiation
Some radioactive materials may emit
more than one kind of radiation
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Alpha Radiation
• Range:
1 to 2 inches
• Shielding:
Paper, Cloth,
Dead Layer of
Skin
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Alpha Radiation (continued)
Biological Hazard
• Not an external radiation hazard
• Easily stopped by the dead layer
of skin
• Internal hazard – If material is
inside the body, then the alpha
radiation reaches live cells.
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Alpha Radiation
(continued)
Sources
• Uranium (nuclear power plant fuel
and nuclear weapons)
• Plutonium (nuclear weapons)
• Americium (smoke detectors)
• Thorium (high-temperature
metals)
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Beta Radiation
• Range:
about 10 feet
• Shielding:
Thick Clothing,
¼ Inch Aluminum,
¼ Inch Plastic
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Beta Radiation (continued)
Biological Hazard
• External hazard to skin and eyes
• Internal hazard if the material that
emits the beta radiation is inside
the body. Then beta radiation
can deposit energy in a small
area of body tissue.
25
Beta Radiation (continued)
Sources
• Used nuclear reactor fuel
• Nuclear weapons fallout (strontium)
• Some industrial radioactive sources such
as cesium
• Tritium in glow-in-the-dark EXIT signs,
watch dials, and night-sights on firearms
• Radioactive nickel in chemical agent
detectors
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Gamma Rays/X-Rays
• Range:
Hundreds of feet
• Shielding:
Inch of Lead,
3 Inches of Steel,
6 inches Concrete,
1 foot of Dirt
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Gamma Rays/X-Rays (continued)
Biological Hazard
• Gamma rays and X-rays easily
penetrate body tissues, outside or
inside of the body.
• Whole body (internal and external)
hazard
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Gamma Rays/X-Rays (continued)
Sources
• Uranium, plutonium, radioactive cobalt,
and cesium
• Industrial radiation sources
• Medical sources, cancer treatment
machines
• Many beta-emitters also emit gamma
radiation.
• Potassium in soil, bananas, and
potassium chloride (salt substitute)
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Neutron Radiation
• Range:
Hundreds of feet
• Shielding:
10 Inches of Plastic,
1 foot of Concrete,
3 feet of Dirt,
3 feet of Water
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Neutron Radiation (continued)
Biological Hazard
• Whole body hazard (external and
internal neutrons are a whole body
hazard).
• Neutrons penetrate body tissues.
• Neutrons cause damage whether the
material is inside or outside of the
body.
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Neutron Radiation (continued)
Sources
• Nuclear reactions inside nuclear
reactor while reactor is operating
• Burst of radiation from exploding
nuclear weapon
• Plutonium, industrial sources, moisture
gauges with californium or mixture of
americium and beryllium
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Comparison of Ionizing Radiation
¼ Inch 3 Inches
1 foot
Aluminum
Lead Lead Concrete
Aluminum
Concrete
Radiation Source
Alpha Radiation
Stopped by a
sheet of paper or
dead layer of skin
Beta Radiation
Stopped by thick layers
of clothing or by a
quarter inch of
aluminum or plastic
Gamma Rays
Stopped by a
few inches of lead or
six inches of concrete
Organic
Tissue
Neutrons
Stopped by a foot
concrete or water
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Particle Size Comparison
Earth
City
Ping Pong Ball
Speck of Dust
Atom
Alpha Particle
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Alpha, Beta, and Neutron
“Particles”
Rifle Cartridge
Radioactive atom
Bullet
Alpha, Beta or Neutron
“Particles”
35
Comparison of Radiation
and Contaminants
• Radiation is energy.
• Radioactive contaminants are materials
that emit radiation.
• Radioactive contaminants are radioactive
atoms that get onto something unwanted
or are in an uncontrolled place.
• Radioactive atoms cannot be neutralized
to make them non-radioactive.
36
Exposure vs. Contamination
External Exposure
External Contamination
37
Internal Contamination
and Internal Exposure
Radioactive material
inside the body
Both contaminated
and exposed
38
ALARA
•
As
• Low
• As
• Reasonably
• Achievable
39
ALARA Video
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
40
ALARA
Minimize time
Maximize distance
Use shielding
41
Review
• What’s the difference if I get exposed or
if I get contaminated?
• How do I protect myself from alpha,
beta, gamma, or neutron radiation?
• How can I practice the principles of
ALARA in this situation?
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