What is Radiation?
Radiation is
energy
transported in the
form of particles
or waves.
Penetration Abilities of Different
Types of Radiation
Alpha Particles
Stopped by a sheet of paper
Radiation
Source
Beta Particles
Stopped by a layer of clothing
or less than an inch of a substance
(e.g. plastic)
Gamma Rays
Stopped by inches to feet of concrete
or less than an inch of lead
Neutrons
Stopped by a few feet of concrete
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Detecting Radiation
Alpha Survey Meter
Beta and Gamma
Survey Meter
Radiation vs. Radioactive Material
• Radiation: energy transported in the form of
particles or waves (alpha, beta, gamma,
neutrons)
• Radioactive Material: material that contains
atoms that emit radiation spontaneously
2
Exposure vs. Contamination
Exposure: irradiation of the
body  absorbed dose
(Gray, rad)
Contamination: radioactive
material on patient
(external)or within patient
(internal)
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4
Basic Radiation Principles
Radiation is energy released from unstable
elements. The energy is released until the
element is stable.
This may take a fraction of a second or billions
of years depending upon the element.
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Basic Radiation Principles…
continued…
Decay (decrease in the radioactivity)
can be determined using half-lives.
A “half-life” is the time it takes for an
isotope to reduce its activity by one
half…
Basic Radiation Principles …
continued…
This means that if, an element has a halflife of five years:
1/2 of the radiation would be present in 5 years
1/4 of the radiation would be present in 10 years
1/8 of the radiation would be present in 15 years
1/16 of the radiation would be present in 20 years
1/32 of the r adiation would b e pr esent in 25 year s
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Basic Radiation Principles …
continued…
U-238 has a 4.47 billion year half-life
Cesium-137 has a 30 year half-life
Cobalt-60 has a 5 year half-life
Iodine-131 has an 8 day half-life
Other sources of ionizing radiation may
decay faster, causing less exposure.
Source: http://www.epa.gov/radiation/radionuclides/ accessed 12/23/2004
Basic Radiation Principles …
continued…
Radiation is everywhere, coming from:
•
•
•
•
the solar system
the atmosphere
the earth (soil, rocks, and water) and
man-made sources.
You cannot see, smell, or feel it.
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Radiation: Overview
 Biological injury
 Ionization of atoms within the cell
 Ionization breaks molecular bonds
 Cell damage occurs when critical cell
structures are affected
Types of Ionizing Radiation
 Alpha particles
 Beta particles
 Gamma rays
 Neutron particles
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Types of Ionizing Radiation
 Alpha particles
Relatively large mass
Consists of two protons and two neutrons
Possesses +2 positive charge striping
electrons from atoms it passes through
Alpha particle decay
U.S. Department of Energy Image
9
Types of Ionizing Radiation
 Alpha particles
Do not travel far
Range in air is 1-2 inches
Completely stopped by the dead layers of the
skin or by clothing
Offer minimal external hazard
Can cause significant regional cellular
damage when internalized
The penetrating power of three types of radiation
U.S. Environmental Protection Agency Illustration
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Types of Ionizing Radiation
 Beta particles
Electrons emitted during decay
Found in fallout
Half the charge of alpha particles
Electrically interacts with passing atoms
Beta particle decay
U.S. Department of Energy Images
11
Types of Ionizing Radiation
 Beta particles
Travel further than alpha particles
Easily shielded by thin plastic, glass,
aluminum or wood
External hazard to skin and eyes
Less dangerous internally but still can cause
significant regional injury
The penetrating power of three types of radiation
U.S. Environmental Protection Agency Illustration
12
Types of Ionizing Radiation
 Gamma rays / X-rays
Electromagnetic wave / no charge
Ionize matter by direct interaction with orbital
electrons
Difference between radiation is only their
source
Best shielded by dense materials
Gamma decay
U.S. Department of Energy Image
Gamma decay
U.S. Department of Energy Image
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Types of Ionizing Radiation
 Gamma rays
Highly penetrating
Can produce whole body exposure
Equally dangerous with external or internal
exposure
The penetrating power of three types of radiation
U.S. Environmental Protection Agency Illustration
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Types of Ionizing Radiation
 Neutron particles
Emitted from unstable atoms during a nuclear
reaction
No electrical charge
Causes damage by direct collision with the
nucleus of another atom
May produce indirect ionization
Types of Ionizing Radiation
 Neutron particles
Highly penetrating; difficult to stop
Best shielded by materials with high hydrogen
content
Cause whole body injury like gamma rays, but
20 times more damaging
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Radioactive Isotopes
 Alpha emitters
Americium-241
Plutonium-239/238
Radium-226
Radioactive Isotopes
 Americium-241
Decay daughter of plutonium
Main threat is heavy metal poisoning
Large quantities : cause whole-body
irradiation
75% of the lung burden is absorbed
Absorbed rapidly from skin wounds
Urinary and hepatic excretion
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Radioactive Isotopes
 Plutonium-238/239
 Produced from uranium in reactors
 Primary fissionable material in nuclear plants and
weapons
 Always contaminated with americium
 Primary toxicity is from inhalation
 GI absorption depends on chemical state
 May be washed from intact skin
Radioactive Isotopes
 Radium-226
Primary alpha emitter, but daughter products
emit beta and gamma rays
Most common exposure is ingestion
Follows calcium to bone deposition
Associated with leukemia, aplastic anemia,
and sarcomas
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Radioactive Isotopes
 Beta emitters
Iodine-131, 132, 134, 135
Phosphorus-32
Strontium-90
Radioactive Isotopes
 Iodine-131, 132, 134, 135
Created during nuclear fission
Found in reactor fuel rods or after a nuclear
explosion
Primary toxicity is to the thyroid gland
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Thyroid Glands
National Institute of Diabetes and Digestive and
Kidney Diseases Image
Radioactive Isotopes
 Phosphorus-32
Found in research labs and medical facilities
Completely absorbed from all sites
Deposited in the bone marrow and other
rapidly replicating cells
Local irradiation causes cell damage
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Radioactive Isotopes
 Strontium-90
Direct fission product of uranium
Daughters emit beta and gamma rays
Readily absorbed via respiratory and GI
routes
~ 50% of dose deposited in bone
Radioactive Isotopes
 Gamma emitters
Cesium-137
Cobalt-60
Uranium-238, 234,235
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Radioactive Isotopes
 Cesium-137
By-product of the manufacture of weaponsgrade radioactive material
Half-life of 31 years
Salt that dissolves easily in water
Emits both gamma and beta radiation
Completely absorbed through the lungs, GI
tract, and wounds
Radioactive Isotopes
 Cobalt-60
Produced by non-radioactive cobalt to intense
radiation in the reactor core
Emits both gamma and beta radiation
Half-life of 5 years
Rapidly absorbed from the lung
< 5% absorption from the GI tract
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Radioactive Isotopes
 Uranium-238,235,234
Natural mix of all three isotopes
Half-lives of 4.5x10 9, 7x108, and 2.5x105
years
Inhaled compounds metabolized and excreted
in urine
Urinary levels of 100 µg per deciliter may
cause renal failure
Absorption is determined by its chemical state
Units of Radiation
 Rad still used widely
 International unit called gray (Gy)
 Quality factor used to adjust for
differences in tissue absorption
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Basic Radiation Principles …
continued…
• Alpha () particles can be blocked by a piece of
paper.
• Beta () particles can be blocked by a firefighter’s
turnout gear, but not a piece of paper.
• If exposed, wash off particles well with soap
and water in a timely manner.
• Note: If particles are ingested, inhaled, or enter the body
through wounds, medical attention is recommended.
Basic Radiation Principles …
continued…
Gamma rays () are a different matter.
• Pure energy, similar to x-rays
• Can be blocked by concrete, lead or steel
• If exposed, medical attention is recommended.
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Nuclear Reaction:
Decontamination
• Primary contaminants will be alpha and
beta emitters
• Simply removing clothing and shoes will
reduce contamination by approximately
90%
Remember 3 Factors
to Minimize Exposure
• Time
• Distance
• Shielding
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RADIOLOGICAL MATERIALS
Technical Emergency Response
Training
49
TIME
Source
Source
Dose
25 mrem
• 100 mrem per hour x 15 min (.25 hour) = 25
mrem
25
DISTANCE
1 meter 1 meter
Source
Source
Dose Rate
100 mrem/hr
25 mrem/hr
SKIN
ALPHA PARTICLE
PAPER
SHIELDING
GAMMA RAYS
LEAD
BETA PARTICLE
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Measurement and Health
Effects of Radiation
Exposures
Measurement
The term used to measure radiation
doses is “rem.”
It measures the effect of radiation on living
tissue, also known as a “biologically
effective dose.”
Typically, exposure is expressed in
“millirems” (mrem) which is onethousandth of a rem.
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Typical Radiation Doses
Flight from Los Angeles to London . . . . 5 mrem
Annual public dose limit . . . . . . . . . . .100 mrem
Annual natural background . . . . . . 300 mrem
Fetal dose limit . . . . . . . . . . . . . . . . . 500 mrem
Annual radiation worker dose limit . 5000 mrem
Emergency: The MDH accepts an emergency
exposure for lifesaving only of 25 to 100 rem.
Note: Workplace exposures required to be “As Low
As Reasonably Achievable” (ALARA)
Factors that Influence Health Effects
of Radiation
• General health of the individual
• Amount (The “threshold dose” means that the
effect is not seen until the absorbed dose is greater
than a certain level.)
• Frequency (acute or somatic)
• Strength of isotope
• Targeted cells or organs receiving the dose
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Uses of Radioactive Material
Uses of radioactive material
Medical applications
include:
• Nuclear medicine
equipment
• Isotopic generators
• Therapy units and seed
implants
• Radiopharmaceuticals
• Computed Tomography
(CT) imaging
Source: FDA, Center for Devices and Radiological Health
http://www.pueblo.gs a.gov/ cic_t ext/h ealth/ fullbody-ctscan/
fullbody
fullbody -ctscan.htm
Accessed 12/21/2004
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Uses of radioactive material
Business applications
include:
•
•
•
•
•
Luminous dials
Moisture and density gauges
Thickness gauges
Rifle sights
Static eliminators
Source: Nuclear Regulatory Commission
http://www.nrc.gov/reading
http://www.nrc.gov/reading-rm/doc-coll
ections/news/2004/04 -004i.html
Accessed 12/21/2004
Uses of radioactive material
Public health applications
include:
•
•
•
•
•
•
Food irradiation
Radiography
Well logging
Chemical agent detectors
XRFs for lead paint analysis
Smoke detectors
http://www.foodprocessing
http://www.foodprocessingtechnology.com/projects/sure/
accessed 12/21/2004
Source: FDA, Center for Devices
and Radiological Health
http://www.pueblo.gs a.gov/ cic_t ext/healt
h/ fullbody-ctscan/what.htm
access ed 12/21/2004
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Potential Radiological Incident?
Accidental (Controlled by regulatory systems)
• The transportation sector (vehicle, rail, ship) carries many
materials across the US. Despite fears of an attack, the most
likely radiological incident remains a transportation
accident involving radioactive materials.
• Nuclear power plants build strong structures and exercise
Intentional (Controlled by legal systems)
• Stolen materials
• Dirty bombs
Damage to a nuclear power
plant is difficult to imagine
US plants: 3 barriers between radioactive
materials and the environment.
The reactor will not explode.
Structures that house reactor fuel are
robust. Fuel is protected from impacts of
large commercial aircraft.
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Damage to a nuclear power
plant is difficult to imagine
…continued…
Professionals discuss, plan, and perform
“exercises” often to rehearse skills and test
possible scenarios:
• At worst, could be a release of radioactive
materials into the air, creating a “plume.”
• May need to evacuate a surrounding area.
• Precautionary medical measures may be
necessary for those caught in the plume or its
expected path down-wind.
Bombs with radioactive material (“Dirty
Bombs” or “RDDs”)
Definition: a conventional bomb surrounded by or filled with
non-nuclear radiological materials. (also called a
radiological dispersal device, or RDD)
Unlikely, and most probable, form of radiological terrorism
Radioactivity would not kill or seriously injure people (but
an explosion might).
Would create fear or chaos: coined a “Weapon of Mass
Disruption.”
Expect significant long-term psychological effects.
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Bombs with radioactive material
…Continued…
An RDD could be
• any size,
• spread radiation, and
• contaminate an area.
This photo was staged, but
several alleged real-life
RDD plots have been
upset.
Photo: www.seattle.gov/mayor/gallery_2003/gallery_TOPOFF2_03.htm
Erik Stuhaug, photographer, accessed 11/10/2004
Summary
 Alpha, beta, gamma, and neutron
radiation
 Alpha particles
No external risk
Produce regional internal injury
 Beta particles
Significant external risk to skin & eyes
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Summary
 Gamma radiation and neutrons
Highly penetrating
Produce whole body exposure
 Units of radiation
Rad and rem
Gray (Gy) and sievert (Sv)
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