Basics of Radiation. 2 Topics Types of Radiation How Radiation Interacts With You Radiation Safety...
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Transcript of Basics of Radiation. 2 Topics Types of Radiation How Radiation Interacts With You Radiation Safety...
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Topics
• Types of Radiation• How Radiation Interacts With You• Radiation Safety• Why Measure Radiation Today• Summary• Radiation Equivalents
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Two Types of Radiation
• Radiation can be non-ionizing or ionizing
• Non-ionizing radiation is generally a low energy electromagnetic wave– Sunlight– Radio waves– Microwaves– Infrared waves
• Mostly harmless
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Ionizing (Nuclear) Radiation
• Has enough energy to ionize (alter) atoms and molecules
• Because it can ionize, it can cause biological damage
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Ionizing Radiation
Ionizing radiation is all around us• Outer space, the earth, and medical treatments
• Low levels of naturally occurring radioactive material are in our environment, the food we eat, and in many consumer products
• Some consumer products also contain small amounts of man-made radioactive material
• Most of your annual dose of radiation comes from Radon gas in your house
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Topics
• Types of Radiation
• How Radiation Interacts With You
• Radiation Safety
• Why Measure Radiation Today
• Summary
• Radiation Equivalents
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What is a Dose of Radiation?
• When radiation hits your body, and its energy is transferred to your tissue, you have received a dose of radiation.
• The more energy deposited, the higher your dose.
• Measured in rem (R).
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What is the Dose Rate of Radiation?
• The amount of radiation given off by a source over time
• Measured in rem per hour (R/h)
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Gatling Gun Analogy
• The number of bullets released per hour is the dose rate
• The number of bullets that hit you is the dose
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Irradiated or Contaminated?
Irradiated
• You are irradiated when radiation hits you
• You do not become radioactive when you are irradiated
• Many foods are irradiated to kill molds and bacteria
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Irradiated or Contaminated?
Contaminated
• Contamination is radioactive dirt
• You can become contaminated by touching radioactive dirt
• Contamination can be washed off like any dirt
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Radioactive Contamination
Radiation cannot make you radioactive*
* Understanding Radiation: Bjorn Wahlstrom (overrides copyright below)
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Radioactive ContaminationRadioactive contamination can stick to clothes and skin. It can be washed away like any dirt*.
* Understanding Radiation: Bjorn Wahlstrom
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Common Doses in Everyday Life
100,000 Average annual chest x-ray exposure2,000,000 Annual exposure from radon gas in homes810,000 Annual exposure at high elevation
10,400,000 Gastro-intestinal Barium x-ray (GI series)
Cause of DoseDose (µR)
1R = 1,000,000 μR
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Acute Radiation Doses
μR R
25,000,000 – 50,000,000 25 - 50First sign of physical effects – drop in white blood cell count
100,000,000 100Vomiting within several hours of exposure
320,000,000 - 360,000,000 320 - 36050% die within 60 days with minimal supportive care
480,000,000 - 500,000,000 480 - 50050% die within 60 day with supportive care
1,000,000,000 1,000 100% die within 30 days
Dose Effects
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Topics
• Types of Radiation
• How Radiation Interacts With You
• Radiation Safety
• Why Measure Radiation Today
• Summary
• Radiation Equivalents
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Radiation Safety
• The fundamental principle of radiation safety is that radiation exposure should be As Low As Reasonably Achievable (ALARA).
• The three factors influencing radiation dose are:– Time– Distance– Shielding
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ALARA - Time
• The less time you’re exposed, the less exposure you get
• Dose = Dose Rate x Time
• Limit your time near the radiation source!
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ALARA - Distance
• The farther away from the source you are, the weaker the source is to you
• Exposure levels are based upon the inverse square law
• Increase the distance between you and the source!
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ALARA - Shielding
• Shielding can reduce or stop radiation from hitting you– α can be absorbed by a piece of paper– β can be absorbed by 1” of aluminum or glass– γ can be absorbed by thick lead shields– n can be absorbed by paraffin, water,
polyethylene• Increase the amount of shielding material
between you and the source!
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Shielding/Attenuating Radiation
Pap
er
Glass, th
in m
etal
Lead
, C
on
crete
W
ater, P
olyeth
ylene
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Topics
• Types of Radiation• How Radiation Interacts With You• Radiation Safety• Why Measure Radiation Today• Summary• Radiation Equivalents
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Radiological Terrorism
Radiological Terrorism is a real and possible threat
• High psychological/emotional impact
• High economic impact
• Many devices are easy to build
• Al Qaeda has threatened radiological terrorism
• It’s already being done
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Threat Comparison
Sev
erity
of
inci
dent
Probability of incident
Stolen nuclear weapon
Improvised nuclear device
RDD
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Radiological Terrorism
• Nuclear warheads use special nuclear materials– Plutonium– Uranium
• Medical and industrial radioactive materials cannot produce a nuclear warhead – they can only be used to contaminate
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Radiological Dispersion Devices
RDDs take two main forms
• A dirty bomb– Radiological material
wrapped in conventional explosives
• A simple radioactive source left discretely in a public place
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Making an RDD
• All you need is radiological material
• Orphan sources– Radiological materials are used everyday in a
variety of applications– Some sources are lost, forgotten, or disposed
of improperly – orphan sources– Over 200,000 available today
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Example of an RDD
• 1 pound of HE, two patient doses of liquid Technetium-99m (Tc-99m) near the HE
• Weather: 30 degrees F, sunny, light winds with gusts of 20 mph
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Commonly Available Isotopes Suitable For RDDs
Radioisotope Gamma Emission Neutron EmissionDetect with Gamma
Sensor*Cobalt-60 Yes No Yes
Cesium-137 Yes No Yes
Iridium-192 Yes No Yes
Stronium-90 No* No Yes
Americium-241 Yes No Yes
Californium-252 Yes Yes Yes
Plutonium-238 Yes Yes Yes
*Can be detected with a gamma sensor because daughter isotope emits gamma.
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Innocent Sources
• Radioactive sources seen in typical day to day operations– Cause innocent alarms– Could be used to disguise a real source
• Containers of tile & bricks containing uranium & thorium
• Containers of bananas & fertilizer containing potassium
• Patients who have received nuclear medicine treatments
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Topics
• Types of Radiation• How Radiation Interacts With You• Radiation Safety• Why Measure Radiation Today• Summary• Radiation Equivalents
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Summary
• Dose is measured in R– Cumulative effect on the
body
• Dose rate is measured R/h– Amount of radiation in your
vicinity
• Contamination is radioactive particles in or on the body
• Irradiation is exposure to a radioactive source
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Questions?
RAE Systems3775 North First Street
San Jose, CA 5134
Voice: 408-952-8200
Fax: 408-952-8480
www.raesystems.com
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Topics
• Types of Radiation• How Radiation Interacts With You• Radiation Safety• Why Measure Radiation Today• Summary• Radiation Equivalents
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Radiation Equivalents
Rem Millirem (mrem)Microrem
(µrem)
1 1,000 1,000,000
0.1 100 100,000
0.01 10 10,000
0.001 1 1,000
0.0001 0.1 100
0.00001 0.01 10
0.000001 0.001 1