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Objectives
• Identify types of radiation• Identify terminology and risks associated with
radiation• Identify self aid procedures for protection against
radiation exposure
Sets the stage for understanding the what/why about your radiation detection equipment
Pretest
• Check your knowledge about radiation• Fill in your answers now• Keep until class is done, compare your answers
Ionizing Radiation
• Ionizing radiation is electromagnetic energy or energetic particles emitted from a source
− Electromagnetic energy: radio waves, light, x-rays, etc. − Source: unstable atoms of any material− Ionize: To strip electrons from other atoms causing
chemical changes in molecules
Alpha Radiation
• Heavy charged particles• Highly ionizing• Not penetrating
− Travel several centimeters in air or a few microns in tissue
− Stopped by paper or clothing
• Internal hazard
Beta Radiation
• High energy small particle• Moderately penetrating
− Up to a few meters in air− Several millimeters in tissue
• Primarily internal hazard, some external
Gamma Radiation or X-rays
• High energy rays• Very penetrating• Difficult to shield• Protective clothing will not protect
against photon radiation• External and internal hazard
Neutron Radiation
• Uncharged high speed particle• Can be very penetrating• Requires special consideration for
shielding• External and internal hazard – but –
not likely to encounter neutron radiation
Examples of RadioactiveMaterials
Substance Emit Use
• Americium 241 a, g Smoke detectors
• Cobalt 60 b, g Medical therapy
• Cesium 137 b, g Many industrial uses
• Radium 226 a Medical therapy
• Uranium 238 a, b, g Reactors and weapons
• Iridium 192 b, g Industrial radiography
Radiation Half-life
• Time required for a radioactive substance to lose half of its radioactivity
− Each radionuclide has a unique half-life− From a fraction of a second to millions of years
Examples:Tc-99m 6.0 hrsI-131 8.05 daysCo-60 5.26 yrsSr-90 28.1 yrsPu-239 24,400 yrsU-238 4,150,000,000 yrs
Units of Measure
• Rad (Gray) = absorbed dose• Roentgen (R) = energy
− Dose rate expressed in R/h, mR/h, μR/h− Counts per minute (cpm) - measure of energy from
surface contamination (not the same as R/hr)
• For gamma and x-ray, 1 R ~ 1 rad
Units of Measure (Cont.)
• Rem (sievert) - amount of damage suspected from a particular type of radiation dose
− (1R = 1 rad = 1 rem) gamma = 20 rem alpha
• Curie (becquerel) - amount of material in terms of its radioactivity
− Compare 1 Ci = 37 billion Bq
Background Radiation
• Natural sources of radiation (~ 260 mrem/yr)− Cosmic radiation− Radioactive material in the environment
• Radon is largest contributor
− Radioactive material in the body
• Manmade sources (~ 100 mrem/yr)− Medical and dental procedures− Releases to the environment− Commercial / industrial sources
Radiation Doses In Perspective
• Natural background and manmade radiation 360 mrem/yr(~20 +/- μR/h is background)
• Diagnostic chest x-ray 10 mrem
• Flight from LA to Paris 4.8 mrem
• Barium enema 800 mrem
• Smoking 1.5 packs per day 16,000 mrem/yr
• Heart catheterization 45,000 mrem
• Mild acute radiation sickness 200,000 mrem
• LD50/60 for radiation 450,000 mrem
ALARA
Goal of exposure management:
keep radiation exposures to a level
As Low As Reasonably Achievable
(ALARA)
Radiation Exposure Risks
s Thyroid Lung
LiverBone
Irradiation Externalcontamination
IncorporationInternalcontamination
Increasing risk
Self Protection Measures
• 1st Avoid exposure and contamination− Detect radiation exposure− Back away when too high
• 2nd Use Personal Protective Equipment (PPE)• 3rd Decontaminate yourself
Distance
1 meter 1 meter
Dose rate is ¼ when distanceis doubled
100 mrem/hr 25 mrem/hr
Source
The “four times” rule
Simplified Radiation PPE
• Protect your respiratory tract− Respirator, surgical mask, etc.
• Protect your skin− Gloves!− Outer clothing− Chemical suit is not always needed
Detect Ionizing Radiation
• Not detected by human senses• Requires use of detection instruments• No single instrument can detect or measure all
types of radiation
can't smell it can't see it
Radiation Detection Instruments
• Dosimeter measures dose received (odometer)− Track personal exposure
• Survey instrument detects and measures dose rate (speedometer)
− Find source of radiation− Find surface contamination
• Area monitor is a fixed site survey meter− Entry alert
Self Decontamination
• Wash it off− Hand washing− Tepid water, mild soap− No scrubbing
• If showering, use shampoo• Remove and launder clothing• Monitor after decon