1. 2 Radiation Safety 3 What is Radiation? Radiation is a form of energy. It is emitted by either...
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Transcript of 1. 2 Radiation Safety 3 What is Radiation? Radiation is a form of energy. It is emitted by either...
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Radiation Safety
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What is Radiation?
� Radiation is a form of energy.
� It is emitted by either the nucleus of an atom or an orbital electron.
� It is released in the form of electromagnetic waves or particles.
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The Electromagnetic SpectrumWaveform of Radiation
NONIONIZING IONIZING
Radio
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
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What is the difference between ionizing and nonionizing radiation?
� Energy levels:Ionizing radiation has enough energy to
break apart (ionize) material with which it comes in contact.
Nonionizing radiation does not.
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Nucleus
Electron
Orbital path
Atomic Structure
� Nucleus - center of atom, consists of protons and neutrons
� Electrons - negatively charged particles that orbit around the nucleus
� Held together by attraction of unlike charges
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Types of Ionizing Radiation
� Important in healthcare settingAlpha particlesBeta particlesGamma raysX-raysNeutrons
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Sources of Exposure
� Naturally occurring sources
� Environmental radiation
� Medical procedures
� Occupational sources
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Sources of Exposure
� Environmental radiationFallout from nuclear weapons testingEffluents from nuclear facilitiesEmissions from consumer products
(televisions, smoke detectors)
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Sources of Exposure
� Medical sourcesX-rays checking for broken bonesImaging with radioactive materialTumor treatments
� Exposures well controlled
� Limited to very specific areas on body
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� Penetrating electromagnetic waves� Originate in outer part of atom� Common example: type used in medical
procedures� Energy inversely proportional to wavelength
The shorter the wave, the stronger the energy
X-Ray
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� Penetration distance depends on energy of radiation and the material being irradiated.Steel needs high energyHuman body needs low energy
� Rays come from outside the body but cause damage inside the body.
X-Ray
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Sources of ExposureExposure Source Exposure Level
Coal-burning power plant 0.165 mrem/year
X-rays from TV set (1 inch) 0.5 mrem/hour
Airplane ride (39,000 ft) 0.5 mrem/hour
Nuclear power plant (normal operations at property line)
0.6 mrem/year
Three-mile Island (dose at plant, duration of accident)
80 mrem
Building materials (concrete) 3 mrem/year
Chest x-ray 8 mrem/year
Shoe-fitting fluoroscope (per use) 170 mrem
Radionuclides in the body (potassium)
39 mrem/year
Dental x-ray 10 mrem/year
mrem = millirem
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Biological Effects of Radiation
� Background exposure is approximately 360 mrem/year
� Effects on body depend on:Type of radiationEnergy of radiationLength of time in body
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Biological Effects of Radiation
Effects from external sourcesdepend on penetrating ability.
AlphaBeta
Gamma or x-ray
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Biological Effects of Radiation
Parentcell
Celldivision
Normal cells
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Biological Effects of Radiation
Irradiatedcell
Celldivision
Cells damaged
Parentcell
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Biological Effects of Radiation
� SomaticAffects cells
originally exposedAffects tissues,
organs, possibly entire body
Effects range from slight skin reddening to death (acute radiation poisoning)
� GeneticAffects cells of future
generationsKeep levels as low
as possible
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Biological Effects of Radiation
MOST SENSITIVE
LEAST SENSITIVE
fetal cellblood cellsintestinal cellsbone marrow cellssperm cells
capillary cells
muscle cellsnerve cells
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Biological Effects of Radiation
� Sources of health hazard data:Early radiation workersMedical personnelPatients treated with radiationRadiation accident survivors
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Units of Measurement
� Quantity or concentration of radiation
� Absorbed dose (rad)
� Dose equivalent man (rem)
� Radiation exposure (R)
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Roentgen (R)
Exposure to x-rays and gamma rays in air is expressed in roentgens (R)
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Radiation Adsorbed Dose
� radAmount of energy released to matter when
radiation comes into contact with itExpressed in rad
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Radiation Equivalent Man
� remInjury from radiation depends on amount of
energy imparted to matterExpressed in remSome types of radiation produce greater
effects than othersAlpha particles produce more energy than beta
particles
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Units of Measurement
� Effect of ionizing radiation is determined by:Energy of radiationMaterial irradiatedLength of exposureType of effectDelay before effect seenAbility of body to repair itself
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Standards and Guides
Why is there a difference between occupational limits and public health limits?
� Occupational limitsHealthy populationAges 18 - 658 hr per day350 days per year
� Public health limitsHealthy and sickAll age groups24-hr per day365 days per year
� Dose limits
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Standards and Guides
Body PartExposed
Permissible Dose(rem per quarter)
Whole body 1.25
Hands, forearms, feet,ankles
18.75
Skin of whole body 7.50
OSHA
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Standards and Guidelines
Body Parts Exposed
Permissible Dose (rem per quarter)
Whole body 0.125
Hands, forearms, feet
1.875
Skin of whole body 0.75
OSHADose Limits for employees 18 Years and Younger
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Standards and Guides
� Radiation area5 mrem in 1 hour or
100 mrem over any 5 consecutive days
� High radiation area100 mrem in 1 hour
� Areas to be labeled Radiation areas High-radiation areas Airborne radioactivity
areas Storage and use areas Containers
Posting Requirements
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Universal symbol
Standards and Guides
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Monitoring Instruments
� Personal monitoring
� Area monitoring
� Surface monitoring
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Monitoring Instruments
� Personal monitoring:Film badges, ringsPocket dosimeter
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Basic Safety Factors
� Keep exposures As Low As Reasonably Achievable (ALARA)TimeDistanceShielding
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Basic Safety Factors
� Time:Keep exposure times
to a minimumMinimizes doseALARA
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Basic Safety Factors
Distance: Inverse square law: by doubling the
distance from a source, the exposure is decreased by a factor of 4.
I1R12 = I2R2
2
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Basic Safety Factors
I1R12 = I2R2
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Inverse Square Law
I1 = initial intensityR1= initial distanceR2 = new distanceI2 = new intensity
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Basic Safety FactorsInverse Square Law
If a source emits 10 mR/hour at a distance of 1 foot, what is the exposure level at 4 feet away?
I2 = I1 x (R12 / R2
2)
I2 = 5 mR/hour x ( 1ft2 / 16 ft2)
I2 = 0.625 mR/hour
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Basic Safety Factors
� Shielding:Encloses the source or isolates workers
from the radioactive environmentMust choose the appropriate shielding
material, depending on the type of radiation present
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Basic Safety Factors
� Shielding
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Basic Safety Factors
� Shielding
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Nonionizing Radiation
� Sun
� Lasers
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Biological Effects
� The eyes are very susceptible to damage from laser light.
� Laser emits either:Infrared (IR) lightUltraviolet (UV) light
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Safety Factors
� Safety glasses are made for a specific wave length of laser light.
� IMPORTANT: Use only the appropriate safety glasses for the laser that you are around.