Radiation Safety

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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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Effects from external sourcesdepend on penetrating ability.

AlphaBeta

Gamma or x-ray

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Parentcell

Celldivision

Normal cells

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Irradiatedcell

Celldivision

Cells damaged

Parentcell

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� 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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MOST SENSITIVE

LEAST SENSITIVE

fetal cellblood cellsintestinal cellsbone marrow cellssperm cells

capillary cells

muscle cellsnerve cells

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� 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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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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� 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


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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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� Time:Keep exposure times

to a minimumMinimizes doseALARA

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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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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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� 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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� Shielding

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� 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.

Radiation Safety

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