Radiation Safety Series 2

8/14/2019 Radiation Safety Series 2

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Radiation Safety Series

Lesson 2

Characteristics of Radiation


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Characteristics of Radiation

Electromagnetic Radiation

X-Ray and Gamma Ray

Particle Radiation


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Has Definite:

Wavelength

Frequency F

Velocity c

F x = c

c = 2.997x108 m/s

186,000 miles per

second


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Electromagnetic Spectra

www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html


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Wavelength and Energy

The energy of

electromagnetic

radiation is inverselyproportional to its

wavelength

Low frequency, long

wavelength, lowenergy


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Electromagnetic Spectrum

All electromagnetic radiation exhibits dualcharacteristics. Some times they act like

waves and sometimes they act like particles. Waves have discreet packets of energy

known as photons.

The spectrum has a gradual shift from onetype of radiation to another according totheir photon energy.


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Electromagnetic waves have no mass and

no electrical charge.

Electromagnetic radiation travels in a

straight line at 186,000 miles per second.


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X-rays and Gamma Rays

In addition to electromagnetic radiation Xand gamma rays penetrate and ionize

matter. X and gamma rays do not make matter

radioactive in the energy ranges we use.

They can not be deflected but they can bescattered.

They are not affected by magnetism.


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Radiation Characteristics


No Mass

No Electric charge

Travels in a Straight Line

Travels at Speed of Light


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X-Rays and Gamma Rays

Penetrates Matter

Ionizes Matter

Cannot be deflected (can scatter)

Not Affected by magnetic fieldsNot Detected by Human Senses


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Alpha, Beta and Neutron

Has Mass

Travels at Sub-Light Speeds

Penetrates Matter Somewhat

Ionizes MatterIs not Detected by Human Senses


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Alpha, Beta and Neutron

All three are particulate radiation

They travel at sub-light speed for short

distances Each penetrates matter to different degrees

Alpha and Beta directly ionize matter

Neutron ionizes matter indirectly Neutron will ionize only if the collision is

inelastic


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Type Mass Charge Energy (MeV)

Neutron 1 A.M.U. 0 0 to >20

Alpha 4 A.M.U. +2 4 to 10

Beta 1/1840 +1 0.025 to 3.15

Gamma 0 0 0.04 to 3.2

X-ray 0 0 up to 30


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Ionization

Radiation and the human body

Non-ionizing radiation

Ionizing radiation

- Photoelectric Effect

- Compton Scatter- Pair Production


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Radiation and the Human Body


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Non-Ionizing Radiation

Occurs in the Ultraviolet range and lower

Electrons are bumped to higher energy

levels but do not have enough energy to be

removed

Molecular vibration contributes to heating

Molecular rotation and torsion result in

heating


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Http://hyperphysics.phy-astr.gsu/hbase/mod4.html


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Ionizing Radiation

Ionization is the ejection

of one or more electrons

from an atom or molecule The classification of

ionizing is a statement

indicating there is enough

quantum energy to ejectone or more electrons

Http://hyperphysics.phy-astr.gsu/hbase/mod4.html


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Mechanisms of Interaction

Photoelectric Effect

Compton Scattering

Electron Positron Pair Production


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Photoelectric Effect

Photon is absorbed

and an electron is

ejected Wave/Particle Duality

Low energy photons

1- Electron isdislodged Http://hyperphysics.phy-astr.gsu/hbase/mod1.html


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Compton Scattering

Higher energy photonsrelative to those thatcause the photoelectriceffect (Medium energy)

Conservation of energyand mass

1- Electron ejected2- Lower energy waveemitted Http://hyperphysics.phy-astr.gsu/hbase/mod1.html
http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/compton.html


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Electron Positron Pair Production

High energy>1.022MeV

Pair production is the

predominant interactionof high energy incident

radiation

An electron and positron

are produced

Positron annihilation


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Radiation Absorption


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Radiation Penetration Power

http://www.ratical.org/radiation/NRBE/NRadBioEffects.html


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Neutron Absorption

Passes through high density material (metal)

Moderated by low density material (plastic)

Highly penetrating Travels 16 feet before it begins to deacy

Half life is ~15 minutes

Speed 2.2 km/s


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Gamma Ray Measurement

The activity of a radioisotope is the number

of disintegrations that occur in a given

radioisotope during a given period of time Activity is measured in Curies which is

defined as 3.7 x 1010 disintegrations per

second (Ci)


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Fundamental Measures

Activity The number of curies for a

radioisotope (Ci)

Curie 3.7 x 1010 disintegrations per second

Half Life The time it takes to reduce the

activity of a radioisotope to one-half


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Half-Life

Activity decreases over time

Half-Life is the measure of the period of

time it takes to reduce the activity to onehalf

Californium 252 effective half-life

2.65 years 252Cf Specific Activity ~20GBq/mg

~536mCi/mg


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Specific Activity

Specific activity is essentially a measure of

of concentration of the activity

252Cf Specific Activity ~20GBq/mg~536mCi/mg

This is activity per milligram


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Works Sited

Partial List:

http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html

www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html

http://hyperphysics.phy-astr.gsu/hbase/mod4.html

http://hyperphysics.phy-astr.gsu/hbase/mod1.html

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/lepton.htm#c5

http://www.ratical.org/radiation/NRBE/NRadBioEffects.html

Radiation Safety Training Series Part 1: Radiation, Rudarmel Enterprises,inc. Lake Oswego, Oregon

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Radiation Safety Series 2