Post on 30-May-2018
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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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Electromagnetic Radiation
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 Radiation
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
Electromagnetic Radiation
No Mass
No Electric charge
Travels in a Straight Line
Travels at Speed of Light
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Radiation Characteristics
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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Radiation Characteristics
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
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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