Radiation Safety Series 2

Radiation Safety Series Lesson 2 Characteristics of Radiation

Characteristics of Radiation • Electromagnetic Radiation • X-Ray and Gamma Ray • Particle Radiation

Electromagnetic Radiation Has Definite: • Wavelength λ • Frequency F • Velocity c Fxλ=c c = 2.997x108 m/s 186,000 miles per second

Electromagnetic Spectra

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Wavelength and Energy • The energy of electromagnetic radiation is inversely proportional to its wavelength • Low frequency, long wavelength, low energy

Electromagnetic Spectrum • All electromagnetic radiation exhibits dual characteristics. 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 one type of radiation to another according to their photon energy.

Electromagnetic Radiation • Electromagnetic waves have no mass and no electrical charge. • Electromagnetic radiation travels in a straight line at 186,000 miles per second.

X-rays and Gamma Rays • In addition to electromagnetic radiation X and 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 be scattered. • They are not affected by magnetism.

Radiation Characteristics Electromagnetic Radiation No Mass No Electric charge Travels in a Straight Line Travels at Speed of Light

Radiation Characteristics X-Rays and Gamma Rays Penetrates Matter Ionizes Matter Cannot be deflected (can scatter) Not Affected by magnetic fields Not Detected by Human Senses

Radiation Characteristics Alpha, Beta and Neutron Has Mass Travels at Sub-Light Speeds Penetrates Matter Somewhat Ionizes Matter Is not Detected by Human Senses

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

Type Neutron Alpha Beta Gamma X-ray

Mass Charge Energy (MeV) 1 A.M.U. 0 0 to >20 4 A.M.U. +2 4 to 10 1/1840 +1 0.025 to 3.15 0 0 0.04 to 3.2 0 0 up to 30

Ionization • Radiation and the human body • Non-ionizing radiation • Ionizing radiation - Photoelectric Effect - Compton Scatter - Pair Production

Radiation and the Human Body

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

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

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 eject one or more electrons

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Mechanisms of Interaction • Photoelectric Effect • Compton Scattering • Electron Positron Pair Production

Photoelectric Effect • Photon is absorbed and an electron is ejected • Wave/Particle Duality • Low energy photons 1- Electron is dislodged

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Compton Scattering • Higher energy photons relative to those that cause the photoelectric effect (Medium energy) • Conservation of energy and mass 1- Electron ejected 2- Lower energy wave emitted

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Electron Positron Pair Production • High energy>1.022MeV • Pair production is the predominant interaction of high energy incident radiation • An electron and positron are produced • Positron annihilation

Positron Annihilation • Positron is the antiparticle of the electron • Identical in mass to the electron but has a positive charge • Two gamma rays emitted in opposite directions

Radiation Absorption

Radiation Penetration Power

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

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

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)

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

Half-Life • • • •

Activity decreases over time Half-Life is the measure of the period of time it takes to reduce the activity to one half Californium 252 effective half-life 2.65 years 252 Cf Specific Activity ~20GBq/mg ~536mCi/mg

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

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