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Slide 1


TEXT VERSION OF SLIDE:

Title: Introduction to Ionizing Radiation

Type: Text Slide

Content:

Bob Curtis
OSHA Salt Lake Technical Center
Supplement to Lecture Outline
V. 10.02

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Slide 2


TEXT VERSION OF SLIDE:

Title: Neutral Atom

Type: Picture Slide

Content: [Includes image of a neutral atom]

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Slide 3


TEXT VERSION OF SLIDE:

Title: Basic Model of a Neutral Atom

Type: Text Slide

Content:

  • Electrons (-) orbiting nucleus of protons (+) and neutrons.
  • Same number of electrons as protons; net charge = 0.
  • Atomic number (number of protons) determines element.
  • Mass number (protons + neutrons) gives mass in terms of 1/12th mass of Carbon atom.

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Slide 4


TEXT VERSION OF SLIDE:

Title: Ionization vs. Exitation

Type: Text Slide

Content:

  • Excitation transfers enough energy to an orbital electron to displace it further away from the nucleus.
  • In ionization the electron is removed, resulting in an ion pair.
    • The newly freed electron (-) and the rest of the atom (+).

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Slide 5


TEXT VERSION OF SLIDE:

Title: Ionizing Radiation

Type: Text Slide

Content:

  • Any electromagnetic or particulate radiation capable of producing ion pairs by interaction with matter.
  • Scope limited to X and gamma rays, alpha particles, beta particles (electrons), neutrons, and charged nuclei.
  • Important biologically since media can be altered (e.g., ionized atom in DNA molecule may be altered, thereby causing cell death, or mutation).

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Slide 6


TEXT VERSION OF SLIDE:

Title: Particulate vs. Electromagnetic Radiations

Type: Text Slide

Content:

  • Particulate Radiations are subatomic particles with mass (e.g., alpha and Beta particles, electrons, neutrons).
  • EM Radiations (X-rays and gamma rays) have no mass and no charge.

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Slide 7


TEXT VERSION OF SLIDE:

Title: Electromagnetic Spectrum

Type: Picture Slide

Content: [Image of the electromagnetic spectrum.]

NON-IONIZING RADIATION
IONIZING RADIATION
RADIO FREQUENCIES
HEAT
      |      
/ LIGHT \
 
GAMMA
MICROWAVES
  \ VISIBLE /
|
XRAYS
ELF VLF LF MF HF VHF UHF SHF EHF
INFRA RED
ULTRAVIOLET

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Slide 8


TEXT VERSION OF SLIDE:

Title: High vs. Low Energy Radiation

Type: Text Slide

Content:

  • Absorption of radiation is the process of transferring the energy of the radiation to the atoms of the media through which it is passing.
  • Higher energy radiation of the same type will penetrate further.
  • Usually expressed in KeV or MeV
  • 1 eV = 1.6 x 10-19 Joules = 1.6 x 10-12 ergs

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Slide 9

TEXT VERSION OF SLIDE:

Title: High vs. Low Energy Transfer (LET)

Type: Text Slide

Content:

  • LET is measured by the ionization density (e.g., ion pairs/cm of tissue) along the path of the radiation.
  • Higher LET causes greater biological impact and is assigned a higher Quality Factor (QF).
    • Example QF values: X, gamma, and beta have QF = 1; alpha QF=20; thermal neutrons QF=3; "fast" neutrons (>10 KeV) QF = 10; fission fragments QF>20.

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Slide 10


TEXT VERSION OF SLIDE:

Title: Alpha Particle

Type: Picture Slide

Content: [Includes image of alpha particle.]

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Slide 11


TEXT VERSION OF SLIDE:

Title: Alpha Particles (or Alpha Radiation)

Type: Text Slide

Content:

  • Helium nucleus (2 neutrons and 2 protons); +2 charge; heavy (4 AMU). Typical Energy = 4-8 MeV;
  • Limited range (<10cm in air; 60µm in tissue);
  • High LET (QF=20) causing heavy damage (4K-9K ion pairs/µm in tissue);
  • Easily shielded (e.g., paper, skin) so an internal radiation hazard.

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Slide 12


TEXT VERSION OF SLIDE:

Title: Beta Particle

Type: Picture Slide

Content: [Image of a beta particle.]

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Slide 13


TEXT VERSION OF SLIDE:

Title: Beta Particles

Type: Text Slide

Content:

  • High speed electron ejected from nucleus; -1 charge; light 0.00055 AMU; Typical Energy = several KeV to 5 MeV;
  • Range approx. 12'/MeV in air, a few mm in tissue;
  • Low LET (QF=1) causing light damage (6-8 ion pairs/µm in tissue);
  • Primarily an internal hazard, but high beta can be an external hazard to skin.

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Slide 14


TEXT VERSION OF SLIDE:

Title: Bremsstrahlung

Type: Picture Slide

Content: [Includes image of bremsstrahlung.]

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Slide 15


TEXT VERSION OF SLIDE:

Title: Bremsstralung (or Braking) Radiation

Type: Text Slide

Content:

  • High speed electrons may lose energy in the form of X-rays when they quickly decelerate upon striking a heavy material.
  • Aluminum and other light (<14) materials and organo-plastics are used for shielding.

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Slide 16


TEXT VERSION OF SLIDE:

Title: Positrons

Type: Text Slide

Content:

  • Beta particles with an opposite (+) charge.
  • Quickly annihilated by combination wtih an electron, resulting in gamma radiation.

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Slide 17


TEXT VERSION OF SLIDE:

Title: Neutrons

Type: Text Slide

Content:

  • Neutrons ejected from a nucleus; 1 AMU; 0 Charge;
  • Free neutrons are unstable and decay by Beta emission (electron and proton separate) with T½ of approx. 13 min;
  • Range and LET are dependant on "speed": Slow (<10 KeV), "Thermal" neutrons, QF=3; and Fast (>10 KeV), QF=10.

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Slide 18


TEXT VERSION OF SLIDE:

Title: Shielding Neutrons

Type: Text Slide

Content:

  • Shielded in stages: High speed neutrons are "thermalized" by elastic collisions in hydrogenous materials (e.g., water, paraffin, concrete).
  • The "hit" nuclei give off the excess energy as secondary radiation (alpha, beta, or gamma).
  • Slow neutrons are captured by secondary shielding materials (e.g., boron or cadmium).

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Slide 19


TEXT VERSION OF SLIDE:

Title: Gamma Ray

Type: Picture Slide

Content: [Includes image of a gamma ray and an x-ray.]

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Slide 20


TEXT VERSION OF SLIDE:

Title: X-Rays and Gamma Rays

Type: Text Slide

Content:

  • X-rays are photons (electromagnetic radiations) emitted from electron orbits, such as when an excited orbital electron "falls" back to a lower energy orbit.
  • Gamma rays are photons emitted from the nucleus, often as part of radioactive decay.

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Slide 21


TEXT VERSION OF SLIDE:

Title: X-rays and Gamma Radiation

Type: Text Slide

Content:

  • Gamma rays typically have higher energy (Mev's) than X-rays (KeV's), but both are unlimited.
  • No mass; Charge=0; Speed = C; Long range (km in air, m in body); Light damage (QF=1);
  • An external hazard (>70 KeV penetrates tissue); Usually shielded with lead or concrete.

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Slide 22


TEXT VERSION OF SLIDE:

Title: Photoelectric Effect

Type: Picture Slide

Content: [Includes illustration of the Photoelectric Effect (primarily low-energy photon). X-Ray of Gamma, ejected photoelectron and E ≲ 0.5 MeV.]

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Slide 23


TEXT VERSION OF SLIDE:

Title: Compton Effect

Type: Picture Slide

Content: [Includes illustration of the Compton Effect (primarily medium energy photon). X-Ray or Gamma Ray, ejected Compton electron, scattered photon of lower energy, and 0.5 ≲ E ≲ 5 MeV.]

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Slide 24


TEXT VERSION OF SLIDE:

Title: Pair Production

Type: Picture Slide

Content: [Includes illustration of a Pair Production (high energy photon, 1.02 MeV). X-Ray or Gamma ray, - negative electron, + positive electron (Positron), positron annihilation, E > 5.]

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Slide 25


TEXT VERSION OF SLIDE:

Title: Radioactive Decay

Type: Text Slide

Content:

  • Matter transforms from unstable to stable energy states.
  • Radioactive materials are substances which spontaneously emit various combinations of ionizing particles (alpha and beta) and gamma rays of ionizing radiation to become more stable.
  • Radioisotopes are isotopes (same number of protons but different numbers of neutrons) which are radioactive.

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Slide 26


TEXT VERSION OF SLIDE:

Title: Decay Series

Type: Picture Slide

Content: [Includes illustration of a decay series.]

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Slide 27


TEXT VERSION OF SLIDE:

Title: Equation Slide

Type: Picture Slide

Content:
Radium → alpha particle + Radon

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Slide 28


TEXT VERSION OF SLIDE:

Title: Equation Slide

Type: Picture Slide

Content:

226 Ra 4 He +2 + 222 Rn
88 2   86

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Slide 29


TEXT VERSION OF SLIDE:

Title: Equation Slide

Type: Picture Slide

Content:

90 Sr → Beta electron + 90 Y
38 39

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Slide 30


TEXT VERSION OF SLIDE:

Title: Proton "Gain" during Beta Decay

Type: Picture Slide

Content: [Image of Proton "Gain" during Beta Decay.]
Neutron = Proton + Electron

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Slide 31


TEXT VERSION OF SLIDE:

Title: Beta Decay

Type: Text Slide

Content:

  • No change in atomic mass; protons increase by 1.
  • Consider a neutron as a proton enbedded with an electron; net charge = 0. When the electron is ejected, a proton is "created", thus increasing the atomic number.

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Slide 32


TEXT VERSION OF SLIDE:

Title: Decay Series

Type: Text Slide

Content:

  • Radioactive parent decays to a "daughter" which may also be radioactive, therefore, is also simultaneously decaying.
  • Resulting exposure is to the combination of both decays (and possibly additional daughters).
  • Radon daughters are an important example of series decay exposure in uranium mines and basements.

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Slide 33


TEXT VERSION OF SLIDE:

Title: Series Decay

Type: Picture Slide

Content: [Includes illustration of a series decay.]

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Slide 34


TEXT VERSION OF SLIDE:

Title:

Type: Picture Slide

Content:

With alpha = 9 Be + 4 He+2 1 neutron + 12 C
4 2 0 6

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Slide 35


TEXT VERSION OF SLIDE:

Title: Monitoring equipment

Type: Picture Slide

Content: [Includes image of monitoring equipment.]

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Slide 36


TEXT VERSION OF SLIDE:

Title: Sliding scale

Type: Picture Slide

Content: [Includes illustration of sliding scale. Estimated first point is 1 at 50%, 2 at 28%, 3 at 20% and 4 at 10%.]

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Slide 37


TEXT VERSION OF SLIDE:

Title: Note common formula structure.

Type: Picture Slide

Content: [Image of common formula]

    At = Aoe(-λt)  
    Nt = Noe(-λt)  
    Ix = Ioe(-µx)  
λ = .693 = Decay Constant
Half - Life
µ = .693 = Linear Coeff. of ABS
Half - VL

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Slide 38


TEXT VERSION OF SLIDE:

Title: Equation

Type: Picture Slide

Content: [Image of an equation]

3 yr = 3(365) = 1095 days
  0.693    
At = A0e-2t = A0e T½    
  -0.693 • 1095
At = (300)e 138.4 = (300)e-5.48
= (300)(0.00416) = 1.25µCi

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Slide 39


TEXT VERSION OF SLIDE:

Title: Equation

Type: Picture Slide

Content: [Image of an equation]

A = Ai (0.5) t
 

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Slide 40


TEXT VERSION OF SLIDE:

Title: Equation

Type: Picture Slide

Content: [Image of an equation]

n = 1095 day  = 791 half lives
138.4 days/half - life
An = 300 (½)7.91 = 300(0.00416) = 1.25µCi

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Slide 41


TEXT VERSION OF SLIDE:

Title: Equation

Type: Picture Slide

Content: [Image of an equation]

I = I0e -0.693 • x = (100)e -0.693(2")(25.4mm/inch
HVL 5mm
= (100)e-7.04 = 100(0.000876) = 0.088R/hr

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Slide 42


TEXT VERSION OF SLIDE:

Title: Calibration Source

Type: Picture Slide

Content: [Includes photo comparing the size of a quarter to a Eberline Cs-7a gamma radioactive material coin.]

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Slide 43


TEXT VERSION OF SLIDE:

Title: Equation

Type: Picture Slide

Content: [Image of an equation]

I1 = ( d1 )2  I1 = 500 d1 = 6 d2 = 50
I2 d2
I2 = I1 = 500 = 500 = 500  =7.2 m R/hr
( d2 )2   (50/6) 2 (833)2 69.4
d1  

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Slide 44


TEXT VERSION OF SLIDE:

Title: Equation

Type: Picture Slide

Content: [Image of an equation]

D = 0.869 ƒ X (R) rads

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Slide 45


TEXT VERSION OF SLIDE:

Title: Equation

Type: Picture Slide

Content: [Image of an equation]

D = (0.869)(0.965)(0.5 x 10-3 R/hr

=0.419m rad/hr

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Slide 46


TEXT VERSION OF SLIDE:

Title: Monitoring equipment

Type: Picture Slide

Content: [Includes image of monitoring equipment.]

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Slide 47


TEXT VERSION OF SLIDE:

Title: Gas Ionization (Regions of Instrument Response)

Type: Picture Slide

Content: [Includes illustration of gas ionization regions of instrument response categorized by number of ion pairs produced. Y-axis - Number of Ion Pairs Produced (Current) -->, X-axis - V -->.]

    5 sections accross the x-axis.
  • First - Recombination
  • Second - Saturation of Ion Chamber {Low sensitivity, High Range, Air} 130 - 300 V
  • Third - Proportionality {High Sensitivity High Range, Air, Argon, Methane} 500 - 5000 V Gas Amplification: 105 - 106
  • Fourth - Geiqer-Mueller {Very High Sensityvity low Range, Argon, Helium} 1000 - 3000 V Gas Amplification: 109 - 1010
  • Fifth - Continuous Discharge

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Slide 48


TEXT VERSION OF SLIDE:

Title: Monitoring equipment

Type: Picture Slide

Content: [Image of a man using a Geiger Counter.]

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Slide 49


TEXT VERSION OF SLIDE:

Title: Monitoring equipment

Type: Picture Slide

Content: [Includes image of monitoring equipment.]

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Slide 50


TEXT VERSION OF SLIDE:

Title: Laboratory Equipment

Type: Picture Slide

Content: [Includes image of laboratory equipment.]

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Slide 51


TEXT VERSION OF SLIDE:

Title: Laboratory Equipment

Type: Picture Slide

Content: [Includes image of laboratory equipment.]

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Slide 52


TEXT VERSION OF SLIDE:

Title: Chemist Working in a Laboratory

Type: Picture Slide

Content: [Includes image of chemist working in laboratory.]

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Slide 53


TEXT VERSION OF SLIDE:

Title: Chemical Storage

Type: Picture Slide

Content: [Includes image of chemical storage room.]

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Slide 54


TEXT VERSION OF SLIDE:

Title: Radioactive Symbols

Type:Picture Slide

Content: [Includes images of a radioactive symbols NFPA 704M Label and a D.O.T. Label.]

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