Radiation Safety Training for Users

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Refresher Training for Users of Radiation
Producing Devices
Elayna Mellas Radiation Safety Officer Environment
al Health Safety Manager Clarkson
University Downtown Snell 155 Tel
315-268-6640 emellas_at_clarkson.edu
This training course has been partially
adapted from slides provided by Steve Backurz,
Radiation Safety Officer of The University of New
Hampshire
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Introduction

• Radiation is a valuable tool used in research at
  Clarkson
• Electron microscopes
• X-ray fluorescence spectrometry
• X-ray diffraction analysis of samples for
  chemistry and engineering research
• Radioactive materials and X-ray machines are very
  safe if used properly and simple precautions are
  followed

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The Basics Definitions

• Radioactivity The spontaneous disintegration or
  decay of an unstable atom, resulting in the
  release of energy (radiation).
• Radiation Energy in the form of particles or
  waves
• Radioactive material Any material that is
  composed of (or contains) radioactive atoms.
• Ion Any atom or molecule with an imbalance in
  electrical charge. Ions are very unstable and
  will seek electrical neutrality by reacting with
  other atoms or molecules
• Activity The number of disintegrations (decays)
  occurring per unit of time.
• Half Life The time it takes for an amount of
  radioactive material to lose half (50) of its
  activity because of decay.

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The Particles
?

• ALPHA PARTICLE (?) A high energy particle
  emitted from the nucleus during the decay of an
  atom.
• Travel a few centimeters in air
• Stopped by a sheet of paper or layer of skin
• Not an external hazard ingestion or inhalation
  concern
• BETA PARTICLE (?) A high energy particle emitted
  from the nucleus during the decay of an atom
• Travel 10 to 20 feet in air
• Stopped by a book
• Shielding high energy betas with lead can
  generate more radiation due to Bremsstrahlung
  x-rays
• GAMMA RADIATION (?) Electromagnetic radiation
  emitted from the nucleus during decay
• No mass, no charge
• Travel many feet in air

?
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• The Electromagnetic Spectrum

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• X-Rays

• Wave type of radiation - non-particulate
• Photons originating from the electron cloud
• Same properties as gamma rays relative to mass,
  charge, distance traveled, and shielding
• Characteristic X-rays are generated when
  electrons fall from higher to lower energy
  electron shells
• Discrete energy depending on the shell energy
  level of the atom
• Bremsstrahlung X-rays are created when electrons
  or beta particles slow down in the vicinity of a
  nucleus
• Produced in a broad spectrum of energies
• Reason you shield betas with low density material

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• Bremsstrahlung Radiation

Energy is lost by the incoming charged particle
through a radiative mechanism
Beta Particle
Bremsstrahlung Photon
-


Nucleus
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• X-Ray Machine Components

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• X-Ray Machine Basics

• kVp - how penetrating the X-rays are
• Mammography - 20 - 30 kVp
• Dental - 70 - 90 kVp
• Chest - 110 - 120 kVp
• mA - how much radiation is produced
• Time - how long the machine is on
• Combination of the above determines exposure

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• Ionization

Ionization by a Beta particle
-
ejected electron
Beta Particle
-
-
-
Colliding Coulombic Fields
The neutral absorber atom acquires a positive
charge
-
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• Gamma Interactions

• Gamma interactions differ from charged particle
  Interactions
• Interactions called "cataclysmic" - infrequent
  but when they occur lot of energy transferred
• Three possibilities
• May pass through - no interaction
• May interact, lose energy change direction
  (Compton effect)
• May transfer all its energy disappear
  (photoelectric effect)

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• Compton Effect

An incident photon interacts with an orbital
electron to produce a recoil electron and a
scattered photon of energy less than the incident
photon
Before interaction
After interaction
Scattered Photon
-
-
-
-
-
-
-
-
Electron is ejected from atom
Incoming photon Collides with electron
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Biological Effects
Effects of Acute Whole Body Exposure on Man

• Acute Exposure
• Large Doses Received in a Short Time Period
• Accidents
• Nuclear War
• Cancer Therapy
• Short Term Effects (Acute Radiation Syndrome 150
  to 350 rad Whole Body)
• Anorexia Nausea Erythema Fatigue
• Vomiting Hemorrhage
• Epilation Diarrhea Mortality

Absorbed Dose (rads) Effect
10,000 Death in a few hours
1,200 Death within days
600 Death within weeks
450 LD 50/30
100 Probable Recovery
50 No observable effect
25 Blood changes definite
5 1st blood changes observed
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Biological Effects

• Chronic Exposure
• Doses Received over Long Periods
• Background Radiation Exposure
• Occupational Radiation Exposure
• 50 rem acute vs 50 rem chronic
• acute no time for cell repair
• chronic time for cell repair
• Average US will receive 20 - 30 rem lifetime
• Long Term Effects
• Increased Risk of Cancer
• 0.07 per rem lifetime exposure
• Normal Risk 30 (cancer incidence)

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• Background Exposure

• Your exposure to radiation can never be zero
  because background radiation is always present
• Natural Sources (Radon), Cosmic, Terrestrial,
  Medical Diagnostic, Consumer Products, etc

Annual Dose from Background Radiation
Total exposure
Man-made sources
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Total US average dose equivalent 360 mrem/year
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Standards for Rad Protection

• Occupational Limits (Researchers)
• 5 rem per year (total effective dose equivalent
  TEDE)
• 50 rem per year (any single organ)
• 15 rem per year lens of the eye
• 50 rem per year skin dose
• Members of Public
• 100 mrem per year
• No more than 2 mrem in any one hour in
  unrestricted areas from external sources
• Declared Pregnant Females (Occupational)
• 500 mrem/term (evenly distributed)
• Declaration is voluntary and must be submitted to
  RSO in writing (see form on website)

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• Clarkson Anticipated
• Worker Radiation Exposure

• Anticipated Exposures Less than the minimum
  detectable dose for film badges (10
  mrem/month) - essentially zero
• Average annual background exposure for U.S.
  population 360 mrem/year
• State and Federal Exposure Limits 5000 mrem/year

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• Uses of Radiation

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Consumer Products

• Building materials
• Tobacco (Po-210)
• Smoke detectors (Am-241)
• Welding rods (Th-222)
• Television (low levels of X-rays)
• watches other luminescent products (tritium or
  radium)
• Gas lantern mantles
• Fiesta ware (Ur-235)
• Jewelry

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Research at Clarkson Using Radiation Sources

• Radioactive Materials (both open and sealed
  sources)
• Gas Chromatographs (sealed sources)
• Liquid Scintillation Counters (sealed sources for
  internal standards)
• X-ray Diffraction equipment
• Electron microscopes
• X-ray fluorescence spectrometer

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• Medical

• Diagnostic
• X-rays
• Nuclear Medicine (Tc-99m, Tl-201, I-123)
• Positron Emission Tomography (PET)
• Therapeutic
• X-rays (Linear Accelerators)
• Radioisotopes
• Brachytherapy (Cs-137, Ir-192, Ra-226)
• Teletherapy (Co-60)
• Radiopharmaceuticals (I-131, Sr-89, Sm-153)

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Reducing Exposure

• The goal of radiation protection is to keep
  radiation doses As Low As Reasonably Achievable
  and eliminate any unnecessary dose to yourself,
  coworkers, and the public
• Clarkson is committed to keeping radiation
• exposures to all personnel ALARA
• What is reasonable?
• Includes
• State and cost of technology
• Cost vs. benefit
• Societal socioeconomic considerations

A s L ow A s R easonably A chievable
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Practicing ALARA
Protect Yourself Your Colleagues!

• Time minimize the time that you are in contact
  with radioactive material to reduce exposure
• Distance keep your distance. If you double the
  distance the exposure rate drops by factor of 4
• Shielding place a barrier between you and the
  radioactive source
• Source Reduction order and use the smallest
  amount of radioactive materials as necessary
• Protective clothing protects against
  contamination only - keeps radioactive material
  off skin and clothes

OPTIMIZE USE OF ALL PROTECTIVE MECHANISMS TO
MINIMIZE DOSE.
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Shielding Recommendations

• Betas (ex 32P)
• Use material with low atomic number, such as
• Plastic, lucite, acrylic
• Wood, paper, cardboard
• Gammas (ex 125I or 51Cr)
• Use material with high atomic number, such as
• Lead, concrete, bricks, stainless steel, cast
  iron

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• External Radiation
• Inverse Square Law

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• Gamma Ray Constant

• Gamma Ray Constant to determine exposure rate
• ??(mSv/hr)/MBq at 1 meter
• Hint multiply (mSv/hr)/MBq by 3.7
• to get (mrem/hr)/uCi
• Exposure Rate Calculation, X (mrem/hr) at one
  meter

X ??????? Where, A Activity (?Ci)
? ??Gamma Ray Constant(mSv/hr)/Mbq
3.7 is the conversion factor
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Sample Calculation

• 5 Curie Cs-137 Source
• Calculate Exposure Rate at 1 meter
• ? 1.032 E-4 mSv/hr/MBq _at_ 1 meter
• X 1.032 E-4 3.7 5 Ci 1000 mCi/Ci 1000
  uCi/mCi
• X 1909 mrem/hour
• X 1.91 rem/hour

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Detecting Contamination
Survey Meters are portable instruments that can
be used to detect most spots of contamination -
except for 3H.
Wipe Testing must always be done for 3H and lower
activities (100 µCi or less) of 35S and 14C.
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Detecting Common Isotopes
3H Liquid Scintillation Counter
14C GM Probe with Survey Meter
32P GM Probe with Survey Meter
33P GM Probe with Survey Meter
35S GM Probe with Survey Meter
51Cr GM or NaI Probe w/ Survey Meter
125I NaI Probe w/ Survey Meter
Sodium Iodide (NaI) Probe
Survey Meter
Geiger- Mueller (GM) Probe
Liquid Scintillation Counter
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Survey Meter Operability
Each USER must verify that the survey instrument
is in good working order before each use.

• Check calibration date (not older than 12
  months)
• Batteries must be fresh / good
• Background count rate
• Detector/instrument must be responsive
• Miscellaneous conditions?
• Check Physical Condition
• Cables, Connections, Damage
• Select Proper Scale
• Response Time (Fast or Slow?)
• Audio (On or Off)

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• CPM DPM

• A radiation detector will not detect every
  disintegration from a source (i.e., they are not
  100 efficient)
• Counts per minute (cpm) is the number of
  disintegrations that a detector sees
• The efficiency of a detector is determined by the
  following
• Efficiency net cpm / dpm
• gross cpm background cpm / dpm

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Survey Meter Background Levels
Remember that background is radiation coming from
the environment, and it cannot be prevented or
eliminated.
Each detector will have its own background level.
1st check the background level - use it as a
baseline. Observed Background Zero
Any reading higher than the background level
means the item is radioactive.
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Regulatory Agencies

• U. S. Nuclear Regulatory Commission
• Regulates the nuclear industry pursuant to the
  Atomic Energy Act
• Regulatory guides published to describe methods
  for complying with regulations
• Agreement States
• Some states have entered into an agreement with
  the NRC to regulate by-product material (and
  small quantities of source and special nuclear
  material)
• Currently, 30 states are agreement states
  including New York

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Radiation at Clarkson

• Activities are licensed by the State of New York
• Radiation Safety Committee has responsibility to
  review, approve, and oversee activities
• Radiation Safety Officer (RSO) runs program
• Clarkson is required to
• Train individuals that use sources of radiation
• Train non-radiation workers that work in the
  vicinity of radiation sources
• Monitor and control radiation exposures
• Maintain signs, labels, postings

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Posting Labeling Notices

• Posting
• New York Notice to employees form
• Caution Radiation Producing Devices or X-Rays

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• Employee Rights
• and Responsibilities

• Right to report any radiation protection problem
  to state without repercussions
• Responsibility to comply with the Radiation
  Protection Program and the RSO's instructions
  pertaining to radiation protection
• Right to request inspection
• in writing
• grounds for notice
• signed
• Responsibility to cooperate with NY State
  inspectors during inspections and RSO during
  internal lab audits

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Inspections

• Inspections
• NY shall be afforded opportunity to inspect at
  all reasonable times
• Records shall be made available
• Inspector may consult with workers privately
• Worker may bring matters to inspector privately
• Workers can request inspection
• Must be in writing
• Name is not revealed

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Internal Audits

• Internal audits by Clarkson RSO are performed in
  all labs on campus
• Looking for same things as state inspector
• Security of radiation producing devices
• Proper procedures in use
• Postings, dosimetry, survey meters, calibrations,
  records of surveys, etc.

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• Your Role
• in Radiation Protection

• Report anything that looks out of the ordinary or
  if you are uncertain about what to do, where to
  go, requirements, exposures
• Call the people on the emergency list
• Ask the Radiation Safety Officer (RSO)
• Elayna Mellas
• 268-6640
• emellas_at_clarkson.edu

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Acknowledgements
This training course has been adapted from
slides provided by Steve Backurz, Radiation
Safety Officer of The University of New
Hampshire and Eric Andersen, Radiation Safety
Officer at the Dana-Farber Cancer Institute.