Radiation Safety Training for Users

1
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
2
Table of Contents
Subject Slides
Nuclear Physics 3-17
Biological Effects 18-43
Radiation Exposure and Dose 31-47
Uses of Radiation 48-51
Radiation Hazards 52-59
Radiation Detection 60-66
Lab Procedures at Clarkson 67-74
3
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

4

• Radioactivity ("Activity")

• Definition A collection of unstable atoms that
  undergo spontaneous transformation that result in
  new elements.
• An atom with an unstable nucleus will decay
  until it becomes a stable atom, emitting
  radiation as it decays
• Sometimes a substance undergoes several
  radioactive decays before it reaches a stable
  state
• The amount of radioactivity (called activity)
  is given by the number of nuclear decays that
  occur per unit time (decays per minute).

5

• Ion

• Any atom or molecule with an imbalance in
  electrical charge is called an ion
• In an electrically neutral atom or molecule, the
  number of electrons equals the number of protons
• Ions are very chemically unstable, and will seek
  electrical neutrality by reacting with other
  atoms or molecules

6

• Radiation

• Definition Energy in the form of particles or
  waves
• Types of Radiation
• Ionizing removes electrons from atoms
• Particulate (alphas and betas)
• Waves (gamma and X-rays)
• Non-ionizing (electromagnetic) can't remove
  electrons from atoms
• infrared, visible, microwaves, radar, radio
  waves, lasers

7

• The Electromagnetic Spectrum

8

• Gamma Radiation

• Wave type of radiation - non-particulate
• Photons that originate from the nucleus of
  unstable atoms
• No mass and no charge
• Travel many feet in air
• Lead or steel used as shielding

9

• 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

10

• Bremsstrahlung Radiation

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


Nucleus
11

• X-Ray Machine Components

12

• 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

13

• Types of Radiation

Mass (amu)
Charge
Travel Distance in Air
4.0000
Alpha
2
few centimeters
Beta Plus
0.0005
1
few meters
few meters
Beta Minus
0.0005
-1
Gamma
0.0000
0
many meters
0.0000
X-Rays
0
many meters
Neutron
1.0000
0
many meters
14

• Interaction of Radiation
• with Matter

• Radiation deposits small amounts of energy, or
  "heat" in matter
• alters atoms
• changes molecules
• damage cells DNA
• similar effects may occur from chemicals
• Much of the resulting damage is from the
  production of ion pairs

15

• Ionization

Ionization by a Beta particle
-
ejected electron
Beta Particle
-
-
-
Colliding Coulombic Fields
The neutral absorber atom acquires a positive
charge
-
16

• 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)

17

• 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
18

• Biological Effects of Radiation

19

• 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

20

• Effects of Acute Whole Body Exposure on Man

21

• 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)

22
Cellular Effects

• Ionization within body tissues similar to water
• Ionization causes many derivatives to be formed
• Peroxides
• Free Radicals
• Oxides
• These compounds are unstable and are damaging to
  the chemical balance of the cell. Various
  effects on cell enzymes and and structures occur.
• Radiation is not the only insult responsible
• Pollutants
• Vitamin imbalance (poor diet)
• Sickness and Disease

23

• Cellular Effects (con't)

• Cells often recover from damage
• Repeated Insults may cause damage to be permanent
• Cell Death
• Cell Dysfunction - tumors, cancer, cataracts,
  blood disorders
• Mitosis (Cell Division) Delayed or Stopped
• Chromosomal breaks
• Organ Dysfunction at High Acute Doses

24

• Variations in Sensitivity

• Wide variation in the radiosensitivity of various
  species
• Plants/microrganisms vs. mammals
• Wide variation among cell types
• Cells which divide are more sensitive
• Non-differentiated cells are more sensitive
• Highly differentiated cells (like nerve cells)
  are less sensitive

25

• Effects on the Fetus

• The fetus consists of rapidly dividing cells
• Dividing cells are more sensitive to radiation
  effects than nondividing cells
• Effects of low level radiation are difficult to
  measure
• A lower dose limit is used for the fetus

26

• Genetic Effects

• It is possible to damage the hereditary material
  in a cell nucleus by external influences like
  Ionizing radiation, chemicals, etc.
• Effects that occur as a result of exposure to a
  hazard while in-utero are called teratogenic
  effects
• Teratogenic effects are thought to be more severe
  during weeks 8-17 of pregnancy - the period of
  formation of the bodys organs
• A higher incidence of mental retardation was
  found among children irradiated in-utero during
  the bombings of Hiroshima and Nagasaki

27

• Maternal Factors Pregnancy

Statistically, a radiation exposure of 1 rem
poses much lower risks for a woman than smoking
tobacco or drinking alcohol during pregnancy
28

• Dose Response Curves

29

• Rate of Absorption

• Most important factor in determining when effects
  will occur
• Recovery is less likely with higher dose rates
  than lower dose rates for an equivalent amount of
  dose more permanent damage
• More recovery occurs between intermittent
  exposures less permanent damage

30

• Area Exposed

• The larger the portion - the more damage (if all
  other factors are the same)
• Blood forming organs are more sensitive
• A whole body dose causes more damage than a
  localized dose (such as in medical therapy).
• Dose limits take this into consideration

31

• Radiation Exposure Dose

32

• Background Exposure

• Your exposure to radiation can never be zero
  because background radiation is always present
• Natural Sources - Radon
• Cosmic
• Terrestrial
• Technologically Enhanced Sources (Man-Made)
• Healing Arts Diagnostic X-rays,
  Radiopharmaceuticals
• Nuclear Weapons Tests fallout
• Industrial Activities
• Research
• Consumer Products
• Miscellaneous Air Travel, Transportation of
  Radioactive Material

33

• Annual Dose from
• Background Radiation

34

• Cosmic Radiation

• 2 x 10 particles (mostly protons) per second are
  incident on the atmosphere
• Energy greater than one BILLION ELECTRON VOLTS
• Interact with atoms in the atmosphere and produce
  secondary particles
• muons, electrons, photons, and neutrons
• responsible for cosmic dose

18
35

• Terrestrial

• Major sources
• Potassium - a few grams per 100 grams of ground
  material
• Thorium and Uranium - a few grams per 1,000,000
  grams of ground material
• Dose due mainly to photons originating near the
  surface of the ground

36

• Radon

• Naturally occurring radioactive gas
• Second leading cause of lung cancer
• Estimated 14,000 deaths per year
• Easy to test for
• short and long term tests available
• EPA guideline is 4 pCi/L
• Fixable
• Radon in water from drilled wells can also be an
  entry method

37

• Exposure, X

• A measure of the ionization produced by
• X or Gamma Radiation in air
• Unit of exposure is the Roentgen

38

• Absorbed Dose, D

• Absorbed Dose (or Radiation Dose) is equivalent
  to the energy absorbed from any type of radiation
  per unit mass of the absorber
• Unit of Absorbed Dose is the rad
• 1 rad 100 ergs/g 0.01 joules/Kg
• In SI notation, 1 gray 100 rads

39

• Dose Equivalent, H

• One unit of dose equivalent is that amount of any
  type of radiation which, when absorbed in a
  biological system, results in the same biological
  effect as one unit of low LET radiation
• The product of the absorbed dose, D, and the
  Quality Factor, Q

H D Q
40

• Units of Dose Equivalent

• Human dose measured in rem or millirem
• 1000 mrem 1 rem
• 1 rem poses equal risk for any ionizing radiation
• internal or external
• alpha, beta, gamma, x-ray, or neutron
• In SI units 1 sievert (Sv) 100 rem
• External radiation exposure measured by dosimetry
  
• Internal radiation exposure measured using
  bioassay sample analysis

41

• Quality Factors for Different Radiations

Quality Factor
X and Gamma Rays
1
Electrons and Muons
1
Neutrons lt 10 kev
5
gt10kev to 100 Kev
10
gt 100 kev to 2 Mev
20
gt2 Mev
10
Protons gt 30 Mev
10
Alpha Particles
20
42

• External Dose

• 2 Standard reference points
• Shallow Dose Live skin tissue at an average
  depth of .007 cm.
• Deep Dose Internal organs close to the body
  surface, 1 cm.
• Shallow Dose Equivalent, SDE
• Alpha radiation not a hazard
• consider beta and gamma radiation.
• Deep Dose Equivalent, DDE
• Alpha and Beta radiation not a hazard.
• For gamma, SDE DDE (typically)

43

• Internal Dose

• All radiation types present a hazard
• 2 Dose quantities
• Committed Dose Equivalent, CDE (specific to a
  particular organ)
• Committed Effective Dose Equivalent, CEDE (sum of
  all organs x weighting factor for importance or
  each specific organ)

44

• Total Effective Dose
• Equivalent, (TEDE)

• Used to combine internal and external doses
• Puts all dose on the same risk base comparison,
  whether from external or internal sources.
• TEDE CEDE DDE
• All units are in rems or Sieverts (Sv)
• All regulatory dose limits are based on
  controlling the TEDE

45
Standards for Rad Protection

• Radiation Protection Program Required
• Occupational Limits
• 5 rem per year TEDE
• 50 rem per year CDE (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)

46

• Declared Pregnant Woman

• Voluntarily informs her employer in writing of
  pregnancy
• Estimated date of conception
• Dose limit is 10 of occupational limit (500
  mrem)
• Avoid substantial variation in dose
• Form for declaring pregnancy is on web site

47

• 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

48

• Uses of Radiation

49
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

50
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

51

• 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)

52

• Radiological Hazards

53
Radiation Protection Basics

• 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
• Lead, water, or concrete for gamma X-ray
• Thick plastic (lucite) for betas

54

• External Radiation
• Inverse Square Law

55

• 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
56
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

57

• Gamma Ray Shielding

• Effectiveness increases with thickness, d (cm)
• Variation with material, (1/cm)
• attenuation coefficients µ
• High Z material more effective
• Water - Iron - Lead
• good - better - best

58

• Shielding Beta Emitters

• Low energy betas (H-3, C-14, S-35) need no
  shielding for typical quantities at Clarkson
• Higher energy beta emitters (P-32) should be
  shielded
• Beta shielding must be low Z material (Lucite,
  Plexiglas, etc.)
• High Z materials, like lead, can actually
  generate radiation in the form of Bremsstrahlung
  X-rays
• Bremsstrahlung from 1 Ci of P-32 solution in
  glass bottle is 1 mR/hr at 1 meter

59

• External vs Internal Dose

• TEDE Total Effective Dose Equivalent
• TEDE DDE CEDE
• Total Dose External Dose Internal Dose
• 1 rem internal (CEDE) same as 1 rem external
  (DDE)
• Internal dose is protracted over several years
  but calculated over 50 years and assigned in the
  year of intake

60

• Radiation Detection

61
Radiation Detector Types

• Solid State Detectors
• Germanium Lithium High Purity
• Silicone Lithium
• Silicone Diode
• Cadmium Telluride

• Gas Filled Detectors
• Geiger Mueller (GM)
• Gas Flow Proportional Counters
• Ionization
• Scintillation Detectors
• Sodium Iodide (NaI)
• Zinc Sulfide (ZnS)
• Anthracene
• Plastic Scintillators

62

• Gas Filled Detectors

• Ionization detectors
• High Cost
• Survey meters
• Reference class calibration chambers
• Proportional counters
• High cost
• Gross laboratory measurements
• Contamination monitors
• Geiger Mueller (GM) detectors
• Low cost
• Survey meters
• Contamination monitors

63

• Scintillation Detectors

• One of the Oldest Detection Methods, Still Widely
  Used Today
• Transducer Converts Radiation Energy to Visible
  Light
• Visible Light Signals Amplified With
  Photomultiplier Tube
• Output PM Tube Signal Processed
• High Efficiency For Photon Detection Compared To
  Gas-Filled Detectors

64

• Use of Survey Instruments

• Check Physical Condition
• Cables, Connections, Damage
• Check for Current Calibration (License
  Requirement)
• Battery Check
• Zero Check
• Response check prior to use
• Select Proper Scale
• Response Time (Fast or Slow?)
• Audio (On or Off)

65

• 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

66
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

67
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

68
Posting Labeling Notices

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

69

• 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

70

• ALARA

• The goal of radiation protection is to keep
  radiation doses As Low As Reasonably Achievable
• 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

71
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

72
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.

73

• 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

74
Acknowledgements
This training course has been adapted from
slides provided by Steve Backurz, Radiation
Safety Officer of The University of New
Hampshire