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Title: Radiation Exposure and


1
Radiation Exposure and Risk Assessment
2
Maximum Permissible DoseGeneral Public
  • Whole Body 1 mSv/year
  • Skin 50 mSv/year
  • Hands Feet 50 mSv/year
  • Lens of the eye 15 mSv/year

3
Nuclear Energy Workers
Who is an NEW? A worker who has a REASONABLE
PROBABILITY of exceeding the 1 mSv limit to the
general public. Registered with the RSO.
4
Maximum Permissible Dose
Nuclear Energy Worker
  • Whole Body 50 mSv/year
  • Skin 500 mSv/year
  • Hands Feet 500 mSv/year
  • Lens of the eye 150 mSv/year

(CNSC)
5
Radiation Exposure of Women Nuclear Energy
Workers
  • Whole Body Limit may not exceed annual limit of 5
    mSv
  • Radiation exposure at the surface of the
  • abdomen may not exceed 4 mSv following
  • declaration of pregnancy
  • Badges changed quarterly

Inform, Review, Reassign, Restrict
6
Radiation CANNOT be
  • Felt
  • Heard
  • Tasted
  • Smelled
  • Seen

Sohow do you know you have had enough?
7
Dosimetry
  • External Personal Monitoring
  • Thermoluminescent dosimeters
  • Lithium Fluoride Crystals
  • Optically read dosimeters LUXEL
  • Skin Dose
  • Body Dose
  • Internal Personal Monitoring
  • Bioassay
  • Urine, saliva, sweat, feces
  • Thyroid
  • Difficult -distribution variability

8
Thermoluminescent Dosimeters
Landauer
Health Canada
9
Optically Read Dosimeters (Landauer)
10
Personal Alarm Dosimeter
11
Who MUST wear a TLD?
A NEW who has a REASONABLE PROBABILITY of
receiving a radiation exposure greater than
5mSv/year (CNSC)
1mSv/year UBC action level
12
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13
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14
How do I estimate my dose?Will I need to be
monitored?
15
External Exposure Estimate
  • Where
  • X Dose (mSv)
  • ? Specific Gamma Ray Constant
  • A Activity (MBq)
  • t Time (hours)
  • d Distance from Source (cm)

16
What is the radiation dose received by a graduate
student working with 185 MBq of Na-22 for two
hours per day for 22 days at a distance of 35 cm
from the source and using no shielding?
  • X Total Dose
  • t 44 hours
  • ? 3.24 (mSvcm2)/(hMBq) at 1 cm
  • A 185 MBq
  • d 35 cm

17
X G A t (D)2
X (3.24) (mSvcm2)/(hMBq) (185 MBq) (44h)
(35cm)2
X 21.5 mSv
18
Who SHOULD NOT wear a TLD?
  • A NEW who has only a
  • REMOTE POSSIBILITY of receiving a
  • radiation exposure greater than 1mSv/yr.
  • Personnel working with low energy betas
  • such as S-35, C-14 and H-3.

19
External Exposure Estimate
  • For gamma radiation

20
ESTIMATION OF EXTERNAL ß-RADIATION DOSE NOT IN
CONTACT WITH SKIN
  • Rule of thumb, valid over a wide range of beta
    energies

Activity (Bq)
Distance from source (m)
Dose Rate (Sv/hr)
  • Assumes point source and no attenuation to air or
    source material
  • Expect large errors beyond 1 m (overestimates
    absorbed dose)

21
Internal Exposure
  • Iodine 125 , 131 Concentrate in thyroid
  • CNSC regulation
  • Contact HSE before using Iodine 125, 131
  • Contact during planning stage
  • Specific monitoring protocols are required

22
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23
Question?
  • A salesman is showing you a new piece of
    equipment which has a radiation trefoil on the
    side. He assures you that the equipment is safe
    because it contains an alpha emitter that has
    been shown to produce 4 roentgens and is in a
    lead sealed casing. He also tells you that other
    users only report about 0.9 mS per yearWill you
    buy it?

24
Section 3 - B.E.I.R
  • Biological Effects of Ionizing
  • Radiation

U.S. National Academy of Sciences Reports
25
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26
Radium Girls
27
B.E.I.R. Human Experience
  • Early martyrs
  • Radium Dial Painters
  • Tuberculosis Patients
  • Survivors of Atomic Bombings
  • Ankylosing Spondylitis Patients
  • Uranium Miners Elliot Lake, Ont.
  • Radiation Institute of Canada

28
Effects Chronic vs. Acute
  • Chronic repeated doses of low levels of
    radioactive materials
  • Acute single or short term doses at higher
    levels
  • Often use one to help understand the other

29
Effects of Radiation Somatic or
Genetic
  • somatic if they become manifest in the exposed
    person
  • Non-reproductive cells
  • genetic if they affect their descendants.
  • Reproductive cells

30
  • Somatic Effects and Risk Factors
  • Age effects are important, age independent risk
    estimates may be inappropriate.
  • Diet, genetics, lifestyle factors can all affect
    outcome
  • Synergistic effects may be important eg.
    Uranium miners smoking

31
  • Cancers induced by radiation are
    indistinguishable from those caused naturally
  • Solid tumours such as breast, lung, thyroid and
    GI are greater numerically than leukemia
  • Risk is greater for women - breast and thyroid
    cancer
  • Cancer complex disease no guarantees

32
30 100 Trillion Cells at Risk
Different Cell Types Different Cell Cycle
Different Cell Targets
33
End Effect of Radiation
Organelle death Cell death Cell
healing Chromosome loss Gene loss Gene
rearrangement
34
DNA Damage
Single Strand Break Double Strand Break Change
or Loss of Base
Bond Breakage- Uncoiling
Intra-Helix Crosslinking Inter-Helix
Crosslinking Inter-Protein Crosslinking
35
Dicentric chromosomes induced by radiation
exposure
Unexposed
Exposed
36
LNT model linear, no threshold
Incidence of effects
37
Incidence of Radium-Induced Malignant
Tumors
38
Atomic bomb victims
Threshold model
Chernobyl
Normal Exposure?
Incidence of effects
Radiation Hormesis
Increasing Radiation Dose
39
Where does our radiation dose come from?
40
Natural Sources
41
Dose Rates Cosmic Rays
Altitude µSv/hr 10 Km 5 6.7 Km 1
Whistler 0.1 Sea Level 0.03
42
Natural Annual Dose Rates Estimated
  • Cosmic 0.45
  • External 0.26
  • Internal 0.27
  • Other lt0.01
  • 1.0 mSv/ year

43
Sources of Total Radiation Exposure in USA
44
Annual Dose Rates Health Care
Medical X-rays 1.03 Dental X-rays 0.03 Nuclear
Medicine 0.01 1.1 mSv/ year
45
Maximum Permissible Doses
  • UBC Workers (members of public) 1 mSv
    per year
  • Nuclear Energy Workers (NEWs ) 10 mSv
    per year

(UBC)
46
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47
Industrial Radiographer
48
Annual Dose Rates 1997
  • Dose Interval
  • mSv
  • 0
  • gt0-1
  • gt1-2
  • gt2-5
  • gt5-20

Number of Workers 4198 516 25 6 2
Average Dose 0.00 0.32 1.48 3.37 6.2
X0.05 mSv
49
Canadian Exposures
50
Acute Effects
2 Gy cell depletion in bone marrow 2-5 Gy
cataracts 10 Gy gastrointestinal syndrome 20
Gy central nervous system
Sv Gy x QF (QF 1 for gamma) SVGy (1 Gy
100rads)
51
Attempted theft of Co-60 source
3 weeks
8 weeks
52
Industrial Radiography
  • Sealed radioactive sources e.g. Iridium 192
  • High activity 58 curies 2.1 TBq

53
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54
WARNING Photo of gross anatomy Viewer
discretion advised.
55
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56
  • Other uses for sealed radioactive sources
  • Internal calibration standards in liquid
    scintillation
  • counters (Cs- 137)
  • Generation of ion current in electron capture
    devices
  • e.g. gas chromatographs (Ni-63)
  • Inventory required for these instruments at
    UBC
  • Industrial uses
  • volume measurement in closed
    vessels
  • thickness measurement gauges
  • food irradiation
  • soil density gauges

57
  • Nuclear Gauges
  • Cs 137 gamma source
  • density gauges
  • Am241/Be neutron source
  • moisture gauges
  • Portable may require TDG training
  • knowledge of regulations, documentation
  • Expect occupational exposure
  • Safety through training manual,
  • courses offered by manufacturer

58
INCIDENCE OF CANCER
BEIR VII 2006
  • Assuming an age/sex distribution similar to the
    entire US population 42/100 people will
    be diagnosed with cancer 42
  • Acute exposure to 1.0 mSv radiation (above
  • background) could result in 1 new cancer
  • per ten thousand 0.01 (LNT model)
  • Risk of cancer after acute exposure to 1.0mSv
  • 42.01

59
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60
ALARA Principle As Low As
Reasonably Achievable
61
Question?
  • Does radiation effect the human body through
    acute or chronic exposures?
  • Why do TB patients have a higher incident of
    breast cancer, but not lung cancer?
  • Different susceptibilities to damage from
    radiation
  • Do sealed sources of radiation have any risk
    associated with them?
  • Yes can still offer significant damage
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