Radiation Protection Fundamentals
Craig Maxwell - RCT
Radiation Protection Group
Lawrence Berkeley National Laboratory
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Objectives
• Familiarize you with some of the basics of Radiation and
Radioactive Decay
• Discuss some of the common instruments found in research labs
• Review control methods used to reduce exposure
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Structure of the Atom
Nucleus
Neutrons
+
++
Protons
Electrons
(Electron Clouds)
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Ionizing radiation
High energy radiation
• Gamma-rays, x-rays - photons
• Particles: alpha, beta, neutron
Ejects electrons from atoms
• Produces an altered atom - an ion
Non-ionizing radiation
Low energy
• Lasers, RF, microwaves, IR, visible
Excites electrons
• Produces heat
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Alpha Decay
4He
Nucleus
Ejected from Nucleus
Your skin will stop it
internal hazard
stopped by paper
found in soil, radon and other
radioactive materials
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Beta Decay
Either too many neutrons or too many protons
skin, eye and internal hazard
stopped by plastic
Naturally occurring in food, air and water
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Gamma / X-ray Decay
•
•
Emission of a photon
Often occurs after  or  when nucleus is in an excited state
stopped by lead
naturally present in soil
and cosmic radiation
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medical uses
Types of Ionizing Radiation
Paper Plastic
Alpha
Helium nucleus (2 protons,
2 neutrons): +2 charge
Beta
Electron: +1 or -1 charge
Gamma and X-rays
Photon: 0 charge
Neutron
Neutron: 0 charge
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Lead
Concrete
Radiation Quantities and Units
Radiation Absorbed Dose
Qty: Dose
Unit: rad (Gray)
1 rad - 1000 mrad
1 rad = 100 erg/gram
1 Gy=100 rad
Radioactivity
Qty: Activity
Unit: Curie (Bequerel)
1 Ci = 1000 mCi
1 Bq = 1 dis per sec
1 Ci = 3.7 e10 Bq
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Radiation Risk
Qty: Dose Equivalent
Unit: rem (Sievert)
1 rem = 1000 mrem
1 Sv=100 rem
Radiation Weighting Factors (WR)
Absorbed dose (Rad/Gy) x WR
=
Equivalent dose (rem)
Photons, electrons & muons (all
energies)
1
Beta & positron
1
Neutrons
5-20
Alpha, fission fragments, heavy
nuclei
20
10CFR835
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Sources of Ionizing Radiation
Radioactive materials
• Naturally occurring (uranium, carbon-14, …)
• Artificial (activated by neutrons from a reactor or
accelerator beam)
Radiation Producing Machines
•X-ray machines (characteristic, bremstrahlung)
• Accelerators (ion beams, neutrons, x-rays)
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Background and Manufactured Radiation In the
U.S. Contributes 360 mrem per year
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Manufactured Sources of Radiation
Cigarette Smoking - 1300 mrem
Medical – 53 mrem
Medical Doses:
A: Dental exam (16 mrem)
B: Mammogram (25 mrem)
C: Tc-99m cardiac function (75 mrem)
D: Cranial CT multiple scans (up to 5 rem)
E: “Full body CT screening” – one scan ( 1 to 2 rem)
F: Spiral whole body CT scan ( 3 to 10 rem)
Building Materials - 3.6 mrem
Smoke Detectors - 0.0001 mrem
Fallout < 1 mrem
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Whole Body Annual Dose Limits
RADIATION WORKER - Federal NRC Limits
Whole Body - 5000 mrem/year
Extremities - 50,000 mrem/year
Skin - 50,000 mrem/year
Eyes - 15000 mrem/year
Pregnant - 500 mrem/term / 50 mrem/month
General Pubic - 100 mrem/year
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Effect of Dose and Dose Rate
5 min
100 rems
Localized effects:
>500 REM Skin –
20 years
radiation burn
Whole body effects:
LD50/30 500 RAD
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Chronic exposures may increase
cancer risk. 100,000 people
exposed to 100 mREM 4 or 5
additional cancers
Risk Perspective
Average Estimated Days Lost Due to Daily Activities
Health Risk
Ave. Est. Days Lost
Unmarried Male
3,500
Cigarette Smoking
2,250
Unmarried Female
1,600
Coal Miner
1,100
25% Overweight
777
Alcohol (U.S. average)
365
Construction Worker
227
Driving a Motor Vehicle
207
100 mrem/year for 70 years
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10
Radiation
vs
Contamination
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Radiation Vs. Radioactive Contamination
Radiation is particles or waves of energy emitted from unstable atoms.
Radioactive Contamination is radioactive material usually in any
location you do not want it.
Exposing a material to radiation does not necessarily make it
radioactive, but radioactive material on a non-radioactive item, makes
the item contaminated.
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Radiation Survey Meters
Two common Ion Chamber radiation survey instruments are:
Victoreen
Bicron
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Beta Contamination Instrument
Ludlum 3
Type: Normally equipped with a GeigerMueller 44-9 (pancake) probe
Detects: Beta, gamma
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Alpha/Beta Contamination Instrument
Ludlum 2224
Type: Plastic scintillation
for beta detection that has
a [ZnS (Ag)] coating for
alpha detection
Detects: Alpha and Beta
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Other Instrumentation
Ludlum 16 with a 44-3 thin
window NaI probe
Liquid Scintillation (LSC)
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Instrument performance
• Dead or low batteries - erratic or no detection
• Calibration has changed - may read high or low
• Defective cable or other problems
• Poor survey technique
– angle of probe to source - only detects part
– to far from source - radiation absorbed by air
– survey too fast – only detects part
You must use them correctly if you expect them to work for you
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Radiation & Contamination
Control Methods
Used to reduce exposure to
radiation and
radioactive material contamination
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Engineering Controls
• Containment
– Glove box
– Glove bag
•Ventilation
– Fume Hood
– Bio Safety Cabinet
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Engineering Controls cont.
• Interlocks
• Tamper-Proof Screws/Bolts
• Flange Padlocks
• Security Seals
• Shielding
• Access controls (e.g. card key)
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Administrative Controls
• Regulations
• Formal Authorizations
• Facility policies and procedures
• Labels, signs, and postings
• Routine radiation surveys
• Machine operational restrictions
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ALARA
As Low As Reasonably Achievable
ALARA Techniques:
• Time - (Reduce)
• Distance – (Increase)
• Shielding – (Proper Shielding)
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Reduce
Radiation
Doses
Control Methods
• Engineering
• Administrative
• ALARA Techniques
• Time
• Distance
• Shielding
• Missing Control
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Exposure Prevention Methods
• Protective clothing such as lab coats, gloves & safety glasses
• Self-monitoring to reduce the spread of radioactive contamination
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Good Work Practices
Use deliberate movements and apply lessons learned from cold
runs (mock-ups).
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Respect and Understand the Postings
Treat all radiological areas as if everything was contaminated.
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Common sources of radioactive
contamination
– Sloppy work practices
– Poor housekeeping
– Opening radioactive materials/systems without proper controls
– Leak or tears in containers
– Damaged Sealed Sources
– Spills
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Upon Completion of Work
Be sure to survey yourself
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Upon Completion of Work
Hand washing is a
good work practice
and an important
final step after
working with any
radioactive material.
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Final Thoughts
• It is our mission to ensure that research and
learning continue in the safest manner possible.
• Be a mentor
• Be a resource
• Lead by example
• Always use best practices
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