Presenter_On-Site_00 1 Radiation Protection Fundamentals Craig Maxwell - RCT Radiation Protection Group Lawrence Berkeley National Laboratory
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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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Nucleus
Neutrons
Protons
Electrons(Electron Clouds)
Structure of the Atom
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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 radiationLow energy
• Lasers, RF, microwaves, IR, visible
Excites electrons• Produces heat
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Alpha Decay4He Nucleus
Ejected from NucleusYour skin will stop it
internal hazard
stopped by paper
found in soil, radon and other radioactive materials
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Beta DecayEither too many neutrons or too many protons
stopped by plastic
skin, eye and internal hazard
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
medical usesnaturally present in soil and cosmic radiation
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Types of Ionizing Radiation
Alpha
Beta
Gamma and X-rays
Neutron
Paper Plastic Lead Concrete
Helium nucleus (2 protons, 2 neutrons): +2 charge
Electron: +1 or -1 charge
Photon: 0 charge
Neutron: 0 charge
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Radiation Quantities and Units
RadioactivityQty: ActivityUnit: Curie (Bequerel) 1 Ci = 1000 mCi 1 Bq = 1 dis per sec 1 Ci = 3.7 e10 Bq
Radiation RiskQty: Dose EquivalentUnit: rem (Sievert) 1 rem = 1000 mrem 1 Sv=100 rem
Radiation Absorbed DoseQty: DoseUnit: rad (Gray) 1 rad - 1000 mrad 1 rad = 100 erg/gram 1 Gy=100 rad
roentgen
equivalent
man
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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
Building Materials - 3.6 mrem
Fallout < 1
Smoke Detectors - 0.0001
Medical – 53 mrem
mrem
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)
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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
100 rems
20 years
5 min
Chronic exposures may increase cancer risk. 100,000 people
exposed to 100 mREM 4 or 5 additional cancers
Localized effects:
>500 REM Skin –
radiation burn
Whole body effects:
LD50/30 500 RAD
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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 10
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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:
VictoreenBicron
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Beta Contamination Instrument
Ludlum 3
Type: Normally equipped with a Geiger-Mueller 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)
Reduce Radiation
Doses
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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