Transcript Radiation Protection: Beyond Time Distance and Shielding

Radiation Protection:
Beyond Time, Distance, and Shielding
Michael J. Zittle, MHP, CHP | Radioactive Materials Compliance Manager
What is Radiation?
• Energy Transfer
– Emission or transmission of energy in the form
of waves or particles through space or through a material medium
• Probability
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Decay/Emission
Interaction
Detection
Damage
Repair
What is Radiation Protection?
The science and practice of protecting people and the
environment from the harmful effects of ionizing radiation
What’s the Big Deal?
What is a Health Physicist?
A professional who protects groups and individuals from
the harmful effects of ionizing radiation.
Our Mantras
• Time (Minimize)
• Distance (Maximize)
• Shielding (Utilize)
Our Philosophy
–A
• As
–L
• Low
–A
• As
–R
• Reasonably
–A
• Achievable
ALARA is a radiation safety principle for minimizing radiation doses and
releases of radioactive materials by employing all reasonable methods
As Low As Reasonably Achievable
• Taking into account:
– State of Technology
– Economics
– Society and Socioeconomics
– Benefits to Public Health & Safety
– Public Policy
– Practicality
What is the basis for ALARA?
• Philosophy based on the conservative
assumption that radiation dose and its
biological effects on living tissues are
modeled by a relationship known as the
“Linear Hypothesis”
NO
“SAFE”
DOSE
• Every radiation dose of any magnitude
– Produces some level of detrimental effects
– Increasing risk of genetic mutations & cancer
• There is NO SAFE DOSE!
• ALARA is not only a sound safety principle, but
is a regulatory requirement for all radiation
safety programs.
• Radiation safety programs attempt to lower
doses received by radiation workers by
utilizing practical, cost effective measures.
How is ALARA Implemented?
• An effective ALARA program is only possible when a
commitment to safety is made by all those involved.
• This includes:
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Management
Radiation Safety Staff
Radiation Safety Committees
All radiation workers
• Radiation Safety Manuals provide guidelines for the
responsibilities and good practices consistent with:
– ALARA concept
– Federal and State regulatory requirements
• These guidelines and regulations require:
– Adherence to legal dose limits for regulatory compliance
AND
– ALARA investigation dose levels which serve as alert points for initiating
a review of the work practices of a radiation worker
Six Fundamental Principles of ALARA
Optimize
resources
Eliminate or
reduce the
source of
radiation
Use radiation
shielding
Contain the
source
Maximize
distance from
a radioactive
source
Minimize
time in a
radiation
field
10 Principles and Commandments of Radiation Protection
• Transcends the easily remembered "List of 3"
– Time, Distance, and Shielding doesn't tell a worker what to do
• Address other risk-limiting and protective measures
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Performance standards
Health education
Engineering requirements
Administrative procedures
Principles - Short Names
Commandments - What To Do
• Familiar - Technical
Hurry (but don't be too hasty...)
#1
Minimize exposure or intake time
Application:
– Install reliable equipment to reduce maintenance
– Provide adequate clearance for maintenance & inspections
– Utilize special tools to speed maintenance and access
– Remove components from radiological area for repair & calibration
– Practice dry runs with non-radioactive sources
– Occupancy and Use Factors
– Planning
Time
Stay away from it
Maximize distance between the source and he subject
– Purely a geometric component (for a point source)
– Inverse Square Law https://www.youtube.com/watch?v=UjJfNkkkFI8
Application:
– Remote handling tools
• Remote manipulators
• Forceps
• “Hot Dog on a Stick”, “Weed Wacker”
• Industrial Radiography Control Drive Cable ~8 meters
– Dose Reduction of 500,000 R/hr
– 1 cm contact -> 8 m
– Exclusion areas – 2 mR/hr, Chernobyl
– Robots
– Large packages with source in center to limit surface dose rates
#2
Distance
Dose Rate at a Distance from Ir-192 Point Source in Rem/hr
Gamma Constant (Γ) = 0.59163 rem/hr-Ci @ 1 meter
Assuming a nominal 100 Ci source = 59.163 rem/hr @ 1 meter
Dose Rate in rem/hr @ various (cm) distances from a 100 Ci Ir-192 Point Source
0.01 m (1 cm)
0.02 m (2 cm)
0.03 m (3 cm)
0.1 m (10 cm)
600,000
150,000
66,000
6000
Dose Rate in rem/hr @ various (m) distances from a 100 Ci Ir-192 Point Source
1m
2m
4m
8m
59
15
4
1
(All values are rounded)
Disperse it and dilute it
Minimize concentration
Maximize dilution
– "The Solution to Pollution is Dilution..."
Application:
– Ventilation (dilution)
– Concentrate HLRW – Yucca Mt., WIPP
– Dilute LLRW – Air and Water Effluent
– Radon dispersal in homes and mines
#3
Dispersal
Use as little as possible
#4
Minimize production and use of radiation and radioactive materials
Application
– Removal of source or source elimination
• X-ray instead of Cs-137
– Source reduction
• Use only as much as you need
• Clean it up and keep it clean
• Delay for decay
– Radioactive decay
• Half-life Animation
– Cyclotron beam alignment
• Minimizes stray radiation and activation products
– Nuclear non-proliferation activities and diplomacy
Source
Reduction
Keep it in
#5
Source
Barrier
Minimize release (contain and confine it)
Maximize absorption (shield)
Application:
– Containment
• leak-tight enclosures
– Ventilation
• circulation, exchange, and filtration of air
– Filtration
• circulation, exchange, processing, and filtration of water or
air
– Shielding - contains (absorbs) radiation
• Lead, concrete, water, plastic, air, etc.
Exhaust
Systems
Fume
Hoods
Shielding
Engineering
Controls
Emission
Control
Systems
Gloveboxes
H20
Filtration
Systems
Keep it out
#6
Personal
Barrier
Minimize entry into the body of radiation and radioactive materials
Application:
– PPE for external radiation
• Lead aprons and gloves
• Thyroid shields
• Thick (shielding) glasses
– PPE for internal radiation
• Respiratory protection
• Protective clothing , “Anti-C’s”
Get it out of you and off of you
#7
Decorporation
Enhance removal or minimize uptake of materials from the body
(after intake or skin contamination)
Decorporation - Since there is no way to remove energy deposited by ionizing radiation
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Removal of radioactive material from the interior or surface of body
Blocking of uptakes by tissues and organs
Application:
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Decontamination – simple washing, “HazMat Decon”
Purging or removal
• Chelating agents – DTPA, Prussian Blue
• Forcing fluid intakes
• Lung lavage
Competitive mass action
• KI pills uptake of radioactive iodine to thyroid
Excision
Limit the damage
#8
Optimize exposure over time and among persons
Scavenge free radicals
Induce repair
Effect Mitigation is not an antidote
– Doesn’t reduce the dose like decorporation
– Reducing the effect of an individual or collective dose
Application:
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Free-radical scavengers – vitamin E, superoxide dismutase
DNA repair mechanism inducers – “Primer Dose”, fractionated doses
Spread dose out over time to allow for repair – avoids acute effects
Spread collective dose among many people and older people (What The ?)
Effect
Mitigation
Choose best technology
Maximize risk-benefit-cost figure
Application:
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Using ionizing radiation technology that produces lower dose
Modifying existing technology
Fastest imaging modality, Processing QA
Substitute non-ionizing radiation technologies
• Shore-fitting fluoroscopes are no longer used
• Ultrasound in lieu of x-rays
• Alternatives to nuclear weapons for destroying an enemy…
– Designing to ALARA uses the cost-benefit process of optimization
#9
Optimal
Technology
Don't compound risks
Minimize exposure to other agents that may work in concert with radiation
Application:
– Genotoxins
– Other agents that cause initiation, promotion, or progression of tumors
– Don’t Smoke…
• Lowers the “background” cancer rate, and therefore
• Lowers the radiogenic cancer rate for a constant relative risk!
#10
Limitation
of Other
Exposures
A few words about transportation
Safety is in the packaging…
The 10 Principles & 10 Commandments of Radiation Protection
Principle
Commandment (familiar)
Commandment (technical)
Time
Hurry, but don’t be hasty
Minimize exposure time/intake time
Distance
Stay away from it
Maximize distance
Dispersal
Disperse it and dilute it
Minimize concentration, maximize dilution
Source Reduction
Use as little as possible
Minimize production and use of radiation and radioactive materials
Source Barrier
Keep it in
Maximize absorption (shield), minimize release (contain and
confine it)
Personal Barrier
Keep it out
Minimize entry into the body of radiation and radioactive materials
Decorporation
Get it out of you and off of you
Maximize removal or blocking of radioactive materials from the
body (after intake or skin contamination)
Effect Mitigation
Limit the damage
Optimize exposure over time and among persons, scavenge free
radicals, induce repair
Optimal Technology
Choose best technology
Optimize risk-benefit-cost figure
Limit Other Exposures Don’t compound risks
Minimize exposure to other agents that may work in concert with
radiation
Strom, Daniel J. “Ten Principles and Ten Commandments of Radiation Protection,” Health Physics 70(3):388-393, 1996.
I. Time
VI. Personal Barrier
Hurry (but don’t be too hasty)
Keep It Out
II. Distance
VII. Decoporation
Stay Away From It
Get it Out of You and Off You
III. Dispersal
VIII. Effect Mitigation
Disperse & Dilute It
Limit the Damage
IV. Source Reduction
IX. Optimal Technology
Use as Little as Possible
Choose Best Technology
V. Source Barrier
X. Limit Other Exposures
Keep It In
Don’t Compound Risks
[email protected]
(206) 616-8901
Michael J. Zittle, CHP
Radioactive Materials Compliance Manager
University of Washington