Radiation Safety
for
Byproduct Material Users
Andy Miller, MS, CHP
Disclaimer
My opinions - Not those of my employer of the HPS
Source for much of the material (especially photographs)
is from:
ORAU
NCRP
Radiation In Our Lives
Overview of Ionizing Radiation
You can not see it, smell it, or feel it
We depend on training and equipment to protect ourselves.
Radiation is relatively simple to measure
Unlike biological agents, we can quickly and conclusively
assess the situation and respond appropriately.
The health effects of radiation have been studied
for over 70 yrs and are well understood for high doses.
Dose limits are well below the doses where health
effects are directly observed.
Sources of Radiation Exposure
Natural Background
•
•
•
•
Space – 5%
Internal – 5%
Terrestrial – 3%
Radon and Thoron – 37%
• Total – 50%
Natural Background
Exposure Category
Internal, inhalation (radon and thoron)
External, space
Internal, ingestion
External, terrestrial
Natural background
EUS
(mrem)
228
33
29
21
311
Medical
•
•
•
•
Computed Tomography (CT) – 24%
Nuclear Medicine – 12%
Interventional Fluoroscopy- 7%
Conventional radiography – 5%
• Total – 48%
Medical
Exposure Category
CT
Nuclear medicine
Interventional fluoroscopy
Conventional radiography
and fluoroscopy
Medical
EUS
(mrem)
147
77
43
33
300
Other
• Consumer activities and products– 2%
• Occupational exposure- < 0.1%
• Industrial exposure- <0.1%
• Total – about 2%
Consumer and Industrial
Exposure Category
Consumer activities and products
Industrial, security, medical,
educational and research
EUS
(mrem)
13
0.3
Average Person
Exposure Category
Natural background
Medical
Consumer activities and products
Industrial, security, medical,
educational and research
Occupational
Total
EUS
(mrem)
311
300
13
0.3
0.5
625
Annual Limits
Type of Exposure
Radiation worker – whole body
Declared pregnant worker
Minors
Members of the public
Does not include background radiation
or medical exposures
Limit
(mrem)
5000
500
100
100
Why do I need to be aware ?
Nuclear medicine patients
Large hospital in town – 25000
patients per year – diagnostic
About 300 per year therapuetic
Scrap metal dealers
Customs & Border Protection
TEMA/ FD / Highway Patrol
Granite Counter Tops
• New York Times article “What’s Lurking in Your Countertop?”
• Some slabs measure approximately 1.5 times background (about
20 μR/h)
• Radium which decays to Radon-222
• Levels are estimated to be about 0.6 pCi/L compared to 4 pCi/L
for EPA guidelines
Fiesta Ware
• 1936 – 1943 – Fiesta Red
Natural Uranium
• 1943 – 1959
No production (WWII)
• 1959 – 1969 - Fiesta Red
Depleted Uranium
• 1969 – 1973
Fiesta Red and Ironstone
Depleted Uranium
• Very easy to detect with a Geiger Counter
• Homer Laughlin Company of WV
• 0.5 to 15 mR/hr
• 14% U by weight of glaze
Vaseline Glass
•1830’s started production
•Natural Uranium
•After 1959
•Depleted Uranium
•Still being made but only for decoration
not for drinking or eating
• Larger pieces can see with a Geiger Counter
• Fenton Glass of WV
• 27 mR/hr contact dose rate
• 2% U by weight of glass
• Fluorescence seen very well under UV light – green glow !!
K-40 Half-life: 1.28 x 109 years
Beta decay (89.3%). The beta
maximum energy is 1.31 MeV
Electron Capture (10.7%).
Gamma Rays: 1461 keV (10.7%)
Daily intake of potassium element: 3.3 grams
Amount of potassium element in body: 140 grams (1.5 pCi/g or 55
Bq/kg of body weight)
Typical K-40 activity in body: 0.1 uCi; This means that there are
over 200,000 atoms of K-40 that decay in the body each minute!
Brazil Nuts
•A mix of :
•Ra-226 (1600 year half life)
•Ra-228 (5.75 year half life)
•1.8 pCi/g Ra-226
•2 pCi/g Ra-228
•Most of the radium ingested is not retained by the body
Kaolin Clay
•White clay
•Mined in GA and AL
•Elevated levels of U and Th decay series
•Radium
• Domestic production now with a different chemical (but the same
trade name)
•International production still uses Kaolin
•0.27 to 0.5 pCi/g of medicine
•1000 pounds per year to exceed limits
Kitty Litter
•Clay
•Bentonite
•Elevated levels of U and Th decay series
•K-40
• Can trip detectors due to large volumes (tractor trailer loads)
•4 pCi/g for Uranium series
•3 pCi/g for the Thorium series
•8 pCi/g for K-40
•4 billion pounds per year purchased
•50000 pounds U – 120000 pounds of Th
Fertilizer
•Phosphorus
•K-40
•N- P-K
• Phosphate mining can be associated with uranium (FL)
• Can trip detectors due to large volumes (tractor trailer loads)
• U-238 22-140 pCi/g
• Th-230 5 – 430 pCi/g
• Ra-226 1 – 24 pCi/g
• Th-232 0.14 to 4.6 pCi/g
Magnesium- Thorium Alloy
• Mag-Thor
•Mg-Th-Zr
•Mg-Th-Zn-Zr
•Mg-Ag-Th-(rare earth) - Zr
• High strength, creep resistance at high T, light weight
• Aircraft engines, helicopter parts, rocket motors
• Parts are about 1.7% Th
• Aircraft maintenance workers – up to 50 mrem/yr
•Grinding cutting issues as well as dose rate
Thoriated Welding rods
• Tungsten Inert Gas (TIG) welding
• Aircraft, petro chemical industries
• High quality welding
• Typically 1-2% thorium can be up to 4%
• Rods are color coded for throia content
• Throium increases the current carrying capacity of the electrode
• Inhalation hazard
• Grinding the tip
• Electrode consumption during welding
• Some estimates as high as 800 mrem per year with no ventilation
Thorium lantern mantles
• 1884 – first production
• Thorium causes and incandescent glow
when heated
• Domestic production stopped
(Coleman) in 1990
• International still ongoing
• Burning the mantle releases airborne activity from decay products
of Thorium
• Approximately 25 million mantles sold in 2000 contained Th
• Playing with ash – 2 mrem estimate
• High estimate of 200 mrem for living indoors with your only
source of light as mantles (4 per year)
• Geiger counter sees this well
Electron tubes and light bulbs
• Electron tubes
• Co-60, Ni-63, Kr-85
• Pm-147, Th-232
• Light bulbs
• H-3, Kr-85, Pm-147, Th-232
• Radioactive materials added to slightly ionize the gas in the tube
to allow for better and faster starting
• Typically pCi quantities
• Consumer product boxes will be labeled with isotope and amount
• Millions of bulbs sold each year
• Doses are much less than 1 mrem
Smoke detectors
• 1940 – first production
• 1951 introduced in US
• Am-241
• alpha emitter
• 1 to 30 uCi – smaller for homes – larger for commercial
• Some older detectors can also contain Ra-226
• Dose estimate is less than 1 mrem per year
• Disposal
• Return to manufacturer
• Landfill
• Multiple units should be shipped as radioactive waste
Static eliminators
• Po-210
• 138 day half life
• alpha emitter
• Litvinenko – London - 2006
• Ionizes the air immediately in front of the device
• Ions produced in the air are attracted to the object that has the
static charge (brush)
• Typical amounts 200 to 500 uCi
• One year replacement recommended
• Small doses but heightened sensitivity due to event
• Mass balances, paint shops
Luminescent paint
• Ra-226 – old
• H-3
• Pm-147
• Beta particles interact with a phosphor to cause the “glow”
• Radium dial painters –
• Radium production stopped in 1978 domestically
• Military equipment (aircraft ,tanks – in museums)
• Easy to detect the Ra-226
• H-3 and Pm-147 more common and much less hazardous
Gun sights
• H-3
• Beta particles interact with a phosphor to cause the “glow”
• About 12 mCi
• Very low energy beta emitter – GM will not work
• Easy to lose
• Exempt distribution
• Would not worry about the radiation as the biggest hazard !
Exit signs
• H-3
• 20 Ci (CURIES !)
• 10-20 year working life
• Beta particles interact with a phosphor to cause the “glow”
• Anyone can buy these without a license
• Some responsibilities for:
• Inventory
• Reporting loss or damage
• Transfer to new owner
• Return to manufacturer
• Radioactive materials
• No eating
• No drinking
• No smoking
Dentures
1940-1970’s
Uranium added for fluorescence
Dose to the gums ??
130 rem per year estimated