Everything You Wanted to Know
About
but Were Afraid…
Alan Fellman, Ph.D., C.H.P.
Dade Moeller, an NV5 Company
Questions to Consider
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Are you safe from radiation at your facility?
How do you know?
What does safe mean?
Who decides if it is safe to work here?
What information will you need
to decide on safety?
• What can/should you do for safety?
Page 2
What is
?
 Simply put, ENERGY, that produces ions when it
interacts with matter!
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Ionizing Radiation
 Dr. Dade Moeller used to say:
“We live in a sea of radiation.”
 People around the world are continually
exposed to radiation from natural sources.
 These sources include:
 Cosmic radiation from outer space.
 Terrestrial radiation (materials in the earth).
Page 4
Radioactive - Why?
 A stable nucleus has a
balanced mix of neutrons
and protons.
 If out of balance, the nucleus
emits radiation and typically
loses mass to become
another, lighter element.
 Over 400 radioactive isotopes
that ultimately decay to a
“stable” elemental form.
Page 5
Half-Life
 A physical property - the time it takes for a
radionuclide to decay to ½ of its original activity.
 Dependent on the decay constant.
 As number of radioactive atoms decreases
through decay, the number of decays per unit
time (the radioactivity) decreases.
Page 6
Example Half-lives
 Uranium-238 (in soil):
 4.5 billion years.
 Radium-226 (in soil - produces radon):
 1,600 years.
 Radon-222 (in soil and air):
 3.8 days.
 Polonium-214 (radon progeny):
 164 microseconds (0.000164 s).
Page 7
(Radio)Activity
 The measure of radioactive decay per time.
 Units (U.S. – derived from radium):
 1 curie = 37 billion disintegrations per second
(dps) = ~1 gram of pure radium-226.
 1 picocurie (pCi) = 0.037 dps.
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(Radio)Activity
 International SI Units:
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Activity: Becquerel (Bq) 1 dps
1 Bq – 1/37,000,000,000 Ci = 0.000000000027 Ci
1 Bq = 27 pCi
Very small number – uses prefixes
(GBq = 109 Bq)
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Definitions
 NORM: Naturally Occurring Radioactive
Material – natural radionuclides in the
environment (uranium, thorium, radium,
radon…). Includes:
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Some oil and gas drilling waste (shale),
Fertilizer (from phosphate ores – uranium),
Rare earth mine tailings (uranium, thorium),
Ceramic products (uranium in clay), and
Welding rods (thorium sands in coatings).
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Definitions
 TENORM: Technologically Enhanced Naturally
Occurring Radioactive Material – natural
material whose radioactive concentrations have
been enhanced by human activities, including:
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Oil & gas pipe scale,
Oil & gas sludge,
Selected mining wastes, and
Coal ash (concentrated uranium & thorium).
Page 11
Radioactive Decay in Thorium and Uranium
Page 12
Example Activities
 Uranium-238 in cup of soil (typical):
 18.5 Bq = 500 pCi (0.7 Bq/g = 1.8 pCi/g).
 Decay chain: 111 Bq = 3,000 pCi (~0.33 Bq/g
= 9 pCi/g).
 ~30 tons of uranium to a depth of five feet of soil
per square mile of the earth’s surface.
 Radon-222 in air:
 0.18 Bq/L (0.5 pCi/L) in outdoor air.
 Concentrates in houses from 2 to over 100 times.
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Detecting Ionizing Radiation
 Discovered Radiation.
 Used photographic plates
to detect X-rays.
 Determined salts of
uranium emitted radiation
that darkened silver salts.
 Photographic film used as
a radiation detector for
decades.
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Alpha Particle
 Helium-4 nucleus (two neutrons, two protons).
 Slow moving, but high energy.
 Cannot penetrate material easily.
 Stopped by one piece of paper.
 Stopped by dead layer of skin.
 Only important if the material is in the human
body (inhalation, ingestion…).
 NORM alpha emitters: uranium-238/-234/-235,
thorium-232/-230/-228, radium-226/-224.
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Beta Particle
 Electron from a neutron, fast moving,
with medium energy.
 Can penetrate material well.
 Stopped by 100 to 150 pieces of paper
 Stopped by 0.5 -1 centimeter of water
 May be a concern when internal or external to
the human body
 Inhalation/ingestion
 NORM beta emitters: thorium-234, radium-228,
lead-214/-212
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Gamma Radiation
 Electromagnetic radiation (photons = pure energy).
 Emitted only by certain nuclei from the nucleus of an
atom.
 Speed of light; low to high energy.
 Highly penetrating.
 Stop half with about 1 cm of lead or 5 to 15 cm of
water.
 External radiation.
 NORM gamma emitters: thorium 234,
radium-226/-224, lead 214/-210.
Page 17
Geiger Counters
 Simple field instruments rely on detecting
ions produced by the radiation.
 Geiger counters can’t
determine energy or
type of radiation.
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Scintillation Detectors
 Emit light when interacting with gamma radiation.
 Photomultiplier tube converts light into an electric
signal.
 Can detect intensity and energy.
 Can be active (Sodium Iodide) or passive
(thermoluminescent dosimeter).
 Not applicable to beta or alpha radiation.
Page 19
Semiconductor Detectors
 Uses strips of silicon or other semiconductor
material that act like diodes under an electric field.
 Radiation produces ionization currents that are
detected and measured (electrons and “holes” in
the semiconductor).
 The currents are proportional to the energy of the
radiation deposited .
 Electronics convert currents into estimates of
deposited energy; allows radionuclide
identification.
Page 20
Two Key Questions
 Is the instrument needed to determine exposure
(dose) rates?
OR
 Is the instrument needed to determine
contamination measurements?
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Exposure Rate Instruments
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Contamination Instruments
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Exposure in Roentgens (R)
(Transfer of Energy)
Definition:
Measure of the charge produced in air from
ionization by x-rays or gamma rays
Units:
R, mR, µR, coulomb / kilogram
Page 24
Radiation Absorbed Dose (rad)
(Energy Absorbed)
Definition:
The energy deposited by ionizing
radiation in a unit mass of material
Units:
gray (Gy) = 100 rad
Page 25
Dose and Dose Equivalent
 Dose = Energy absorbed per unit mass.
 U.S Units: Rad = 100 erg/g
 SI Units: Grey = 1 joule/kg = 100 rad
 Different radiations do different amounts of
biological damage (from ionization).
 Units:
 U.S. Units: rem (where 1 mrem = 0.001 rem)
 SI Units: Sv (Sievert) = 100 rem
Page 26
Dose Equivalent (rem)
(Health Risk)
Definition:
A common scale for equating relative hazard
of various types of ionizing radiation in terms
of equivalent risk
Units: H = D × wr
rem = rad × wr
sievert (Sv) = 100 rem
Page 27
Dose Equivalent Example
 Your employee received 4 rad alpha,
1 rad beta, 2 rad X-ray, and 2 rad gamma.
What is the dose equivalent?
H = ( D ⋅ Wr )α + ( D ⋅ Wr ) β + ( D ⋅ Wr ) X + ( D ⋅ Wr )γ
= ( 4 ⋅ 20) + (1 ⋅ 1) + ( 2 ⋅ 1) + ( 2 ⋅ 1)
= 85 rem
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For X-rays and Gamma-rays Only
 1 R = 1 rad = 1 rem
 Implications?
Page 29
Ionizing Radiation – Why Worry?
 Ionizing radiation can lead to:
 Acute effects – high levels of radiation produce
effects such as nausea, fatigue, increased
temperature, blood changes, and death.
 Delayed effects – lower levels of radiation can
produce cancer, shortened lifespan, and
cataracts.
 Radiation is a weak carcinogen compared to
other materials.
Page 30
Estimated Dose to U.S. Citizens
Average U.S.
mSv/y
(mrem/y)
Source
Radon
Terrestrial
Cosmic
2.3
0.28
0.27
(230)
(28)
(27)
Medical Total
Other (Occupational)
29.8
0.37
(298)
(37)
Page 31
Sources of Radiation Dose
Where EUS 62 mSv (620 mrem) and the total from medical procedures is about 48%
(Source, NCRP Report No. 160, 2010)
Page 32
Minimizing Radiation Dose
 Time:
 Minimize time spent near a radiation source.
 Distance:
 Dose rate rapidly decreases with distance – stay
away from radiation sources.
 Shielding:
 Dose rate reduction.
Page 33
Radiation Levels at Oil and Gas Industry
Facilities
 Sources
 Pennsylvania DEP TENORM Study Report
 Incidental TENORM: A Guidance for State
Solid Waste Managers; Association of State
and Territorial Solid Waste Management
Officials
 An Overview of NORM in the Petroleum
Industry; ANL/DOE
 Radiation Protection and the Management of
Radioactive Wastes in the O&G Industry;
IAEA
Page 34
External Exposure
 PADEP looked at various types of facilities; found very little
potential for external doses exceeding the 100 mrem/yr public
limit
 Marcellus Shale
 Drill cuttings typically < 20 uR/h
 Sludges up to 150 uR/h
 Equipment surfaces in processing facilities typically 5 – 100
uR/h, but occasionally several thousand uR/h
 IAEA – “external dose rates from NORM…are usually so low
that protective measures are not needed.”
 Well heads
10 – 2,250 uR/h
 Production lines
30 – 400 uR/h
 Separators
up to 1,500 uR/h
Page 35
Potential Internal Exposure
 Most likely an issue at natural gas
processing facilities due to presence of Pb210 and Po-210 on surfaces; can be as high
as several thousand pCi/g
 Why? Because natural gas typically contains
10 – 1,000 pCi/L radon-222 gas
 Minimal contribution to lung dose from
increase in airborne radon
Page 36
Potential Internal Exposure (continued)
 From TENORM in:
 Produced water; up to 2,000 pCi/L total Ra
 Scales; up to several thousand pCi/g total Ra
 Sludges; up to several hundred pCi/g total Ra
 Risk of ingesting or inhaling NORM is minimized by:
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Use protective clothing, respirators as appropriate
No eating, drinking, etc.
Keep NORM contamination wet
Implement good housekeeping to prevent spread of
NORM contamination
Page 37
Radiological Health Risk (Cutting Right
To The Chase)
 Perception
 All radiation is lethal
 Being irradiated is not normal and is
something to be feared
 Powerful carcinogen
 Reality
 No sound evidence of carcinogenicity at low
doses
 Abundance of studies showing threshold
and/or hormesis
Page 38
LNT – What It Is
 Method of estimating
cancer risk from radiation
 High doses - Risk increases linearly
 Low doses – extrapolated,
Large errors
 Key, troubling aspects:
 No threshold
 Any dose increases risk
 Teaches us to be afraid of
Low doses
Page 39
LNT – No Basis In Biology
 All cells respond to stimuli, so LNT can be
rejected based on basic biology.
 Why would we extrapolate low dose effects
from high dose effects?
Page 40
Flawed Logic Behind LNT
Low dose
small amt DNA damage
may result in mutations
more cancer cells
and a higher cancer incidence
Page 41
Summary
 We live in a sea of radiation
 Three major types: alpha, beta, gamma
 Radiation detection – not all radiation is made
equal
 Sources/dose/exposure – what do we need to
quantify and what does it mean?
 LNT and Radiation Risk – keep it real!!!
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Alan Fellman, Senior Health Physicist
301-990-6006
[email protected]
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