This paper will discuss how the radioactive decay of naturally occurring radon-222 present in just-produced natural gas can lead to deposition of its radiogenic daughter, lead-210, and the subsequent radiogenic progeny within natural gas handling and onward processing facilities. It will be shown that these radionuclides can accumulate to potentially problematic activities that upon interaction with lubricating grease, which may have an elevated lithium content, can pose an additional worker safety issue and disposal challenge. The 22.3-year half-life of lead-210 will also allow for a multi-decade period of accumulation to occur and to persist after plant operations have ceased. The far shorter half-lives of its radiogenic progeny, especially that of polonium-210 (138 days), causes secular equilibrium to be quickly approached during operations and being achieved soon after plant operations have halted. The consequences of the highly efficient and unintended concentration of radon-222 and resultant enhanced lead-210 accumulation in cryogenic propane and propylene plants will be examined. A particular focus will be on the consequences of lithium present within grease that can preferentially concentrate radon-222 and lead-210 and its subsequent progeny in terms of neutron generation potential and consequences for adverse worker exposure. Specifically, the interaction between high energy alpha emissions produced during polonium-210 decay and lithium-7 (Po/Li) will be scrutinized with the ensuing neutron fluence generation estimated and the associated radiological risk.

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UNDERSTANDING LEAD-210-MEDIATED NEUTRON RADIATION
FROM TENORM CAN MAXIMIZE WORKER SAFETY
Donald Carpenter, PG Arcadis
Allison Wilding, CHP Arcadis
Les Skoski, Ph.D. RSO Arcadis
Thomas Fischer, PE Arcadis
William Thompson, PE NorthWestern Energy
Waste Management 2019 Conference
March 4, 2019

2. © Arcadis 2019
Unique
Geochemical
Behavior of
each
Radionuclide
must be
considered
Two different forms of TENORM
can be generated:
1) Radium-enriched Barium Sulfate
scale
2) Lead-210 from Radon-222
present in natural gas and
subsequently in propane and
propylene processing circuits
Lead-210 and its Decay Products Result From
Uranium Present in Reservoir Rock

3. © Arcadis 2019
Multiphasic Composition
Gas, Oil, and Produced Fluid
Radium-226 → Radon-222
Natural Gas Stream
CH4
CH4 CH4
CO2
CH4
CH4
C2H6
C3H8
H2S
Rn-222 Rn-222
Rn-222
CH4
CH4 CH4
CO2
CH4
CH4
C2H6
C3H8
H2S
Rn-222 Rn-222
Rn-222
Separation of Natural Gas From Produced Fluid
and Oil Also Results in the Removal of Radon Gas

4. © Arcadis 2019
Continued Radioactive Decay of Radon-222 Results
in Lead-210 Production and TENORM Formation
Radon-222 → Lead-210
Lead-210 in areas of Ra-222 concentration
CH4
CH4 CH4
CO2
CH4
CH4
C2H6
C3H8
H2S
Rn-222
Natural Gas Stream
Rn-222
Rn-222
Pb-210
Pb-210
Gas stream-entrained Lead-210 particles are also available for deposition within the processing facility

5. © Arcadis 2019
Commonality of Boiling Points Allows Radon-222 to
be Preferentially Partitioned into Propane/Propylene
-180
-160
-140
-120
-100
-80
-60
-40
-20
0
Methane Ethane Radon Propylene Propane Butane
Boiling Point (C°) of Gasses
“Radon Concentration Window”

6. © Arcadis 2019
This Results in the Dominant Partitioning of
Radon-222 into Propane/Propylene Fractions
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
Methane "Other Gasses" Propane
Rn-222
Up to a 75% Transfer Efficiency
Composition of a Typical Natural Gas (by Volume)

7. © Arcadis 2019
Consequently Radon-222 Activity Within
Propane/Propylene is Significantly Increased
0
200
400
600
800
1000
1200
1400
Methane Propane
Radon-222 Activity (pCi/L)
Lead-210 will concentrate in
propane/propylene processing
treatment trains
1,165 pCi/L
37 pCi/L

8. © Arcadis 2019
-
50,000
100,000
150,000
200,000
250,000
300,000
Lead-210 Activities (pCi/g)
Result can be Highly Elevated Lead-210
Activities in Impacted Portions of Plants
Maximum literature reported
value 1,100,000 pCi/g

9. © Arcadis 2019
The Lead-210 Sub-Chain Consists of Non-Gamma
Emitting Beta and Alpha Decays
Consider “in-growth” of progeny
Bismuth-210 5-Day Half Life
Essentially always in secular
equilibrium with parent

10. © Arcadis 2019
138-Day Half-Life of Polonium-210 Allows
Secular Equilibrium to also be Quickly Achieved
0%
25%
50%
75%
100%
0.0 0.5 1.0 1.5 2.0
Percentage of Polonium-210 Activity Relative
to Parental Lead-210
Po-210
Years

11. © Arcadis 2019
0
200
400
600
800
1000
1200
Alpha + Beta Radiation Counts per Minute
Background
Select samples at 20x background
Data consistent with isolated
accumulations of elevated Lead-210,
Bismuth-210, and Polonium-210
Radiological Data Document Preferential
Concentration of Pb-210 and its Decay Products

12. © Arcadis 2019
Highest Alpha and Beta Radiation Readings were
Associated with Lubrication Grease
Lithium is present in about 73% of all
greases
Greases can contain up to 7.5% lithium
stearate [LiO2C(CH2)16CH3]
Lithium represents about 2.4%, by weight,
of the stearate or about 1,800 mg/Kg in
the grease
1,100,000 pCi/g of Polonium-210 equates
to 2.4 * 10-4 mg/Kg
> 6 orders of magnitude of “excess”
Lithium mass

13. © Arcadis 2019
High Energy Polonium-210 Alpha Particle Interaction
with Lithium-7 (Po/Li) Results in Neutron Production
7Li + 4He → 10B + ᶯ + ᵧ
210Po → 206Pb + 4He
210Po + 7Li → 206Pb + 10B + ᶯ + ᵧ
Ratio of 3 neutrons per 1,000,000 alpha decays
Insufficient alpha energy to achieve required
“Neutron Reaction Threshold” to transmute Lithium-6
Lithium-7 forms 92.4% of natural lithium

14. © Arcadis 2019
-
100
200
300
400
500
600
700
800
900
1,000
0 50,000 100,000 150,000 200,000
Relationship of mrems per Year versus Activity of Polonium-210
(pCi/g)
Bounding Case Modeling of the Po/Li Reaction
Documents Potentially Adverse Neutron Generation
Polonium-210 (pCi/g)
mrems per Year
As noted, Lead-210 and
Polonium-210 activities can
significantly exceed this threshold
86,500 pCi/g

15. © Arcadis 2019
These Conditions are Conducive to Adverse
Neutron Fluence Generation
Proximity
High
Sustained
Production
Rate
Propane
Propylene
Circuit
Lithium-
Bearing
Grease
“Average” Radon-222 activity
in natural gas is sufficient

16. © Arcadis 2019
Safety Programs Must Include Differing Penetration
Potentials for Optimal Shielding Material Identification
Alpha
Beta
Gamma & Bremsstrahlung
Neutron
Paper Plastic Lead Concrete
Helium nucleus (2 protons, 2 neutrons): +2 charge
Electron: +1 or -1 charge
Photon: 0 charge
Neutron: 0 charge

17. © Arcadis 2019
Consequently Neutron Fluence can also Pose a
Non-Intrusive External Radiation Source
90 Units
10% reduction by
steel pipe wall
Adverse neutron fluence may be detectable via surface scanning
Can be proactively conducted prior to intrusive efforts helping to
maximize worker safety and proper material handling

18. © Arcadis 2019
It is not the “Presence” of Lead-210-Related Radiation
that is Problematic, it is its “Unexpected” Presence
Adverse worker exposure
Halting of scheduled work
Potentially problematic disposal
Significant cost and scheduling-related impacts
With proactive identification Lead-210-related radiation simply becomes another
“special waste” issue to be addressed during the course of the project

19. © Arcadis 2019
Understanding Lead-210-Mediated Neutron Radiation
from TENORM can Maximize Worker Safety
 Lead-210 and its Decay Products Result From Uranium Present in Reservoir Rock
 Commonality of Boiling Points Allows Radon-222 to be Preferentially Partitioned
into Propane / Propylene
 Highest Alpha and Beta Radiation Readings were Associated with Lubrication
Grease
 High Energy Polonium-210 Alpha Particle Interaction with Lithium-7 (Po/Li)
Results in Neutron Production
 Bounding Case Modeling of the Po/Li Reaction Documents Potentially Adverse
Neutron Generation
 It is not the “Presence” of Lead-210 that is Problematic, it is its “Unexpected”
Presence

20. © Arcadis 2019
Thank you!
donald.carpenter@arcadis.com
DONALD J. CARPENTER
Senior Vice President & Chief Geochemist
Registered and Certified Professional Geologist
AIPG, AK, IN, NY, PA, WI
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