October 1975
Environmental Monitoring Series
CARBON-14
REAC
Environmental Monitor
Off!
U.S.
oratory
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S.
Environmental Protection Agency, have been grouped into five series.
These five broad categories were established to facilitate further
development and application of environmental technology. Elimination
of traditional grouping was consciously planned to foster technology
transfer and a maximum interface in related fields. The five series
are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved
methods and instrumentation for the identification and quantification
of environmental pollutants at the lowest conceivably significant
concentrations. It also includes studies to determine the ambient
concentrations of pollutants in the environment and/or the variance
of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical
Information Service, Springfield, Virginia 22161.
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EPA-600/4-75-011
October 1975
ANALYSIS OF CARBON-14 AND TRITIUM IN REACTOR STACK GAS
by
Seymour Gold
Radiochemistry and Nuclear Engineering Branch
Environmental Monitoring and Support Laboratory
Cincinnati, Ohio 45268
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and
Support Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
11
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FOREWORD
Environmental measurements are required to determine the quality
of ambient waters and the character of waste effluents. The Environmental
Monitoring and Support Laboratory - Cincinnati conducts research to:
o Develop and evaluate techniques to measure the presence
and concentration of physical, chemical, and radiological
pollutants in water, wastewater, bottom sediments, and
solid waste.
o Investigate methods for the concentration, recovery, and
identification of viruses, bacteria and other microbiological
organisms in water. Conduct studies to determine the responses
of aquatic organisms to water quality.
o Conduct an Agency-wide quality assurance program to assure
standardization and quality control of systems for monitoring
water and wastewater.
With future reliance on nuclear power stations for energy sources
as a possibility, environmental monitoring programs must be improved and
tested to measure accurately the radiation exposure to concerned indivi-
duals. The Environmental Protection Agency has been engaged in studies
of this nature to develop methodology and to provide information for
evaluating such monitoring programs. One aspect of this type of study is
the development of a technique to measure the concentration and the
chemical species of two biologically significant radiogases, H and
which are discharged into the environment by these power stations.
Dwight G. Ballinger
Acting Director
Environmental Monitoring and Support Laboratory
Cincinnati
iii
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ABSTRACT
The analysis of gases from nuclear power stations includes
determination of tritium and l^C in several molecular forms. In this
procedure, tritium water vapor is collected in a freeze trap, and -^C
(as C02) is collected by precipitation in bubblers.
Water vapor, hydrogen, carbon dioxide, and methane gas carriers are
added to a gas sample. The sample is drawn into the gas analysis system
by means of a vacuum pump and is flushed through the system with purified
air. HTO is collected in a freeze trap at -80't, and 14-C02 ^-s precipitated
as barium carbonate with freshly prepared barium hydroxide in a bubbler.
Water mist from the bubblers is then removed from the gas stream as the
sample passes through a silica gel spray trap. The gas is then passed
through the catalytic oxidation chamber, which converts the remaining
gaseous hydrogen and carbon compounds to water and carbon dioxide. The
water is collected in a second freeze trap, and the C02 is precipitated
in a second bubbler. The water fractions are weighed and then rinsed with
dioxane into plastic vials and counted by liquid scintillation. The
barium carbonate precipitates are centrifuged, washed, and transferred to
stainless steel planchets for weighing. The precipitates are then
transferred to glass vials and counted by liquid scintillation as a
suspension.
Minimum detectable levels for both -*H and -"-^C are 0.4 picocuries
per sample for samples varying in size from 1 cc to 20 liters.
iv
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ACKNOWLEDGEMENTS
The valuable assistance of Mrs. Betty Jacobs, Physical Science
Technician, in the initial stages of the investigation is gratefully
acknowledged. In addition, Mrs. Eleanor Martin, Physical Science
Technician, and Mr. David Currie, University of Cincinnati Co-op Student,
tested the procedure and provided pertinent comments toward its operation.
Their efforts are also greatly appreciated.
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INTRODUCTION
The analysis of gases from nuclear power stations includes
determination of tritium and ^C in several forms. In this procedure,
tritium water vapor and l^C in C02 are collected in a freeze trap and by
chemical absorption, respectively. All other species of -*H and l^C are
catalytically oxidized at 550 C to water and C02 and then collected as
above. Early workers used copper oxide to convert hydrogen and carbon
monoxide to 1^0 and C02.'l»2) More recently, (3) tritium in the atmosphere
has been oxidized to HTO with palladium. In this procedure, a more active
catalyst is used to convert all forms of hydrogen and carbon compounds,
including methane, ™' to H20 and C02.
Water vapor, hydrogen, carbon dioxide, and methane gas carriers are
added to a gas sample. The sample is drawn into the gas analysis system
by means of a vacuum pump and is flushed through the system with purified
air. HTO is collected in a freeze trap at -80C and 1^C02 is precipitated
as barium carbonate with freshly prepared barium hydroxide. (->) Water mist
from the bubblers is removed from the gas sample at this point by passing
it through a silica gel spray trap. The gas is then passed through a
catalytic oxidation chamber that converts the remaining gaseous hydrogen
and carbon compounds to water and carbon dioxide. The water is collected
in a freeze trap, and the C02 is collected as barium carbonate in a
bubbler, as before. The water is rinsed with dioxane into a plastic vial
and counted by liquid scintillation. The barium carbonate precipitates
are centrifuged, washed, and transferred to stainless steel planchets for
weighing. The precipitates are then transferred to glass vials, and
counted by liquid scintillation as a suspension.(°)
MATERIALS AND METHODS
REAGENTS
Acetone
Barium chloride, BaCl2: 0.5 M (C02-free)
Carbon dioxide carrier: gas
1,4-Dioxane, C4Hg02: scintillation grade
Distilled water: boiled (C02~free)
Dry ice
Hydrogen carrier: gas
Methane carrier: gas
Palladium sponge (+40 mesh); supplier: Mathey Bishop, Malvern, PA
Scintillation solution (dioxane), prepared reagent
Scintillation solution (toluene), prepared reagent
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Sodium hydroxide, NaOH: 18 M (CC^-free)
Toluene, €51150113: scintillation grade
Prepared Reagents:
Scintillation solution (dioxane) for tritiated water: mix thoroughly
7 g PPO, 1.5 g bis-MSB, and 120 g naphthalene diluted to 1 liter with
1,4-dioxane (scintillation grade). Use 16 ml per sample.
Scintillation solution (toluene) for Barium l^Carbonate: dissolve
6 g PPO, 0.25 g dimethy1-POPOP diluted to 1,000 ml with toluene
(scintillation grade). Add 45 g Cab-o-sil and stir with a magnetic
stirrer. Use 16 ml per sample.
EQUIPMENT
Tube furnace with temperature controller to operate at 550 + 20 C
with a minimum heating length of 10 cm.
Pyrex tube, 9-mm OD. Fill to 10 cm length with catalyst and place
catalyst tube within furnace.
Gas handling system (see Figure 1):
Freeze traps (see Figure 2)
Flowmeter with range of 100 to 1,000 cc per min
Gas bottle, glass sample holder, 500 cc
Gas bubblers (midget impingers) (see Figure 3)
Glass-teflon needle valve to regulate flow
Glass stopcocks, straight and three-way, standard taper plugs
with 2-mm bore
Manometer, 0 to 8,000 mm Hg range
Pyrex tubing, 7-mm OD
Rubber tubing for connections
Vacuum pump
Air purification:
Three tubes consisting of indicating silica gel, Ascarite 8-20
mesh, and 13X-1.68 mm molecular sieve pellets (see Figure 1 for
order),
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Rubber
Septum
Ascorite
Mercury
Manometer•/
MAIN ~
SAMPLE
INTAKE
Dry Ice and
Acetone
System
Cut-Off
Valve
CO. Bubblers
Figure 1. Gas handling system
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14/20 Joint
I4/2O Joint
Figure 2. Freeze trap assembly.
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rd
E
o
to
£
v
.24/40 Joint
Figure 3. Gas bubbler
"midget impinger"
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GAS ANALYSIS METHOD
A. Flushing the gas handling system (Figure 4).
With the pump running and the furnace at the proper temperature, open
all valves necessary to allow air to flow through valves U-5, S-2,
S-l, U-2, U-l, L-l, and L-2; have valves U-3 and U-4 closed. Flush
the system for 10 min at 500 ml per min, or longer. When flushing
the system, substitute glass tubing in place of the freeze traps and
bubblers.
B. Evacuating gas sample bottle (Figure 5).
1. After flushing the system, close valves U-5, L-l, and L-2. Adjust
valve U-l to connect manometer and leg between U-l and L-l to system.
Adjust valve U-3 to evacuate sample bottle (open to system, closed to
air intake). Open valve U-4 to start evacuation. At this point, S-2,
S-l, and U-2 are also open.
2. When 0-mm pressure is reached, turn valve U-3 to allow clean, dry
air to enter sample bottle; then turn the valve to evacuate again.
Repeat twice.
3. Close valves U-3 and U-4.
C. Preparing the gas sample bottle for blank run.
1. Flush the system (see A) and evacuate the gas sample bottle (see B)
2. When evacuation is completed, close valves S-2 and S-l to hold
vacuum in sample bottle, and leg between S-2 and U-5.
3. Shut off valve U-4. Open valve U-3 to allow the rest of the
system to come to equilibrium with the atmosphere. Then shut off
valve U-3.
D. Filling the gas sample bottle for normal sample run (Figure 6).
1. Flush the system (see A) and evacuate the sample bottle (see B).
When evacuation is complete, close valve S-2 to keep sample from
going into the line above sample bottle. Valves S-l, U-2, and U-l
should be open.
2. Attach sample to main sample intake. Calculate pressure needed
to fill sample bottle with the volume desired for analysis as follows:
Volume of gas (room conditions) in bottle
pressure in bottle .. £ i_ ^-i
= —c : : x volume of bottle.
atmospheric pressure
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Rubber
Septum
Ascorite
U-
Dry Ice
Acetone
System
Cut-Off
Valve
C02 Bubblers
Figure 4. Gas flow through the system.
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00
U-!
S-l
U-2
U-3
EVACUATE
U-4
Figure 5. Evacuating the gas sample bottle.
L-2 A (
System
Cut-Off
Valve
Vacuum
Pump
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S-2
Mercury
MonometerV Gos
jf_ Sample
MAIN ~
SAMPLE
INTAKE
Bottle
U-l W S-l
U-2
Figure 6. Filling the evacuated gas bottle with the sample.
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Open valve L-l to allow sample to flow from main sample intake to gas
bottle. Shut L-l when desired pressure is reached. Now close S-l.
Flush the lines between L-l and S-l alternating vacuum and clean air,
using valve U-2.
E. Adding carrier to the sample bottle.
1. Carriers are added to the sample bottle by first injecting them
into the rubber septum above sample bottle. Fill a hypodermic syringe
with the proper amount of carrier and inject through rubber cap. With
valve S-l closed, open valve S-2 to allow carrier to be drawn into
bottle, then close the valve. When adding water to the sample, allow
air into the line first so that the vacuum will not cause the addition
of more than is required. After carriers are added, open valves S-2
and U-5 to equalize pressure with the atmosphere in all lines except
for gas bottle between S-l to U-5.
2. Disconnect the manometer by turning valve U-l. Connect lower
system with upper system by turning valve L-l.
F. Gas flow during analyses (Figure 4).
1. After sample bottle has been prepared and carriers added, place
freeze traps and bubblers in proper positions. Cool the bottom of the
freeze trap in a dry ice/acetone mixture in dewar containers. Close
needle valve. Open valves L-2, L-l, U-l, U-2, and S-2; then open
needle valve slowly until a few bubbles escape in bubblers.
2. Open valve S-l slowly, watching bubblers to be sure that there is
no excess pressure or vacuum in the sample bottle. Open valve U-5
slowly, then adjust needle valve to proper flow rate. Allow gas sample
to flow through for a time equal to 6 x [(vol. sample bottle, cc)/flow
rate in cc/min)] + 5 min. Upon completion of analysis, close valve
L-2, remove freeze traps and bubblers, and replace with glass tubing.
10
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PROCEDURE
Procedure time for one sample is 2 to 3 hours, depending on sample
size.
1. Connect the apparatus for gas analysis as shown in Figure 1.
2. Prepare fresh reagent in the bottom of each of the two pairs of gas
bubblers (Figure 3) by mixing approximately 20 ml boiled distilled
water, 1.0 ml 0.5 M BaCl2 solution (CC^-free), and 10 drops 18 M NaOH
(CC^-free) in each bubbler. (Two bubblers are used in series to en-
sure absorption of any CC>2 not trapped in the first bubbler.) Bring
volume to 25 ml with additional boiled distilled water. Close the
bubblers and seal the ends of the inlet and outlet tubes with rubber
tubing seals (a short piece of rubber tubing with a piece of solid
glass rod in one end) to prevent absorption of C02 from the air.
3. Weigh two freeze trap assemblies (Figure 2) to + 0.1 mg. Each
assembly consists of a freeze trap with a hollow glass stopper at the
inlet end and a small rubber tubing seal at the outlet end.
4. Flush the system as described in A of the preceding section and
evacuate the gas bottle as in B.
5. Prepare the gas sample bottle either for a blank or for the gas sample
to be analyzed as in the preceding sections C or D. Place bubblers
and freeze traps in the system. Cool freeze trap with dry ice/acetone
mixture. Add 3 cc CC^ carrier, 3 cc CH^ carrier, and 10 cc H^ carrier
at room conditions as in section E. Add 3.0 mg water with a microliter
syringe if the sample contains no water vapor.
6. With the furnace temperature at 550 C, pass the gas sample through
the system at a rate of approximately 100 cc/min, as in section F.
7. After the sample has been completely swept from the sample chamber,
turn off the vacuum pump. Remove the bubblers and attach rubber
tubing seals. Remove the freeze traps and seal with hollow glass
stopper and rubber tubing seals (see step 3).
8. Transfer each of the solutions containing the BaCO-j from the first
pair of bubblers with boiled distilled water, in a wash bottle, to
two 50-ml polypropylene tubes with caps, and heat in a warm-water
bath. Cap the tubes, centrifuge, discard the supernatants, and
combine the precipitates. Do the same for the second pair of bubblers.
9. Wash each of the combined precipitates with 30 ml boiled distilled
water. Cap the tubes and centrifuge and discard the wash solutions.
10. Take up each precipitate in 5 ml boiled distilled water and transfer
quantitatively to tared stainless steel planchets. Dry under a heat
11
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lamp, cool to room temperature, and weigh. Calculate theoretical
yields from carrier volume by correcting to STP conditions. (At 20C
and 760 mm, the 3.0 cc C02 or 3.0 cc Ctfy should give 24.61 mg BaC03
for a 100 percent chemical yield.
11. Quantitatively scrape each dry BaC03 precipitate from the planchets
with a clean rubber policeman and transfer each one to a glass
scintillation vial. Add 15 ml scintillation solution (toluene), and
shake thoroughly. Place in liquid scintillation counter and allow
samples to dark adapt before counting.
12. Prepare background and standard -C samples as follows:
background - 15 ml scintillation solution (toluene)
20 mg BaC03
100 X toluene
standard - 15 ml scintillation solution (toluene)
20 mg BaC03
100 X !4c std in toluene.
Count alternately with samples at predetermined settings.
13. After the two freeze traps containing HTO have reached room temperature,
weigh carefully. Determine yields, corrected to STP conditions. (The
3.0 cc CH^ + 10 cc H2 should give 11.98 mg H2) for a 100 percent
chemical yield. )
14. Rinse the water sample from each trap into separate glass scintillation
vials with 4 ml each of dioxane. To each, add 16 ml of scintillation
solution (dioxane) and mix thoroughly. Place in liquid scintillation
counter and allow to dark adapt before counting.
15. Prepare background and HTO standard samples as follows:
^H background - 16 ml scintillation solution (dioxane)
3.5 ml dioxane
500 X H20 (distilled)
% standard - 16 ml scintillation solution (dioxane)
3.5 ml dioxane
500 X tritiated water.
Count alternately with samples at predetermined settings.
12
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CALCULATION
Calculate the concentration of the tritium and -^C activity in
picocuries per milliliter as follows:
D =
2.22 x EVR
where: C = net count rate, counts per min
E = counter efficiency for tritium or for
V = milliliters of sample used
R = fractional chemical yield
2.22 = conversion factor from d/m to picocuries.
METHOD CAPABILITIES
The sensitivity of this method is shown in Table 1. The decontami-
nation factor is greater than 10 since no other nuclides are detectable
in the counting vial.
Table 1. Sensitivity
Nuclide
3H
14C
Counting
efficiency
44%
62%
Background
c/m
8.4
18.4
MDL*
(pCi/cc)
0.4/1 cc sample
0.001/400 cc "
0.4/1 cc sample
0.001/400 cc "
Average
chemical
yield
100
100
* The minimum detectable level when counted 3 times for 300 min each.
13
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REFERENCES
Taylor, Guy B., An Apparatus for the Analysis of Complex Mixtures of
Gas, Ind. Eng. Chem. 6:845-848 (1914).
Burrelle, G. A. and Oberfell, C. G., The Use of Copper Oxide for
Fractionation Combustion of Hydrogen and Carbon Monoxide in Gas
Mixtures, Ind. Eng. Chem. 8:228-231.
Ostland, M. G., A Rapid Field Sampling for Tritium in Atmospheric
Hydrogen, Report ML 70075, Rosenstiel School of Marine and Atmospheric
Sciences, Univ. of Miami, Miami, Florida (1970).
Anderson, R. B. , Stein, K. C., Feenan, J. J. and Hofer, L. J. E.,
Catalytic Oxidation of Methane, Ind. & Eng. Chem. 53,10:809-812 (19611.
Wilson, C. L. and Wilson, D., Comprehensive Analytical Chemistry,
Vol. 1A, Classical Analysis, Elsevier Publishing Co., New York, N. Y.,
1959, p. 306.
Ott, D. G., Richmond, C. R., Trujillo, T. T. and Foreman, H. , Cab-o-Sil
Suspensions for Liquid Scintillation Counting, Nucleonics 17,9:106-108
(1959).
14
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/4-75-011
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
ANALYSIS OF CARBON-14 AND TRITIUM IN REACTOR STACK GAS
5. REPORT DATE
October 1975 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Seymour Gold
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
10. PROGRAM ELEMENT NO.
1HA327
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
In-house
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The analysis of gases from nuclear power stations include determination of tritium
and C in several molecular forms. In this procedure, tritium water vapor is col-
lected in a freeze trap, and ^C (as C02) is collected by precipitation in bubblers.
Water vapor, hydrogen, carbon dioxide, and methane gas carriers are added to a gas
sample. The sample is drawn into the gas analysis system by means of a vacuum pump
and is flushed through the system with purified air. HTO is collected in a freeze
trap at -80°C, and l C02 is precipitated as barium carbonate with freshly prepared
barium hydroxide in a bubbler. Water mist from the bubblers is then removed from
the gas stream as the sample passes through a silica gel spray trap. The gas is then
passed through the catalytic oxidation chamber, which converts the remaining gaseous
hydrogen and carbon compounds to water and carbon dioxide. The water is collected in
a second freeze trap, and the C02 is precipitated in a second bubbler. The water
fractions are weighed and then rinsed with dioxane into plastic vials and counted by
liquid scintillation. The barium carbonate precipitates are centrifuged, washed, and
transferred to stainless steel plachets for weighing. The precipitates are then
transferred to glass vials and counted by liquid scintillation as a suspension.
Minimum detectable levels for both 3H and 14C are 0.4 picocuries per sample for
samples varying in size from 1 cc to 20 liters.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Carbon-14
Tritium
Flue gases—combustion products
13-B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
21
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
U. S. GOVERNMENT PRINTING OFFICE 1975-657-695/5327 Region No. 5-11
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