EMSL-LV-0539-17
RADIOCHEMICAL ANALYTICAL PROCEDURES FOR
ANALYSIS OF ENVIRONMENTAL SAMPLES
U.S. ENVIRONMENTAL. PROTECTION AGENCY
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
March 1979
Prepared under
Memorandum of Understanding
No. EY-76-A-08-0539
for the
U.S. DEPARTMENT OF ENERGY
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DISCLAIMER
This report was prepared as an account of work sponsored by the United
States Government. Neither the United States nor the United States Department
of Energy, nor any of their employees, nor any of their contractors, subcon-
tractors! or their employees, make any warranty, express or implied, or assume
any legal liability or responsibility for the accuracy, completeness, or use-
fulness of any information, apparatus, product or process disclosed, or repre-
sent that its use would not infringe privately owned rights.
This document is available to the public through the National Technical
Information Service, U.S. Department of Commerce, Springfield, Virginia 22161.
Price code: paper copy A06, microfiche A03
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EMSL-LV-0539-17
RADIOCHEMICAL ANALYTICAL PROCEDURES FOR
ANALYSIS OF ENVIRONMENTAL SAMPLES
Edited by
F. B. Johns, P. B. Hahn, D. J. Thome, and E. W. Bretthauer
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Las Vegas, Nevada 89114
March 1979
Prepared under
Memorandum of Understanding
No. EY-76-A-08-0539
for the
U.S. DEPARTMENT OF ENERGY
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ABSTRACT
This manual is a compilation of the chemical and physical procedures
used at the Environmental Monitoring and Support Laboratory-Las Vegas for
determining radionuclides in environmental surveillance samples. It super-
sedes the "Handbook of Radiochemical Analytical Methods" published as
EPA-680/4-75-001 in February 1975.
It should be noted that the procedures in the current compilation are
intended for use in processing relatively large numbers of samples in the
shortest possible time for environmental radiological surveillance and,
therefore, in some cases represent a compromise between precise analytical
determination and adequate determination for surveillance purposes.
ii
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ADDENDUM AND CORRECTION
RADIOCHEMICAL ANALYTICAL PROCEDURES FOR ANALYSIS OF ENVIRONMENTAL SAMPLES,
U.S. Environmental Protection Agency, EMSL-LV-0539-17, March 1979.
Isotoplc Determination of Plutonium, Uranium, and Thorium in Water, Soil, Air
and Biological Tissue, page 33.
If a sample has not previously been dry ashed, the ion exchange separation can
be modified to isolate polonlum-210 in addition to uranium and thorium.
Add Po-208 or Po-209 tracer along with other Isotoplc tracers prior to wet
decomposition of the sample and proceed to step 10.3.8.
URANIUM (page 43}
10.3.8 Remove Iron from the column with a fresh solution prepared by mixing
109 ml of 12N. hydrochloric acid with 31 ml of distilled water and 5
ml* of 50% hydriodlc add. Rinse the column reservoir three times with 15-ml
portions of this solution and elute at 3 ml/rain. Add an additional 100 ml of
the solution and elute at the same rate. Discard the eluates.
10.3.9 Rinse the column with two 15-ml portions of 9N. hydrochloric acid
followed by 5 ml 1.2]* hydrochloric acid to remove residual hydriodic
ac'1d. Discard the eluates.
10.3.10 Elute uranium with 50 ml 1.2N. hydrochloric add at 3 ml/mln.
Collect the eluate in a 100-ml glass beaker. Add 0.5 ml
concentrated sulfuric acid to the beaker and evaporate to fumes of sulfuric
add. Add 5 drops 30% hydrogen peroxide and again evaporate to sulfuric acid
fumes. Save for electrodeposition of uranium, step (10.4.12).
* Correction from 50 ml
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POLONIUM-2LO
NOTE: If polonium Is not to be determined follow original
Instructions except for correction noted for the uranium separation.
10.3.lOa Elute polonium with 150 ml concentrated (1614) nitric add at a rate
of 1 ml/min. collect the eluate 1n a 250 ml beaker.
NOTE: If the column 1s to be used for the subsequent thorium separation,
Immediately pass 30 ml 7.2N, nitric add through the column to avoid
possible decomposition of the resin. The resin 1n the column should not be
allowed to remain in concentrated nitric acid for extended periods of time due
to potential safety considerations.
10.3.10b Add 0.5 ml concentrated sulfur1c acid to the polonium eluate and
evaporate to fumes of sulfuric add to expel the nitric acid. If
the solution turns dark during the evaporation, decompose any organic matter
with the addition of a small amount of 30% hydrogen peroxide (drops to few
ml). Do not allow the sample to go to dryness.
10.3.10c After the sample has been evaporated to sulfuric acid fumes to expel
nitric add and any hydrogen peroxide, remove from the hot plate and
add 5 ml 1.2N. HCL. Transfer to a 20 ml plastic liquid scintillation vial with
an additional 5 ml 1.2N HCl.
10.3.10d Place a nlckle disc (diameter equal to outside diameter of vial
mouth) on the mouth of the vial and seal with a plastic cap having a
plastic Insert (not aluminum foil).
10.3.10e Invert vial and allow to set for 3-4 days to spontaneously plate the
polonium on the nickle disc.
10.3.10f Remove disc, rinse with water followed by ethanol, allow to dry and
count on an alpha spectrometer for Po-210 and the Po tracer.
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THORIUM
10.3.11 Evaporate the combined 9IY thorium eluates (from step 10.3.4) to dry-
ness on a hot plate. Dissolve the residue with 20 ml 7.2N^ nitric
acid, plus 5 drops of 30% hydrogen peroxide. Cover and reflux for 45 minutes
i
on the hot plate. Add 3 more drops 301 hydrogen peroxide and continue to heat
for 15 minutes. Cool to room,temperature.
10.3.12 Transfer the solution to the column reservoir, rinsing the beaker
with a minimum of 7.2N. nitric acid. Elute at 3 ml/min and discard
the eluate. Rins* the reservoir with three 10-ml portions 7.2N. nitric acid
and drain at the same rate. Wash the column with 100 ml 7.2£ nitric acid and
>
discard eluate.
10.3.13 Rinse the reservoir with 5 ml 9N hydrochloric acid and drain at 3
ml/min. Discard the eluate. Elute the thorium with 100 ml 9N.
hydrochloric acid at 3 ml/min and collect the eluate In a 150-ml glass beaker.
Add 0.5 ml concentrated sulfuHc acid to the beaker and evaporate to sulfuHc
acid fumes. Add 5 drops 30% hydrogen peroxide and again evaporate to sulfurlc
acid fumes. Continue with the electrodeposltlon of thorium at step (10.4.12).
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TABLE OF CONTENTS
Page
Determination of Gross Alpha and Beta in Water 1
Determination of Gross Beta Activity in Airborne Particulates ... 6
Determination of Radon-222 in Air, Water, and Natural Gas 10
Determination of Radium-226 and Radium-228 in Water, Soil, Air, and
Biological Tissue 19
Isotopic Determination of Plutonium, Uranium, and Thorium in Water,
Soil, Air, and Biological Tissue 33
Analysis of Polonium-210 in Soil and Air Filters 49
Determination of Strontium-89 and Strontium-90 in Milk 55
Determination of Strontium-89 and Strontium-90 in Water, Vegetation,
Soil, and Biological Tissue 65
The Collection and Determination of Tritium in Air 74
Determination of Low-Level Tritium in Water (Alkaline Electrolytic
Enrichment) 81
Determination of Tritium in Water and Biological Tissue (Direct
Method) 87
Isotopic Analysis by Gamma Ray Spectra Using Lithium-Drifted
Germanium Detectors 92
Isotopic Analysis by Gamma Ray Spectroscopy Using Thallium-Activated,
Sodium Iodide Crystals 96
Determination of Radiokrypton, Radioxenon, and Tritiated Methane
in Air 102
ili
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LIST OF FIGURES
Number Page
1 Typical adsorption curves 5
2 Radon separation apparatus 16
3 Radon bubbler 17
4 Radon emanation apparatus 18
5 Radon bubbler 30
6 Radon emanation apparatus 31
7 Lucas scintillation cell 32
8 Ion exchange column, strontium elution . . 63
9 Typical efficiency curves 64
10 Ion-exchange apparatus 73
11 Field box 79
12 Field station 80
13 Alkaline electrolysis cell 86
14 Distillation apparatus 91
15 Noble gas separation apparatus ...... 109
iv
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DETERMINATION OF GROSS ALPHA AND BETA IN WATER
1. Principle
1.1 All natural waters contain varying amounts of radioactivity, either
natural or man-made. A screening technique is used to determine the
quantities of alpha or beta emitting radionuclides present. A known volume of
sample is concentrated, dried in a planchet and counted in a low-background
internal proportional counter. The activity determined by this method is not
indicative of any specific nuclide. Tritium and other volatile radionuclides
(for example, radioiodine) cannot be determined by this method.
2. Application
2.1 The method is applicable for the analysis of either total, dissolved,
or suspended solids in water for gross alpha and beta.
3. Range
3.1 No range has been established.
4. Interferences
4.1 The evaporated sample residue, by acting as an absorber for the alpha
and beta particle, is the largest interference. Moisture absorbed or
trapped by the residue also serves as an interference.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest concen-
tration of radioactive material sampled that has a 95% probability of
being validly detected.
A.66 S
LLD =
2.22 x E x S
where 4.66 = 2/2 k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
S, = standard deviation of the background
b
2.22 = dpm/pCi
E = fractional counting efficiency
S = sample size
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
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6. Precision and accuracy
6.1 Gross alpha and beta measurements by this method have an inherent
inaccuracy in that samples may contain alpha and beta emitters with
energies different from the calibration standards. In such circumstances, the
counting efficiencies (cpm/dpm) used will not produce accurate information for
the radionuclides in the sample. Therefore, this method is, at best, good only
for semiquantitative analysis. The importance of precision (or repeatability)
is that a given water source may be checked periodically for gross alpha and
beta and any significant changes in the results from one time to the next may
require specific analysis. It is necessary then that such changes be real and
not a result of poor precision.
6.2 Analytical results of spiked water containing 50 pCi cesium-137 and
5 pCi/liter americium-241 indicate accuracies with deviations from
known values of less than 10% at the 95% confidence level.
7. Shipment and storage of samples and sample stability
7.1 Samples for gross alpha and beta analysis must be preserved with 20
ml of concentrated nitric acid per 3.7 liters. However, judgment
must be made before acidifying as to type of analysis desired. If total gross
alpha and beta are required, the acid treatment must be made at time of sam-
pling. If a differentiation between dissolved versus suspended radionuclides
is desired, the sample should be filtered in the field, acid added to the aque-
ous portion and the two fractions submitted to the laboratory.
7.2 With proper preservation the storage time of the sample depends en-
tirely on the half-life of the contained radionuclides.
8. Reagents
8.1 Alcohol, ethyl: 95% reagent grade
8.2 Nitric acid, concentrated: 70% reagent grade
8.3 Nitric acid, 3N: Add 187 ml concentrated nitric acid to 600 ml dis-
tilled water. Cool, and dilute to 1000 ml.
9. Apparatus
9.1 Beakers: 250 ml
9.2 Cylinder, graduated: 200 ml
9.3 Hot plate
9.4 Low-background, thin-window proportional counter
9.5 Planchets: 2-inch
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10. Procedure
10.1 Transfer a 200-ml portion of the well-shaken acidified sample to a
250-ml beaker. If the sample has not been filtered and the activity
of the suspended solids is required, filter a 1000-ml portion through a Whatman
No. 2 filter paper. Add a 200-ml portion of the filtrate to a 250-ml beaker.
10.2 Add 10 ml concentrated nitric acid and evaporate slowly to near dry-
ness. Quantitatively transfer to a tared planchet using 3N_ nitric
acid. Evaporate and dry at 105° C. Cool. Weigh for self-absorption correction
and count for 50 minutes in the low-background proportional counter.
10.3 Place the filter (either from the field or laboratory) in a tared
planchet, saturate with ethyl alcohol and ignite. Cool, weigh for
self-absorption correction and count for 50 minutes in a low-background propor-
tional counter.
11. Calibration
Counting efficiency of the low-background beta counter is determined
by three factors: geometry, backscatter, and self-absorption. The
first two, geometry and backscatter, are fairly well established for each in-
strument, while the third, self-absorption, is dependent on the sample. There-
fore, "self-absorption curves", similar to the curves illustrated in Figure 1,
must be prepared. Samples with known activity but with varying sample weights
are prepared and the data plotted as indicated in Figure 1. The cesium-137 and
americium-241 standards are both traceable to the National Bureau of Standards.
11.1 Prepare reference data for counting efficiency versus water solids
by adding known amounts of standard cesium-137 to varying aliquots
of tap water. Add 5 ml concentrated nitric acid.
11.2 Evaporate to near dryness and quantitatively transfer to a tared
planchet. Dry and heat to 105 C. Cool and reweigh.
11.3 Repeat 11.1 and 11.2 using americium-241.
11.4 Count gross beta standard for 50 minutes and gross alpha standards
for 100 minutes.
11.5 Correct counting data for background and plot counting efficiency
versus mg of solids on planchet.
11.6 Calculate % alpha activity that is detected in beta channel of
counter.
12. Quality control
12.1 Every tenth sample is reprocessed as a blind duplicate, and bi-monthly
cross-check samples are obtained from the Quality Assurance Branch,
EMSL-LV. A close evaluation of these data is made and corrective action taken
as indicated.
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13. Calculations
13.1 Gross alpha (pCi/1) = y^
fc fafc
EV
where A = net counts per minute
2.22 = dpm/pCi
E = fractional counting efficiency
(obtained from calibration curve)
V = volume (liters)
13.2 Gross beta (pCi/liter) = f^lv
where A = net counts per minute
D = fraction of alpha activity
2.22 = dpm/pCi
E = fractional counting efficiency
(obtained from calibration curve)
V = volume of sample (liters)
14. References
14.1 Handbook of Radiochemical Analytical Methods, EPA-680/4-75-001
February 1975.
14.2 Tentative Reference Method for the Measurement of Gross Alpha and
Gross Beta Radioactivities in Environmental Waters, EPA-680-4/75-005,
June 1975.
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0.6
0.4
0.2
Tl I I I 1 I I I 1 I I I I I I I I I I I I I T I I I I I I I I I I I I
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
SAMPLE THICKNESS, mg/cm2
Figure 1. Typical Adsorption Curves.
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DETERMINATION OF GROSS BETA ACTIVITY
IN AIRBORNE PARTICULATES
1. Principal
1.1 All airborne participate samples contain both natural and man-made
radioactivity. A screening technique is used to determine the quan-
tities of beta-emitting nuclides. Based on results obtained from this screen-
ing technique, the need for radiochemical analysis is determined.
2. Application
2.1 This method is applicable for determination of gross beta concentra-
tion of airborne particulates collected on a filter, or any other
material collected on a filter, where self-absorption can be ignored (for ex-
ample, swipes).
3. Range
3.1 In reality there is no upper range. A practical upper range is ap-
proximately 5 x 10s beta counts per minute. Above this level, there
is a significant decrease in counting efficiency.
A. Interferences
A.I Since this is a gross analysis, there are no interferences from other
nuclides. Samples collected over a long period of time, or samples
collected in an area with a high concentration of airborne particulate matter,
may result in filter overloading. Part of the collected particulate matter
may then flake off the filter, yielding a nonrepresentative sample.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest concen-
tration of radioactive material sampled that has a 95% probability of
being validly detected.
A. 66 S.
b
LLD = 2.22 x E x S
where A.66 = 2^2 k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
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Sfe = standard deviation of the background
2.22 = dpm/pCi
E = fractional counting efficiency
S = sample size
6. Precision and accuracy
6.1 Inaccuracies are primarily attributable to samples containing beta
emitters of different energies than the calibration standards, a
large amount of particulate matter being accumulated on the filter creating
some self-absorption, and some of the collected particulate matter flaking off
the filter.
6.2 Analyzing filters containing known amounts of strontium-90 and ce-
sium-137 produces results within 10% of the known value at the 95%
confidence level. For standard samples close to background, the 95% confi-
dence interval is approximately 5 pCi per filter.
7. Shipment and storage of samples and sample stability
7.1 Most filters are received in the mail. Therefore, careful handling
is not of prime consideration.
8. Reagents
8.1 No reagents are used.
9. Apparatus
9.1 Proportional beta counter with 12.7-cm window
9.2 Filters; various types as required. No larger than 10.2 cm.
10. Procedure
10.1 Air filter samples with their field data sheets enclosed are received
in the mail and their receipt date is documented.
10.2 The air filter is placed in a glassine envelope. The information
from the field data sheet is then recorded on an IBM Hollerith punch
card. The filter, data sheet, and punch card, along with two duplicate punch
cards, are sent to the gross beta counting room.
10.3 Three beta counts are made. The first count is made when the sample
is received in the counting room, the second count is made at the
date of collection plus 5 days, and the third count is made at the date of
collection plus 12 days. If the sample has not been received by the date of
collection plus 4 days, the first count is cancelled. If the sample is re-
ceived after the date of collection plus 5 days, the sample receives an initial
beta count upon receipt and a second beta count 7 days later.
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10.4 If the initial beta count exceeds 50 counts per minute, an isotopic
analysis by gamma spectroscopy is performed.
10.5 A daily gross beta report is compiled based on the gross beta anal-
yses completed on the previous day.
10.6 The last 2 beta counts are used to calculate a gross beta concentra-
tion at the midpoint of collection. This extrapolated gross beta
concentration is compiled each month into a monthly gross beta report, contain-
ing the results for all air sampling stations active during that month.
11. Calibration
11.1 A 10-cm diameter glass-fiber filter is sprayed with 6 coats of Krylon
and then mounted on an 11 1/2-cm diameter stainless steel planchet.
A calibrated NBS strontium-90, yttrium-90 standard is pipetted uniformly over
the surface of the filter resulting in a standard filter containing approxi-
mately 2.0 x IQ1* disintegrations per minute of strontium-90 and yttrium-90.
11.2 The standard filter is beta-counted.
__. . net counts per minute
11.3 Counting efficiency = -*;
dpm of standard
12. Quality control
12.1 Each morning a background and a strontium-90, yttrium-90 standard are
counted. The results are recorded and appropriate quality control
charts are maintained.
13. Calculations
13.1 Daily gross beta concentration
Gross beta (pCi/md) = -=-
£
where cpm = gross counts-bkg counts/counting time
2.22 = dpm/pCi
E = counting efficiency
V = sample volume (m3)
13.2 Monthly gross beta concentration
/ T \ lt2
Gross beta (pCi/m3) = A_ [ r= =-y)
2\TA" (T2 - V/
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where A- = gross beta activity (pCi/m3) from the
sample collection plus 5-day beta count
T -
TA = _A_
A- = gross beta activity (pCi/m3) from the
sample collection plus 12-day beta count
T = date of midpoint of sample collection
T_ = date of sample collection plus 5-day
beta count
T. = date of sample collection plus 12-day
beta count
T. is the estimated age of the fission product material collected on the fil-
A
ter at T_. If the date of fission is known, rather than estimating T., the
£. A
date may be entered into the computer program MBETA75 via a control card for
the exact calculation of T.. Also, the value of the exponent of 1.2 in the
gross beta calculation formula can be changed by changing a single FORTRAN
statement.
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DETERMINATION OF RADON-222 IN AIR, WATER, AND NATURAL GAS
1. Principle
1.1 Radon-222, the first decay product of radium-226, occurs in various
amounts in all geological formations. It is constantly being re-
leased to the atmosphere. The half-life of radon-222 is 3.825 days. There-
fore, a fairly fast method of analysis is required for its determination.
Direct alpha scintillation counting is possible if the radon-222 levels are
above 2 pCi/liter. If radon-222 levels are less than 2 pCi/liter, a concen-
tration step must be incorporated.
1.2 The decay of radon-222 leads to two additional short-lived alpha-
emitting progeny. These two isotopes will ingrow to 97% of equili-
brium in 4 1/2 hours, and will thus lead to an increase in count rate. Theo-
retically, 1 pCi of radon-222 at equilibrium should have a disintegration rate
of 6.6 counts per minute.
2. Application
2.1 This method is applicable for the determination of radon-222 in air,
water, and natural gas.
3. Range
3.1 No upper range has been established; however, samples of air and
water have been analyzed that have contained 6 x 105 pCi/liter radon-
222.
4. Interferences
4.1 Other alpha-emitting gaseous nuclides will interfere. The principle
interference is radon-220, which can be eliminated by allowing it to
decay and filtering out the daughter products.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
4.66 S
LLD
2.22 x E x S
* HASL Procedures Manual, J. H. Barley, editor, pages D-08-01/12, August 1977.
10
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where 4.66 = 2^2 k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
S, = standard deviation of the background
2.22 = dpm/pCi
E = fractional counting efficiency
S = sample size
6. Precision
6.1 The precision at 1 pCi/liter is estimated at + 20% below 1 pCi/liter
and + 10% above 1 pCi/liter.
7. Shipment and storage of samples and sample stability
7.1 Shipment to the laboratory must be by the most expeditious method.
The analysis must be performed as soon as possible for all sample
types.
7.2 It is impossible to store any of the sample types because of the
short half-life of the radon-222.
8. Reagents
8.1 Ascarite, 20 to 30 mesh.
8.2 Charcoal, coconut, 4 to 10 mesh.
8.3 Drierite, 10 to 20 mesh.
8.4 Helium, purified, store for 6 months or longer.
9. Apparatus
9.1 A manifold system as illustrated in Figure 2.
9.2 TI is a steel ball trap.
9.3 DI is an Ascarite and Drierite trap.
9.4 GI and Ci are charcoal traps.
9.5 Scintillation cell.
9.6 Alpha scintillation counter.
9.7 Vacuum pump.
LIQUIDS
9.8 An apparatus for radon de-emanation as illustrated in Figure 4.
11
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10. Procedure
GASES
Samples are usually collected in a 30-liter Tedlar bag, a 2-liter
glass flask, or as a compressed gas.
10.1 Attach sample container to the "sample-in" line (Figure 1). Evacu-
ate all lines, bulb A, and scintillation cell 1. Record room pres-
sure and temperature.
10.2 Transfer all of the 2-liter sample to bulb A, or bring bulb A to at-
mospheric pressure with the bag sample or compressed gas sample.
10.3 Fill scintillation cell 1, located at B (Figure 2X with sample.
10.A Immediately count scintillation cell for 30 minutes. If count rate
is 0.3 cpm or greater, prepare a duplicate as in 10.3. Hold cell
for 4 1/2 hours to allow radon and its progency to reach equilibrium and count
for 30 minutes.
10.5 If count rate is less than 0.3 cpm, continue by adding an ice water
bath to TI, and a dry ice acetone (DIA) bath to Ci and C£.
10.6 Establish flow, bulb A -» Tj * DI -» GI -» C2 -» vacuum; continue flow
until pressure in bulb A returns to room pressure.
10.7 Close all stopcocks and turn off vacuum pump.
10.8 Remove DIA from GI and replace with a furnace preheated to 350 C.
Establish flow helium -» CL allow helium to mix in GI for one min-
ute. Transfer helium and radon to scintillation cell.
10.9 Repeat 10.8 five times, then establish flow helium -> Cz and repeat
10.8 five times. Do not exceed atmospheric pressure in the scintil-
lation cell.
10.10 Place cell in radon counting apparatus and count at 30-minute inter-
vals until the ingrowth of the radon daughters is complete.
NATURAL GAS
10.11 Attach sample bottle to "sample-in" through an Ascarite-Drierite
drier tube.
10.12 Evacuate all transfer lines and scintillation cell. Check for leaks.
Gradually open regulator valve and transfer sample to scintillation
cell. Record pressure and temperature. Three cells should be prepared for
triplicate analysis.
10.13 Place cells in radon counting apparatus and count at 30-minute inter-
vals until the ingrowth of the radon daughters is complete.
12
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WATER
Sampling for radon in water is the most important facet. The solubility
of radon in water depends on the temperature, pressure, the concentration of
other gases, and dissolved solids. Therefore, in sampling, all of these para-
meters must be maintained. The use of a radon bubbler (Figure 3) to collect
the samples is necessary.
A. From a flowing pipe:
Attach a length of tubing to the sampling valve and place it in the
bubbler. Carefully open valve and allow the water to overflow the bubbler.
Allow flow for 5 minutes. Seal bubbler immediately and return to laboratory
for analysis. Do not allow air space in bubbler.
B. From an open body of water:
Evacuate the bubbler and immerse completely. Open and close the
valves while under water. Return the bubbler to the laboratory for analysis.
10.14 Figure 4 illustrates the apparatus for radon transfer from the bub-
blers. Weigh and attach the bubbler containing the sample to the
expansion bulb.
10.15 Open stopcock A and apply vacuum to system. When the right-hand leg.
of the U-tube manometer has reached its maximum height, close stop-
cock A. The system should be left in this configuration for 3 to 5 minutes.
If the mercury begins to drop in the right-hand leg, check the glass joints
and rubber tubing connections for leaks. Apply a very light coating of Dow-
Corning silicone grease to connection if necessary, and repeat system inte-
grity check.
10.16 Open stopcocks A and B and permit the mercury in the right-hand leg
of manometer to reach its maximum height. Close stopcock A and check
for leaks as in 10.15.
10.17 Connect dry, aged air with gum rubber tubing to the radon bubbler.
The air pressure should be limited to two psi.
10.18 Start de-emanation slowly to prevent pressure surge. After bubbling
has ceased, open stopcock D slowly. Adjust flow of aged air. Thirty
minutes is required to complete the de-emanation.
10.19 When mercury in both legs of the manometer is equal, shut stopcocks
D, C, and B in that order.
10.20 Remove the scintillation chamber and place in light-tight counting
cabinet for the 4 1/2-hour ingrowth period.
10.21 Remove and clean the bubbler. Reweigh for sample size.
13
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11. Calibration
RADON IN AIR AND NATURAL GAS
Known amounts of radon are added to various volumes of air or natural gas
and analyzed by the applicable method.
11.1 Dilute a National Bureau of Standards radium-226 standard to 100 pCi/
liter with distilled water.
11.2 Transfer 10 ml of this diluted standard to a radon bubbler and seal.
11.3 After allowing the radon-222 to ingrow to equilibrium with the par-
ent radium-226 (approximately 30 days) de-emanate into a two-liter
flask using either compressed air or natural gas.
11.4 Use the appropriate method to analyze for radon-222.
11 i r~n va~+~r - cpm at equilibrium
11.5 Cell Factor = f .- ^ --
pCi of standard
WATER
11.6 Using the diluted standard in 11.2, allow the radon-222 to equili-
brate, de-emanate into a scintillation cell. Hold for 4 1/2 hours
before counting.
11.7 Cell Factor = ^g^o^^andard""
12. Quality Control
12.1 Every tenth air sample is analyzed in duplicate, and natural gas
samples are routinely analyzed in triplicate.
12.2 The sample for radon-222 in water is destroyed during analysis.
Therefore, the collection of duplicates is necessary.
13. Calculations
13.1 Air and natural gas
Radon-222 (pCi/liter) = p * Q
where A = net counts per minute
F = cell factor
S = sample size, liters
13.2 Water
Radon-222 (pCi/liter) = j-^-g
14
-------
where A = net counts per minute
F = cell factor
S = sample size, kilogram
13.3 For reporting purposes, the radon-222 calculated in 13.1 and 13.2 is
back calculated to mid-point of collection.
Radon-222 (pCi/liter) = radon-222 x e At
Mid-point of collection
where X = .00755 hours or .18127 days
t = time since mid-point of collection
15
-------
BULB A
VACUUM
SCINTILLATION
CELL
VACUU
SAMPLE IN
STEEL
BALLS
DRIERITE
SCINTILLATION
CELL
DIGITAL
MANOMETER
Figure 2. Radon Separation Apparatus.
-------
7mm O.D.
Corning No. 2
or Equivalent
Bubble Trap
7mm ID.
Rigidity Brace
7mm Capillary Tubing
T/2mm I.D.
Fritted Glass Disc
10-15 micron pores
Volume to be kept
at minimum
Figure 3. Radon Bubbler.
17
-------
SCINTILLATION CELL
TO VACUUM PUMP 1
1
OPEN END MANOMETER
CAPILLARY T-TUBE
THERMOMETER CAPILLARY
DRIERITE
THERMOMETER CAPILLARY
EXPANSION CHAMBER
AIR FROM A COMPRESSED
AIR REGULATOR
RADON BUBBLER
Figure 4. Radon Emanation Apparatus.
18
I.D.
-------
DETERMINATION OF RADIUM-226 AND RADIUM-228
IN WATER, SOIL, AIR AND BIOLOGICAL TISSUE
1. Principle
1.1 A sequential method for the determination of radium-226 and radium-
228 is described.
1.2 Radium is precipitated with barium sulfate. Barium-radium-sulfate
is dissolved in a pentasodlum diethylenetriaminepentaacetate solu-
tion and transferred to an emanation tube and the radon allowed to come to
equilibrium, approximately 30 days. Radium-226 (Ti = 1602 years) decays by
alpha emission to radon-222. Radon-222 (T, = 3.825 days), a noble gas, is
separated and collected from the liquid by a de-emanation technique. The ra-
don-222 is counted by alpha scintillation 4 1/2 hours after de-emanation, at
which time the short-lived progeny have reached 97+% of equilibrium.
1.3 The radium solution from the radium-226 determination is saved and
the radium is reprecipitated. Radium-228 (T, =6.1 years) is a beta
emitter and decays to actinium-228 (T, = 6.13 hours). \he actinium is allowed
to ingrow for 3 days and is extractedArtth 2-di-ethylhexylphosphoric acid and
back-extracted with nitric acid. The actinium-228 is beta-counted in a low-
level proportional counter.
2. Application
2.1 This method is applicable for the determination of radium-226 and
radium-228 in water, soil, air, biological tissues, and biological
fluids.
3. No range has been determined; however, samples that contain 100 nCi
of radium-226 have been analyzed.
4. Interferences
4.1 Radium-223 (T, = 11.43 days) and radon-219 (T, = 3.92 seconds) will
interfere in samples of fresh uranium mill effluents. This inter-
ference in water and soil samples is small and may be eliminated in mill ef-
fluents by allowing the radon-219 to decay and transferring the radon-222 to
a separate scintillation detector and recounting.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
19
-------
4.66 Sb
LLD= 2.22 x E x S
where 4.66 = 2/2 k, where k is the value for the upper percentile of
the standardized normal varlate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
S. = standard deviation of the background
2.22 = dpm/pCi
E = fractional counting efficiency
S = sample size
6. Precision and accuracy
The expected precision for radium-226, based on the 95% confidence
level analytical error, is 0.3 pCl/liter for samples up to 1.0 pCi/
liter and 30% for samples above 1.0 pCi/liter. These are the values used in
the Duplicate Analysis Program and are recommended by the Quality Assurance
Branch.
Over a period of 2 years, 9 crosa-check samples containing known
amounts of radium-226 were received from the Quality Assurance Branch.
None of these results were outside the 3-sigma control limits.
7. Shipment and storage of samples and sample stability
7.1 Water: The water sample must be adjusted to pH 1 with nitric acid.
If suspended solids are present and separate analyses are required
for the suspended and dissolved solids, the sample must be filtered in the
field and the water adjusted to pH 1 with nitric acid. Water samples after
pH adjustment may be preserved for 6 months.
7.2 Urine: The sample should represent a 24-hour composite.
7.3 No special precautions are necessary for other sample types.
8. Reagents
8.1 Acetic acid, concentrated: Reagent grade.
8.2 Acetic acid, 6N: Add 345 ml reagent grade glacial acetic acid to
500 ml distilled water and dilute to 1000 ml.
8.3 Actinium wash solution: Dissolve 100 g reagent grade monochloroace-
tic acid, 2.4 ml of 41% pentasodium dlethylenetriaminepentaacetate
(NasDTPA), 25.4 g sodium hydroxide in 800 ml distilled water and dilute to
1000 ml.
8.4 Air, aged: Commercial grade compressed air. Store for at least 6
months before use.
8.5 Barium carrier, 10 mg/ml: Dissolve 19.0 g reagent grade barium ni-
trate in 800 ml distilled water and dilute to 1000 ml.
20
-------
8.6 Barium carrier, 5 mg/ml: Dissolve 4.75 g barium nitrate in 400 ml
distilled water and dilute to 500 ml.
8.7 Pentasodium diethylenetriaminepentaacetate (NasDTPA) reagent grade,
0.17M: Add 400 ml of distilled water to 209 ml 41% solution DTPA.
Filter through glass fiber wool with suction. Dilute to 1000 ml with distilled
water. Adjust to pH 12 with perchloric acid or sodium hydroxide.
8.8 2-di-ethylhexylphosphoric acid (HDEHP), 15% in n-heptane: Dilute
150 ml HDEHP to 1000 ml with n-heptane. Transfer to a 2-liter sepa-
ratory funnel. Wash twice with 200 ml of a one-to-one mixture 2M diammonium
citrate and concentrated ammonium hydroxide, and twice with 200 ml 4N nitric
acid.
8.9 Hydrofluoric acid, 48%: Reagent grade.
8.10 Hydrochloric acid, concentrated: Reagent grade.
8.11 Hydrochloric acid, 4N: Add 333 ml concentrated hydrochloric acid to
600 ml distilled water. Cool and dilute to 1000 ml.
8.12 Hydrochloric acid, 2N: Add 167 ml concentrated hydrochloric acid to
600 ml distilled water. Cool and dilute to 1000 ml.
8.13 Hydrogen peroxide, 30%: Reagent grade.
8.14 Lead carrier, 100 mg/ml: Dissolve 165.6 g reagent grade lead nitrate
in 800 ml distilled water and dilute to 1000 ml.
8.15 Monochloroacetic acid, 2M: Dissolve 189 g reagent grade monochloro-
acetic acid in 1000 ml distilled water.
8.16 Nicholson's Flux: In a 500-ml platinum dish, add 65.8 g potassium
carbonate, 50.5 g sodium carbonate, 33.7 g sodium tetraborate-decohy-
drate and 30 mg barium sulfate. Mix and fuse. Cool and grind to pass a 10-
mesh screen.
8.17 Nitric acid, concentrated (70%): Reagent grade.
8.18 Nitric acid, IT: Add 63 ml concentrated nitric acid to 600 ml
distilled water. Cool and dilute to 1000 ml.
8.19 Phosphoric acid, concentrated: Reagent grade.
8.20 Sodium sulfate, 20%: Dissolve 20 g anhydrous sodium sulfate in
80 ml distilled water and dilute to 100 ml.
8.21 Sodium sulfate 2.5%: Dissolve 2.5 g anhydrous sodium sulfate in 80
ml distilled water, add 1 ml concentrated sulfuric acid, dilute to
100 ml with distilled water.
21
-------
8.22 Sulfuric acid, concentrated: Reagent grade.
9. Apparatus
9.1 Low background beta counter.
9.2 Parr acid digestion bomb.
9.3 Radon bubbler (Figure 5).
9.4 Radon transfer apparatus (Figure 6).
9.5 Scintillation cell (Figure 7).
10. Procedure
WATER
10.1 Transfer 1500-ml sample to a 2-liter beaker. Adjust pH to approxi-
mately 1.0 with concentrated nitric acid and add 200 mg lead carrier.
10.2 Add 100 ml concentrated sulfuric acid and heat at 70° C with stir-
ring for 1 hour. Allow the lead sulfate to settle overnight. De-
cant, discard the supernate, and transfer precipitate to a 40-ml centrifuge
tube using distilled water. Centrifuge, and discard the supernate.
10.3 Add 1 ml concentrated acetic acid, 6 ml 41% Na5DTPA and 1 ml dis-
tilled water. Add stir bar and heat with stirring until dissolution
is complete.
10.4 Transfer the solution to radon bubbler (Figure 1). Do not exceed 9
ml total volume. Seal bubbler with Pyseal cement and allow the radon
to ingrow. De-emanate as in section 10.46.
SOIL, MILL TAILINGS AND ORES
10.5 Weigh, in a porcelain crucible, a suitable portion of sample £not
over 1 gram) on an analytical balance. Heat overnight at 600 C.
Cool.
10.6 Add 7 ml 48% hydrofluoric acid to the Parr acid digestion bomb and
then slowly transfer the sample into the acid. Seal bomb and heat
in an oven at 150° C for 2 to 3 hours, cool. (Caution: Never allow tempera-
ture to exceed 150° C and use sufficient care in opening bomb).
10.7 Transfer to 50-ml platinum dish using minimum distilled water and
add 5 ml concentrated nitric acid. Evaporate to dryness and cool.
10.8 Add 5 ml 48% hydrofluoric acid and 5 ml concentrated nitric acid
and again evaporate to dryness and cool.
22
-------
10.9 Add 4 ml concentrated sulfuric acid, dropwise to rinse the sides of
the dish. Place the dish on a hot plate, swirl the dish to slow re-
action, if needed. Add remainder of the sulfuric acid.
10.10 Add 2 g anhydrous sodium sulfate, heat dish on hot plate until liq-
uid has evaporated. Heat dish carefully over a low flame, swirling
melt to facilitate dissolution of sample. Do not heat after clear fusion has
been obtained.
10.11 Transfer the dish and cake to a 400-ml beaker, containing 100 ml
distilled water. Add, with caution, 30 ml concentrated hydrochloric
acid and 30 ml concentrated sulfuric acid. Remove dish, rinse with distilled
water, and save for step 10.15 in this procedure. Heat, with stirring, until
cake has dissolved.
10.12 Add 5 ml of 10-mg/ml barium carrier. Add the carrier dropwise,
letting the first drop become well mixed before adding the next
drop. Repeat this until 4 or 5 drops have been added, then add the rest of
the carrier.
10.13 Cover with watch glass and bring to a boil. Cool and add 5 ml 30%
hydrogen peroxide. Allow to settle overnight.
10.14 Filter through a Millipore filter, type HA 0.45 micron. Wash beaker
and precipitate with 2.5% sodium sulfate in 1% sulfuric acid. Dis-
card filtrate. Save 400-ml beaker for step 10.18 of this procedure.
10.15 Place filter in 50-ml platinum dish. Ash and cool.
10.16 Add 4 g Nicholson flux. Heat over a blast burner until the melt is
clear. Cool.
10.17 Place dish and cake in 400-ml beaker (saved from 10.11) containing
100 ml distilled water. Add 20 ml concentrated sulfuric acid.
After cake has dissolved, remove dish, rinsing with distilled water. (Save
for step 10.20 of this procedure). Cover and let set overnight.
10.18 Filter through a Millipore filter, type HA 0.45 micron. Wash beaker
and precipitate with 2.5% sodium sulfate in 1% sulfuric acid. Dis-
card filtrate.
10.19 Place filter in 50-ml platinum dish. Ash and cool.
10.20 Add 1 ml concentrated phosphoric acid, carefully heat and swirl un-
til a clear solution is obtained. Cool.
10.21 Dissolve, with heat, the barium phosphate in 40 ml of 4N hydrochloric
acid and evaporate to 2 ml. Add 5 ml 2N hydrochloric acid with heat
and transfer to radon bubbler. Do not exceed 9 ml. Seal bubbler with Pyseal
cement and allow the radon to ingrow and collect. De-emanate as indicated in
section 10.43.
23
-------
GLASS-FIBER AIR FILTERS
The unused filters are weighed on an analytical balance and the
tare is recorded on the glassine envelope.
10.22 Reweigh the used filter or filters. Transfer to a 400-ml Teflon
beaker. (If polonium-210 is requested, add polonium-208 tracer).
10.23 Add 30 ml concentrated hydrofluoric acid and 30 ml concentrated
nitric acid. Heat at reflux for several days, adding more acid
as necessary, until a white solution and precipitate is obtained.
10.24 Add 30 ml concentrated hydrochloric acid and heat to dryness.
Repeat two more times.
If uranium, thorium, or polonium analyses are requested, dissolve
residue in 6N hydrochloric acid and transfer to a 100-ml volumetric
flask and dilute to mark with 6N hydrochloric acid. Mix by shaking. Trans-
fer 50 ml for radium analysis to a 250-ml beaker. Continue at 10.25.
10.25 Add with stirring, 5 ml of 10 mg/ml barium carrier and 20 ml con-
centrated sulfuric acid. Cool and let set overnight.
10.26 Cover with watch glass and bring to a boil. Cool and add 5 ml 30%
hydrogen peroxide. Allow to settle overnight.
10.27 Filter through a MiHipore filter, type HA 0.45 micron. Wash beaker
and precipitate with 2.5% sodium sulfate in 1% sulfuric acid. Dis-
card filtrate. Save 400-ml beaker for step 10.18 of this procedure.
10.28 Place filter in 50-ml platinum dish. Ash and cool.
10.29 Add 4 g _Nicholson's flux. Heat over a blast burner until the melt
is clear. Cool.
10.30 Place dish and cake in 400-ml beaker (saved from 10.11) containing
100 ml distilled water. Add 20 ml concentrated sulfuric acid.
After cake has dissolved, remove dish, rinsing with distilled water. (Save
for step 10.20 of this procedure). Cover and let set overnight.
10.31 Filter through a Millipore filter, type HA 0.45 micron. Wash beaker
and precipitate with 2.5% sodium sulfate in 1% sulfuric acid. Dis-
card filtrate.
10.32 Place filter in 50-ml platinum dish. Ash and cool.
10.33 Add 1 ml concentrated phosphoric acid, carefully heat and swirl until
a clear solution is obtained. Cool.
10.34 Dissolve, with heat, the barium phosphate in 40 ml of 4N hydrochloric
acid and evaporate to 2 ml. Add 5 ml 211 hydrochloric acid with heat
and transfer to radon bubbler. Do not exceed 9 ml. Seal bubbler with Pyseal
24
-------
cement and allow the radon to ingrow and collect. De-emanate as indicated in
section 10.43.
AIR FILTER, MICROSORBAN
10.35 Place weighed filter in a 1000-ml Pyrex beaker. (Add polonium and
uranium tracers if sample is to be split for polonium and uranium
analysis). Add 25 ml concentrated sulfuric acid to a l-to-4 filter composite
(40 ml of acid if a larger composite or 20 cm x 25 cm (8" x 10") filter
is to be analyzed).
10.36 Heat on a hot plate with high heat until dense white fumes are visi-
ble. Remove from hot plate and carefully wash the sides of the
beaker with 30% hydrogen peroxide and concentrated nitric acid. Reheat to
fumes. Repeat the hydrogen peroxide and nitric acid until all organic mate-
rial is gone.
10.37 Evaporate to approximately 10 ml, cool and transfer to a 250-ml Tef-
lon beaker. Rinse well with distilled water. Add 30 ml hydrofluoric
acid and 30 ml concentrated nitric acid. Cover and digest overnight with me-
dium heat.
10.38 Heat to dense white fumes to remove the hydrofluoric and nitric acid.
Cool and transfer to a 100-ml volumetric flask with distilled water.
Dilute to 100 ml.
10.39 Transfer a 50-ml aliquot to a 250-ml beaker. Add 1 ml of 5-mg/ml lead
carrier dropwise with stirring. Let set overnight.
10.40 Decant, discard the supernate, and transfer to a 40-ml centrifuge
tube using distilled water. Centrifuge, and discard the supernate.
10.41 Add 1 ml concentrated acetic acid, 6 ml NasDTPA and 1 ml distilled
water. Add stir bar and heat with stirring until dissolution is
complete.
10.42 Transfer the solution to radon bubbler (Figure 5). Do not exceed
9 ml total volume. Seal bubbler with Pyseal cement and allow the
radon to ingrow. De-emanate as in section 10.44.
RADON DE-EMANATION
'Figure 6 illustrates the assembled apparatus.
10.43 Attach a scintillation chamber to the manometer. Attach the radon
bubbler containing the sample to an Ascarlte-Drierite drying tube
and a short length of thermometer tubing with short lengths of gum rubber tub-
ing.
10.44 Open stopcock A and apply vacuum to system. When the right-hand leg
of the U-tube manometer has reached its maximum height, close stop-
cock A. The system should be left in this configuration for 3 to 5 minutes.
If the mercury begins to drop in the right-hand leg, check the glass joints
and rubber tubing connections for leaks. Apply a very light coating of Dow-
Corning Silicone grease to connection if necessary, then repeat system integ-
rity check.
25
-------
10.45 Open stopcock A and B and permit the mercury in the right-hand leg
of manometer to reach its maximum height. Close stopcock A and check
for leaks as in 10.32.
10.46 Connect dry aged air with gum rubber tubing to the radon bubbler.
The air pressure should be limited to two psi.
10.47 Start de-emanation by opening stopcock C slowly to prevent pressure
surge. After bubbling has ceased, open stopcock D slowly. Adjust
flow of aged air. Thirty minutes is required to complete the de-emanation.
10.48 When mercury in both legs of the manometer is equal, shut stopcocks
D, C, and B in that order.
10.49 Remove the scintillation chamber and place in light-tight counting
cabinet for the 4-1/2-hour ingrowth period.
10.50 Remove the purged bubbler and save for the radium-228 determination.
RADIUM-228 DETERMINATION
10.51 After radon de-emanation, transfer the sample from the radon bubbler
to a 40-ml centrifuge tube. Wash bubbler with 411 hydrochloric acid
and force through glass frit with suction. Add with stirring 2 ml concentrated
sulfuric acid and 1 ml 20% sodium sulfate. Digest 5 to 10 minutes in hot water
bath, cool and centrifuge.
10.52 Decant supernate and save precipitate.
10.53 Add 15 ml of 0.17M DTPA to the precipitate. Place in boiling water
bath and heat with stirring for 10 minutes to dissolve the pre-
cipitate. (If lead was used as radium carrier, 10 mg Ba^+ must be added as
radium carrier.) Add 1 ml 20% sodium sulfate solution and enough water to
bring solution to 28 ml. Add 2 ml 6M acetic acid. Continue to heat in bath
with stirring for 5 minutes. Cool for 5 minutes in ice water bath. Centri-
fuge and discard supernate.
10.54 Add 15 ml 0.17M DTPA and stir bar to the precipitate. Place in boil-
Ing water bath and heat with stirring until the precipitate has dis-
solved. Add 1 ml 20% sodium sulfate solution. Add water to bring volume to
28 ml. Add 2 ml 6M acetic acid. Record time TI when 2 ml 6M acetic acid is
added. (Tj time is start of ingrowth of actinium-228.) Continue to heat in
boiling water with stirring for 5 minutes. Cool for 5 minutes in ice water.
Add 4 drops 2.5-mg/ml barium carrier with stirring, with 5-second intervals
between drops. Cool for another 10 minutes, then centrifuge, discard the
supernate.
10.55 Add 5 ml water to 40-ml centrifuge tube containing the barium sulfate
and allow at least 30 hours ingrowth of 6.13-hour actinium-228.
26
-------
10.56 At the end of the ingrowth period, dissolve the barium sulfate in
15 ml 0.17M DTPA. Add 1 ml 20% sodium sulfate, dilute to 28 ml with
water, and reprecipitate the barium sulfate with 2 ml 6N acetic acid. Record
time of this precipitation as T2. Digest in boiling water bath for 5 minutes.
Cool in ice bath.
10.57 Centrifuge and decant the supernate into a clean 40-ml centrifuge
tube. Before returning tube upright, rinse walls very carefully
with 2 to 3 ml of water. Do not disturb the precipitate. Add wash solution
to the clean AO-ml centrifuge tube.
10.58 Add 1 ml 5-mg/ml barium carrier to the centrifuge tube containing
the supernate. Stir. Place in boiling water bath, heat with stir-
ring for 5 minutes. Cool in ice water bath for 5 minutes. Centrifuge.
10.59 Decant the supernate into 125-ml separatory funnel containing 5 ml
2M monochloroacetic acid. Discard the barium sulfate precipitate.
10.60 Add 10 ml washed 15% HDEHP in n-heptane to the 125-ml separatory
funnel. Shake vigorously for 2 minutes (relieve pressure as needed)
and discard the aqueous phase.
10.61 Wash organic phase for 1 minute with two 10-ml portions of actinium
wash solution. Discard the aqueous phases.
10.62 Add 10 ml IN nitric acid, mix phases for 1 minute, draw off aqueous
phase into 2-inch planchet. Evaporate to dryness.
10.63 Repeat step 10.62 using 5 ml BJ nitric acid, discard organic phase.
10.64 Continue heating the planchet until all possible nitric acid vapor
has been removed, cool.
10.65 Place in low-background beta counter and count for 50 minutes. Re-
cord count time, T3, as end of actinium-228 decay.
11. Calibration
Known amounts of radium-226 are added to the various sample types
and these samples are then analyzed in accordance with the various procedures.
11.1 Reagents
11.1.1 Dilute a National Bureau of Standards radium-226 standard to 100
pCi/liter using distilled water. Adjust pH to 1 with concentrated
nitric acid.
RADIUM-226
11.2 Procedure
11.2.1 Add 1 ml of the 100-pCi/ml radium-226 standard to appropriate sample
size for the sample type and proceed with the method for that sample.
27
-------
11.2.2 After counting the radon, use the following equation, which
includes ingrowth, decay, counting efficiency, de-emanation efficiency,
and chemical yield, to determine scintillation cell factor.
Cell factor = cp^ at equilibrium
pCi of standard
Scintillation cells should be numbered and a record kept of the in-
dividual cell factors.
RADIUM- 228
None of the suppliers of radionuclide standards distribute a radium-
228 standard. A thorium-232 standard supplied by Amersham is being
used for standardization. This standard was prepared in 1906 and the radium-
228 has ingrown to equilibrium.
11.2.3 Weight 0.100 g of the thorium-232 standard. Dissolve and dilute to
100 ml with distilled water.
11.2.4 Pipet 10 ml of the dilute standard to a 40-ml centrifuge tube. Add
10 mg barium carrier and 2 ml concentrated sulfuric acid. Digest 5
to 10 minutes in a hot water bath. Cool and centrifuge.
11.2.5 Decant supernate and save precipitate. Proceed as indicated in the
radium-228 determination, Section 10.40.
11.2.6 Use data obtained to determine combined yield and counting efficiency.
Yield and counting efficiency =
where cpm = counts per minutes obtained on weightless planchet
dpm = disintegrations per minute calculated from thorium-232
concentration in standard
12. Quality Control
Every tenth sample is recycled as a blind duplicate. The results
of the duplicates are subject to standard statistical tests and re-
sults outside the control limits are examined for possible remedial action.
Standard samples are received from the Quality Assurance Branch.
If the results are unsatisfactory, the reason for the problem is
found and all results during the questionable time are evaluated for possible
remedial action.
13. Calculation
13.1 Radium-226
28
-------
Radium-226 (pCi/liter or g)
F x
where A = net counts per minute
F = cell factor (as determined in 11.2.2)
S = sample size, liters or grams
13.2 Radium-228
Radium-228 (pCi/liter or g) =
2.22 x EY x (l-e"Xtl) x (e~At2) x V
where A = net counts per minute
2.22 = disintegration per minute/pCi
EY = combined fractional counting efficiency and chemical yield
ti = T2 - TI (ingrowth of actinium-228) (hours)
t2 = Ta - T£ (decay of actinium-228) (hours)
X = ln2/TJs = 0.113 (hours)
V = sample size (liter or gram)
14. References
Johns, F. B. "Handbook of Radiochemical Methods." EPA-680/4-75-001.
February, 1975.
Percival, D. R. and D. B. Martin. "Analytical Chemistry 46." 1974.
Sill, C. W. and C. P. Willis. "Analytical Chemistry 37." 1965.
29
-------
7mm O.D.
Corning No. 2
or Equivalent
Bubble Trap
7mm I.D.
Rigidity Brace
7mm Capillary Tubing
11/2mm I.D.
Fritted Glass Disc
10-15 micron pores
Volume to be kept
at minimum
Figure 5. Radon Bubbler.
30
-------
TO VACUUM PUMP L
SCINTILLATION CELL
OPEN END MANOMETER
CAPILLARY T-TUBE
THERMOMETER CAPILLARY
DRIERITE
ASCARITE
THERMOMETER CAPILLARY
AIR FROM A COMPRESSED
AIR REGULATOR
RADON BUBBLER
I.D.
Figure 6. Radon Emanation Apparatus.
31
-------
67 mm
90 mm
Clear Silica
Window
Corning No. 2
or Equivalent
Brass Collar
Kovar Metal
B50 mm $|
Figure 7. Lucas Scintillation Cell.
32
-------
ISOTOPIC DETERMINATION OF PLUTONIUM, URANIUM,
AND THORIUM IN WATER, SOIL, AIR, AND BIOLOGICAL TISSUE
1. Principle
1.1 Samples are decomposed utilizing techniques of nitric-hydrofluoric
acid digestion or ignition. The residues are dissolved in dilute
nitric acid and successive sodium and ammonium hydroxide precipitations are
performed in the presence of boric acid to remove fluoride and soluble salts.
The hydroxide precipitate is dissolved, the solution is adjusted to 911 in hy-
drochloric acid, and plutonium and uranium are adsorbed on an anion exchange
column; separating them from thorium. Plutonium is eluted with hydrobromic
acid. Iron is removed from the column by washing with hydriodic acid and the
uranium is eluted with dilute hydrochloric acid. The thorium is converted to
a nitrate form and adsorbed on the same anion exchange column, separating it
from calcium and other interferences. The thorium is then eluted with 9IJ hy-
drochloric acid. The actinides are electrodeposited on stainless steel discs
from an ammonium sulfate solution and subsequently counted by alpha spectro-
metry. Chemical yields are determined by the recovery of internal tracer
standards (plutonium-236, uranium-232, and thorium-234) added at the beginning
of the analysis.
2. Application
2.1 This method is appropriate for the analysis of isotopic plutonium,
uranium, and thorium, together or individually, in soil, water, air
filters, urine, or ashed residues of vegetation, animal tissues, and bone.
3. Range
3.1 This method is designed to detect environmental levels of activity
as low as 0.02 picocuries per sample. To avoid possible cross-con-
tamination, sample activities should be limited to 25 picocuries or less.
3.2 Optimum sample sizes for each of the sample types are listed below.
Smaller samples may be analyzed with a commensurate loss in sensi-
tivity. Larger samples may introduce interferences and insoluble residues
which prevent satisfactory analysis.
3.3 Sample Type Optimum Size
Animal tissue ash 10 grams
Bone ash 10 grams
Vegetation ash 10 grams
Soil 10 grams
33
-------
Sample Type Optimum Size
Glass-fiber filters 12-4" circles or
1-8" x 10" rectangle
Organic filters 12-4" circles
Water 1 liter
Urine 1 liter
4. Interferences
4.1 Internal tracer standards must be purified at intervals to remove
progeny which might contribute to background activities or inter-
fere with subsequent analyses. Thorium-228 will be present in aged plutonium-
236 or uranium-232, which must be compensated for, if thorium-228 is to be de-
termined.
4.2 If present, lead-210 will be co-plated with plutonium giving rise to
alpha interference by ingrowing polonium-210. This can be minimized
by counting the sample within a few days of separation before sufficient polo-
nium-210 ingrowth has occurred.
4.3 Samples containing high levels of phosphate, such as fertilizer, or
high levels of barium sulfate, as in glass-fiber filters, may result
in low actinide yields.
5. Lower limit of detection
5.1 The lower limit of detection* (LID) is defined as the smallest concen-
tration of radioactive material sampled that has a 95% probability of
being validly detected.
3.29 SQ
LLD = 2.22 x E x S
where 3.29 = K + K.
a p
K = the value for the upper percentile of the standardized
0 normal variate corresponding to the preselected risk
for concluding falsely that activity is present (a) =
0.05
K_ = corresponding value for the predetermined degree of
confidence for detecting the presence of activity
(1-B) = 0.95
S = estimated standard error for the net sample activity
o
2.22 = dpm/pCi
E = fractional counting efficiency
S = sample size
6. Precision and accuracy
* HASL procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
34
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7. Shipment and storage of samples and sample stability
7.1 Vegetation, urine, and animal tissue samples should be preserved by
refrigeration, freezing, or the addition of formaldehyde until ashing
takes place. Water should be acidified with 20 ml concentrated nitric acid
per 3.7 liters of sample. Soil, air filters, and ash may be stored indefini-
tely.
8. Reagents
8.1 Alkaline ethyl alcohol: Adjust the pH of 95% ethanol to 8 with
ammonium hydroxide.
8.2 Ammonium hydroxide, concentrated (14N): Reagent grade.
8.3 Ammonium hydroxide, (1.4N): Add 100 ml concentrated ammonium hy-
droxide to 800 ml distilled water. Cool and dilute to 1000 ml.
8.4 Ammonium hydroxide, (0.7N): Add 50 ml concentrated ammonium hy-
droxide to 900 ml distilled water. Cool and dilute to 1000 ml.
8.5 Ammonium hydroxide-ammonium nitrate solution (0.101J NH^OH-O.ION
NHijNOs): Dissolve 8.0 g of reagent grade ammonium nitrate in 500 ml
distilled water. Add 7 ml of reagent grade, concentrated ammonium hydroxide
and dilute to 1000 ml.
8.6 Boric acid, powder: Reagent grade.
8.7 Calcium chloride (2N): Dissolve 111 g of calcium chloride (CaCl2)
in 900 ml distilled water. Cool and dilute to 1000 ml.
8.8 Dichromate cleaning solution: Dissolve 50 g sodium dichromate in
25 ml of water. Cautiously add concentrated sulfuric acid (a few
drops at a time) until further additions cause little reaction. Make up to
1000 ml with concentrated sulfuric acid.
8.9 Ferric chloride 0.3N (5.6 mg Fe/ml): Dissolve 27 g of reagent grade
ferric chloride (FeCl36!!20) in 300 ml of 6IJ hydrochloric acid. Di-
lute to 1000 ml with distilled water.
8.10 Hydriodic acid, concentrated (50%): Reagent grade.
8.11 Hydrobromic acid, concentrated (49%): Reagent grade.
8.12 Hydrochloric acid, concentrated (12N): Reagent grade.
8.13 Hydrochloric acid, 9Jfl: Add 750 ml concentrated hydrochloric acid
to 200 ml distilled water. Cool, then adjust the final volume to
1000 ml with distilled water.
35
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8.14 Hydrochloric acid, 61N: Add 500 ml concentrated hydrochloric acid
to 450 ml distilled water. Cool, then adjust the final volume to
1000 ml with distilled water.
8.15 Hydrochloric acid, 1.2N: Add 100 ml concentrated hydrochloric acid
to 850 ml distilled water. Cool, then adjust the final volume to
1000 ml with distilled water.
8.16 Hydrofluoric acid, concentrated (48%): Reagent grade.
8.17 Hydrogen peroxide, concentrated (30%): Reagent grade.
8.18 Ion exchange (anion) resin, Bio-Rad AG 1-X2, chloride form, 50-100
mesh.
8.19 Nitric acid, concentrated (16N): Reagent grade.
8.20 Nitric acid, 7.2N: Slowly add 455 ml concentrated nitric acid to
500 ml distilled water. Cool, then adjust the final volume to 1000
ml with distilled water.
8.21 Nitric acid, 4N: Slowly add 250 ml concentrated nitric acid to 800
ml distilled water. Cool, then adjust the final volume to 1000 ml
with distilled water.
8.22 Potassium fluoride, anhydrous, granular: Reagent grade.
8.23 Silica sand, spherical grained, 60-200 mesh (must be free of radio-
chemical contaminants).
8.24 Sodium bisulfite, powder: Reagent grade.
8.25 Sodium hydroxide, pellets: Reagent grade.
8.26 Sodium hydroxide, 12.5N: Dissolve 100 g sodium hydroxide pellets in
150 ml distilled water. Cool, then adjust volume to 200 ml.
8.27 Sulfuric acid, concentrated (36N): Reagent grade.
8.28 Sulfuric acid, 3.61*: With caution, add 100 ml concentrated sulfuric
acid to 850 ml distilled water. Cool, then adjust the volume to 1000
ml with distilled water.
8.29 Sulfuric acid, 0.3611: With caution, add 10 ml concentrated sulfuric
acid to 900 ml distilled water. Adjust to 1000 ml with distilled
water.
8.30 Thymol blue indicator, 0.02%: Dissolve 0.02 g thymol blue in 10 ml
ethanol. Dilute to 100 ml with distilled water.
36
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8.31 Tracer solutions: Purified and calibrated solutions of plutonium-236
(^5 pCi/ml), uranium-232 (^5 pCi/ml), and thorium-234 (^100 pCi/ml)
dissolved in 4N nitric acid.
9. Apparatus
9.1 Alpha spectrometric analyzer: A counting system consisting of a
multichannel analyzer, biasing electronics, a printer, a vacuum
pump and silicon surface barrier detectors operated in vacuum chambers.
9.2 Blast burner: Adjustable. High temperature.
9.3 Caps: Black resin, poly-seal liner, 22 mm, GCMI 400-thread design.
9.4 Centrifuge: 50-ml, 250-ml, and 500-ml capacity.
9.5 Centrifuge bottles: 50 ml plastic disposable, 250 ml Pyrex, 500 ml
Pyrex.
9.6 Chromatographic column: A 250-mm by 14.5-mm i.d. tube with a 250-ml
reservoir, and a stopcock with a Teflon plug, a course fritted glass
disc is fused in the tube just above the stopcock to support the resin.
9.7 Electrolysis apparatus: 10-volt, 5~amp capacity.
9.8 Muffle furnace: Capable of reaching 750°C.
9.9 Neoprene sheet: 0.079-cm (1/32-inch) thickness.
9.10 Platinum or platinum-iridium anode: 1.27-cm (1/2-inch) diameter,
0.08-cm (1/32-inch) platinum or platinum-iridium disk having six
0.32-cm (1/8-inch) perforations and attached at the center to a 10-cm (4-inch)
length of 0.16-cm (1/16-inch) platinum or platinum-iridium rod.
9.11 Rivets: //BS-4830 Dot Speedy rivets, solid brass, Carr Fastener
Company, Cambridge, Massachusetts.
9.12 Stainless steel disks: 1.91-cm (3/4-inch) diameter, 0.38-mm (15-mil)
thick, type 304 stainless steel planchets pre-polished to a mirror
finish.
9.13 Teflon beakers and covers: Griffin, Chemware, 100 ml, 250 ml, and
500 ml.
9.14 Vials: Polyethylene, 25-ml screw cap, Packard #6001075.
10. Procedure
10.1 Sample Preparation
37
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ANIMAL TISSUE ASH AND VEGETATION ASH
10.1.1 Transfer 10 g of previously ground and homogenized ash into a 250-ml
graduated borosilicate beaker. Add 1 ml each of the appropriate
tracers, (plutonium-236, uranium-232, or thorium-234) and 40 ml concentrated
nitric acid. Cover and boil until it evaporates to dryness.
10.1.2 Wet the residue with concentrated nitric acid with intervening evap-
orations until a light-colored residue is obtained, then allow the
nitric acid to evaporate. (If the residue is a porous black char following
step 10.1.1, it will speed matters to ignite the sample in a muffle overnight
at 600-700° C before proceeding with the nitric acid digestion in 10.1.2.)
10.1.3 Transfer the residue to a 100-ml Teflon beaker using concentrated
nitric acid. Evaporate twice with intervening additions of 10 ml of
concentrated nitric acid and 15 ml of 48% hydrofluoric acid.
10.1.4 Evaporate the contents of the Teflon beaker to dryness. Add 10 ml
6N hydrochloric acid, evaporate to dryness, then dissolve the resi-
due in 50 ml 6N hydrochloric acid. Transfer the solution to a 1000-ml Pyrex
beaker rinsing with 6N hydrochloric acid.
10.1.5 Dilute the solution to 600 ml with 6N hydrochloric acid. Add 20 ml
2jtf calcium chloride and heat to the boiling point. While stirring,
add concentrated ammonium hydroxide until precipitation begins and then add
40 ml in excess. Set the beaker aside to cool.
10.1.6 Remove the supernatant liquid by aspiration, and transfer the re-
maining slurry to a 500-ml centrifuge bottle. Centrifuge and dis-
card the supernatant liquid. Dissolve the precipitate with a volume of 12N_
hydrochloric acid equal to that of the precipitate.
10.1.7 Transfer the solution to a 150-ml graduated borosilicate beaker and
dilute to 60 ml with 6N hydrochloric acid. Continue to step 10.3.2
of the separation procedure.
BONE ASH
10.1.8 Weigh 1 g ash into a tared 100-ml Teflon beaker. Add 60 ml 6N hy-
drochloric acid, a few drops 30% hydrogen peroxide, and 1 ml each
of the appropriate tracer solutions. Cover and digest overnight on a hot plate.
10.1.9 Transfer the solution to a 50-ml centrifuge tube using 6N_ hydrochlo-
ric acid and centrifuge. Pour the supernatant liquid into a 150-ml
graduated borosilicate beaker and set aside. Return the residue to the Teflon
beaker using 10 ml 48% hydrofluoric acid and 5 ml concentrated nitric acid.
Evaporate this solution to dryness.
10.1.10 Wet the residue with 30% hydrogen peroxide and evaporate to dryness.
Add 10 ml 61J hydrochloric acid and evaporate to dryness. Add 5 ml
6N_ hydrochloric acid and one drop 30% hydrogen peroxide. Heat to dissolve the
residue and add the solution to the supernatant liquid in the glass beaker.
38
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10.1.11 Adjust the combined liquid volume to 60 ml by evaporation or by ad-
dition of 6N hydrochloric acid. Proceed to step 10.3.2 of the sep-
aration procedure.
GLASS-FIBER FILTERS
10.1.12 Place filter or filters in a 400-ml Teflon beaker, 250-ml platinum
dish. Add appropriate tracers (1 ml each), then wet the sample with
concentrated nitric acid. Add 10 ml 48% hydrofluoric acid and evaporate on a
hot plate to dryness.
10.1.13 Repeat acid additions and evaporations until the silica has been vol-
atilized.
10.1.14 Add 30 ml concentrated nitric acid and again evaporate to dryness.
Repeat.
10.1.15 Add 30 ml concentrated nitric acid, 5 g boric acid and 1 ml 0.3N
ferric chloride. Evaporate to approximately 10 ml.
10.1.16 Dilute to 100 ml with distilled water and heat to dissolve salts.
10.1.17 Add 12.5N sodium hydroxide until precipitation ceases (pH 9), then
add 15 g sodium hydroxide pellets. Cover and boil for 1 to 2 hours
on a hot plate.
10.1.18 Continue at step 10.1.24 of the soil preparation.
SOIL
10.1.19 Weigh 10 g of soil, which has been previously ground to 100 mesh, in-
to a porcelain crucible. Heat overnight at 700° C. Cool and trans-
fer to a 200-ml Teflon beaker. Add 1 ml each of the tracers plus 1 ml 0.3N
ferric chloride. Cautiously add 60 ml 16N nitric acid and 30 ml 48% hydro-
fluoric acid, allowing time between additions for foaming to subside. Cover
with a Teflon lid and digest on a 400° C hot plate for 1 to 2 hours. Never
let volume go below 20 ml.
10.1.20 Remove from the hot plate and cool slightly before adding 30 ml each
of 16N nitric acid and 48% hydrofluoric acid. Digest without the
lid with intermittent stirring for 1 hour.
10.1.21 Cool, then carefully add 20 ml concentrated hydrochloric acid with
stirring. Digest on the hot plate for 45 minutes.
10.1.22 With stirring, add 5 g of boric acid powder. After 15 minutes di-
gestion, add 0.2 g of sodium bisulfite crystals and continue heating
until the volume is reduced to approximately 20 ml.
10.1.23 Dilute to 50 ml with distilled water. Add 50% sodium hydroxide solu-
tion until precipitation ceases (pH 9), then add 15 g of sodium hy-
droxide pellets. Cover and boil for 1 to 2 hours on a hot plate.
39
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10.1.24 Transfer the solution and precipitate to a 500-ml Pyrex centrifuge
bottle using distilled water. Centrifuge for at least 15 minutes at
1500 rpm. Decant and discard the supernate. Add approximately 10 ml concen-
trated nitric acid to the original Teflon beaker, cover, and reflux on the hot
plate to dissolve any remaining residue.
10.1.25 Add approximately 1 g boric acid to the centrifuge bottle and stir
the mixture with a stream of distilled water from a wash bottle.
Add the nitric acid from the Teflon beaker, rinsing with distilled water.
Rinse the beaker with an additional 10 ml concentrated nitric acid and add to
the bottle. Warm on a hot plate for a few minutes to complete the dissolution.
10.1.26 Add 200 ml of distilled water and adjust the pH to 9 with UN ammo-
nium hydroxide. Adjust the volume to 450 ml and centrifuge at 1500
rpm for 15 minutes. Decant and discard supernate.
10.1.27 Dissolve the precipitate with a minimum of concentrated hydrochloric
acid. Warm on a hot plate to speed dissolution. Transfer back to
the Teflon beaker with approximately 30 ml of distilled water. Add 50% sodium
hydroxide until precipitation ceases, then add 15 g sodium hydroxide pellets.
Cover and boil for 1 hour.
10.1.28 Transfer the solution and precipitate back to the centrifuge bottle
with distilled water. Adjust the volume to 450 ml and centrifuge
for 15 minutes at 1500 rpm. Decant and discard supernate. Add 10 ml concen-
trated hydrochloric acid to the Teflon beaker, cover, and reflux on the hot
plate for a few minutes.
10.1.29 Transfer the hydrochloric acid from the Teflon beaker to the centri-
fuge bottle, rinsing with distilled water. Rinse the beaker with an
additional 10 ml concentrated hydrochloric acid and add to the bottle. Warm
on a hot plate to aid dissolution.
10.1.30 Add 200 ml of distilled water, then adjust the pH to 9 with concen-
trated amonium hydroxide. Increase the volume to 450 ml with dis-
tilled water then centrifuge at 1500 rpm for 15 minutes. Discard supernate.
10.1.31 Add a minimum volume of concentrated hydrochloric acid to the preci-
pitate. Swirl to dissolve the precipitate, then transfer to a grad-
uated 150-ml beaker rinsing with 6N[ hydrochloric acid. Adjust the solution
volume to 40 ml with 6N hydrochloric acid and proceed with step (10.3.2) of
the separation procedure.
URINE
10.1.32 Measure the sample volume with a graduated cylinder and transfer it
into a beaker with a capacity approximately 50% larger than the sam-
ple. Rinse the sample container with concentrated hydrochloric acid, using 40
ml of acid per liter of sample. Add this rinse to the sample. Rinse the con-
tainer again with 60 ml of concentrated nitric acid. Set aside this rinse for
later use.
40
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10.1.33 Add the appropriate tracers, 10 ml 211 calcium chloride, and a volume
of 30% hydrogen peroxide equal to the volume of concentrated hydro-
chloric acid used in the previous step. Place a Teflon stirring rod in the
beaker and heat to the boiling point. When foaming subsides, cover the beaker
and allow the solution to simmer for 1 hour.
10.1.34 Add the concentrated nitric acid rinse to the beaker and continue to
simmer for another hour.
10.1.35 While stirring the hot solution, add concentrated ammonium hydroxide
slowly until precipitation begins and then add an excess equal to 60
ml of ammonium hydroxide per liter of original sample. Cover the beaker and
set aside to cool.
10.1.36 Remove the supernatant liquid by aspiration and discard. Transfer
the remaining slurry into a 50-ml plastic centrifuge tube using 0.711
ammonium hydroxide. Centrifuge and discard the supernate.
10.1.37 Rinse the sample beaker with approximately 10 ml of concentrated ni-
tric acid and transfer to the residue in the centrifuge tube. Shake
to dissolve the precipitate, then transfer the solution to a 250-ml beaker us-
ing about 5 ml of concentrated nitric acid as a rinse. Cover the beaker with
a watch glass and boil on a hot plate until the residue is dry.
10.1.38 Wet the residue alternately with 30% hydrogen peroxide and concentra-
ted nitric acid with intervening evaporations until a white ash is
obtained and then allow all of the nitric acid to evaporate.
10.1.39 Add 50 ml 61) hydrochloric acid and boil until the volume is reduced
to 25 ml. Add 6N hydrochloric acid to increase the volume to 50 ml.
Proceed at step (10.3.2) of the separation procedure.
WATER
10.1.40 Add appropriate tracers, 5 ml 0.3N ferric chloride, and 20 ml of 30%
hydrogen peroxide to 1 liter of sample, previously preserved by the
addition of 20 ml concentrated nitric acid per gallon of water. Simmer until
the hydrogen peroxide has decomposed.
10.1.41 While stirring, add concentrated ammonium hydroxide to the hot solu-
tion until precipitation begins and then add 15 ml in excess. Con-
tinue heating until the precipitate has coagulated, then allow to cool.
10.1.42 Remove the supernatant liquid by aspiration and transfer the preci-
pitate to a centrifuge tube using 0.7N ammonium hydroxide. Add ap-
proximately 10 ml of concentrated nitric acid to the beaker, cover, and reflux
on the hot plate to dissolve any remaining residue. Cool and set aside.
10.1.43 Dissolve the precipitate in the centrifuge tube by adding a volume
of concentrated hydrochloric acid equal to the volume of the pre-
cipitate. Centrifuge and decant the supernate into a 150-ml Pyrex beaker.
41
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10.1.44 Using a minimum of concentrated nitric acid, transfer any insoluble
residue from the tube to a 100-ml Teflon beaker. Add the nitric
acid solution from the original beaker in step (10.1.42) and evaporate to dry-
ness on the hot plate.
10.1.45 Add 10 ml 48% hydrofluoric acid and 5 ml concentrated nitric acid.
Evaporate to dryness. If any organic material remains, wet the res-
idue with 30% hydrogen peroxide and evaporate to dryness.
10.1.46 Add 10 ml 6N hydrochloric acid and evaporate to dryness. Add 5 ml
6N hydrochloric acid and one drop 30% hydrogen peroxide. Heat to
dissolve the residue and add the solution to the supernatant liquid from step
(10.1.43). Evaporate the combined solutions to 60 ml and continue with step
(10.3.2).
10.2 Ion Exchange Column Preparation
10.2.1 Remove fines from the resin by repeated suspension in distilled water
and decantation. Add concentrated hydrochloric acid equal to 10% of
the volume of slurry to shrink the resin. Transfer the resin to the column in
slurry form to give a settled resin bed of 20 ml volume. Add dry 60 to 200
mesh silica sand to a depth of 15 mm through a layer of 1.211 hydrochloric acid.
The sand prevents resuspension of the resin and, by its capillarity, stops the
flow between additions of reagents enabling unattended operation.
10.3 Ion Exchange Separations
10.3.1 Immediately prior to use, condition the ion exchange column with 100
ml of 9N hydrochloric acid containing a drop of 30% hydrogen peroxide
at a flow rate of 6 ml/min.
10.3.2 Add a volume of 12N hydrochloric acid to the sample that is equal to
the volume of the 6N solution to adjust the acid concentration to 911.
Add one drop 30% hydrogen peroxide for each 10 ml of 9N solution, cover with
a watch glass, and heat the solution to 80-90 C for 1 hour. Cool to room
temperature.
10.3.3 Transfer the sample to the column reservoir using 9]J hydrochloric
acid as a rinse. If barium chloride, sodium chloride, or other solid
matter is present, filter the solution into the reservoir through a plug of
glass wool in the stem of a funnel.
10.3.4 Pass the 9_N sample solution through the column at a flow rate of 3
ml/min. Flush the reservoir three times with 15-ml volumes of 911
hydrochloric acid and drain each rinse at 3 ml/min. Combine and save the 911
eluates for thorium analysis.
10.3.5 Wash the column with an additional 50 ml 911 hydrochloric acid con-
taining one drop of 30% hydrogen peroxide. Elute at 3 ml/min and
discard eluate. If plutonium analysis is not required, proceed to step 10.3.8.
42
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PLUTONIUM
10.3.6 Elute plutonium from the column using 25 ml 49% hydrobromic acid at
3 ml/rain. Collect the eluate in a 100-ml Fyrex beaker. Wash the
column with an additional 50 ml 49% hydrobromic acid and combine with the 25-
ml eluate.
10.3.7 Add 0.5 ml of concentrated sulfuric acid to the sample solution and
evaporate at low heat to fumes of sulfuric acid. Add two drops of
30% hydrogen peroxide and again evaporate to sulfuric acid fumes. Save this
fraction for electrodeposition of plutonium, step (10.4.12).
URANIUM
10.3.8 Remove iron from the column with a fresh solution prepared by mixing
109 ml of 12N hydrochloric acid with 31 ml of distilled water and 50
ml of 50% hydriodic acid. Rinse the column reservoir three times with 15-ml
portions of this solution and elute at 3 ml/min. Add an additional 100 ml of
the solution and elute at the same rate. Discard the eluates.
10.3.9 Rinse the column with two 15-ml portions of 9N hydrochloric acid
followed by 5 ml 1.2N hydrochloric acid to remove residual hydriodic
acid. Discard the eluates.
10.3.10 Elute uranium with 50 ml 1.2N hydrochloric acid at 3 ml/min. Collect
the eluate in a 100-ml glass beaker. Add 0.5 ml concentrated sulfur-
ic acid to the beaker and evaporate to fumes of sulfuric acid. Add 5 drops 30%
hydrogen peroxide and again evaporate to sulfuric acid fumes. Save for elec-
trodeposition of uranium, step (10.4.12).
THORIUM
10.3.11 To prepare the column for thorium, add 100 ml 1.211 hydrochloric acid
to the column reservoir and elute at 3 ml/min. Discard the eluate.
Add 150 ml 7.2N nitric acid and elute at 3 ml/min. Discard the eluate.
10.3.12 Evaporate the combined 9K[ thorium eluates (from step 10.3.4) to dry-
ness on a hot plate. Dissolve the residue with 20 ml 7.2JH nitric
acid, plus 5 drops of 30% hydrogen peroxide. Cover and reflux for 45 minutes
on the hot plate. Add 3 more drops 30% hydrogen peroxide and continue to heat
for 15 minutes. Cool to room temperature.
10.3.13 Transfer the solution to the column reservoir, rinsing the beaker
with a minimum of 7.2N nitric acid. Elute at 3 ml/min and discard
the eluate. Rinse the reservoir with three 10-ml portions 7.214 nitric acid
and drain at the same rate. Wash the column with 100 ml 7.21? nitric acid and
discard eluate.
10.3.14 Rinse the reservoir with 5 ml 911 hydrochloric acid and drain at 3
ml/min. Discard the eluate. Elute the thorium with 100 ml 91* hy-
drochloric acid at 3 ml/min and collect the eluate in a 150-ml glass beaker.
43
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Add 0.5 ml concentrated sulfuric acid to the beaker and evaporate to sulfuric
acid fumes. Add 5 drops 30% hydrogen peroxide and again evaporate to sulfuric
acid fumes. Continue with the electrodeposition of thorium at step (10.4.12).
10.4 Electrodeposition
CONSTRUCTION OF ELECTRODEPOSITION CELLS
10.4.1 Cut a 1.43-cm (9/16-inch) hole in the bottom of the polyethylene
vial with a sharp cork borer. Improve the seal by abrading the
threaded end with wet //320 waterproof emery paper held against a flat surface.
Finish with wet #600 emery paper.
10.4.2 Remove the polyethylene liner from a 22-mm Poly-Seal cap. With a
cork borer or leather punch, cut out the polyethylene tube from the
liner. The conical part of the liner is used as a cover for the cell to mini-
mize escape of spray.
10.4.3 Drill a 0.355-cm (0.140-inch, #28 drill) hole through the center of
the cap. Bevel the edge of the hole on the inside of the cap with
a reamer.
10.4.4 Cut a 1.91-cm (3/4-inch) disc from 0.079-cm neoprene sheeting with
a cork borer or a die. Cut a 0.317-cm (1/8-inch) hole in the center
of the disc with a cork borer or leather punch.
10.4.5 Place the washer in the cap and pass the shank of the rivet through
the washer and the hole in the cap.
CLEANING
10.4.6 Remove any surface film of oil from the polyethylene body of the cell
with acetone followed by water.
10.4.7 Completely immerse the body of the cell in dichromate-sulfuric acid
cleaning solution for 2 to 3 hours. Rinse off the cleaning solution
with water and immerse the cell in 4N nitric acid for at least 1 hour. Rinse
and immerse in distilled water until ready to use.
10.4.8 The cleaning process renders the polyethylene hydrophilic, provided
the cell is kept continuously wet after having been cleaned. The
polyethylene parts of used cells can be rinsed and then cleaned by the direc-
tions given in 10.4.7 except that the immersion in dichromate sulfuric acid
cleaning solution is limited to 1 hour. Clean the caps and neoprene washers
by immersing for a few minutes in 4N nitric acid and then rinse with water.
ASSEMBLY
10.4.9 Connect one hole of a 2-hole #6 rubber stopper to an aspirator pump
with a length of rubber tubing.
44
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10.4.10 Rinse the polyethylene cell with distilled water but do not dry.
Hold the planchet centered against the threaded end of the cell and
place the rubber stopper against the other end of the cell. Apply suction by
placing a finger over the open hole of the stopper. The vacuum will hold the
planchet in a centered position while the cap assembly is screwed on. Fill
the cell halfway with water and alternately apply and release the vacuum. The
flexing will cause the planchet to seat more firmly against the cell. Check
to see that no stream of air bubbles rises through the water when vacuum is
applied. If the vacuum is great enough, the water may boil, but the boiling
is easily distinguished from air leakage.
10.4.11 Fill the assembled cell to the top with water to preserve the hydro-
philic character of the cell until ready to add sample.
ELECTRODEPOSITION
10.4.12 Add 3 ml of water to the cool sulfuric acid sample solution. Replace
the watch glass and warm the solution for a minute or two on a hot
plate and then allow to cool.
10.4.13 Add 4 drops 0.02% thymol blue sodium salt. Neutralize the solution
to the salmon-pink endpoint (pH 2) by blowing gaseous ammonia over
the surface while swirling the solution. The gaseous ammonia is obtained from
a polyethylene wash bottle having the inner portion of the delivery tube re-
moved and containing concentrated ammonium hydroxide. If the endpoint is over-
stepped to a yellow color, add 3.6N sulfuric acid, a drop at a time, until the
solution turns pink.
10.4.14 Pour the neutralized solution into the plating cell. Draw 6 ml 3.611
sulfuric acid into a pipette and use this in small increments to
rinse the beaker three or more times. Add the rinses to the cell.
10.4.15 Neutralize the solution again to pH 2 with gaseous ammonia. The
solution should have a straw color when viewed from the top and a
slight pinkish cast when viewed through the sides of the cell. If the endpoint
is overstepped, use 3.6N sulfuric acid, a drop at a time, to return the solu-
tion to the proper color.
10.4.16 Lower the platinum anode into the solution until the bottom edge of
the anode is about 2 mm above the shoulder of the cell. If set too
deep, gas bubbles will be trapped and cause fluctuation of the current. When
the current is first turned on, it will be about 0.8 ampere. As the solution
warms, the current will increase and must be readjusted to 1.2 amperes when it
rises above this value. After 15 to 30 minutes, the current will stabilize and
electrolysis can be allowed to continue at 1.2 ampere without attention for a
total electrolysis time of 1.5 to 2 hours.
10.4.17 With current on, add 10 ml of 10% ammonium hydroxide and continue
the electrolysis for 1 minute. Lift the anode out of the cell and
then switch off the current. Pour the solution out of the cell and rapidly
flood the cell three times with 0.IN ammonium nitrate 0.Ill ammonium hydroxide
solution. Disassemble the cell and quickly wash the planchet with a stream
45
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of alkaline ethyl alcohol. Touch a piece of filter paper to the edge of the
planchet to adsorb the film of alcohol.
10.4.18 Place the disc in a cupped planchet and heat for 10 minutes on a
hot plate. Cool and count the sample for 1000 minutes by alpha
spectrometry.
11. Calibration
APPARATUS AND SUPPLIES
11.1 Windowless 2ir gas flow proportional counter.
11.2 National Bureau of Standards (NBS) amerlcium-241 point source, ap-
proximately 2 x 105 dpm deposited on platinum and certified to ± 1%
of its stated activity.
11.3 Stainless steel discs, 2-inch diameter; mirror finish.
CALIBRATION OF THE 2ir COUNTER
11.4 Refer to manufacturer's procedure manual for calibration procedures.
11.5 Determine the counting efficiency of the 2ir counter by counting the
NBS americium-241 standard. Accumulate approximately 5 x 105 counts.
Calculate the counting efficiency by dividing the counts per minute by the cer-
tified disintegration rate (dpm).
11.6 Correct the counting efficiency for the difference in backscatter
between platinum and stainless by dividing the calculated efficiency
above by 1.023.
STANDARDIZATION OF TRACERS
11.7 All tracers are checked for non-isotopic alpha-emitting contaminants
by electrodeposition and alpha spectrometry. If non-isotopic con-
taminants are found or known to be present, the tracer must be purified before
standardization (Sill, 1974).
11.8 Transfer a 100- to 250-yl aliquot of the isotopically pure stock
tracer (^500 pCl/ml in a 211 nitric acid) to each of three 5-cm (2-
inch) stainless steel planchets.
11.9 Allow the solutions to evaporate to complete dryness at room temper-
ature.
11.10 Heat each planchet over a blast burner just to the first dull red
glow. Then quickly lower the temperature by placing the planchet on
a cold steel surface to minimize oxidation of the plate.
11.11 Count each planchet in the 2ir counter, collecting at least 101* counts
to ensure adequate statistical precision. Verify the 2ir counter
counting efficiency before and after counting.
46
-------
11.12 Electrodeposit approximately 250 pCi of the isotopically pure tracer
as described in sections 10.3.7 and 10.4.12.
11.13 Count the electroplated source on an alpha spectrometer for 100 min-
utes. Calculate the fraction of the total number of counts in the
alpha spectrum that is due to the tracing nuclide 236Pu or 2t|3Am. This frac-
tion is the correction factor to be applied to the counting rates of the eva-
porated sources in the 2ir counter.
11.14 Calculate the activity concentration of the tracer (pCi/ml) by mul-
tiplying the observed 2rr counting rates of the evaporated sources
by the correction factor (Step 11.13) and dividing by the 2ir counter efficiency
(Step 11.6) and 2.22 dpm/pCi.
CALIBRATION OF THE ALPHA SPECTROMETER
11.15 Because a point-source standard electrodeposited on platinum (the
NBS americium-241 source) cannot be used to calibrate an alpha spec-
trometer for use with diffuse sources electrodeposited on stainless steel, a
secondary standard must be employed.
11.16 Standardize a secondary source (such as one prepared in Step 11.12
or any alpha activity electrodeposited as described in Sections
10.3.7 and 10.4.12 through 10.4.18) by counting with the 2n counter until at
least 10^ counts have been collected.
11.17 Count the secondary source with the alpha spectrometer until at least
101* counts have been collected. Calculate the spectrometer efficien-
cy by multiplying the source's counting rate on the spectrometer (summed over
the entire energy range) by the 2ir counting efficiency and dividing by the
source's counting rate on the 2ir counter.
12. Quality Control
Approximately 10% of all samples are recycled as blind duplicates.
The results are evaluated by standard statistical tests, and correc-
tive action is taken, if necessary.
Data obtained from efficiency determinations are plotted on line
graphs to indicate the condition of the detectors and various elec-
tronic components.
13. Calculations
CALCULATION OF SAMPLE ACTIVITY (R)
1-3'1 (A - Ai) x F x D)
(R) isotope activity (pCi/unit) =
(B - BI) x (sample size)
47
-------
CALCULATION OF THE TWO-SIGMA ERROR (E)
13.2
A! B BI
Ts TB
(B - Bi)2
where: A = gross sample counts per minute which appear in the alpha
energy region characteristic of the specific nuclide being
analyzed
AI = background counts per minute in the same alpha energy
region (channels) as "A" above
B = gross tracer counts per minute from the sample disc
BI = background counts per minute in the same alpha energy
region (channels) as "B" above
F = tracer activity in picocuries added to the sample
D = fractional decay of the tracer between the time of its
standardization and the time of the sample count
T = sample counting time in minutes
S
T = reagent blank (background) counting time in minutes
B
14. References
Burney, 6. A. and R. M. Harbour. Radiochemistry of Neptunium. National
Academy of Sciences - National Research Council. NAS-NS-3060 (1974).
Sill, C. W., K. W. Puphal, and F. D. Hindman. Simultaneous Determination
of Alpha-Emitting Nuclides of Radium Through Californium in Soil. Analyt-
ical Chemistry 4£:1725 (1974).
Sill, C. W. Purification of Radioactive Tracers for Use in High Sensitiv-
ity Alpha Spectrometry. Analytical Chemistry 46:1426 (1974).
Sill, C. W. Simultaneous Determination of 238U, 23l*U, 230Th, 226Ra, and
210Pb in Uranium Ores, Dusts, and Mill Tailings. Health Physics. Vol. 33,
No. 5, November 1977. pp 393-404.
Talvitie, N. A. Radiochemical Determination of Plutonium in Environmental
and Biological Samples by Ion Exchange. Analytical Chemistry 43:1827
(1971).
Talvitie, N. A. Electrodeposition of Actinides for Alpha Spectrometric
Determination. Analytical Chemistry ^4:280 (1972).
U.S. Atomic Energy Commission. Measurement of Radionuclides in the En-
vironment - Sampling and Analysis of Plutonium in Soil. U.S. AEC Regula-
tory Guide 4.5 (1974).
48
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ANALYSIS OF POLONIUM-210 IN
SOIL AND AIR FILTERS
1. Principle
1.1 Samples are decomposed by digestion with hydrofluoric acid and ni-
tric acid in the presence of lead carrier and a polonium-208 tracer.
Polonium is co-precipitated with lead sulfide from a dilute acid solution sepa-
rating it from calcium, iron and other interferences. The sulfide precipitate
is dissolved in dilute hydrochloric acid and polonium is spontaneously depos-
ited on a nickel disk. Polonium-210 and the polonium-208 tracer are measured
by alpha spectrometry.
2. Application
2.1 This method is appropriate for the analysis of up to 1 gram of soil
or one 10-cm (4-inch) diameter glass-fiber air filter.
3. Range
3.1 This method is designed to detect environmental levels of activity
approaching 0.02 picocurie per sample. To avoid possible cross-con-
tamination and contamination of the alpha detectors, sample activities should
be limited to 25 picocuries or less.
4. Interferences
4.1 Samples containing extremely high levels of polonium-210 will result
in invalid analyses by interfering with the determination of the polo-
nium-208 tracer recovery. Samples should be screened by gross alpha counting
to determine the proper sample aliquot.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
3.29 S
o
LLD = 2.22 x E x S
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
49
-------
where 3.29 - K + KQ
a p
Ka = the value for the upper percentile of the standardized
normal variate corresponding to the preselected risk
for concluding falsely that activity is present (a) =
0.05
Kg = corresponding value for the predetermined degree of
confidence for detecting the presence of activity
(1-g) = 0.95
S = estimated standard error for the net sample activity
2.22 = dpm/pCi
E = fractional counting efficiency
S = sample size
5.2 The sensitivity for an analysis is proportional to the actinide yield,
the counter efficiency, and the length of alpha count. The sensitiv-
ity for an analysis having a 100% yield and employing a 1000-minute count on a
counter having a counting efficiency of 0.20 cpm/dpm is 440 counts/picocurie.
6. Precision and accuracy
7. Shipment and storage of samples and sample stability
7.1 Samples should be analyzed as soon as possible after collection to
avoid appreciable decay or ingrowth of the relatively short-lived
polonium-210 in the sample, depending on its state of equilibrium, with its
parent lead-210.
8. Reagents
8.1 Ammonium hydroxide, concentrated (14N): Reagent grade.
8.2 Ammonium hydroxide, (1.4N): With stirring, add 100 ml concentrated
ammonium hydroxide to 800 ml of distilled water. Dilute to 1000 ml.
8.3 Citric acid, (40% w/v): Dissolve 40 g of reagent grade citric acid
in 100 ml of distilled water.
8.4 Ethyl alcohol, (95%): Reagent grade.
8.5 Hydrochloric acid, concentrated (121*): Reagent grade.
8.6 Hydrochloric acid, (0.5N): Add 42 ml of 121? reagent grade, hydro-
chloric acid to 900 ml of distilled water. Dilute to 1000 ml with
distilled water.
8.7 Hydrofluoric acid, concentrated (48%); Reagent grade.
8.8 Hydroxylamine hydrochloride (50% w/v): Dissolve 100 g of reagent
grade hydroxylamine hydrochloride in 100 ml of distilled water.
8.9 Lead carrier, (10 rag/ml): Dissolve 1 g of lead nitrate
in 100 ml 4N nitric acid.
8.10 Nitric acid, concentrated (16N): Reagent grade.
8.11 Polonium-208 tracer: 5 pCi/ml in 4N nitric acid.
50
-------
8.12 Thioacetamide, (10% w/v): Dissolve 50 g of reagent grade thioaceta-
mide in 500 ml of distilled water.
9. Apparatus
9.1 Alpha spectrometric analyzer: A counting system consisting of a
multichannel analyzer, biasing electronics, a printer, a vacuum
pump and silicon surface barrier detectors operated in vacuum chambers.
9.2 Caps: Black resin, Poly-Seal liner, 22-mm GCMI thread design.
9.3 Centrifuge tubes: 50-ml, disposable.
9.4 Centrifuge
9.5 Deposition cells with 1.91-cm (3/4-inch) polished nickel disks.
9.5.1 Cut a 1.43-cm (9/16-inch) hole in the bottom of the polyethylene
vial with a sharp cork borer. Improve the seal by abrading the
threaded end with wet #320 waterproof emery paper held against a flat surface.
Finish with wet #600 emery paper.
9.5.2 Remove the polyethylene liner from a 22-mm Poly-Seal cap.
9.5.3 Cut a 1.91-cm (3/4-inch) disc from 0.079-cm neoprene sheeting with
a cork borer or a die. Place the disc in the cap.
9.5.4 Cleaning
9.5.5 Completely immerse the body of the cell in dichromate-sulfuric acid
cleaning solution for 2 to 3 hours. Rinse off the cleaning solution
with water and immerse the cell in 4N nitric acid for at least one hour. Rinse
and immerse in distilled water until ready to use.
9.5.6 The cleaning process renders the polyethylene hydrophilic, provided
the cell is kept continuously wet after having been cleaned. The
polyethylene parts of used cells can be rinsed and then cleaned by the direc-
tions given in 9.5.5, except that the immersion in dichromate sulfuric acid
cleaning solution is limited to one hour. Clean the caps and neoprene washers
by immersing for a few minutes in 419 nitric acid and then rinse with water.
9.5.7 Assembly
Connect one hole of a 2-hole #6 rubber stopper to an aspirator pump
with a length of rubber tubing.
9.5.8 Rinse the polyethylene cell with distilled water but do not dry.
Hold the nickel disc centered against the threaded end of the cell
and place the rubber stopper against the other end of the cell. Apply suction
by placing a finger over the open hole of the stopper. The vacuum will hold
the planchet in a centered position while the cap assembly is screwed on. Fill
the cell halfway with water and alternately apply and release the vacuum. The
flexing will cause the planchet to seat more firmly against the cell.
51
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9.5.9 Check to see that no stream of air bubbles rises through the water
when vacuum is applied. If the vacuum is great enough, the water
may boil, but the boiling is easily distinguished from air leakage.
9.5.10 Fill the assembled cell to the top with water to preserve the hydro-
philic character of the cell until ready to add sample.
9.6 Neoprene sheet: 0.079-cm (1/32-inch) thickness.
9.7 pH meter.
9.8 Steam or hot water bath.
9.9 Stirrer.
9.10 Teflon beakers: 100-ml.
9.11 Vials: Polyethylene, 25-ml screw cap, Packard //6001075.
10. Procedure
10.1 Weigh and transfer 0.5 to 1.0 grams dried soil, or a 10-cra (4-inch)
diameter air filter, into a 100-ml Teflon beaker. Keep filter as
flat and close to bottom as possible. Add 1 ml polonium tracer and 1 ml lead
carrier.
10.2 Add 10 ml concentrated nitric acid and 10 ml 48% hydrofluoric acid
and place on hot plate. Evaporate to dryness without bringing to
a boil. Repeat 3 more times.
10.3 Add 10 ml concentrated nitric acid and evaporate to dryness. Repeat
2 more times.
10.4 Add enough concentrated nitric acid and heat to dissolve salts. Add
10 ml water and filter through a Whatman //42 filter, using a dispos-
able funnel into a disposable 50-ml centrifuge tube. Wash filter with 10 ml
water followed by 10 ml 0.05N hydrochloric acid.
10.5 Evaporate the solution in the centrifuge tube to dryness in a steam
bath. Redissolve with 1 ml concentrated hydrochloric acid. Add 10
ml water and adjust pH to 3.5-4.0 with 0.511 hydrochloric acid and/or 1.4II am-
monium hydroxide. ~"
10.6 Add 5 ml of 10% thioacetamide solution and digest for 1 to 2 hours
on the steam bath. Cool. Centrifuge. Decant and discard the super-
natant liquid.
10.7 Dissolve the precipitate with 1 ml concentrated hydrochloric acid.
Repeat steps 10.5 and 10.6.
10.8 Dissolve the residue with 1 ml concentrated hydrochloric acid while
heating on the steam bath. Add 5 ml water and filter through a What-
man #42 filter (using a disposable funnel) into a new 50-ml disposable centri-
52
-------
fuge tube. Wash the filter with 1 ml water and 1 ml 0.5N hydrochloric acid.
10.9 Transfer to a deposition cell with a minimum of water and add 2 ml
40% citric acid solution and 2 ml hydroxamine hydrochloride. Add
water until cell is 3/4 full. Place cell in a hot water bath at 80° C and stir
for 1 to 1 1/2 hours to plate the polonium.
10.10 Remove the cell from the hot water bath and discard the solution.
10.11 Wash the deposition cell with distilled water and then with ethyl
alcohol.
10.12 Heat the disc (in an aluminum planchet) on a hot plate (200° C to
250 C) for 20 minutes. Cool and count in an alpha spectrometer.
11. Calibration
11.1 Calibration of the polonium-208 tracer is performed by co-deposition
with standardized polonium- 210 solutions and by liquid scintillation
counting.
12. Quality Control
13. Calculations
CALCULATION OF SAMPLE ACTIVITY (R)
13.1
(R) isotope activity (PCi/unit) * * '* *
,p x / , ^
(B - BI) x (sample size)
CALCULATION OF THE TWO SIGMA ERROR (E)
13.2
AI B BI
T T T T
(E) = 2R / Ts TB . Ts TB
(A - AO2 (B - Bi)2
where A = gross sample counts per minute which appear in the
polonium-210 energy region
AI = background counts per minute in the same alpha energy
region (channels) as "A" above
B = gross tracer counts per minute from the sample disc
BI = background counts per minute in the same alpha energy
region (channels) as "B" above
F = tracer activity in picocuries added to the sample
D = fractional decay of the tracer between the time of its
standardization and the time of the sample count
53
-------
I = sample counting time in minutes
S
T_ = background counting time in minutes
B
14. References
Figgins, P. E., Radlochemistry of Polonium. National Academy of
SciencesNational Research Council. NAS-NS 3037. (1961)
Harley, J. H., HASL Procedures Manual. U.S. Atomic Energy Commis-
sion. HASL-300. (1972)
54
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DETERMINATION OF STRONTIUM-89
AND STRONTIUM-90 IN MILK
1. Principle
1.1 Milk with added carriers and disodium ethylenediaminetetraacetate
(Na_ EDTA) is passed through a cation exchange resin. The alkali
metals and most alkaline earths are adsorbed on the cation resin, and the com-
plexed calcium passes through unabsorbed. The alkaline earth metals are re-
moved from the cation resin by elution with a sodium chloride solution and pre-
cipitated as carbonates. Barium is removed by chromate precipitation. Stron-
tium- 89 and strontium-90 are determined by counting twice, once immediately
after separation and again after yttrium-90 ingrowth. Chemical yield is deter-
mined gravimetrically.
2. Application
2.1 This method is applicable for the determination of strontium-89 and
strontium-90 in raw, pasturized, and homogenized milk.
2.2 Strontium-89 and strontium-90 in sour milk may be determined by this
method using the batch process described in 10.14.
3. Range
3.1 No range has been established.
4. Interferences
4.1 Cream in raw milk must be separated prior to passing the milk through
the resin as it will coat the resin exchange sites. The cream may be
removed without affecting results as the strontium is complexed only with the
protein.
4.2 Other radionuclides usually present in milk do not interfere.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
4.66 S.
b
LLD = 2.22 x E x S
* HASL Procedures Manual, J. H. Barley, editor, pages D-08-01/12, August 1977.
55
-------
where 4.66 = 2/2 k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is
present («) = .05.
S. = standard deviation of the background
2.22 = dpm/pCi
E = fractional counting efficiency
S = sample size
6. Precision and accuracy
6.1 The expected precision for strontiun-90, based on the 95% confidence
level analytical error, is 3.0 pCi/1 up to a concentration of 30 pCi/1
and 10% above 30 pCi/1. The expected precision of strontium-89, based on the
95% confidence level analytical error, is 10 pCi/1 up to a concentration of 100
pCi/1 and 10% above 100 pCi/1. These precision values are those used in the
duplicate analysis program and recommended by EMSL-LV Quality Assurance Branch.
7. Shipment and storage of samples and sample stability
7.1 Milk samples should be preserved with 15 ml of 37% formaldehyde
solution. Refrigerated samples will be usable (as samples) for 10 to
12 weeks.
8. Reagents
8.1 Ammonium acetate buffer solution. pH 5.2: Dissolve 153 g ammonium
acetate in 800 ml distilled water, and 28.6 ml glacial acetic acid.
Adjust to pH 5.2 using either ammonium hydroxide or acetic acid. Dilute to
1000 ml with distilled water.
8.2 Ammonium hydroxide, concentrated: Reagent grade.
8.3 Ammonium hydroxide, 6N: Dilute 400 ml concentrated ammonium hydrox-
ide to 1000 ml with distilled water.
8.4 Barium carrier, 40 mg/ml: Dissolve 76.2 g barium nitrate in 800 ml
distilled water and dilute to 1000 ml.
8.5 Complexing solution: Dissolve 216 g disodium ethylenediaminetetra-
+ acetate in 250 ml water. Add 10 ml Sr2 carrier (40 mg/ml, 10 ml
Ba2 carrier (40 mg/ml), and 200 ml ammonium acetate buffer (pH 5.2). Adjust
the pH to 5.2 using approximately 70 ml 6IJ ammonium hydroxide; dilute to 3
liters with distilled water. Readjust pH to 5.2 before using.
8.6 Dowex 50W-X 8: 50-100 Mesh
8.7 Ethylenediaminetetraacetate disodium (Na2 EDTA), 3%: Dissolve 33.3 g
Na2 EDTA in 900 ml distilled water; adjust pH to 5.2 with ammonium
acetate buffer solution; dilute to 1000 ml with distilled water. Readjust pH
to 5.2 just prior to use.
56
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8.8 Nitric acid, concentrated: Reagent grade.
8.9 Nitric acid, 90%: Reagent grade.
8.10 Nitric acid, IN; Add 62.5 ml concentrated nitric acid to 800 ml
distilled water. Cool, and dilute to 1000 ml.
8.11 Sodium carbonate, 3N: Dissolve 159 g sodium carbonate in 800 ml
distilled water and dilute to 1000 ml.
8.12 Sodium chloride, 4N: Dissolve 234 g sodium chloride in 800 ml
distilled water and dilute to 1000 ml.
8.13 Sodium chloride, 1.5N; Dissolve 88 g sodium chloride in 800 ml
distilled water and dilute to 1000 ml.
8.14 Sodium chromate, IN: Dissolve 81 g sodium chromate in 800 ml
distilled water and dilute to 1000 ml.
8.15 Sodium hydroxide, 611: Dissolve 240 g sodium hydroxide in 800 ml
water. Cool and dilute to 1000 ml.
8.16 Strontium carrier, 40 mg/ml: Dissolve 96.6 g strontium nitrate in
800 ml distilled water and dilute to 1000 ml.
9. Apparatus
9.1 Ion exchange columns (Figure 8)
9.2 Low background beta counter
10. Procedure
FRESH MILK
10.1 Add 300 ml EDTA complexing solution to 1 liter milk, filter through
cheesecloth and mix well. Pour sample into funnel (Figure 8). Re-
move screw cap from bottom of cation column and allow milk to pass through at
gravity flow (approximately 100 ml/min).
10.2 Wash resin with three 100-ml portions of hot distilled water, leaving
enough water on columns to keep them wet. Attach stopcock assembly
(Figure 8) to bottom of cation column. Add 800-ml hot (60° C) distilled water
and allow to flow through the column at a rate of 100 ml/min.
10.3 Wash column with 800 ml 3% EDTA (pH 5.2) at a flow of 20 ml/min to
remove residual calcium; then wash column with 200 ml distilled water.
10.4 Wash adsorbed EDTA from column with 200 ml 1.5N sodium chloride at
10 ml/min. Place 500 ml 4N sodium chloride in funnel and let it
flow through column at rate of 20 ml/min.
57
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10.5 Collect the first 400 ml of eluent at a flow rate of 20 ml/min in a
500-ml centrifuge bottle. See 10.13 to regenerate the resin.
10.6 Add 1 ml 6N sodium hydroxide to the 400-ml strontium-barium fraction,
and with stirring add 10 ml 3N sodium carbonate. Continue stirring
for 30 minutes. An occasional sample will not precipitate. Warming the solu-
tion with stirring will usually bring down the precipitate. Centrifuge, and
discard supernate.
10.7 Dissolve precipitate with 5 ml IN nitric acid and transfer to 40-ml
centrifuge tube. Add 5 ml ammonium acetate buffer solution (pH 5.2).
Adjust pH to 4.6 with concentrated ammonium hydroxide and/or III nitric acid.
Heat in water and add 1 ml sodium chromate. Stir for 10 minutes to precipitate
barium. Centrifuge, and discard precipitate. Repeat.
10.8 Add 2 ml concentrated ammonium hydroxide to supernate and swirl tube
to mix well. Add 2 ml 311 sodium carbonate to reprecipitate strontium.
Centrifuge, and discard supernate.
10.9 Wash precipitate with distilled water. Centrifuge, and discard super-
nate. Repeat.
10.10 Dissolve precipitate in a maximum of 6 ml 6N nitric acid. Add 30 ml
90% nitric acid to solution to precipitate strontium nitrate. Cool
solution in an ice bath. Centrifuge, and discard supernate. Record time and
date as Tj (start of yttrium ingrowth).
10.11 Transfer precipitate to a clean, tared planchet with a minimum of
distilled water. Dry, cool, and weigh. Count on a low-background
beta counter.
10.12 Count again 7 days later for yttrium-90 ingrowth and strontium-89
decay.
10.13 To prepare the resin in the Na form, wash 170 ml of resin (H form)
with 1000 ml of AN sodium chloride eluted at 10 ml/min, followed by
400 ml of 5% sodium hydroxide at 10 ml/min, then 1000 ml distilled water at 10
ml/min flow rate. Pack column and add glass-fiber filter to top of column.
SOUR MILK
10.14 Add 300 ml EDTA cotnplexing solution to 1 liter of milk. Stir, adjust
pH to 5.2 with ammonium hydroxide.
10.15 Add 40 ml cation resin to solution and stir for 15 minutes using a
magnetic stirrer. Allow resin to settle and decant milk into another
beaker containing 40 ml cation resin. Stir again for 15 minutes on a magnetic
stirrer. Allow resin to settle and discard the milk.
10.16 Combine the two 40-ml portions of resin and wash several times with
distilled water to remove milk and cream. Transfer resin into an
80-ml polyethylene column attached to the top of a 45-ml polyethylene column
containing 30 ml cation resin.
58
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10.17 Attach reservoir to top of columns.
10.18 Continue with the procedure for fresh milk beginning with step 10.3.
11. Calibration
Counting efficiency of the low-background beta counter is determined
by three factors; geometry, backscatter, and self-absorption. The
first two, geometry and backscatter, are fairly well established for each in-
strument while the third, self-absorption, is dependent on the sample. There-
fore, "self-absorption curves" similar to the curves illustrated in Figures 2
and 3, must be prepared. Samples with known activity, but with varying sample
weights, are prepared and the data plotted as indicated in Figures 2 and 3.
The strontium-89, strontium-90/yttrium-90 standards are traceable to the Na-
tional Bureau of Standards.
11.1 Reagents
11.1.1 Strontium nitrate stock solution, 20 mg/ml: Dissolve 20 g strontium
nitrate in 800 ml distilled water and dilute to 1000 ml.
11.1.2 Strontium-89, ^1000 pCi/ml: Prepare by diluting a National Bureau
of Standards standard with distilled water.
11.1.3 Strontium-go/yttrium-go, ^1000 pCi/ml: Prepare by diluting a Na-
tional Bureau of Standards standard with distilled water.
11.1.4 Nitric acid, 90%: Reagent grade.
11.1.5 Nitric acid, 6N: Add 375 ml of concentrated nitric acid to 600 ml
of distilled water. Cool and dilute to 1000 ml.
11.1.6 Yttrium carrier, 5 mg/ml: Dissolve 6.15 g yttrium oxide in a minimum
of concentrated nitric acid. Dilute to 1000 ml with distilled water.
11.2 Strontium-89 calibration
11.2.1 Weigh 1.0 g strontium-89 solution into each of ten 40-ml centrifuge
tubes. Pipet, in increasing quantities, 1 to 10 ml of the strontium
nitrate stock solution into these tubes. Mix well.
11.2.2 Transfer to a tared planchet. Rinse centrifuge tubes twice with dis-
tilled water and evaporate to dryness.
11.2.3 Dry planchet at 105° C. Cool and reweigh.
11.2.4 Count planchet in low-background beta counter for 50 minutes.
11.2.5 Plot data on graph paper. Recount, or replace any sample that ap-
pears to be more than 2 sigma out of line.
59
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11.3 Strontium-90, yttrium-90 calibration
Counting efficiencies must be determined for strontium-90, yttrium-
90, and the mixture of strontium-90 and yttrium-90.
11.3.1 Weigh 1.0 g of strontium-go/yttrium-go standard into each of ten 40-
ml centrifuge tubes. Pipet, in increasing quantities, 1 to 10 ml of
strontium nitrate stock solution. Bring all volumes to 15 ml with distilled
water.
11.3.2 Add 2 ml 6N sodium hydroxide and 10 ml 3N sodium carbonate. Heat
with stirring for 5 minutes. Cool and centrifuge. Discard super-
nate. Record the time as I\. Hold for 2 weeks or longer to allow the Ingrowth
of yttrium-90.
11.3.3 At the end of the yttrium-90 Ingrowth, dissolve the strontium car-
bonate with a minimum of 6 ml 6N nitric acid; add 1 ml yttrium car-
rier (5 mg/ml). Add 30 ml 90% nitric acid to precipitate the strontium nitrate.
Cool in an ice bath for 30 minutes and centrifuge. Transfer the supernate (yt-
trium-90) to a tared planchet and start to evaporate the acid.
11.3.4 Redissolve the strontium nitrate in a minimum of 6N nitric acid. Add
30 ml 90% nitric acid. Cool in an ice bath, and centrifuge. Transfer
the supernatant liquid to the planchet in 11.3.3 and continue evaporation. When
the planchet is dry, flame to remove any excess nitric acid. Cool and reweigh.
Count in a low-background beta counter for 50 minutes.
11.3.5 Redissolve the strontium nitrate from 11.3.4 in a minimum of water
and transfer to a tared planchet. Evaporate to dryness, flame, cool,
and reweigh. Count in a low-background beta counter for 50 minutes.
11.3.6 After the first count of the strontium-90 planchet, continue addition-
al counting daily for 2 weeks. Then count on every second day for 2
additional weeks. Plot strontium-90/yttrium-90 counts per minute versus stron-
tium-90 counts per minute. This will generate a series of curves based on sam-
ple weights.
11.3.7 Plot data obtained in 11.3.4 and 11.3.5 on graph paper. Recount,
or replace any sample that appears to be more than 2 sigma out of
line. Figure 9 illustrates typical curves.
12. Quality Control
Reference standards and backgrounds are counted with each set of sam-
ples and the counts plotted on control charts. Counts which fall out-
side the warning and control limits are evaluated for appropriate remedial ac-
tion.
Standard samples are received from the EMSL-LV Quality Assurance
Branch. These samples are analyzed and the results are evaluated by
the Quality Assurance Branch and the evaluation returned to the analyst. If
the results are unsatisfactory, the reason for the problem is found and all re-
sults during the questionable time period are evaluated for possible remedial
action.
60
-------
Approximately 10% of all samples are recycled as blind duplicates.
The results of the duplicates are subjected to standard statistical
tests and listed in a computer printout both as individual results and as a
tabular summary. Results outside control limits are examined for possible re-
medial action.
13. Calculations
13.1 Strontium-90
AB CTI i
strontium-90 (pCl/llter) = (i + EF)A . (1 + GH)C "
where A = decay of strontium-89 from the time of collection to the
time of first count
B = net counts per minute of total strontium on second count
C = decay of strontium-89 from the time of collection to the
time of second count
D = net counts per minute of total strontium on first count
E = ratio of the counting efficiencies (yttrium-90/
strontium-90) on the second count
F = yttrium-90 ingrowth from the time of separation to the
time of the second count
G = ratio of the counting efficiencies (yttrium-90/
strontium-90) on the first count
H = ingrowth of yttrium-90 from time of separation to time
of first count
I = fractional counting efficiency of strontium-90
J = fractional chemical yield of strontium
K = adsorption factor for strontium-90
L = sample volume (liters)
13.2 Strontium-89
strontium-89 (pCi/liter) = A " (j; + BC)D x
2.22FGHI
where A = net counts per minute of total strontium on the first
count
B = yttrium-90 ingrowth from separation to first count
C = ratio of the counting efficiencies (yttrium-90/
strontium-90) on the first count
D = net counts per minute of strontium-90 (determined by
calculation)
E = decay of strontium-89 from time of collection to time
of first count
F = adsorption factor for strontium-89
G = fractional chemical yield of strontium
H = sample volume (liters)
I = fractional counting efficiency of strontium-90
61
-------
14. References
Velton, R. J., Resolution of Strontium-89 and Strontiunt-90 in Environmen-
tal Media by an Instrument Technique. Nuclear Instrumental Methods 42:169.
(1966).
62
-------
ADJUSTABLE
VALVE
Figure 8. Ion Exchange Column, Strontium Elution.
63
-------
TYPICAL BETA EFFICIENCIES OF SR-90 AND Y-90
.480
.460
.440
.420
.400
u
2 .380
o
.360
.340
.320
.300
.280
Y-90
SR-90
Y-90 + SR-90 IN EQUILIBRIUM
J 1 L
J_J I I I 1 1 L
0 20 40 60 80 100 120 140 160 180 200 220 240 260 TOTAL MILLIGRAMS
0 , 2 3 4 5 6 7 8 9 10 11 12 13 MILLIGRAMS/CM1
SAMPLE THICKNESS
STRONTIUM NITRATE PRECIPITATE ON A TWO INCH PLANCHET
Figure 9. Typical Efficiency Curves.
64
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DETERMINATION OF STRONTIUM-89 AND STRONTIUM-90
IN WATER, VEGETATION, SOI1, AND BIOLOGICAL TISSUE
1. Principle
1.1 Vegetation and animal tissue samples are dry ashed at 600° C to re-
move all organic material. The ash Is dissolved in hydrochloric acid
and the appropriate carrier is added. After the addition, of disodium ethylenedia-
minetetraacetate, the sample is passed through a chromatographic column to remove
the compressed calcium. The strontium fraction is retained and subsequently
eluted with hydrochloric acid. After precipitation as a carbonate, it is con-
verted to a nitrate and mounted for counting.
1.2 Disodium ethylenediaminetetraacetate is added to a water sample and
the strontium is determined, as described in 1.1. Chemical yield is
determined gravimetrically.
1.3 Soil samples are fused with a mixture of sodium hydroxide-sodium car-
bonate. The fused mass is dissolved in hydrochloric acid, and the
strontium is recovered by the ion-exchange method.
2. Application
2.1 This method is applicable for the determination of strontium-89 and
strontium-90 in freshwater, seawater, soil, vegetation, and animal
tissue.
3. Range
3.1 No range has been established.
4. Interferences
4.1 Magnesium is the most common interference, and must be removed by
precipitating the magnesium complex.
4.2 Other radionuclides usually present do not interfere.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
65
-------
4.66 S,
LLD = b
2.22 x E x S
where 4.66 = 2/2~ k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05.
S = standard deviation of the background
2.22 = dpm/pCi
E = fractional counting efficiency
S - sample size
6. Precision and accuracy
6.1 The expected precision for strontium-89 and strontium-90 based on
the 95% confidence level in food, soft tissue, bone, and water is
3.0 pCi/liter or gram up to a concentration of 30 pCi/liter or gram and 10%
above 30 pCi/liter. These precision values are those used in the duplicate
analysis program and recommended by the EMSL-LV Quality Assurance Branch.
7. Shipment and storage of samples and sample stability
7.1 Water samples must be preserved with 15 ml of concentrated nitric
acid per 3.7 liters (one gallon). Soil samples require no preserva-
tion and vegetable or animal tissue must be kept refrigerated. With the proper
preservation, samples may be stored for several years for strontium-90 analysis.
If strontium-89 analysis is required, samples should be analyzed within two
months of collection time.
8. Reagents
8.1 Ammonium acetate buffer solution, pH 5.2: Dissolve 153 g ammonium
acetate in 800 ml distilled water and add 28.6 ml glacial acetic
acid. Adjust to pH 5.2 using either ammonium hydroxide or acetic acid. Dilute
to 1000 ml with distilled water.
8.2 Ammonium hydroxide, concentrated: Reagent grade.
8.3 Ammonium hydroxide, 611: Dilute 400 ml concentrated ammonium hydrox-
ide to 1000 ml with distilled water.
8.4 Barium carrier, 40 mg/ml: Dissolve 76.2 g barium nitrate in 800 ml
distilled water and dilute to 1000 ml.
8.5 Calcium carrier, 2M: Dissolve 328.2 g calcium nitrate in 800 ml
distilled water, and dilute to 1000 ml.
8.6 Ethylenediaminetetraacetate disodium (EDTA): Reagent grade.
8.7 EDTA, 6%: Dissolve 66.6 g EDTA in 900 ml distilled water, and di-
lute to 1000 ml.
66
-------
8.8 Hydrochloric acid, 6N: Add 500 ml concentrated hydrochloric acid
to 400 ml distilled water. Cool, and dilute to 1000 ml.
8.9 Nitric acid, concentrated: Reagent grade.
8.10 Nitric acid, 90%: Reagent grade.
8.11 Nitric acid, IN: Add 62.5 ml concentrated nitric acid to 800 ml
distilled water. Cool, and dilute to 1000 ml.
8.12 Sodium carbonate, 3N: Dissolve 159 g sodium carbonate in 800 ml
distilled water and dilute to 1000 ml.
8.13 Sodium chloride, 4N: Dissolve 234 g sodium chloride in 800 ml
distilled water and dilute to 1000 ml.
8.14 Sodium chloride, 1.5N: Dissolve 88 g sodium chloride in- 800 ml
distilled water and dilute to 1000 ml.
8.15 Sodium chromate, IN: Dissolve 81 g sodium chromate in 800 ml
distilled water and dilute to 1000 ml.
8.16 Sodium hydroxide, 6N: Dissolve 240 g sodium hydroxide in 800 ml
water. Cool, and dilute to 1000 ml.
8.17 Strontium carrier, 40 rag/ml: Dissolve 96.6 g strontium nitrate
in 800 ml distilled water and dilute to 1000 ml.
9. Apparatus
9.1 Parr acid digestion bomb.
9.2 Low-background beta counter.
9.3 Furnace, muffle.
10. Procedure
FOOD, VEGETATION, OR ANIMAL TISSUE
10.1 Dry ash all samples at 600° C to remove all organic matter. Do not
exceed 600° C.
10.2 Weigh amount of sample and add carrier as indicated in the following
table, into a 250-ml beaker. Add 20 ml 6N hydrochloric acid and with
gentle heat dissolve the residue. Add 100 ml distilled water. If insoluble
residue (silica) is present, filter, wash residue twice with 100-ml portions
of distilled water, and add to filtered solution. Discard residue.
67
-------
Various Sample Types, Sample Sizes, and Carriers
Sample
Type
Food
Bone
Vegetation
Tissue
Sample
Size
(8)
10
2
2 or 5
2
Strontium
carrier
(ml)
2
2
2
2
Calcium
carrier
(ml)
__
1
1
Barium
carrier
(ml)
5
5
5
5
10.3 Add filtrate to 500 ml 6% EDTA solution and adjust to pH 3.8 with
concentrated ammonium hydroxide. Stir vigorously for 75 minutes to
precipitate the magnesium salt of EDTA. Allow precipitate to settle overnight.
10.4 Filter, and collect the filtrate. Adjust to pH 4.6 with ammonium
hydroxide. Add 20 ml sodium acetate buffer solution. Readjust pH
to 4.6 with either ammonium hydroxide or acetic acid.
10.5 Quantitatively transfer to the 1000-ml graduated cylinder, dilute
to 1000 ml with distilled water. Mix.
10.6 Prepare ion-exchange resin by passing 1000 ml 4N sodium chloride
over 170 g of the resin in a column at a flow of 10 ml/min. Follow
with 400 ml 5% sodium hydroxide and then with 1000 ml distilled water at a flow
of 10 ml/min.
10.7 Assemble apparatus as illustrated in Figure 10. Adjust solution flow
through resin column to 10 ml/min. Stop flow when just enough solu-
tion remains to cover resin. Discard effluent.
10.8 Transfer 600 ml 2% EDTA, adjusted to pH 5.1 with ammonium hydroxide,
to the reservoir and adjust flow to 20 ml/min. Wash column with 200
ml distilled water at a flow of 20 ml/min. Discard washing.
10.9 Place 460 ml 1.5N hydrochloric acid in reservoir, and elute at a
flow rate of 8 ml/min. Discard first 60 ml of effluent. Collect
the strontium fraction in the next 400 ml in an 800-ml beaker.
10.10 Add 200 ml concentrated ammonium hydroxide to the strontium fraction.
Slowly add 10 ml 3N sodium carbonate, and stir for 30 minutes.
10.11 Filter through Millipore filter //URWPO-2400. Rinse the beaker with
distilled water. Police sides and bottom of beaker. Wash walls of
beaker and filter with ethyl alcohol.
10.12 Wash precipitate from filter into a 40-ml centrifuge tube using a
minimum of distilled water. Dissolve precipitate with a maximum of
6 ml 6N nitric acid. Add 30 ml 90% nitric acid to precipitate the strontium
68
-------
nitrate. Cool solution in ice bath. Centrifuge, and discard supernate. Re-
cord data and time as TI (start of yttrium ingrowth).
10.13 Transfer precipitate to a clean, tared planchet with a minimum of
distilled water. Dry, cool, and weigh. Count on a low-background
beta counter.
10.14 Count again seven days later for yttrium-90 ingrowth and strontium-89
decay.
FRESHWATER
10.15 Add 33.3 g EDTA, 2 ml strontium carrier, 1 ml each barium and cal-
cium carrier, to 100-ml water sample. Adjust pH to 4.6 with ammo-
nium hydroxide and proceed as in step 10.4.
SEAWATER
10.16 Add 2 ml strontium carrier and 1 ml each of barium and calcium car-
rier to 1000 ml of the sample. Stir and heat to boiling.
10.17 Adjust pH to 10.0 with sodium hydroxide. Add 20 ml 3N sodium car-
bonate. Stir and continue heating until precipitate forms. Cool
overnight and decant supernate.
10.18 Dissolve precipitate with 200 ml 6N hydrochloric acid. Adjust vol-
ume to 1000 ml with distilled water, and filter. Discard filter.
Add 33.3 g EDTA with stirring and adjust pH to 3.8 with ammonium hydroxide.
Proceed as in step 10.4.
BONE
10.19 Dissolve 2.0 g of ash in 20 ml 6N hydrochloric acid. When dissolved,
add 1000 ml of distilled water, carriers as indicated in table, and
proceed as in step 10.4.
11. Calibration
Counting efficiency of the low-background beta counter is determined
by three factors; geometry, backscatter, and self-absorption. The
first two, geometry and backscatter, are fairly well established for each in-
strument, while the third, self-absorption, is dependent on the sample. There-
fore, "self-absorption curves" similar to the curves illustrated in Figures 2
and 3, must be prepared. Samples with known activity, but with varying sample
weights, are prepared and the data plotted as indicated in Figures 2 and 3.
The strontium-89, strontium-90/yttrium-90 standards are traceable to the Na-
tional Bureau of Standards.
11.1 Reagents
11.1.1 Strontium nitrate stock solution, 20 mg/ml: Dissolve 20 g strontium
nitrate in 800 ml distilled water and dilute to 1000 ml.
69
-------
11.1.2 Strontium-89, 'vlOOO pCi/ml: Prepare by diluting a National Bureau
of Standards standard with distilled water.
11.1.3 Strontium-go/yttrium-go, M.OOO pCi/ml: Prepare by diluting a National
Bureau of Standards standard with distilled water.
11.1.4 Nitric acid, 90%: Reagent grade.
11.1.5 Nitric acid, 6N: Add 375 ml of concentrated nitric acid to 600 ml of
distilled water. Cool and dilute to 1000 ml.
11.1.6 Yttrium carrier, 5 mg/ml: Dissolve 6.15 g yttrium oxalate in a mini-
mum of concentrated nitric acid. Dilute to 1000 ml with distilled
water.
11.2 Strontium-89 calibration
11.2.1 Weigh 1.0 g strontium-89 solution into each of ten 40-ml centrifuge
tubes. Pipet, in increasing quantities, 1 to 10 ml of the strontium
nitrate stock solution into these tubes. Mix well.
11.2.2 Transfer to a tared planchet. Rinse centrifuge tubes twice with dis-
tilled water and evaporate to dryness.
11.2.3 Dry planchet at 105° C. Cool and reweigh.
11.2.4 Count planchet in low-background beta counter for 50 minutes.
11.2.5 Plot data on graph paper. Recount, or replace, any sample that appears
to be more than 2 sigma out of line.
11.3 Strontium-90, yttrium-90 calibration
Counting efficiencies must be determined for strontlum-90, yttrium-90,
and the mixture of strontium-90 and yttrium-90.
11.3.1 Weigh 1.0 g of strontium-90/yttrium-90 standard into ten 40-ml centri-
fuge tubes. Pipet in increasing quantities, 1 to 10 ml of strontium
nitrate stock solution, bringing all volumes to 15 ml with distilled water.
11.3.2 Add 2 ml 6N sodium hydroxide and 10 ml 3N sodium carbonate. Heat with
stirring for five minutes. Cool and centrifuge. Discard supernate.
Record the time as Tj. Hold for two weeks or longer to allow the ingrowth of
yttrium-90.
11.3.3 At the end of the yttrium-90 ingrowth period, dissolve the strontium
carbonate with a minimum of 6 ml 6JN nitric acid; add 1 ml yttrium
carrier (5 mg/ml). Add 30 ml 90% nitric acid" to precipitate the strontium
nitrate. Cool in an ice bath for 30 minutes; centrifuge. Transfer the super-
nate, containing the yttrium, to a tared planchet and start to evaporate the
acid.
70
-------
11.3.4 Redissolve the strontium nitrate in a minimum of 6N nitric acid.
Add 30 ml 90% nitric acid. Cool in an ice bath, and centrifuge.
Transfer the supernatant liquid to the planchet in 11.3.3 and continue eva-
poration. When the planchets are dry, flame to remove any excess nitric acid.
Cool and reweigh. Count in a low-background beta counter for 50 minutes.
11.3.6 After counting the strontium-90 planchet, continue counting dally
for two weeks. Then count on every second day for two weeks. Plot
strontium-90/yttrium-90 counts per minute versus strontium-90 counts per min-
ute. This will generate a series of curves based on sample weights.
11.3.7 Plot data obtained in 11.3.4 and 11.3.5 on graph paper. Recount, or
replace, any sample that appears to be more than two sigma out of
line.
12. Quality Control
Reference standards and backgrounds are counted periodically and
counts plotted on control charts. Counts which fall outside the
warning and control limits are evaluated for appropriate remedial action.
Standard samples are received from the EMSL-LV Quality Assurance
Branch. These samples are analyzed and the results are evaluated
by the Quality Assurance Branch and evaluation returned to analyst. If the
results are unsatisfactory, the reason for the problem is found and all re-
sults during the questionable time period are evaluated for possible remedial
action.
Approximately 10% of all samples are recycled as blind duplicates.
The results of the duplicates are subjected to standard statistical
tests and listed in a computer printout both as individual results and as a
tabular summary. Results outside control limits are examined for possible re-
medial action.
13. Calculations
13.1 Strontium-90
A t* f^t\ 1
strontium-90 (pCi/g or liter)
(1 + EF)A - (1 + GH)C 2.22IJKL
where A = decay of strontium-89 from the time of collection to the time
of first count
B = net counts per minute of total strontium on second count
C = decay of strontium-89 from the time of collection to the time
of second count
D = net counts per minute of total strontium on first count
E = ratio of the counting efficiencies (yttrium-90/strontium-90)
on the second count
F = yttrium-90 ingrowth from the time of separation to the time
of the second count
G = ratio of the counting efficiencies (yttrium-90/strontium-90)
on the first count
71
-------
H = ingrowth of yttrium-90 from time of separation to time of
first count
2.22 = dpm/pCi
I = fractional counting efficiency of strontium-90
J = fractional chemical yield of strontium
K = adsorption factor for strontium-90
L sample (grams or liters)
13.2 Strontium-89
strontium-89 (pCi/g or liter) = A - (1 + BC)D
2.22FGHI
where A = net counts per minute of total strontium on the first
count
B = yttrium-90 ingrowth from separation to first count
C = ratio of the counting efficiencies (yttrium-90/strontium-90)
on the first count
D = net counts per minute of strontium-90 (determined by
calculation)
E = decay of strontium-89 from time of collection to time of
first count
2.22 dpm/pCi
F = adsorption factor for strontium-89
G fractional chemical yield of strontium
H = sample size (grains or liters)
14. References
Velton, R. J., Resolution of Strontium-89 and Strontium-90 in Environmen-
tal Media by an Instrument Technique. Nuclear Instrumental Methods 42:169.
(1966).
72
-------
A
1000 ml
SEPARATORY
FUNNEL
CATION RESIN
COLUMN
Figure 10. Ion-Exchange Apparatus.
73
-------
THE COLLECTION AND DETERMINATION OF
TRITIUM IN AIR
1. Principle
1.1 This method describes a procedure for the collection and determina-
tion of tritium as hydrogen and as moisture in the atmosphere. The
atmospheric sample is passed through a molecular sieve to remove the water
vapor. Tritium-free hydrogen is added as a carrier. The carrier, hydrogen
and atmospheric hydrogen, are converted to water using a palladium black cat-
alyst. This water is collected in a second molecular sieve trap. The water
collected on these traps is removed by heating and is subsequently analyzed
for tritium.
2. Application
2.1 This method is applicable for the collection and determination of
tritium in air. A one-week sample is usually collected.
3. Range
3.1 No range has been determined.
4. Interferences
4.1 Gaseous radionuclides that might be collected on the molecular sieve
and subsequently removed are the only interferences.
5. Lower limit of detection
5.1 The lower limit of detection* (LID) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
4.66 S,
LLD - b
2.22 x E x S
where 4.66 = 2/2 k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
S, = standard deviation of the background
b
2.22 = dpm/pCi
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
74
-------
E = fractional counting efficiency
S - sample size
6. Precision and accuracy
6.1 The estimated precision at the 1 pCi/m3 level is ± 10 percent.
7. Shipment and storage of samples and sample stability
7.1 Samples are collected on a weekly basis and returned to the labora-
tory. Analysis should be performed within 48 hours.
8. Reagents
8.1 Electrolyte, 2% sodium hydroxide: Dissolve 20 g sodium hydroxide
pellets in 800 ml low-level-tritium distilled water and dilute to
1000 ml.
8.2 Liquid scintillation cocktail: Prepare by dissolving 8.0 g 2.5-
diphenyloxazole (PPO), 1.5 g p-bis-(O-methylstyrl) - benzene (BIS-
MSB), and 120 g naphthalene in 800 ml spectrographic grade p-dioxane and di-
lute to 1000 ml. Store in amber bottle. The solution is not usable after one
month.
8.3 Molecular sieve-4A, 1/8" x 3/16" pellets:
8.4 Palladium black catalyst: Prepare by slurring 250 g of filter-grade
asbestos in 1000 ml low-level-tritium distilled water. Add 10 g pal-
ladium chloride dissolved in 25 ml concentrated hydrochloric acid. Stir for 5
minutes and add 50 ml concentrated ammonium hydroxide and 100 ml 37% formalde-
hyde (solution should be black). Continue stirring for 10 minutes. Filter
and wash with low-level-tritium distilled water. Dry at 350° C before using.
9. Apparatus
The total sampler consists of two parts: a "field box," and a
permanently located field station.
"FIELD BOX"
9.1 A foam-filled box with cutouts for the traps.
9.2 Ml and M2 trap: 250 g molecular sieve-4A heated to 350° C and eva-
cuated at 1 mm of mercury pressure.
9.3 MH trap, 75 mm x 25 mm: 400 g molecular sieve-4A heated to 350° C
and evacuated at 1 mm of mercury pressure.
9.4 Hydrogen generator: Consists of a 200-ml plastic bottle with two
platinum electrodes.
75
-------
"FIELD STATION"
9.5 Refrigerator: approximately 2.5 cu ft
9.6 Rectifier: 1 amp capacity
9.7 Pump: fish tank
9.8 Flowmeter: 0 to 10 ml/min
9.9 Meter: dry gas
LABORATORY
9.10 Furnace: 350° C
9.11 Trap, Johns
9.12 Tube, connecting
9.13 Dewar, 1000-ml
9.14 Pump, vacuum, 130 1/min
9.15 Bottle, weighing
9.16 Pipet, disposable, 5 ml
9.17 Vial, polypropylene, 25 ml
10. Procedure
10.1 Label glass traps with station number and position, i.e., Ml, M2,
MH. Record weight and other data on worksheet.
10.2 Fill the electrolytic cell with 70 ml electrolyte, weigh, and record.
10.3 Place traps and electrolytic cell in the "field box" and make con-
nection as illustrated in Figure 11.
SAMPLER PREPARATION IN THE FIELD
10.4 Connect "field box" to system, Figure 12.
10.5 Turn on pump and check for leaks. This is accomplished by pinching
intake hose and observing the float in the flowmeter. Float should
return to zero. All leaks must be corrected before proceeding.
10.6 Remove clamp from electrolytic cell.
10.7 Install a new chart in the recording thermometer.
76
-------
10.8 Record gas meter reading, air flow-rate, date and hour, sampler num-
ber, and station sample card.
SAMPLE REMOVAL
10.9 Check for leaks as before and note on worksheet if any were observed.
10.10 Record flow, gas meter reading, date and time on the sample card.
Remove temperature chart. Return it with the sampler and sample card.
LABORATORY DISASSEMBLY
10.11 Remove and weigh the electrolytic cell and glass traps. Record on
worksheet.
WATER RECOVERY
10.12 Place Ml or MH trap in distillation unit. Adjust heat to obtain
350 C in 30 minutes. Distill the water into the trap cooled in
liquid nitrogen. Use helium as a carrier. All of the water should distill in
one hour. If weight of water on Ml or MH is less than 9 g, add appropriate
volume of distilled low-level-tritium well water to make 10 ml before distil-
lation.
10.13 Turn off the helium carrier gas and vacuum; remove the trap from
liquid nitrogen. Allow trap to come to room temperature. Record
weight of water recovered on worksheet.
10.14 Pipet 5 ml of water into a liquid scintillation vial and add 20 ml
liquid scintillation solution. Prepare a background and standard
vial. Place in liquid scintillation spectrometer and allow to dark-adapt for
24 to 36 hours before counting.
10.15 De-gas M2 as in steps 10.11 and 10.12 for reuse. Do not save this
water.
11. Calibration
12. Quality Control
12.1 A portable sampler is being used to collect a duplicate sample at
various sampling stations. This sample is analyzed as a blind dupli-
cate to collect sampling error information.
13. Calculations
V, x p, x 273
13.1 Volume sample at STD (M3)
760 x (273 +
where V.. = volume collected (m^)
P = average barometric pressure
77
-------
273 = absolute temperature equal to 0 C
760 = mm of mercury at sea level
T., = average temperature (from temperature chart)
* V,
nl "Ml
13.2 Tritium as water (pCi/m3 air) =
o
where A... = pCi/1 of water recovered from Ml
V,,, = volume of water recovered from Ml
Ml
V = volume of sample from 13.1
A. y
13.3 Tritium as hydrogen (pCi/m3) =
Vo HE
where A.^ = pCi/ml of water recovered from MH
V = volume of water recovered from MH
Mil
V = volume of sample from 13.1
o
_ _ weight water on MH _
K ~ weight loss from cell - weight water on MH
78
-------
AIR OUT
AIR IN
FROM
CATALYST
TO CATALYST
\y
PLATINUM
ELECTRODES
ELECTROLYTIC
CELL
Figure 11. Field Box
79
-------
oo
o
VALVE TO
ADJUST
FLOW
BATTERY
CHARGER
DRY GAS
METER
CHARGER
& PUMP
ELECTRICAL
CONNECTIONS
Figure 12. Field Station.
-------
DETERMINATION OF LOW-LEVEL TRITIUM IN WATER
(Alkaline Electrolytic Enrichment)
1. Principle
Distilled water with added sodium hydroxide is slowly electrolyzed
at a constant temperature. The protium atom is preferentially
evolved leaving the tritium atom behind. The complete theoretical discussion
of the separation is presented by Ostund, 1962.
2. Application
2.1 The method is applicable for the determination of tritium at low
levels for all distilled waters.
3. Range
An upper level of 250 pCi/liter has been established. Cross-contam-
ination becomes a problem at higher ranges.
4. Interferences
4.1 Other radionuclides and stable elements present in water do not
interfere.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
4.66 S.
LLD- b
2.22 x E x S
where 4.66 = 2/2 k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
S, = standard deviation of the background
b
2.22 = dpm/pCi
E «> fractional counting efficiency
S = sample size
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
81
-------
6. Precision and accuracy
7. Shipment and storage of sample and stability
7.1 Samples must be collected in glass without preservatives. A minimum
of 300 ml are needed for the analysis. Samples may be stored one
year in glass.
8. Reagents
8.1 Carbon dioxide, gas, commercial grade
8.2 Potassium permanganate crystal, reagent grade
8.3 Silver nitrate, crystal, reagent grade
8.4 Sodium hydroxide, pellets, reagent grade
9. Apparatus
9.1 Bottle: 500-ml screw cap
9.2 Condenser, Liebig: 300-mm
9.3 Constant current supply: 3 amp and 0.3 amp are required
9.4 Constant temperature bath: maintained at 4° C
9.5 Electrolytic cell: (Figure 13)
9.6 Flask, round bottom: 1000-ml
9.7 Flask, volumetric: 200-ml
9.8 Pipet, disposable: 5-ml
9.9 Pipet, volumetric: 50-ml
9.10 Pump, vacuum:
9.11 Trap, receiving: 50-ml
9.12 Tube, adapter: 105°
9.13 Tube, connecting: 75°
9.14 Tube, connecting: 35/40 to 18/9
10. Procedure
10.1 Transfer 300 to 500 ml of sample to a 1000-ml flask. Any settled
solids may be discarded. Add a few crystals of potassium permanga-
nate to form a permanent pink-colored solution. Add one boiling chip.
82
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10.2 Distill to dryness, discarding first few drops. Collect in a glass
screw-top bottle.
10.3 Clean the electrolytic cells with distilled water, rinse with ethyl
alcohol, and bake dry at 350 C. Cool.
10.4 Pipet 50 ml of the sample into the electrolytic cell. Add 1 g (7
pellets) sodium hydroxide pellets. Dissolve by capping and mixing
thoroughly. (A 2% sodium hydroxide solution is required as serious corrosion
problems will result.)
10.5 Remove stopper and insert the clean iron-nickel electrode assembly.
Add the glass tops with red and black leads extending through the
side arm.
10.6 Prepare a low-level standard (20 to 30 TU) and a background (antique
water) sample for each group of eight samples. Place all electro-
lytic cells in constant temperature bath. Fill 200-ml volumetric flasks with
a portion of sample, standard, or background.
10.7 Connect all cells in series and connect the iron electrode to the
positive lead of the constant current power supply and connect the
nickel electrode to the negative lead of the power supply.
10.8 Activate the 3-amp power supply and observe the meter reading. The
amp-meter should indicate 3 amperes and the voltmeter should indicate
2.7 volts times the number of cells being used. A lower voltage reading indi-
cates a short circuit and a higher reading indicates an open circuit. Correc-
tive action must be made.
10.9 Cover cells with protective cover as explosions have occurred from
this point on.
10.10 When the sample has decreased in volume by 50% (usually 24 hours),
readjust volume to 50 ml with an aliquot from the 200-ml volumetric
flask. Repeat until all of the 200 ml have been added to the cell.
10.11 Permit the volume to decrease to 25 ml, then decrease the current to
0.3 amp. Continue the electrolysis until the volume decreases to 4
or 5 ml. (If the levels of solution in the cells are not all even, disconnect
those that are finished and continue electrolysis.)
10.12 Remove the cells from the constant temperature bath. Replace top
and electrode assembly with glass cap.
10.13 Bubble carbon dioxide gas through remaining liquid for 3 to 4 minutes.
Replace cap with glass stopper.
10.14 Connect the electrolytic cell to the tared trap with a ground joint
adapter. Place a plug of glass wool in the adapter to eliminate
entrainment. Connect the assembly to a vacuum pump.
83
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10.15 Immerse trap in liquid nitrogen and apply vacuum. When initial gas-
sing and boiling ceases, apply heat to electrolytic cell. Continue
heating until all visible water has been distilled. Discontinue heat but con-
tinue to evacuate for 10 to 15 minutes.
10.16 Disconnect the apparatus, capping the trap. Allow the trap to return
to room temperature and weigh.
10.17 Transfer the water from the trap to a tared scintillation vial.
Weigh and record the weight of water transferred.' If needed, add
low-tritium water to the vial until it contains 5 ml.
10.18 Add liquid scintillation cocktail to all vials and prepare one count-
ing standard and one background.
10.19 Place in liquid scintillation spectrometer and dark-adapt for 24 to
36 hours before counting.
10.20 Count each sample twice for 100 minutes each time or until the sta-
tistics on 2 succeeding counts are within 2 sigma of each other.
11. Calibration
11.1 Prepare an enrichment curve by enriching a set of standard tritium
samples using the same procedure as for the unknowns. Allow the
final volume of enriched solution to vary so that different points are ob-
tained for the construction of the curve.
12. Quality control
12.1 As the activity of many of the samples is below the minimum detect-
able concentration, samples with higher activities are recycled as
blind duplicates.
13. Calculations
A « H
Tritium (TU) = 2.22 x 3.25 x 0.005 * Eff x D x E
where A = gross counts per minute
B = background counts per minute
2.22 = dpm/pCi
3.25 = pCi/TU
0.005 = sample volume counted, liters
Eff = fractional counting efficiency
D = sample dilution factor (volume of sample
divided by volume counted, if dilution to
5 ml is necessary)
E = enrichment factor (from calibration graph)
-------
14. References
14.1 Ostund, H. G., Werney, E. The Electrolytic Enrichment of Tritium
and Deuterium for Natural Tritium Measurements. Proceedings of Tri-
tium in the Physical and Biological Sciences. IAEA, Vienna 1962.
14.2 Barley, J. H. HASL Procedure Manual. HASL-300.
85
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50ml
25m!
F
2.5ml
...
II
A-A'
Iron Cathode
Nickel Cathode
₯
Spray
Shield
rO
n
A1
cm
Figure 13. Alkaline Electrolysis Cell.
86
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DETERMINATION OF TRITIUM IN WATER AND BIOLOGICAL TISSUE
(Direct Method)
1. Principle
1.1 A portion of sample is distilled to remove contaminants. Several
different techniques are used to recover a pure distilled fraction.
These techniques include azeotopic distillation, vacuum distillation, and am-
bient pressure distillation. Details of these techniques will be discussed
under procedure sections. After distillation, an aliquot is mixed with liquid
scintillation solution and counted in a. liquid scintillation spectrometer.
Standards and background samples are prepared and counted with each group of
samples.
2. Application
2.1 This method is applicable for the determination of tritium in water,
vegetation, animal tissue, blood, and urine.
3. Range
3.1 No range has been established.
4. Interferences
4.1 Volatile radionuclides are the common interference. Alcohols, acids,
most OH-radicals and hydrocarbons are common chemical interferences,
but all may be eliminated by proper sample preparation.
4.2 Light and chemical phosphorescence must be considered. These can
be eliminated by allowing the sample to dark-adapt for 24 to 36
hours.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
4.66 S,
LLD - b
2.22 x E x S
* HASL Procedures Manual, J. H. Barley, editor, pages D-08-01/12, August 1977.
87
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where 4.66 = 2^2 k, where k is the value for the upper percentlle of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
S. - standard deviation of the background
b
2.22 - dpm/pCi
E = fractional counting efficiency
S = sample size
6. Precision and accuracy
6.1 The expected precision for tritium in water, based on a 95% confi-
dence level analytical error, below 4000 pCi is given by the expres-
sion:
%2o = 33970x(pCi/l)~°'9067
and 20% above 4000 pCi/1. These are the values used in the Duplicate Analysis
Program and are recommended by the EMSL-LV Quality Assurance Branch.
6.2 Over a period of 3 years, 12 cross-check samples containing known
amounts of tritium in water, and 12 cross-check samples containing
known amounts of tritium in urine were received from the Quality Assurance
Branch. None of the results obtained were outside the three-sigma control
limits.
7. Shipment and storage of samples
7.1 Water samples should be collected in glass with no preservatives.
7.2 Biological samples should be kept refrigerated until time of analy-
sis.
8. Reagents
8.1 Cyclohexane: Reagent grade.
8.2 Liquid scintillation solution: Prepare by dissolving 8.0 g 2,5-di-
phenyloxazole (PPO), 1.5 g p-bis-(0-methylstyrl)-benzene (BIS-MSB),
and 120 g napthalene in 800 ml spectrographic grade p-dioxane and dilute to
1000 ml. Store in amber bottle. The solution ia not usable after one month.
8.3 Silver nitrate, crystals: Reagent grade.
9. Apparatus
9.1 Condensers, Liebig: 100 mm, 300 mm
9.2 Desiccator, vacuum
9.3 Flasks, boiling: 1 neck: 100 ml, 1000 ml
88
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9.4 Trap, Barret
9.5 Trap, Johns
9.6 Tube, connecting: 105°, 75°
Assembled apparatus is illustrated in Figure 14.
10. Procedure
WATER
10.1 Distill 10- to 50-ml portion of sample just to dryness. Vent the
first steam and collect the distillate in a cold trap. If radio-
iodine is present, add 0.1 g silver nitrate before distillation.
10.2 Pipet a 5-ml portion of the distillate into a polyethylene counting
vial. Add 20 ml of liquid scintillation solution.
10.3 Prepare a background and standard by pipetting 5 ml of low-tritium
water and 5 ml of a diluted National Bureau of Standards standard
into polyethylene counting vials. Add 20 ml of liquid scintillation solution
to each vial.
10.4 Mix all solutions and place in liquid scintillation spectrometer.
Allow to light-adapt for 24 hours or longer. Count for two 100-min-
ute intervals or until successive counts are within 2 sigma.
MILK, BLOOD, AND URINE
10.5 Add 50 ml of sample and 50 ml cyclohexane to boiling flask. Assemble
apparatus as illustrated in Figure 14.
10.6 Bring to boiling and collect distillate in Barret trap. Continue
distillation until 15 to 20 ml of water are collected. Allow phases
to separate and water phase to clear (usually overnight).
10.7 Proceed as in 10.2 for the tritium determination.
VEGETATION OR ANIMAL TISSUE
10.8 Add 100 to 200 g of vegetable material or 25 to 50 g of animal tis-
sue to a vacuum desiccator. Cool trap with liquid nitrogen and apply
vacuum.
10.9 Allow the vacuum distillation to continue for several hours until 15
to 20 ml of water are collected.
10.10 Proceed as in 10.1.
89
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11. Calibration
11.1 The prime consideration in calibration of a liquid scintillation
spectrometer after an initial determination of operating conditions
is to maximize the counting efficiency with the lowest background. The so-
called "Figure of Merit" is accomplished by adjusting upper and lower discri-
mination and gain control as necessary (see Manufacturer's Operator's Manual).
12. Quality Control
12.1 A background and standard are counted along with each group of 10
samples. The data recorded daily on a control chart provide an in-
dication of instrument performance.
13. Calculation
WATER, URINE, MILK, AND BLOOD
13.1 Tritium (pCi/liter) = *°°° A"B
where A = gross counts per minute
B = background counts per minute
2.22 = dpm/pCi
C - fractional counting efficiency determined
with the standard counted with each group
D = sample size (usually 5 ml)
VEGETATION OR ANIMAL TISSUE
13.2 Tritium (pCi/g) = E x Tritium (pCi/ml)
where E = fractional water composition (ml/g)
90
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DRYING
TRAP
-
*
*
CONDENSER
BARRET
DISTILLATION
RECEIVER
1000 ml FLASK
HEATER
Figure 14. Distillation Apparatus.
91
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ISOTOPIC ANALYSIS BY GAMMA RAY SPECTRA USING LITHIUM-
DRIFTED GERMANIUM DETECTORS
1. Principle
1.1 Environmental levels of gamma-emitting radionuclides in a multitude
of natural matrices are identified and quantitated by gamma scintil-
lation spectroscopy. However, in numerous cases the success in resolving com-
plex spectra is limited by reason of resolution. In cases where peak multi-
plets are within the resolution limits of the scintillation detector, computer
deconvolution becomes impossible. These cases require the employment of a
solid state "high resolution" detector generally constructed of lithium-drifted
germanium, Ge(Li). The average resolution advantage of a high-volume Ge(Li)
detector over a Nal(Tl) scintillation detector is about 40. For this reason,
Ge(Li) detectors are used for the analysis of gamma-emitting radionuclides in
the environment.
2. Application
2,1 This method is applicable for analysis of gamma-emitting radio-
nuclides with gamma energies ranging from nearly 60,000 electron
volts (60 keV) to approximately 2,000,000 electron volts (2 meV).
3. Range
3.1 There is no upper range for Ge(Li) gamma spectroscopy. The elec-
tronics have an upper limit of approximately 3 x 10° detector counts
per minute (cpm). If a sample contains radionuclide concentrations resulting
in a count rate greater than 3 x 106 cpm, then either the distance between the
sample and detector is increased or an aliquot of the sample is analyzed.
4. Interferences
4.1 The use of Ge(Li) detectors has greatly reduced the problem of in-
terferences between gamma photons of nearly identical energies.
Spectral peaks containing multiple energy contributions may be deconvoluted
when actual photon energies are within 1 keV.
5. Minimum detectable concentrations
5.1 The minimum detectable concentrations (MDC's) of radionuclides vary
according to the particular branching ratio of a radionuclide upon
disintegration, the counting geometry, the photon energy, sample size, and the
actual counting time of detection. One-thousand-minute counts are reasonable
for low-level environmental samples. The MDC of cesium-137 for such a count
time is approximately 5 picocuries per total sample. This is based on a 200-ml
sample placed directly upon the detector.
92
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6. Precision
6.1 The 95% confidence interval for a result obtained by gamma spectro-
scopy is approximately ± the MDC for samples with gamma activities
close to background and ± 10% for samples with "higher" activities, i.e., the
95% interval is ± the MDC or ± 10%, whichever is greater. This is based on
nonoverlapping gamma photopeaks. In the case of photopeak multiplets, the pre-
cision decreases nonlinearly with the degree of peak overlap.
7. Shipment and storage of samples
7.1 Samples containing or suspected of containing short-lived isotopes
require expeditious handling. Care should be exercised with all sam-
ples to assure that they are, and remain, representative and homogeneous. This
may require the addition of acid to water samples to prevent dissolved radio-
nuclides from plating out on the sample container walls, or the addition of
formaldehyde to aid in the preservation of milk samples, etc.
8. Reagents
8.1 Radon-free water is used for dilution of aqueous samples to a con-
stant volume.
9. Apparatus
9.1 Either a 4096- or a 2048-channel multichannel analyzer spectrometer
with output compatible to standard computer readable media.
9.2 Large-volume Ge(Li) detector.
10. Procedure
10.1 Prepare homogeneous sample in a standard geometry for counting. This
geometry must be equivalent to one for which the detector has been
calibrated to generate an appropriate efficiency vs. energy curve.
10.2 Place sample in counting configuration.
10.3 Refer to manufacturer's operating manual for data acquisition and
computer operation.
10.4 Print spectrum and/or store on appropriate computer-compatible device.
11. Calibration
11.1 To energy-calibrate, cadmium-109 with a gamma emission at 88 keV and
yttrium-88 with a gamma emission at 1836 keV are used. By juggling
the amplifier's "gain" and the analog-to-digital converter's "zero offset", the
centroids of these peaks are placed in the appropriate locations for a linear
"energy-versus-channel-number" calibration. For the 0.5-keV-per-channel cali-
bration, the 88-keV peak centroid is placed at channel 176 and the 1836-keV
peak centroid at channel 3672. Due to the high resolution and stability of
current Ge(Li) detectors, there should be negligible differential nonlinearity.
93
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11.2 Efficiency calibration is achieved by counting a standard in a given
geometry where the concentrations of the isotopes are known. The re-
sult of this calibration is an eff iciency-versus-energy curve in units of counts
per gamma. A mixed-radionuclide source is generally used which produces peaks
well spaced and distributed throughout the normal analysis range.
12. Quality Control
12.1 The Ge(Li) system is energy- calibrated daily and efficiency- calibrated
as needed. Logs of pertinent calibration data are maintained.
12.2 Approximately 10% of all samples submitted for gamma spectrum analy-
sis are resubmitted as blind samples. The results of these duplicate
analyses are subjected to standard statistical tests. A summary of the results
from the statistical tests, along with the Individual analytical results, is
listed in a computer printout. Results outside control limits are examined for
possible remedial action.
12.3 Standard samples are received from the EMSL-LV, Quality Assurance
Branch, International Atomic Energy Agency in Austria, and the World
Health Organization in France. These samples are analyzed and the results are
analyzed by the originating office. If the results are unsatisfactory, the
reason for the anomaly is found and all results generated during the question-
able time period are evaluated for possible corrective action.
13. Calculations .
13.1 Isotopic identifications from Ge(Li) gamma spectral data are made
as follows:
a. Identify all peak energies.
b. Calculate all peak areas by integrating the peak region and
subtracting the area beneath the continuum.
c. Identify isotopes by the presence or absence of appropriate
photopeaks and their ratios to each other.
13.2 The concentration calculation for each isotope is:
Isotopic Concentration (^"oiTsi^ = 2.22 * B x E x S x T
where A = peak area above continuum (counts)
B = branching ratio for the gamma ray of the
particular isotope in question (gammas/
disintegration)
E = fractional detector efficiency at photopeak energy
(counts /gamma)
S = sample size
T = count length (minutes)
94
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13.3 The 2-sigma counting error is calculated by:
,. 2/A + 2C
Error (%) = -. x
where C = photopeak area below continuum (counts)
13.4 The above three paragraphs, 13.1, 13.2, and 13.3, yield results at
the time of count. To extrapolate to the time of collection, the
following formula is applied:
C = CeXAt
o
where C = concentration at midpoint of collection
C = concentration at time of count
A = In 2/half-life (days)
At = time of count minus time at mid-point of
collection (days)
13.5 The 2-sigma counting error expressed as a percent does not change
under the extrapolation of 13.4. Therefore, the 2-sigma counting
error expressed in units of concentration is:
Error (concentration) = r°^. x c
1(JU o
95
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ISOTOPIC ANALYSIS BY GAMMA RAY SPECTROSCOPY
USING THALLIUM-ACTIVATED, SODIUM IODIDE CRYSTALS
1. Principle
1.1 Environmental samples contain varying amounts of naturally occurring
and man-made radionuclides. Analysis of a sample's gamma ray spectrum
generated by a thallium-activated, sodium iodide crystal provides a rapid
method requiring minimal sample preparation for identifying and quantifying
the gamma-emitting radionuclides which are present.
2. Applica'tion
2.1 This method is applicable for analyzing all types of samples which
can be homogeneously placed in a standard counting geometry and con-
tain radionuclides emitting gamma rays with energies ranging from approximately
60 thousand electron volts (60 keV) to 2 million electron volts (2 MeV).
3. Range
3.1 There is no upper range for Nal(Tl) gamma spectroscopy. The elec-
tronics have an upper limit of approximately 1 x 106 detector counts
per minute (cpm). If a sample contains radionuclide concentrations, resulting
in a count rate of greater than 1 x 105 cpm, then either the distance between
the sample and detector is increased or an aliquot of the sample is analyzed.
4. Interferences
4.1 If the spectra for 2 or more radionuclides have an overlapping photo-
peak, but the remainder of their spectra are dissimilar with non-over-
lapping photopeaks, then the spectrum of a sample containing these nuclides can
be resolved with an increase in the error terms associated with the nuclides.
If the nuclides have identical or very similar spectra, the spectrum of a sample
containing these nuclides cannot be directly resolved by this method.
5. Minimum detectable concentrations
5.1 The minimum detectable concentrations (MDC's) of individual radionu-
clides are dependent upon the following factors:
a. branching ratio of radionuclide in question
b. energy of gamma rays being emitted
c. sample size
d. the geometry in which the sample is contained
e. length of count
f. number of gamma-emitting radionuclides present in the sample.
96
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For example, if cesium-137 is the only radionuclide present in a 3.5-liter liq-
uid sample contained in a 4.0-liter MarineHi beaker and counted for 100 min-
utes, then the cesium-137 MDC is approximately 5 picocuries per liter (pCi/1).
6. Precision
6.1 The 95% confidence interval for a result obtained by gamma spectros-
copy is approximately ± the MDC for samples with gamma activities
close to background or ± 10% for samples with "higher" activities, i.e., the
95% confidence interval is ± the MDC or ± 10%, whichever is greater. This is
based on non-overlapping gamma photopeaks. In the case of photopeak multiplets,
the precision decreases with the degree of overlap.
7. Shipment and storage of samples
7.1 Samples containing or suspected of containing short-lived radionu-
clides require expeditious handling. Care should be exercised with
all samples to assure that they are, and remain, representative and homogeneous.
This may require the addition of acid to water samples to prevent dissolved nu-
clides from plating-out on the sample container's walls, the addition of form-
aldehyde to aid in the preservation of milk samples, etc.
8. Reagents
8.1 Radon-free water is used for dilution of aqueous samples to a con-
stant volume.
9. Apparatus
9.1 Beaker, Marinelli; aluminum, 4-liter.
9.2 Can; aluminum, 200-ml.
9.3 Container; polyethylene, 400-ml.
9.4 Crystal; 4 by 4 Nal(Tl).
9.5 Planchets; stainless steel, 5-cm.
9.6 Planchets; stainless steel, 11-1/2-cm.
9.7 Spectrometer; Gamma.
9.8 Computer.
10. Procedure
10.1 Prepare homogeneous sample in a standard geometry. The standard geo-
metries are:
a. sample contained in 5-cm diameter stainless steel planchet.
b. sample contained in 11-1/2-cm diameter stainless steel planchet.
97
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c. aqueous sample contained in 400-ml polyethylene container.
d. aqueous sample contained in 200-ml sealed aluminum can.
e. soil sample equivalent in volume to 100 ml of water contained
in 200-ml sealed aluminum can.
f. Aqueous sample (3.5-liter)contained in 4-liter aluminum Marinelli
beaker.
10.2 Place sample in counting configuration and initialize gamma spectro-
meter to acquire gamma ray spectrum.
10.3 Print and/or store spectrum on appropriate computer compatible device.
10.4 Perform manual or computer resolution of spectrum.
11. Calibration
11.1 Bismuth-207 emits gamma rays with energies of 0.5696 MeV and 1.0634
MeV. While counting a bismuth-207 standard, adjust the amplifier
gain and threshold controls until the 0.5696 MeV gamma forms a photopeak whose
centroid is in channel 57 and the 1.0634 MeV gamma forms a photopeak whose cen-
troid is in channel 106.3. The 200-channel gamma spectrometer is now calibra-
ted from 0 to 2 MeV at 10 keV per channel.
11.2 The capability to quantitate a particular radionuclide from a gamma
ray spectrum is achieved by counting a known standard of that radio-
nuclide in each geometry used.
12. Quality Control
12.1 Each Nal(Tl) gamma spectrometer is energy-calibrated daily. Logs and
quality control charts are maintained.
12.2 Known standards for quantitation are counted as needed.
12.3 Approximately 10% of all samples submitted for gamma spectrum analy-
sis are resubmitted as blind samples. The results of these duplicate
analyses are subjected to standard statistical tests. A summary of the results
from the statistical tests, along with the individual analytical results, are
listed in a computer printout. Results outside control limits are examined for
possible remedial action.
12.4 Standard samples are received from the EMSL-LV, Quality Assurance
Branch, International Atomic Energy Agency in Austria, and the World
Health Organization in France. These samples are analyzed and the results are
analyzed by the originating office. If the results are unsatisfactory, the
reason for the anomaly is found and all results generated during the question-
able time period are evaluated for possible corrective action.
13. Calculations
13.1 Nuclides are identified by the presence or absence.of photopeaks and
their ratios to each other.
98
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13.2 Identified radionuclides are manually quantitated by:
a. integrating one of its photopeaks
b. subtracting the area of the photopeak beneath the continuum
c. comparing the cpm found in this net area to the cpm found in
the corresponding area of a known standard of that radionuclide
counted in the same geometry on the same gamma spectrometer.
13.3 A computer program, known as ALPHA M, is used to identify and quanti-
tate radionuclides from Nal(Tl) gamma spectra. ALPHA M requires that
for each radionuclide contained in the sample to be analyzed, there must be a
spectrum of that radionuclide acquired from counting a standard of known acti-
vity.
13.4 The assumption made by ALPHA M is that a complex spectrum of a sample
containing several radionuclides is equal to the sum of spectra of
the individual radionuclides.
13.5 An example follows: Assume there is a sample containing a known
quantity of iodine-131 and cesium-137. Further assume there is a
standard containing a known amount of iodine-131 equal to 10 times the amount
of Iodine-131 contained in the sample and a second standard containing a known
amount of cesium-137 equal to 20 times the amount of cesium-137 contained in
the sample. Then ALPHA M assumes:
S = 0.1 I + 0.2 Cs + e
where S = sample spectrum
I = iodine-131 standard spectrum
Cs = cesium-137 standard spectrum
e = difference between S and 0.1 I + 0.2 Cs
which is primarily due to counting error
13.6 Then, if an unknown sample containing iodine-131 and cesium-137 is
gamma-counted, a model of the resulting spectrum is
S = 61 I + 82 Cs + e
where S = unknown sample spectrum
Sl» 82 = parameters to be estimated
13.7 There may be a change in gain or threshold between the acquisition
of the known standard spectra and the acquisition of the unknown sam-
ple spectrum. To compensate for this possibility, variables for the gain and
threshold, denoted G and T, respectively, are added to the model resulting in
S = Bi I + 82 Cs + 33 G + Bit T + e
13.8 Estimates of $i> @2> 3s, and 84 are obtained by applying standard
weighted least squares techniques. Estimates of 81 and 02 yield es-
timates of the amount of iodine-131 and cesium-137 contained in the unknown sam-
ple since the amount of iodine-131 in the unknown sample is estimated by multi-
plying the activity of the iodine-131 standard by BI- Similarly ($2 estimates
the amount of cesium-137 present in the unknown sample.
99
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13.9 Estimates of the variances associated with the amounts of iodine-131
and cesium-137 present in the unknown sample are calculated from the
variances associated with BI and 82 respectively. (The mathematical derivations
and formulas are beyond the scope of this method. See Draper and Smith, 1966,
for formulas). Thus, the errors associated with the iodine-131 and cesium-137
concentrations are statistical errors based on the least squares estimation of
f$l and 82-
13.10 This least squares procedure can be generalized so that an unknown
sample containing n nuclides can be described by the model
s = e^ + M + ... + BnNn + e^ G + an+2 T + .
where S = unknown sample spectrum
31 = least squares parameters to be estimated, 1 = 1, 2
n+2
N. = individual standard spectrum of nuclide i, i = 1, ..., n.
G = gain at time of acquisition of standard spectra
T = threshold at time of acquisition of standard spectra
13.11 With the exception of potassium-40, ALPHA M yields results in picocur-
ies per unit of size ± the 2-sigma statistical error in picocuries
per unit of size. Potassium-40 is reported as stable potassium in units of
grams per unit of size ± the 2-sigma statistical error also in grams per unit
of size. To extrapolate to the concentration at the time of sample collection,
the following formula is applied:
AAt
Co = C x e
where Co = concentration at midpoint of collection
C = concentration at time of count
X = In 2/half-life (days)
At = time of count minus time at midpoint of
collection (days)
14. References
14.1 Kanipe, L. G., S. K. Seale, and W. S. Liggett, "Least Squares Resolu-
tion of Gamma Ray Spectra in Environmental Monitoring." Unpublished
paper prepared under project number E - AP78BDI for the Office of Research and
Development, U.S. Environmental Protection Agency.
14.2 Schonfeld, E.,'A. H. Kibbey, and W. Davis, 1965. Determination of
Nuclide Concentrations in Solutions Containing Low Levels of Radio-
activity by Least Squares Resolution of the Gamma Ray Spectra, ORNL-3744. Oak
Ridge National Laboratory, Oak Ridge, Tennessee.
100
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14.3 Schonfeld, E. 1966. ALPHA M - An Improved Computer Program for
Determining Radioisotopes by Least Squares Resolution of the Gamma
Ray Spectra. ORNL-3975. Oak Ridge National Laboratory, Oak Ridge, Tennessee.
14.4 Draper, N. R. and H. Smith, Applied Regression Analysis. New York:
John Wiley and Sons, Inc., 1966.
101
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DETERMINATION OF RADIOKRYPTON, RADIOXENON,
AND TRITIATED METHANE IN AIR
Principle
1.1 The noble gases and initiated methane are separated and collected
from atmospheric samples by a series of cryogenic-gas chromatographic
techniques. Water and carbon dioxide are removed by molecular sieve-13X at
room temperature. Krypton, xenon, and methane are collected on charcoal at
liquid nitrogen temperature. They are transferred to molecular sieve-5A where
they are separated from any remaining oxygen, argon, nitrogen, and each other.
The separated gases are transferred to liquid scintillation vials and counted
in a liquid scintillation spectrometer.
2. Application
2.1 This method is applicable for the determination of krypton-85, -85m,
-87, -88, xenon-133, -135, and tritium as methane in samples of air.
3. Range
3.1 No range has been established, however, samples have been analyzed
at the 5 nCi/liter level.
4. Interference
4.1 Radon-222 will interfere with the xenon analysis. Thismay be elim-
inated through degassing of the various adsorption columns.
5. Lower limit of detection
5.1 The lower limit of detection* (LLD) is defined as the smallest con-
centration of radioactive material sampled that has a 95% probability
of being validly detected.
4.66 S.
LLD = b
2.22 x E x S
where 4.66 = 2/2~ k, where k is the value for the upper percentile of
the standardized normal variate corresponding to the pre-
selected risk for concluding falsely that activity is pre-
sent («) = .05
S, = standard deviation of the background
2.22 - dpm/pCi
E = fractional counting efficiency
S = sample size
* HASL Procedures Manual, J. H. Harley, editor, pages D-08-01/12, August 1977.
102
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6. Precision and accuracy
7. Shipment and storage of samples and sample stability
7.1 As most of these samples are in the form of compressed air, they
cannot be shipped by air (commercial carrier).
7.2 Storage time depends on the shortest half-life of the radionuclide
of interest.
8. Reagents
8.1 Acetone: commercial grade
8.2 Alcohol, ethyl: 95%
8.3 Charcoal, coconut: 16 to 20 mesh, 30 to 50 mesh
8.4 Helium: reagent grade
8.5 Liquid scintillation cocktail: Dissolve 1.5 g 2,5-diphenyloxazole
(PPO) and 300 mg l,4-bis-2-(4-methyl-5-phenyloxazole)-benzene (di-
methyl-POPOP) in 800 ml spectrographic grade toluene and dilute to 1000 ml
with toluene. De-gas by heating to reflux temperature.
8.6 Molecular sieve-5A: 30 to 60 mesh
8.7 Molecular sieve-13X: 1/8" x 3/16" pellets
8.8 Xenon carrier: Reagent grade
9. Apparatus
The apparatus is similar to that illustrated in Figure 15. The var-
ious components, from left to right are:
9.1 Molecular-sieve-13X: A 40 mm ID trap packed with 200 g 1/8" x 3/16" pel-
lets of molecular sieve 13X.
9.2 Pre-cooler: 150 cm of 12-mm OD glass tubing
9.3 Pressure gauge: 0 - 760 mm of mercury
9.4 GI: 40 mm ID trap packed with 100 g of 16 to 20 mesh charcoal
9.5 MSi and MS2: 150 cm of 12-mm OD tubing packed with 30 to 60 mesh
molecular sieve-5A
9.6 V-13: Two-position, 6-port valve
9.7 C2: 20-cm length of 1/8" copper tubing packed with 0.3 g of 30 to 50
mesh activated charcoal
103
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9.8 Liquid scintillation vial: 20-ml vial with Luer joint and valve
9.9 Manometer, digital: 0 to 100 mm of mercury
9.10 Dewar flask: 500- and 1000-ml
9.11 Electric furnace: capable of attaining 350 C
9.12 Immersion heater: 500-W
9.13 liquid scintillation spectrometer
It is not possible to show on the line drawing all the valving and
vacuum connections necessary for the operation. However, a purified
helium supply is connected to the two flowmeters, and a mechanical vacuum pump
is connected at both vacuum connections.
Thermistors, located in the outlets of GI, MSi, and MS 2, are used to
detect the gas elution. The thermistor detector unbalances a Whet-
stone bridge circuit which in turn drives a pen on a recorder. A continuous
record of the location of the various gases is thus maintained throughout the
separation.
10 . Procedure
10.1 De-gas all traps at 350° C and evacuate until a pressure of 10 torr
is obtained. Cool and fill traps with helium. Zero the thermistors
with a flow of helium. Cool the pre-cooler, GI , MSi, and MSa, with liquid ni-
trogen (LN) .
10.2 Record the weight of the sample bottle and connect to the sample in-
let port. Establish sample flow through mol-seive * pre-cooler *
GI * vacuum. Adjust pressure to approximately 350 mm of mercury by means of
the needle valve on sample bottle. (Reduced pressure is necessary to avoid
condensation of liquid air in the system.)
10.3 Continue the transfer of sample to GI until the pressure drops to
less than 10 mm of mercury. Close inlet valve. Remove sample bottle
and reweigh (difference in weight = sample size).
10.4 Close valve C and B, open valve D, and establish helium flow (600-
800 ml/min) through GI * thermistor 1 * vent. Remove LN from GI and
replace with dry ice acetone slush (DIA). Continue this flow until most all
the air is removed as evidenced by a return of the pen recorder to the base
line (approximately 55 minutes). Close vent valve and helium flow.
10.5 Leave DIA on GI and establish helium flow GI » thermistor 1 -
-» vent 2. MSi and MS 2 are in LN when flow is stabilized. Remove
DIA from GI and replace with electric furnace and heat to 350 C.
104
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10.6 Continue heating until all of the gases are transferred to MS]. This
is indicated by a return to base line by the pen on the recorder. (A
shift in base line is usually noted at this point which is due to a higher
temperature of the gases entering the thermistor cell.)
10.7 Close vent valve and helium vent valve. Open high vacuum valve to
Ci and continue heating until a pressure of <10~^ torr is obtained.
GI is ready for another run.
10.8 Establish helium flow (200 to 250 ml/min) MSi * thermistor 2 * vent
2. Remove LN from MS} and replace with a -32° C alcohol bath. After
2 to 3 minutes, a sharp increase is noted on the recorder as the argon and oxy-
gen are eluted. Continue the flow until the pen returns to the base line.
10.9 Rearrange helium flow MSi -» thermistor 2 * MS 2 * vent 3. Continue
flow until krypton is eluted from MSi (approximately 12 to 14 min-
utes) .
10.10 Quickly rearrange helium flow MSi * vent 2 (MS 2 and vent 3 closed).
Replace the alcohol with cold water (20° C) and elute the nitrogen to
vent. Watch the elution of nitrogen carefully, and by rearranging the flow
MSi * thermistor 2 -» MS2 * vent 3, transfer the last of the nitrogen peak to
MS 2 (this is mostly methane).
10.11 Place immersion heater in cold water bath and heat until carbon mon-
oxide and xenon are transferred to MS 2 (approximately 10 minutes).
Remove boiling water from
10.12 Place a clean liquid scintillation vial and valve in position. Evac-
uate C2 by heating with a heat gun until pressure is >10 ** torr.
Place LN on G£.
10.13 Arrange helium flow MSi -» MSi -» thermistor 3 -» vent. Remove LN from
MS 2 and replace with -32 C alcohol bath. A small oxygen peak is
noted in 2 to 3 minutes. When the krypton peak appears, immediately close
vent 3 and open V-13, collect the krypton in C^. When the pen on the recorder
returns to the base line, close V-13, open vent 3, and allow the helium to con-
tinue to flow.
10.14 Remove the helium in C-z by evacuating until a pressure of <0.1 mm
of mercury is attained. Close vacuum valve and heat C2 to transfer
the krypton to the vial. When pressure has stabilized, record pressure and
temperature. Close the Luer valve and remove valve and vial from system. Add
liquid scintillation cocktail to vial and place in liquid scintillation spec-
trometer.
10.15 Transfer methane and xenon to liquid scintillation vials as described
in 10.12, 10.13, and 10.14.
10.16 Count the separated samples for four 50-minute intervals.
105
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11. Calibration
11.1 KRYPTON-85
Prepare counting standards by diluting a National Bureau of Standards
(NBS) krypton-85 standard with xenon. (AIL commercial krypton cur-
rently available contains krypton-85). Add scintillation cocktail and count in
liquid scintillation spectrometer (as in 10.16) to determine counting efficien-
cy.
Counting efficiency (C.E.)
cpm-bkg
C.E.
dpm(standard)
where cpm = average of four 50-minute counts
bkg = background in counts per minute
dpm = activity of standard as of counting time
11.2 XENON
As the beta energy of the xenons is similar to that of krypton-85
and the beta spectrum of the krypton-85 in a liquid scintillation
spectrometer is broad, the same counting efficiency is used for xenon.
Tritiated methane
11.3 Prepare counting standards by diluting a tritiated toluene standard,
traceable to the NBS, and counting as in 10.16.
12. Quality Control
12.1 Every tenth sample is reanalyzed as a blind internal
duplicate.
12.2 An eleventh station is rotated from sampling site to sampling site.
The results, when compared to the routine station results, are used
to determine sampling error.
12.3 At one-year intervals, a large sample, ^10 cubic meters, is collected
and analyzed in one-cubic-meter portions to determine a standard de-
viation for the method.
13. Calculations
-- - v x P x 273
x (2?3 + t)
where V = volume of krypton in vial
v = vial volume
p = vial pressure
t = temperature (degrees Celsius)
106
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13.2 Krypton-85(pCi/m3)
1.14 A
2.22 * C.E. x V * S
where A = gross cpm-bkg cpta
2.22 = dpm/pCI
C.E. = fractional counting efficiency
V = volume krypton counted
weight of sample
1293 (weight in grams of 1 m* dry air)
13.3 XENON
, .. v x p x 273
VXe(ml) = 760 x (273 + t)
where V = volume of xenon in vial
A&
v = volume of vial
p = vial pressure
t = temperature (degrees Celsius)
13.4 Xenon-133 or Xenon-135(pCi/m3) = , ,, ^
&.£& x l<.. _
where A = gross cpm-bkg cpm
VcXe = volume Xe carrier added (ml)
2.22 = dpm/pCi
C.E. = fraction counting efficiency
S = sample size (m3)
V,, = volume xenon counted (ml)
Xe
13.5 Tritiated methane (CH3T)
The assumption is made that normal air contains 2 ml methane/m3.
v x p x 273
CH. = 760 x (273 + t)
4
-where V_u = volume of methane in counting vial
CH4
v = volume of vial
p = pressure in vial
t = temperature (degress Celsius)
2 x A
13.6 Tritiated methane (pCi/m3) = ^ 22 x C E x~~V
where 2 = volume of methane in air (ml)
A = gross cpm-bkg cpm
2.22 = dpm/pCi
C.E. = fractional counting efficiency
Vo = volume of methane counted (ml)
CHT
S = sample size (m3)
107
CHT
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14. References
14.1 Johns, F. B. Handbook of Radiochemlcal Analytical Methods, EPA
680/4-75-001, February 1975.
108
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PRESSURE GUAGE
O
SAMPLE
IN
o
\o
VENT, VAC He IN
E^FCS
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553 Regional Administrator, EPA, Region VIII, Denver, CO
554 Regional Radiation Representative, EPA, Region VIII, Denver, CO
555 State of Colorado
556 State of Utah
557 Regional Administrator, EPA, Region IX, San Francisco, CA
558 Regional Radiation Representative, EPA, Region IX, San Francisco, CA
559 State of Arizona
560 State of California
561 State of Nevada
562 Eastern Environmental Radiation Facility, EPA, Montgomery, AL
563 Library, EPA, Washington, DC
564 Kenneth M. Oswald, LLL, Mercury, NV
565 Roger E. Batzel, LLL, Livemore, CA
566 James E. Carothers, LLL, Livermore, CA
567 John C. Hopkins, LASL, Los Alamos, NM
568 Jerome E. Dummer, LASL, Los Alamos, NM
569 B. P. Smith, REECo, Mercury, NV
570 Arden E. Bicker, REECo, Mercury, NV
571 A. W. Western, REECo, Mercury, NV
572 Savino W. Cavender, M.D., REECo, Mercury, NV
573 Carter D. Broyles, Sandia Laboratories, Albuquerque, NM
574 George E. Tucker, Sandia Laboratories, Albuquerque, NM
575 Albert E. Doles, Eberline Instrument Co., Santa Fe, NM
576 Robert H. Wilson, University of Rochester, Rochester, NY
I'O
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577 Richard S. Davidson, Battelle Memorial Institute, Columbus, OH
578 J. P. Corley, Battelle Memorial Institute, Richland, WA
579 John M. Ward, President, Desert Research Institute, University
of Nevada, Reno, NV
580 DOE/HQ Library, Attn: Eugene Rippeon, DOE, Washington, DC
581-605 Technical Information Center, Oak Ridge, TN (for public availability) (25)
606-607 T. F. Cornwell, DMA, DOE, Washington, DC (2)
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