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Cañon City Milling Facility
Cañon City, Colorado
PROCEDURE
Radiochemical Procedure for Radium-228
Number: 5-10
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Version: 3
10-28-13
Radiochemical Procedure for Radium-228 by Actinium-228
1.0 Purpose
This procedure describes the method that is used to preconcentrate radiochemical
isotopes for Beta decay counting, such that an Isotope concentration can be determined
for Ra-228 by counting the Ac-228 daughter. This is a modified version of EPA Method
904.0, Radium-228 Analysis by Gas Flow Counter.
2.0 Applicability
This procedure applies to samples being analyzed for Total Dissolved Solids (TDS) at the
Cotter Corporation (N.S.L.) “Cotter” Canon City Milling Facility’s Analytical Laboratory.
Samples analyzed by this procedure are water samples from the Cotter Canon City Milling
Facility and surrounding areas, including samples from the Schwartzwalder Mine in Golden
Colorado. These samples are derived from wells, surface runoff, streams or rivers, tailings
and previous mining operations.
2.1 Summary of the Method
2.1.1
Radium is concentrated using a Barium Sulfate precipitation. The Barium
Sulfate is converted to Barium Carbonate that is purified into Barium
Chloride and put into in-growth in EDTA. After in-growth the Ac-228 is
purified, and then precipitated using Yttrium Oxalate. The Yttrium
Oxalate precipitate is counted by gas flow proportional counting (Beta).
Ra-228 in the original solution is calculated after correcting for Barium
and Yttrium carrier recovery, Ac-228 in-growth and decay during
counting.
2.2 Interferences
2.2.1
Exposing the sample to open air during purification and filter mounting
can introduce Radon into the final precipitation that can produce a false
positive. Covering the samples during the process greatly reduces any
interference from Radon.
3.0 Other Documents
3.1 References:
3.1.1 Quality Assurance Program Plan for Environmental and Occupational
Sampling and Monitoring Studies for the Cotter Corporation Canon City
Milling Facility and Lincoln Park, Colorado Superfund site. Revision May
22, 2009.
3.1.2 Cotter Analytical Procedure SOP 3-2, Standard/Source and Reagent
Preparation.
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3.1.3
Cotter Analytical Procedure SOP 3-3, Calibration and Verification of
Laboratory Balances and Weights.
3.1.4
Cotter Analytical Procedure SOP 3-4, Calibration and Verification of
Laboratory Pipettes.
3.1.5
Cotter Analytical Procedure SOP 3-5, Counting and Analysis of
Radiochemistry samples.
3.1.6
Cotter Analytical Procedure SOP 5-1, Gross Alpha and Beta
Measurements of Air Sample Filters.
3.1.7
Cotter Analytical Procedure SOP D-01, Preparation of Soil, Sediment,
Filter, Urine, Fecal and Vegetation (Biota) for Radiochemical Analysis.
3.1.8
EPA Method 904.0, Radium-228 Analysis by Gas Flow Counter.
3.1.9
Material Safety Data Sheets (MSDS)
3.2 Appendices: none
3.3 Exhibits
3.3.1
N/A
4.0 Equipment and Materials
4.1 Equipment
4.1.1 Analytical balance, 100.0000 to 0.0001 g, Scientech or equivalent.
4.1.2
Auto pipettes, 10 - 100 µl, 50 - 250 µl, 100 -1000 µl, 500-5000 µl, 100010000 µl etc., Eppendorf or equivalent.
4.1.3
Centrifuge tubes 50 ml, polypropylene with conical bottoms, Corning or
equivalent, with caps and graduations.
4.1.4
Centrifuge, 4000 rpm, Thermo Electron or equivalent.
4.1.5
Centrifuge tube racks, plastic or Styrofoam. To hold samples during
analysis and to set samples in shaker. VWR or equivalent.
4.1.6
Disposable pipette, half ml graduations up to 2 ml, VWR or equivalent.
4.1.7
Drying Oven, set at approximately 70 º C, VWR or equivalent.
4.1.8
Erlenmeyer Flask, 250 ml, Pyrex or equivalent.
4.1.9
Filters, 47 mm, 0.100, 0.200 and 0.45 µm, Pall or equivalent.
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4.1.10 Gelman 47 mm Magnetic seal plastic funnel with 1000 ml Erlenmeyer
filter flask, or equivalent.
4.1.11 Fume hood with scrubber system.
4.1.12 Glass Beakers 800, 1000 and 1500 ml etc., VWR or equivalent.
4.1.13 Glass watch glasses, 4˝, 4.5˝ and 5˝, VWR or equivalent.
4.1.14 Graduated Cylinders, Class A, 100, 250 and 1000 ml, Kimble or
equivalent.
4.1.15 Hot plate, heating/stirring to 500 C, VWR or equivalent.
4.1.16 Hot water bath, 1500 ml Pyrex beaker, or equivalent, with tap water
heated to near boiling on a stirring hot plate.
4.1.17 Ice water bath, 1500 Nalgene beaker, or equivalent, with tap water and ice.
4.1.18 Kimwipes, Kimtech Science Brand.
4.1.19 Microwave oven for “Sample Heating Only”, “No Food”.
4.1.20 Planchettes for sample mounting, flat, double sided tape, 1.9375˝,
Murphy Die or equivalent.
4.1.21 Polypropylene bottles, VWR or equivalent, 1000 ml, 500 ml etc.
4.1.22 Protean Low-background gas proportional counters and software, or
equivalent.
4.1.23 Refrigerator/Freezer, “Samples Only”, “No Food”.
4.1.24 Shaker system, low and high speed, Eberbach or equivalent.
4.1.25 Syringe, filter, 25 mm, 0.45 μm, Luer-Lok, PTFE, Pall or equivalent.
4.1.26 Syringe, plastic, non sterile, 30 ml, Luer-Lok, BD or equivalent.
4.1.27 Squeeze bottles, 250, 500 and 1000 ml, Nalgene or equivalent.
4.1.28 Teflon stir bars, 1.5˝, VWR or equivalent.
4.1.29 Tray with Cover for planchettes, approximately 8.5˝ x 11˝, HD plastic
Flambeau fishing lure box, Walmart or equivalent.
4.1.30 Tweezers for filter paper, VWR or equivalent.
4.1.31 Vacuum for sample filtration, lab unit, Grainger or equivalent.
4.1.32 Vaneometer, Dwyer 480 or equivalent.
4.1.33 Volumetric Flasks, class A (100 ml, 200 ml, 500 ml and 1000 ml), VWR
or equivalent.
4.1.34 Vortex, variable speed, VWR or equivalent.
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4.2 Materials and Reagents
4.2.1
All reagent preparation is documented in the reagent logbook. The dilute
solution shall be labeled with Solution I.D., along with the date of
preparation, expiration date, the logbook number, and preparer’s
information. In addition, any appropriate health and safety labels shall be
applied as per SOP 3-2, Standard/Source and Reagent Preparation.
4.2.2
Ammonium Oxalate, (NH4)2C2O4· H2O, Baker, Analyzed Reagent or
equivalent.
4.2.3
5 % Ammonium Oxalate Solution. Dissolve 5 g Ammonium Oxalate in
100 ml DI water.
4.2.4
Ammonium sulfate, (NH4)2SO4, F.W. 132.14, reagent, Granular, BDH or
equivalent.
To be deleted, not used.
4.2.5
Ammonium Sulfide, (NH4)2S, FW 68.15, Solution 20-24 %, Mallinckrodt
or equivalent.
4.2.6
Ammonium Sulfide, 2 % solution, (V/V): Add approximately 70 ml of DI
water to a 100 ml volumetric flask, add 10 ml of ammonium sulfide
solution, while swirling. Dilute to volume with DI water and transfer to a
polypropylene bottle, label.
4.2.7
ASTM Type II Deionized Water (DI water).
4.2.8
Barium chloride, BaCl22H20, F.W. 244.27, reagent, EMD or equivalent.
4.2.9
Barium Carrier 10% Solution (W/V): Add approximately 700 ml of DI
water to a 1500 ml beaker, add 100 g of barium chloride. Swirl to
dissolve. Using a Graduated Cylinder, dilute to 1000 ml with DI water.
Transfer to 1000 ml polypropylene bottle, label.
4.2.10 EDTA(Ethylenedinitrilo)-tetraacetic Acid, Disodium Salt Dihydrate,
(Na2C10H14O8N2·2H2O), F.W. 372.24, EM or equivalent.
4.2.11 0.25 M EDTA Solution: While stirring, slowly dissolve 20 g of NaOH
pellets to approximately 800 ml of DI water in a 1500 ml beaker. Add 93 g
of EDTA, stir until dissolved. Using a Graduated Cylinder, dilute to 1000
ml with DI water. Swirl to dissolve. Filter through 0.100 µm filter paper.
Transfer to 1000 ml polypropylene bottle, label.
4.2.12 Hydrochloric acid, HCl, F.W. 36.46, concentrated (36-38 %), BDH or
equivalent.
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4.2.13 Hydrochloric acid, 7 N: Using a graduated cylinder, add approximately
400 ml DI water to a 1500 ml beaker. Using a graduated cylinder, slowly
add approximately 583 ml of concentrated hydrochloric acid while
swirling. Using a Graduated Cylinder, dilute to 1000 ml with DI water.
Transfer to 1000 ml polypropylene bottle, label.
4.2.14 Lead Nitrate, Pb(NO3)2, F.W. 331.2, Alfa Aesar or equivalent.
4.2.15 Lead Carrier Solution: Add 24 g of Lead Nitrate in 800 ml of DI water in a
clean 1500 ml beaker, also add 2 ml of concentrated Nitric acid while
stirring until dissolved. Using a Graduated Cylinder, dilute to 1000 ml
with DI water. Transfer to 1000 ml polypropylene bottle, label.
4.2.16 Nitric acid (16 N HNO3), F.W. 63.01, reagent BDH -concentrated, 68.070.0% or equivalent.
4.2.17 Nitric acid, 2 N: Add approximately 750 ml of DI water to a 1000 ml
volumetric flask, using a graduated cylinder, slowly add 125 ml of
concentrated nitric acid while swirling. Dilute to volume with DI water.
4.2.18 Potassium carbonate. (K2CO3), F.W. 138.2, BDH or equivalent.
4.2.19 1 M Potassium Carbonate: dissolve 138g Potassium Carbonate in 700 ml of
DI water in a clean 1500 ml beaker. Using a Graduated Cylinder, dilute to
1000 ml with DI water. Transfer to 1000 ml polypropylene bottle, label.
4.2.20 P-10 gas, 90 % Argon, 10 % Methane, Ultra P-10 grade or equivalent.
4.2.21 Sodium Hydroxide (NaOH) pellets, reagent, F.W. 40, EMD or equivalent.
4.2.22 Sodium Hydroxide, 40 % (W/V): Add approximately 300 ml of DI water
to a 1000 ml beaker. While swirling, slowly add 200 g of Sodium
Hydroxide pellets. Allow to cool. Using a Graduated Cylinder, dilute to
500 ml with DI water. Transfer to a 500 ml polypropylene bottle, label.
4.2.23 Sodium Sulfate, Na2SO4, granular, reagent, F.W. 142.04, VWR or
equivalent.
4.2.24 Yttrium(III) Oxide, Y2O3, F.W. 225.81, Alfa Aesar or equivalent.
4.2.25 Yttrium Carrier: Add 23 g of Yttrium Oxide to an Erlenmeyer flask
containing 20 ml of DI water. Add stir bar and heat/stir to near boiling.
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Slowly add 30 ml of concentrated Nitric acid to dissolve Yttrium Oxide.
Allow to cool. Add 70 ml of concentrated Nitric acid. Using a Graduated
Cylinder, dilute to 1000 ml with DI water. Transfer to a 1000 ml
polypropylene bottle, label.
4.2.26 Y Wash solution: approximately 20 ml of 40 % Sodium Hydroxide in 1 L
of DI water.
4.2.27 Th-232/Ra-228/Ac-228 in Equilibrium (NIST-traceable (or equivalent))
for Calibration, Ra-228 analysis. Ac-228 H.L(Half Life) = 6.13 hrs or
0.25542 days.
4.2.28 Second Source Th-232/Ra-228/Ac-228 in Equilibrium (NIST-traceable (or
equivalent)) for LCS and MS, Ra-228 analysis.
5.0 Responsibility
5.1 Analyst
5.1.1
Perform pre-concentration of Isotopes from various matrices for
radiochemistry counting per this method.
5.2 Peer Reviewer
5.2.1
Verify preparation of samples as per this method.
5.3 Quality Assurance Coordinator
5.3.1
Review of sample preparation and QA parameters.
5.4 Laboratory Manager
5.4.1
Review sample preparation and QA parameters as a function of data
review.
6.0 Prerequisite Information
6.1 Definitions:
6.1.1
Heat Conditioned 50 ml Centrifuge Tubes: A Corning 50 ml centrifuge
tube that has been heated in the drying oven two different nights to
eliminate error due to heating weight loss and has had the final tare weight
recorded(along with unique identification).
6.2 Safety
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Note: The following steps are performed as frequently as necessary to
prepare samples for analysis.
6.2.1
Review MSDS for reagents used in this procedure.
6.2.2
Analyst shall wear appropriate protective clothing and equipment to
prevent splashes from coming in contact with skin or eyes.
6.2.3
Using the Vaneometer, verify daily before use such that the 100 +/- 10
Ft./Min average air velocity is being pulled into the hood.
Take six readings, three across the top and three across the bottom of the
hood opening, average the readings and verify the velocity is within limits.
Adjustments in flow can be made by adjusting the hood sash. Identify
daily hood height with adjustable magnets.
Document in the Hood Velocity and Wash down logbook.
NOTE: If hood can not be adjusted such that the air flows meet the
100 +/- 10 Ft./Min, tag hood out of service and Contact Lab Manager
or Designee before proceeding.
6.2.4
All sample pre-concentrations and separations are performed in a working
fume hood as per Section 6.2.
6.3 Preparation of Standards
6.3.1
As per SOP 3-2, Standard/Source and Reagent Preparation.
6.3.2
Carriers: Barium and Yttrium Carriers added to determine sample
recoveries.
6.3.2.1
Standardization of Barium Chloride Carrier
6.3.2.1.1
Set up five standards by adding 1.000 ml of 10 %
Barium Chloride solution into each of five pre-Heat
Conditioned Centrifuge tubes (tubes should have been
tared after conditioning).
6.3.2.1.2
Evaporate solution to dryness in a drying oven
overnight.
6.3.2.1.3
Remove dried Barium standards from the oven and
allow to cool for approximately 10 minutes.
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6.3.2.2
6.3.2.3
PROCEDURE
Radiochemical Procedure for Radium-228
Number: 5-10
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6.3.2.1.4
Weigh heat conditioned tube and Ba-precipitate.
6.3.2.1.5
Determine average precipitate weight and %
RSD(Relative Standard Deviation) of those weights.
The average precipitate weight will be used for the
recovery calculation. The % RSD should be within 5 %
or the process should be repeated until it does.
Standardization Yttrium Carrier.
6.3.2.2.1
Set up five standards by adding 1.000 ml of 10 %
Yttrium Carrier solution into each of five 50 ml
Centrifuge tubes.
6.3.2.2.2
Add 2.0 ml of 2 N nitric acid to each standard. Also
add 2.0 ml of 5 % Ammonium Oxalate solution. Swirl.
6.3.2.2.3
Heat samples in microwave to near boiling. Swirl,
cover centrifuge tube with cap and let samples sit.
6.3.2.2.4
Proceed with sections 7.3.17 to 7.3.30.
6.3.2.2.5
Determine average precipitate weight and % RSD of
those weights. The average precipitate weight will be
used for the recovery calculation. The % RSD should
be within 5 % or the process should be repeated until it
does.
Yttrium Carrier Background Determination
6.3.2.3.1
Place the Yttrium Carrier Standards(now background
standards) from Section 6.4.2.2 in a covered plastic tray
and wait four hours to count them on the Protean.
6.3.2.3.2
Count the Yttrium Carrier background standards for the
same amount of time as the samples. Usually 7 hr.
6.3.2.3.3
Create an Ac-228 counting table using the Protean
software. Enter the Net background counts for each
detector used so the instrument will subtract off that
background for samples counted in that detector.
6.4 Quality Control
6.4.1
Any discrepancies to this procedure will be noted on the case narrative for
each batch of samples.
6.4.2
Verify that the number of control samples required have been prepared for
the batch. Verify the frequency of quality control samples is based on a
batch of 20 samples or less, of a similar matrix processed at the same time.
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6.4.3
Verify that balances and auto pipettes to be used in this procedure have
received Quality Control checks as per SOP 3-3, Calibration and
Verification of Laboratory Balances and Weights and SOP 3-4,
Calibration and Verification of Laboratory Pipettes.
6.4.4
Preparation Blank
6.4.4.1
Analyze a Preparation Blank with each batch of 20 samples.
6.4.4.2
For aqueous sample Preparation Blanks, DI water is used in the
same volume as the sample volume.
6.4.4.2.1
6.4.4.3
6.4.5
The result of the Preparation Blank should be below the
MDA(minimum detectable activity) of the method. If not, note
any discrepancies in the case narrative for that batch of samples
and refer to Lab Manager before reanalyzing batch to resolve
any problems that may have arisen.
Laboratory Control Sample, LCS
6.4.5.1
Analyze a LCS sample with each batch of 20 samples.
6.4.5.2
The LCS is prepared by spiking an aliquot of the Preparation
Blank with Ra-228 at a concentration between 1 g/L and 50
g/L. Then take that solution through the analysis with the
samples.
6.4.5.3
The percent recovery is calculated according to the following:
R
Where:
Add the DI water to the Preparation Blank beaker,
acidify to less than 2 pH using Nitric Acid. Then take
that solution through the analysis with the samples.
R:
LCS:
s:
LCS
s
Percent Recovery
Laboratory Control Sample Results
amount of spike added (in concentration units)
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6.4.5.4
6.4.6
6.4.7
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The Percent Recovery for the LCS shall be within the required
control limits of 80-120%. If the recovery is not within control
limits note any discrepancies in the case narrative and refer to
Lab Manager before reanalyzing batch to resolve any problems
that may have arisen.
Duplicate
6.4.6.1
Analyze a duplicate sample with each batch of 20 samples.
6.4.6.2
Using the acceptance ranges as per section 10.2.2.2.1 of
Reference 3.1.1 (QAPP) calculate the RPD (Relative Percent
Difference of less than or equal to 20 %) and the RD (Relative
difference less than or equal to 1).
6.4.6.3
If the RPD and/or the RD are not within control limits note any
discrepancies in the case narrative and refer to Lab Manager
before reanalyzing batch to resolve any problems that may
have arisen.
Matrix Spike
6.4.7.1
Analyze a Matrix Spike with each batch of 20 samples.
6.4.7.2
The aliquot used for the Matrix Spike must be the same sample
as the aliquot used for the original sample and the duplicate.
6.4.7.3
For aqueous samples the added analyte concentration must be
the same as that used in the Laboratory Control Sample.
6.4.7.4
Calculate the percent recovery for the Matrix Spike as follows:
R
Cs  C
*100
s
Where:
R:
Cs :
C:
S:
Percent Recovery
Measured concentration in spiked sample matrix
Measured concentration in un-spiked sample
amount of analyte added to sample matrix
6.4.7.5
The recovery of the Matrix Spike should be within the
designated acceptance range of 80-120 %. If it is not within
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control limits note any discrepancies in the case narrative and
refer to Lab Manager before reanalyzing batch to resolve any
problems that may have arisen.
6.4.8
6.4.9
Ac-228 Efficiency Calibration for Protean Instrument
6.4.8.1
Take five Ac-228 Second Source samples and a preparation
blank through the procedure and count them.
6.4.8.2
Using the activity of the Second Source standard, Y carrier
recovery, Ba carrier recovery, in-growth of the Ac-228 from
the second source standard and the decay of the Ac-228 after
purification for counting, determine the efficiency of the
Protean gas flow proportional detectors. (Decay of the second
source standard will be negligible because it is supported by
Th-232).
6.4.8.3
Calculate the difference between the Protean daily Beta source
efficiency and the Ac-228 Second Source efficiency to
determine the correction to be used when determining the Ra228 result.
Ac-228 Result Calculations
6.4.9.1
pCi/L = Net CPM/Sample Size (L)*Detector Efficiency*Ac228 Efficiency Correction*2.22*Ac-228 Ingrowth*Ac-228
Decay*Y Recovery*Ba Recovery
Net CPM(Counts per Minute) = Gross CPM – (cross talk
Alpha into Beta) – background CPM.
Sample Size = units are g, L, filter or ml etc.
Detector Efficiency = A known Ac-228 source is used to
determine the Efficiency of the Protean detector. See section
6.5.8.
DPM(Disintegrations Per Minute) = is a measure of the
intensity of the source of radioactivity.
Efficiency Ac-228 Yttrium Oxalate = CPM of Yttrium
Oxalate Precipitate / (DPM Ac-228 added(activity in pCi*2.22
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DPM/pCi) *Yittrium Oxalate Recovery *Barium Chloride
recovery * Ac-228 Ingrowth*Ac-228 Decay
Ac-228 Efficiency Correction = the ratio difference between
the Ac-228 efficiency and the Cl-36 source efficiency is
determined.
2.22 (DPM/pCi) = The conversion from disintegrations per
minute to picocuries.
Ac-228 Ingrowth = 1-e–( ln2/ 0.25542(days))( Ac-228 Ingrowth Time Days)
Ac-228 Ingrowth Time Days = time from the start of the Ac228 ingrowth in days (Section 7.2.18) to the end of the Ac-228
ingrowth in days (Section 7.3.8).
Ac-228 Decay Factor = e–( ln2/ 0.25542 (days))( Ac-228 DecayTime Days)
Decay Time Days = time from the end of the Ac-228 Ingrowth
in days (Section 7.3.8) to the start of count time in days +
(count time in days/2 (halfway through the count time))
Yttrium Oxalate Recovery = (weight of Y2(C2O4)3 .10H2O
precipitate plus filter (g) – weight of filter (g)), see section
6.4.2.2.
Barium Chloride Recovery = (weight of BaCl2 precipitate plus
centrifuge tube (g) – weight of centrifuge tube (g)), see section
6.4.2.1 Ac-228 Result Calculations
6.4.10 MDA (Minimum Detectable Activity) =
MDA = (2.71 + 4.65 * Sqr (Background CPM * Count Time)) / (Eff
Yttrium Oxalate(Ac-228)) * (SampleSize) * (Count Time) * (2.22
(DPM/pCi))* (Yttrium Oxalate Recovery) * (Barium Chloride
Recovery) * (Ac-228 Ingrowth) * (Ac-228 Decay)
Where:
Count Time = time sample counted in minutes
6.4.11 Uncertainty Calculation
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Uncertainty = Sqr (AA ^ 2 + BB ^ 2 + CC ^ 2 + DD ^ 2 + EE ^ 2) /
_(Eff Yttrium Oxalate(Ac-228)) * SampleSize * 2.22 (DPM/pCi) *
(Barium Chloride Recovery * Yittrium Oxalate Recovery) * Ac-228
Ingrowth * Ac-228 Decay
AA = (Sqr (Background CPM * CountTime)) / CountTime
BB = (Sqr(Gross CPM * CountTime)) / CountTime
CC = NetCPM * (% RSD calibration / 100) / Sqr (N of standards)
% RSD calibration = (percent relative standard deviation) = Standard
Deviation of the Yttrium Oxalate(Ac-228)) standard efficiency used
for calibration / mean of the efficiency used for calibration.
DD = NetCPM * ( % Ac-228 Standard Certificate Uncert / 100) /
Sigma(1.96)
EE = (Sqr(Gross CPM*Count Time * .10))/Count Time
Method Uncertainty = 0.10(10 %) which is a summation of the
estimated errors in the preparation for the samples to be counted. ( 1
% error in initial sample aliquot + 1 % error in initial Barium carrier
pipetting + 1% error in the initial Yttrium Carrier pipetting + 2 %
error in determining Baruim recovery +2% error in determining
Yttrium Carrier recovery + 3 % error in determining Ac-228
efficiency.)
7.0 Procedure
7.1 Water Sample Preparation for Sulfate Precipitation
7.1.1
Measure the desired amount (usually 1.0 liter) for each sample into a 1500
ml glass beaker. Add a stir bar and place on a heating/stirring hotplate in a
fume hood. (Sample solutions from soils, filters, biota etc., can be
analyzed using this method after they have been placed in solution as per
SOP D-1).
7.1.2
Set up the appropriate controls (preparation blanks, laboratory control
samples, duplicates and matrix spikes as per section 6.5). Carry the
samples and controls through the rest of the procedure.
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7.1.3
While stirring, add 10 mL of concentrated HCl per liter of sample, to each
sample. Then add 1.000 mL of standardized 10% BaCl2 solution to each
sample.
7.1.4
Heat samples to near boiling and turn off heat.
7.1.5
Add approximately 35 g of Na2SO4 per liter of sample.
7.1.6
Stir slowly for approximately 30 minutes, remove the stir bar, and allow
the precipitate to settle.
7.1.7
Decant as much liquid as possible.
7.1.8
Transfer the barium sulfate precipitate to a 50-mL centrifuge tube. Rinse
the last of the precipitate into the tube with DI water, and cap the tube.
Centrifuge and decant mother solution and wash to waste. Proceed to the
Barium Carbonate Conversion, Section 7.2.
7.2 Barium Carbonate Conversion
7.2.1
Add 30 mL of 1 M potassium carbonate to each barium sulfate sample
precipitate. Tightly cap the centrifuge tube. Shake to break up the
precipitate.
7.2.2
Heat in a near boiling water bath for approximately 120 minutes, swirling
the precipitate every 15 minutes.
7.2.3
Remove the samples from the water bath and allow them to cool at room
temperature for approximately 10 minutes. Chill in freezer for
approximately 30 minutes.
7.2.4
Centrifuge on medium high setting for approximately 5 min. Decant the
supernate to waste.
7.2.5
Add 5 mL of 7 M HCl to the barium carbonate sample precipitate. Swirl
to dissolve the precipitate. Add 25 mL of concentrated HCl. Cap the tube
and shake for approximately 2 minutes.
7.2.6
Chill the samples in a freezer for approximately 30 min.
7.2.7
Centrifuge on medium high setting for approximately 5 min. Decant the
supernate to waste.
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7.2.8
Add 2 mL of DI water to each sample precipitate. Cap and swirl the tubes
until the barium chloride precipitate is dissolved.
7.2.9
If the solution is clear proceed to step 7.2.11.
7.2.10 If the solution appears cloudy, centrifuge the water solution on high
setting for at least 5 minutes, and then decant the supernate into a clean
50-mL centrifuge tube. Discard the original centrifuge tube to waste.
7.2.11 Add 25 mL of concentrated HCl acid. Cap and shake the samples for at
least 2 minutes.
7.2.12 Chill the samples in a freezer for approximately 30 minutes.
7.2.13 Centrifuge on medium high setting for approximately 5 minutes. Decant
the supernate to waste.
7.2.14 Add 2 mL of water to each sample precipitate. Cap and swirl the tubes
until the barium chloride precipitate is dissolved.
7.2.15 If the solution is clear, proceed to 7.2.17.
7.2.16 If the solution appears cloudy, centrifuge the water solution on high
setting for approximately 6 minutes and decant the supernate into the
clean tared 50-mL centrifuge tubes in step 7.2.17. Discard the original
centrifuge tube to waste.
7.2.17 Tare a set of clean dry, twice heat conditioned 50 ml centrifuge tubes and
record the weights.
7.2.18 Decant the water solution into the tared centrifuge tubes, and add 25 mL
of concentrated HCl acid. Cap and shake the samples for at least 2
minutes.
Record this time as the start of the Ra-226/228 daughters ingrowth.
7.2.19 Chill the samples in a freezer for approximately 30 minutes.
7.2.20 Centrifuge on medium high setting for approximately 5 minutes. Decant
the supernate to waste.
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7.2.21 Evaporate the sample barium chloride precipitate to dryness using a drying
oven. The samples need to be completely dry and free of acid so that the
weight of the sample can be used for recovery.
7.2.22 Allow the samples to cool to room temperature (approximately 10
minutes). Weigh the samples and record the weights.
7.3 Ac-228 Separation, Purification and Recovery
7.3.1
7.3.2
Add 15 ml of EDTA solution, to the dried barium chloride precipitate
centrifuge tube. Cap the tube (the cap may not seal as easily as normal
because the tube has been heated). Swirl and heat, as needed, to dissolve
the precipitate.
Allow the Ac-228 in the samples time to in-grow to near 100 %
equilibrium with the Ra-228 (Ac-228 H.L. = 6.13 hr, approximately 30 hr
in-growth or more).
7.3.3
Add 1.0 ml of Pb (Lead) Carrier and 1.000 ml of Yttrium Carrier.
7.3.4
Add 0.3 ml of 2 % Ammonium Sulfide solution, swirl to mix.
7.3.5
Using a disposable pipette add 11 drops of 40 % NaOH while swirling to
precipitate the lead sulfide.
7.3.6
Swirl the samples intermittently for approximately 15 minutes.
7.3.7
Centrifuge samples on high for approximately 3 minutes and then filter the
supernate through a clean 25 mm 0.45 µm, syringe filter using a 30 ml
Luer-Lok Syringe into a clean DI water washed 50 ml centrifuge tube.
7.3.8
Add 8 ml of 40% NaOH to the samples and tightly cover the tube with a
cap. Heat samples for approximately 10 minutes in a Hot water bath.
Record this time as the end of the Ac-228 in-growth and the start
of the Ac-228 decay.
7.3.9
Chill samples in an Ice bath for approximately 10 minutes.
7.3.10 Centrifuge the samples on high for approximately 6 minutes.
7.3.11 Decant the supernate to waste.
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7.3.12 Add approximately 35 ml of the Y DI water wash. Cap and shake the
samples to dissolve any excess impurities.
7.3.13 Chill samples in an Ice bath for approximately 10 minutes.
7.3.14 Centrifuge the sample on high for approximately 7 minutes and decant the
supernate to waste.
7.3.15 Add 2 ml of 2 N Nitric Acid to the washed YOH precipitate. Swirl and
heat in microwave to dissolve.
7.3.16 Add 2 ml of 5 % Ammonium Oxalate to precipitate Yttrium Oxalate.
Heat the solution in the microwave to near boiling. Allow the sample to
sit for a few minutes.
7.3.17 Label the back of a 1.375” flat planchette, that has double sided tape
attached on top, with the sample and batch information.
7.3.18 Remove the double sided tape cover and place the tape cover on the
analytical balance. Tare the balance.
7.3.19 Remove the tape cover from the balance and place back on the planchette
as it was originally configured.
7.3.20 Place a 0.200 µm 47 mm filter on top of the double sided tape.
7.3.21 Place the planchette and filter back on the analytical balance and record
the weight. Repeat steps 7.3.17 through 7.3.21 for every sample in the
batch.
7.3.22 Place the filter from the weighed filter/planchette set-up on bottom part of
47 mm filter funnel. Wet with DI water such that the filter lays flat.
Attach magnetic top to bottom filter funnel.
7.3.23 Filter sample precipitate solution and rinse with 5-10 ml DI water.
7.3.24 Remove the double sided tape cover and expose the double sided tape.
7.3.25 Remove top of filter funnel. Using clean filter forceps remove filter from
funnel bottom and center the wet filter on the double sided tape planchette.
7.3.26 Press the filter down around the edges to allow it to adhere to the tape.
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7.3.27 Wipe the tweezers down with a Kimwipe between each sample to prevent
contamination.
7.3.28 Place sample planchettes in plastic tray and place tray in a drying oven for
approximately 30 minutes.
7.3.29 Remove tray from the drying oven and allow sample planchettes to cool
for approximately 7 minutes uncovered. Cover samples for approximately
20 minutes. Weigh the samples and Record the weights.
7.3.30 Wait approximately 4 hours from the Ac-228 separation from Ra-228 and
count in beta counter for 420 minutes as per Cotter Analytical Procedure
SOP 3-5, Counting and Analysis of Radiochemistry samples.
8.0 NOTES
8.1 For samples high in sulfide (hydrogen sulfide smells like rotten eggs), add 25 mL of
concentrated Nitric acid per liter of sample. While stirring, bring that sample to
boiling for about an hour or until the sulfide smell dissipates. Allow samples to cool
to below boiling and continue with section 7.1.3.
8.2 Lab wastes are disposed to Pond 3 through piping.
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