EPA402-R-10-001a
www.epa.gov/narel
October 2011
Revision 0.1
Rapid Radiochemical Method for
Americium-241 in Water
for Environmental Remediation Following
Homeland Security Events
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Radiation and Indoor Air
National Air and Radiation Environmental Laboratory
Montgomery, AL 36115
Office of Research and Development
National Homeland Security Research Center
Cincinnati, OH 45268
-------
Americium-241 in Water: Rapid Method for High Activity Samples
Revision History
Revision 0
Original release.
02/23/2010
Revision 0.1
Corrected typographical and punctuation errors.
Improved wording consistency with other methods.
Corrected specification of analytical balance (6.1) to 10^-g
readability.
Added pH paper to list of equipment and supplies (6.6).
Added equations in 12.1.2 that allow theoretical calculation of
the MDC and critical level for different decision error rates.
Updated footnote 2 to further clarify origin of critical value
and minimum detectable concentration formulations.
Updated rounding example in 12.2.2.2 for clarity.
(Deleted Appendix (Composition of Atlanta tap waster) as
irrelevant.
10/28/2011
This report was prepared for the National Air and Radiation Environmental Laboratory of the Office of
Radiation and Indoor Air and the National Homeland Security Research Center of the Office of Research
and Development, United States Environmental Protection Agency. It was prepared by Environmental
Management Support, Inc., of Silver Spring, Maryland, under contracts 68-W-03-038, work assignment
43, and EP-W-07-037, work assignments B-41 and 1-41, all managed by David Carman. Mention of trade
names or specific applications does not imply endorsement or acceptance by EPA.
-------
AMERiciUM-241 IN WATER:
RAPID METHOD FOR HIGH-ACTIVITY SAMPLES
1. Scope and Application
1.1. The method will be applicable to samples where radioactive contamination is either
from known or unknown origins. If any filtration of the sample is performed prior to
starting the analysis, those solids should be analyzed separately. The results from the
analysis of these solids should be reported separately (as a suspended activity
concentration for the water volume filtered), but identified with the filtrate results.
1.2. The method is specific for 241 Am in drinking water and other aqueous samples.
However, if any isotopes of curium are present in the sample, they will be carried with
americium during the analytical separation process and will be observed in the final
alpha spectrum.
1.3. The method uses rapid radiochemical separation techniques for determining americium
in water samples following a radiological or nuclear incident. Although the method can
detect concentrations of24 Am on the same order of magnitude as methods used for the
Safe Drinking Water Act (SDWA), the method is not a substitute for SDWA-approved
methods for 241Am.
1.4. The method is capable of achieving a required method uncertainty for 241 Am of 1.9
pCi/L at an analytical action level of 15 pCi/L. To attain the stated measurement quality
objectives (MQOs) (see Sections 9.3 and 9.4), a sample volume of approximately 200
mL and count time of at least 1 hour are recommended. The sample turnaround time
and throughput may vary based on additional project MQOs, the time for analysis of
the final counting form, and initial sample volume. The method must be validated prior
to use following the protocols provided in Method Validation Guide for Qualifying
Methods Used by Radiological Laboratories Participating in Incident Response
Activities (EPA 2009, reference 16.5).
1.5. The method is intended to be used for water samples that are similar in composition to
drinking water. The rapid 241 Am method was evaluated following the guidance
presented for "Level E Method Validation: Adapted or Newly Developed Methods,
Including Rapid Methods" in Method Validation Guide for Qualifying Methods Used
by Radiological Laboratories Participating in Incident Response Activities (EPA 2009,
reference 16.5) and Chapter 6 of Multi-Agency Radiological Laboratory Analytical
Protocols Manual (MARLAP 2004, reference 16.6). Multi-radionuclide analysis using
sequential separation may be possible using this method in conjunction with other rapid
methods.
9/11
1.6. The method is applicable to the determination of soluble Am. The method is not
applicable to the determination of 241Am in highly insoluble particulate matter possibly
present in water samples contaminated as a result of a radiological dispersion device
(ROD) event.
2. Summary of Method
2.1. The method is based on a sequence of two chromatographic extraction resins used to
concentrate, isolate, and purify americium by removing interfering radionuclides as
well as other components of the water matrix in order to prepare the americium fraction
for counting by alpha spectrometry. The method utilizes vacuum-assisted flow to
10/28/2011 1 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
improve the speed of the separations. Prior to the use of the extraction resins, the water
sample is filtered as necessary to remove any insoluble fractions, equilibrated with
243Am tracer, and concentrated by evaporation or calcium phosphate precipitation. The
sample test source (STS) is prepared by microprecipitation with NdFs. Standard
laboratory protocol for the use of an alpha spectrometer should be used when the
sample is ready for counting.
3. Definitions, Abbreviations, and Acronyms
3.1. Analytical Protocol Specifications (APS). The output of a directed planning process
that contains the project's analytical data needs and requirements in an organized,
concise form.
3.2. Analytical Action Level (AAL). The term "analytical action level" is used to denote the
value of a quantity that will cause the decisionmaker to choose one of the alternative
actions.
3.3. Analytical Decision Level (ADL). The analytical decision level refers to the value that
is less than the AAL and based on the acceptable error rate and the required method
uncertainty.
3.4. Discrete Radioactive Particles (DRPs or Hot Particles). Particulate matter in a sample
of any matrix where a high concentration of radioactive material is contained in a tiny
particle (um range).
3.5. Multi-Agency Radiological Laboratory Analytical Protocols Manual (See Reference
16.6.).
3.6. Measurement Quality Objective (MQO). MQOs are the analytical data requirements of
the data quality objectives and are project- or program-specific. They can be
quantitative or qualitative. MQOs serve as measurement performance criteria or
objectives of the analytical process.
3.7. Radiological Dispersal Device (ROD), i.e., a "dirty bomb." This is an unconventional
weapon constructed to distribute radioactive material(s) into the environment either by
incorporating them into a conventional bomb or by using sprays, canisters, or manual
dispersal.
3.8. Required Method Uncertainty (Z/MR). The required method uncertainty is a target value
for the individual measurement uncertainties, and is an estimate of uncertainty (of
measurement) before the sample is actually measured. The required method uncertainty
is applicable below an AAL.
3.9. Required Relative Method Uncertainty (
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
individual detector's alpha energy resolution characteristics and the quality of the final
precipitate that is counted.
4.2. Non-Radiological: Very high levels of competing higher valence anions (greater than
divalent such as phosphates) will lead to lower yields when using the evaporation
option due to competition with active sites on the resin. If higher valence anions are
present, the phosphate precipitation option may need to be used initially in place of
evaporation. If calcium phosphate coprecipitation is performed to collect americium
(and other potentially present actinides) from large-volume samples, the amount of
phosphate added to coprecipitate the actinides (in Step 11.1.4.3) should be reduced to
accommodate the sample's high phosphate concentration.
5. Safety
5.1. General
5.1.1. Refer to your safety manual for concerns of contamination control, personal
exposure monitoring and radiation dose monitoring.
5.1.2. Refer to the laboratory chemical hygiene plan (or equivalent) for general safety
rules regarding chemicals in the workplace.
5.2. Radiological
5.2.1. Hot Particles (DRPs)
5.2.1.1. Hot particles, also termed "discrete radioactive particles" (DRPs), will
be small, on the order of 1 mm or less. Typically, DRPs are not evenly
distributed in the media and their radiation emissions are not uniform
in all directions (anisotropic). Filtration using a 0.45-um or finer filter
will minimize the presence of these particles.
5.2.1.2. Care should be taken to provide suitable containment for filter media
used in the pretreatment of samples that may have DRPs, because the
particles become highly statically charged as they dry out and will
"jump" to other surfaces causing contamination.
5.2.1.3. Filter media should be individually surveyed for the presence of these
particles, and this information should be reported with the final sample
results.
5.2.2. For samples with detectable activity concentrations of this radionuclide, labware
should be used only once due to potential for cross contamination.
5.3. Procedure-Specific Non-Radiological Hazards
Particular attention should be paid to the use of hydrofluoric acid (HF). HF is an
extremely dangerous chemical used in the preparation of some of the reagents and in
the microprecipitation procedure. Appropriate personal protective equipment (PPE)
must be used in strict accordance with the laboratory safety program specification.
6. Equipment and Supplies
6.1. Analytical balance with a 10^-g readability or better.
6.2. Cartridge reservoirs, 10- or 20-mL syringe style with locking device, or equivalent.
6.3. Centrifuge able to accommodate 250-mL flasks.
6.4. Centrifuge flasks, 250-mL capacity.
6.5. Filter with 0.45-um membrane.
10/28/2011 3 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
6.6. pH paper.
6.7. Filter apparatus with 25-mm-diameter polysulfone filtration chimney, stem support, and
stainless steel support. A single-use (disposable) filter funnel/filter combination may be
used, to avoid cross-contamination.
6.8. 25-mm polypropylene filter, 0.1-um pore size, or equivalent.
6.9. Stainless steel planchets or other sample mounts able to hold the 25 mm filter.
6.10. Tweezers.
6.11. 100-uL pipette or equivalent and appropriate plastic tips.
6.12. 10-mL plastic culture tubes with caps.
6.13. Tips, white inner, Eichrom part number AC-1000-IT, or equivalent.
6.14. Tips, yellow outer, Eichrom part number AC-1000-OT, or equivalent.
6.15. Vacuum box, such as Eichrom part number AC-24-BOX, or equivalent.
6.16. Vortex mixer.
6.17. Vacuum pump or laboratory vacuum system.
6.18. Miscellaneous laboratory ware, plastic or glass, 250 mL and 350 mL.
7. Reagents and Standards
Note: All reagents are American Chemical Society (ACS) reagent grade or equivalent unless otherwise
specified.
Note: Unless otherwise indicated, all references to laboratory water should be understood to mean Type I
Reagent water. All solutions used in microprecipitation should be prepared with water filtered through a
0.45-um (or better) filter.
7.1. Am-243 tracer solution: 6-10 dpm of 243Am per aliquant, activity added known to at
least 5% (combined standard uncertainty < 5%).
7.2. Ammonium hydrogen phosphate (3.2 M): Dissolve 106 g of ammonium hydrogen
phosphate ((NH/^HPO/t) in 200 mL of water, heat gently to dissolve, and dilute to 250
mL with water.
7.3. Ammonium hydroxide (15 M): Concentrated NH/iOH, available commercially.
7.4. Ammonium thiocyanate indicator (1 M): Dissolve 7.6 g of ammonium thiocyanate
(NFLjSCN) in 90 mL of water and dilute to 100 mL with water. An appropriate quantity
of sodium thiocyanate (8.1 g) or potassium thiocyanate (9.7 g) may be substituted for
ammonium thiocyanate.
7.5. Ascorbic acid (1 M): Dissolve 17.6 g of ascorbic acid (CeHgOe) in 90 mL of water and
dilute to 100 mL with water. Prepare weekly.
7.6. Calcium nitrate (0.9 M): Dissolve 53 g of calcium nitrate tetrahydrate (Ca(NO3)2'4H2O)
in 100 mL of water and dilute to 250 mL with water.
7.7. Ethanol, 100%: Anhydrous C2HsOH, available commercially.
7.7.1. Ethanol (-80% v/v): Mix 80 mL 100% ethanol and 20 mL water.
7.8. Ferrous sulfamate (0.6 M): Add 57 g of sulfamic acid (NF^SOsH) to 150 mL of water,
heat to 70°C. Slowly add 7 g of iron powder (< 100 mesh size) while heating and
stirring with a magnetic stirrer until dissolved (may take as long as two hours). Filter
the hot solution using a qualitative filter, transfer to flask, and dilute to 200 mL with
water. Prepare fresh weekly.
7.9. Hydrochloric acid (12 M): Concentrated HC1, available commercially.
10/28/2011 4 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
7.9.1. Hydrochloric acid (9 M): Add 750 mL of concentrated HC1 to 100 mL of water
and dilute to 1 L with water.
7.9.2. Hydrochloric acid (4 M): Add 333 mL of concentrated HC1 to 500 mL of water
and dilute to 1 L with water.
7.9.3. Hydrochloric acid (1 M): Add 83 mL of concentrated HC1 to 500 mL of water
and dilute to 1 L with water.
7.10. Hydrofluoric acid (28 M): Concentrated HF, available commercially.
7.10.1. Hydrofluoric acid (0.58 M): Add 20 mL of concentrated HF to 980 mL of
filtered demineralized water and mix. Store in a plastic bottle.
7.11. Neodymium standard solution (1000 ug/mL): May be purchased from a supplier of
standards for atomic spectroscopy.
7.12. Neodymium carrier solution (0.50 mg/mL): Dilute 10 mL of the neodymium standard
solution (7.11) to 20.0 mL with filtered demineralized water. This solution is stable.
7.13. Neodymium fluoride substrate solution (10 |ig/mL): Pipette 5 mL of neodymium
standard solution (7.11) into a 500-mL plastic bottle. Add 460 mL of 1-M HC1 to the
plastic bottle. Cap the bottle and shake to mix. Measure 40 mL of concentrated HF in a
plastic graduated cylinder and add to the bottle. Recap the bottle and shake to mix
thoroughly. This solution is stable for up to six months.
7.14. Nitric acid (16 M): Concentrated HNO3, available commercially.
7.14.1. Nitric acid (3 M): Add 191 mL of concentrated HNO3 to 700 mL of water and
dilute to 1 L with water.
7.14.2. Nitric acid (2 M): Add 127 mL of concentrated HNO3 to 800 mL of water and
dilute to 1 L with water.
7.14.3. Nitric acid (0.5 M): Add 32 mL of concentrated HNO3 to 900 mL of water and
dilute to 1 L with water.
7.15. Nitric acid (2M) - sodium nitrite (0.1 M) solution: Add 32 mL of concentrated HNO3
(7.14) to 200 mL of water and mix. Dissolve 1.7 g of sodium nitrite (NaNC^) in the
solution and dilute to 250 mL with water. Prepare fresh daily.
7.16. Nitric acid (3 M) - aluminum nitrate (l.OM) solution: Dissolve 213 g of anhydrous
aluminum nitrate (A1(NO3)3) in 700 mL of water. Add 190 mL of concentrated HNO3
(7.14) and dilute to 1 L with water. An appropriate quantity of aluminum nitrate
nonahydrate (375 g) may be substituted for anhydrous aluminum nitrate.
7.17. Phenolphthalein solution: Dissolve 1 g of phenolphthalein in 100 mL 95% isopropyl
alcohol and dilute with 100 mL of water.
7.18. TRU Resin: 2-mL cartridge, 50- to 100-|j,m mesh size, Eichrom part number TR-R50-S
and TR-R200-S, or equivalent.
7.19. UTEVA Resin: 2-mL cartridge, 50- to 100-|j,m mesh size, Eichrom part number UT-
R50-S and UT-R200-S, or equivalent.
8. Sample Collection, Preservation, and Storage
8.1. No sample preservation is required if sample is delivered to the laboratory within 3
days of sampling date/time.
8.2. If the dissolved concentration of americium is sought, the insoluble fraction must be
removed by filtration before preserving with acid.
8.3. If the sample is to be held for more than 3 days, concentrated HNO3 shall be added to
achieve a pH<2.
10/28/2011 5 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
9. Quality Control
9.1. Batch quality control results shall be evaluated and meet applicable Analytical Project
Specifications (APS) prior to release of unqualified data. In the absence of project-
defined APS or a project-specific quality assurance project plan (QAPP), the quality
control sample acceptance criteria defined in the laboratory quality manual and
procedures shall be used to determine acceptable performance for this method.
9.1.1. A laboratory control sample (LCS) shall be run with each batch of samples. The
concentration of the LCS shall be at or near the action level or level of interest
for the project.
9.1.2. One method blank shall be run with each batch of samples. The laboratory
blank should consist of laboratory water.
9.1.3. One laboratory duplicate shall be run with each batch of samples. The
laboratory duplicate is prepared by removing an aliquant from the original
sample container.
9.1.4. A matrix spike sample may be included as a batch quality control sample if
there is concern that matrix interferences may compromise chemical yield
measurements or overall data quality.
9.2. The source preparation method should produce a sample test source whose spectrum
shows the full width at half maximum (FWHM) of-60-80 keV for each peak in the
spectrum. Precipitate reprocessing should be considered if this range of FWHM cannot
be achieved.
9.3. This method is capable of achieving a WMR of 1.9 pCi/L at or below an action level of 15
pCi/L. This may be adjusted in the event specific MQOs are different.
9.4. This method is capable of achieving a ^MR 13% above 15 pCi/L. This may be adjusted if
the event specific MQOs are different.
9.5. This method is capable of achieving a required minimum detectable concentration
(MDC)of 1.5pCi/L.
10. Calibration and Standardization
10.1. Set up the alpha spectrometry system according to the manufacturer's
recommendations. The energy range of the spectrometry system should at least
include the region between 3 and 8 MeV.
10.2. Calibrate each detector used to count samples according to ASTM Standard Practice
D7282, Section 18, "Alpha Spectrometry Instrument Calibrations" (see Reference
16.3).
10.3. Continuing Instrument Quality Control Testing shall be performed according to
ASTM Standard Practice D7282, Sections 20, 21, and 24.
11. Procedure
11.1. Water Sample Preparation
11.1.1. As required, filter the 100- to 200-mL sample aliquant through a 0.45-um
filter and collect the sample in an appropriate size beaker.
11.1.2. Acidify the sample with concentrated HNOs to a pH of less than 2.0 by
adding enough HNOs. This usually requires about 2 mL of HNOs per 1000
mL of sample.
10/28/2011 6 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
94^
11.1.3. Add 6-10 dpm of Am as a tracer, following laboratory protocol.
Note: For a sample approximately 100 mL or less, the evaporation option is
recommended. Proceed to Step 11.1.5. Otherwise, go to Step 11.1.4.
11.1.4. Calcium phosphate coprecipitation option
11.1.4.1. Add 0.5 mL of 0.9-M Ca(NO3)2 to each beaker. Place each
beaker on a hot plate, cover with a watch glass, and heat until
boiling.
11.1.4.2. Once the sample boils, take the watch glass off the beaker and
lower the heat.
11.1.4.3. Add 2-3 drops of phenolphthalein indicator and 200 |jL of 3.2 M
(NH4)2HPO4 solution.
11.1.4.4. Add enough concentrated NiLiOH with a squeeze bottle to reach
the phenolphthalein end point and form Ca^O^ precipitate.
NH/jOH should be added very slowly. Stir the solution with a
glass rod. Allow the sample to heat gently to digest the
precipitate for another 20-30 minutes.
11.1.4.5. If the sample volume is too large to centrifuge the entire sample,
allow precipitate to settle until solution can be decanted (30
minutes to 2 hours) and go to Step 11.1.4.7.
11.1.4.6. If the volume is small enough to centrifuge, go to Step 11.1.4.8.
11.1.4.7. Decant supernatant solution and discard to waste.
11.1.4.8. Transfer the precipitate to a 250-mL centrifuge tube, completing
the transfer with a few milliliters of water, and centrifuging the
precipitate for approximately 10 minutes at 2000 rpm.
11.1.4.9. Decant supernatant solution and discard to waste.
11.1.4.10. Wash the precipitate with an amount of water approximately
twice the volume of the precipitate. Mix well using a stirring rod,
breaking up the precipitate if necessary. Centrifuge for 5-10
minutes at 2000 rpm. Discard the supernatant solution.
11.1.4.11. Dissolve precipitate in approximately 5 mL concentrated HNCb.
Transfer solution to a 100-mL beaker. Rinse centrifuge tube with
2-3 mL of concentrated HNCb and transfer to the same beaker.
Evaporate solution to dryness and go to Step 11.2.
11.1.5. Evaporation option to reduce volume and to digest organic components
11.1.5.1. Evaporate sample to less than 50 mL and transfer to a 100-mL
beaker.
Note: For some water samples, CaSO4 formation may occur during
evaporation. If this occurs, use the Ca3(PO4)2 precipitation option in Step
11.1.4.
11.1.5.2. Gently evaporate the sample to dryness and redissolve in
approximately 5 mL of concentrated HNOs.
11.1.5.3. Repeat Step 11.1.5.2 two more times, evaporate to dryness, and
go to Step 11.2.
10/28/2011 7 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
11.2. Actinide Separations Using Eichrom Resins
11.2.1. Redissolve Ca3(PO4)2 residue or evaporated water sample
11.2.1.1. Dissolve either residue with 10 mL of 3-M HNO3 - 1.0-M
A1(N03)3.
Note: An additional 5 mL may be necessary if the residue volume is large.
11.2.1.2. Add 2 mL of 0.6-M ferrous sulfamate to each solution. Swirl to
mix.
Note: If the additional 5 mL was used to dissolve the sample in Step
11.2.1.1, add a total of 3 mL of ferrous sulfamate solution.
11.2.1.3. Add 1 drop of 1 -M ammonium thiocyanate indicator to each
sample and mix.
Note: The color of the solution turns deep red, due to the presence of
soluble ferric thiocyanate complex.
11.2.1.4. Add 1 mL of 1 -M ascorbic acid to each solution, swirling to mix.
Wait for 2-3 minutes.
Note: The red color should disappear, which indicates reduction of Fe+3
to Fe+2. If the red color still persists, then additional ascorbic acid solution
has to be added drop-wise with mixing until the red color disappears.
Note: If particles are observed suspended in the solution, centrifuge the
sample. The supernatant solution will be transferred to the column in
Step 11.2.3.1. The precipitates will be discarded.
11.2.2. Setup of UTEVA and TRU cartridges in tandem on the vacuum box system
Note: Steps 11.2.2.1 to 11.2.2.5 deal with a commercially available filtration system.
Other vacuum systems developed by individual laboratories may be substituted here
as long as the laboratory has provided guidance to analysts in their use.
11.2.2.1. Place the inner tube rack (supplied with vacuum box) into the
vacuum box with the centrifuge tubes in the rack. Fit the lid to
the vacuum system box.
11.2.2.2. Place the yellow outer tips into all 24 openings of the lid of the
vacuum box. Fit in the inner white tip into each yellow tip.
11.2.2.3. For each sample solution, fit in a TRU cartridge on to the inner
white tip. Ensure the UTEVA cartridge is locked into the top end
of the TRU cartridge.
11.2.2.4. Lock syringe barrels (funnels/reservoirs) to the top end of the
UTEVA cartridge.
11.2.2.5. Connect the vacuum pump to the box. Turn the vacuum pump on
and ensure proper fitting of the lid.
10/28/2011 8 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
IMPORTANT: The unused openings on the vacuum box should be
sealed. Yellow caps (included with the vacuum box) can be used to plug
unused white tips to achieve good seal during the separation.
11.2.2.6. Add 5 mL of 3-M HNOs to the funnel to precondition the
UTEVA and TRU cartridges.
11.2.2.7. Adjust the vacuum pressure to achieve a flow-rate of ~1 mL/min.
IMPORTANT: Unless otherwise specified in the procedure, use a flow
rate of ~1 mL/min for load and strip solutions and ~3 mL/min for rinse
solutions.
11.2.3. Preliminary purification of the americium fraction using UTEVA and TRU
resins
11.2.3.1. Transfer each solution from Step 11.2.1.4 into the appropriate
funnel by pouring or by using a plastic transfer pipette. Allow
solution to pass through both cartridges at a flow rate of ~1
mL/min.
11.2.3.2. Add 5 mL of 3-MHNO3 to each beaker (from Step 11.2.1.4) as a
rinse and transfer each solution into the appropriate funnel (the
flow rate can be adjusted to ~3 mL/min).
11.2.3.3. Add 5 mL of 3-M HNOs into each funnel as a second column
rinse (flow rate ~3 mL/min).
11.2.3.4. Separate UTEVA cartridge from TRU cartridge. Discard
UTEVA cartridge and the effluent collected so far. Place new
funnel on the TRU cartridge.
11.2.4. Final americium separation using TRU cartridge
Note: Steps 11.2.4.1 to 11.2.4.3 may be omitted if the samples are known not to contain
plutonium
11.2.4.1. Pipette 5 mL of 2-M HNO3 into each TRU cartridge from Step
11.2.3.4. Allow to drain.
11.2.4.2. Pipette 5 mL of 2-MHNO3- 0.1-MNaNO2 directly into each
cartridge, rinsing each cartridge reservoir while adding the 2-M
HNO3-0.1-MNaNO2.
IMPORTANT: The flow rate for the cartridge should be adjusted to ~1
mL/min for this step.
Note: Sodium nitrite is used to oxidize any Pu+3 to Pu+4 and enhance the
Pu/Am separation.
11.2.4.3. Allow the rinse solution to drain through each cartridge.
11.2.4.4. Add 5 mL of 0.5-M HNOs to each cartridge and allow it to drain.
Note: 0.5-M HNO3 is used to lower the nitrate concentration prior to
conversion to the chloride system.
10/28/2011 9 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
11.2.4.5. Discard the load and rinse solutions to waste.
11.2.4.6. Ensure that clean, labeled tubes (at least 25-mL capacity) are
placed in the tube rack.
11.2.4.7. Add 3 mL of 9-M HC1 to each cartridge to convert to chloride
system. Collect eluate.
11.2.4.8. Add 20 mL of 4-M HC1 to elute americium. Collect eluate in the
same tube.
11.2.4.9. Transfer the combined eluates from Steps 11.2.4.7 and 11.2.4.8
to a 50-mL beaker.
11.2.4.10. Rinse tube with a few milliliters of water and add to the same
beaker.
11.2.4.11. Evaporate samples to near dryness.
Important: Do not bake the residue.
11.2.4.12. Allow the beaker to cool slightly and then add a few drops of
concentrated HC1 followed by 1 mL of water.
11.2.4.13. Transfer the solution from Step 11.2.4.12 to a 10-mL plastic
culture tube. Wash the original sample vessel twice with 1-mL
washes of 1M HC1. Transfer the washings to the culture tube.
Mix by gently swirling the solution in the tube.
11.2.4.14. Proceed to neodymium fluoride microprecipitation in Step 11.3.
11.2.4.15. Discard the TRU cartridge.
11.3. Preparation of the Sample Test Source
Note: Instructions below describe preparation of a single Sample Test Source. Several STSs can
be prepared simultaneously if a multi-channel vacuum box (whale apparatus) is available.
11.3.1. Add 100 jiL of the neodymium carrier solution to the tube from Step
11.2.4.14 with a micropipette. Gently swirl the tube to mix the solution.
11.3.2. Add 10 drops (0.5 mL) of concentrated HF to the tube and mix well by
gentle swirling.
11.3.3. Cap the tube and place it in a cold-water bath for at least 30 minutes.
11.3.4. Insert the polysulfone filter stem in the 250-mL vacuum flask. Place the
stainless steel screen on top of the fitted plastic filter stem.
11.3.5. Place a 25-mm polymeric filter face up on the stainless steel screen. Center
the filter on the stainless steel screen support and apply vacuum. Wet the
filter with 100% ethanol, followed by filtered Type I water.
Caution: There is no visible difference between the two sides of the filter. If the filter is
turned over accidentally, it is recommended that the filter be discarded and a fresh
one removed from the container.
11.3.6. Lock the filter chimney firmly in place on the filter screen and wash the
filter with additional filtered Type I water.
10/28/2011 10 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
1 1.3.7. Pour 5.0 mL of neodymium substrate solution down the side of the filter
chimney, avoiding directing the stream at the filter. When the solution
passes through the filter, wait at least 15 seconds before the next step.
1 1.3.8. Repeat Step 1 1.3.7 with an additional 5.0 mL of the substrate solution.
1 1.3.9. Pour the sample from Stepl 1.3.3 down the side of the filter chimney and
allow the vacuum to draw the solution through.
1 1.3.10. Rinse the tube twice with 2 mL of 0.58 M HF, stirring each wash briefly
using a vortex mixer, and pouring each wash down the side of the filter
chimney.
11.3.11. Repeat rinse using 2 mL of filtered Type I water once.
11.3.12. Repeat rinse using 2 mL of 80% ethyl alcohol once.
Note: Steps 11.3.10 and 11.3.12 were shown to improve the FWHM in the alpha
spectrum, providing more consistent peak resolution.
1 1.3.13. Wash any drops remaining on the sides of the chimney down toward the
filter with a few milliliters of 80% ethyl alcohol.
Caution: Directing a stream of liquid onto the filter will disturb the distribution of the
precipitate on the filter and render the sample unsuitable for a-spectrometry
resolution.
1 1.3.14. Without turning off the vacuum, remove the filter chimney.
11.3.15. Turn off the vacuum to remove the filter. Di scard the filtrate to waste for
future disposal. If the filtrate is to be retained, it should be placed in a plastic
container to avoid dissolution of the glass vessel by dilute HF.
1 1.3.16. Place the filter on a properly labeled mounting disc. Secure with a mounting
ring or other device that will render the filter flat for counting.
1 1.3.17. Let the sample air-dry for a few minutes and when dry, place in a container
suitable for transfer and submit for counting.
Note: Other methods for STS preparation, such as electroplating or
microprecipitation with cerium fluoride, may be used in lieu of the neodymium
fluoride microprecipitation, but any such substitution must be validated as described
in Section 1.4.
12. Data Analysis and Calculations
12.1. Equation for determination of final result, combined standard uncertainty, and
radiochemical yield (if requested):
The activity concentration of an analyte and its combined standard uncertainty are
calculated using the following equations:
and
10/28/2011 11 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
where:
ACn = activity concentration of the analyte at time of count, (pCi/L)
At = activity of the tracer added to the sample aliquant at its reference
date/time, (pCi)
Ra = net count rate of the analyte in the defined region of interest (ROI),
in counts per second
Rt = net count rate of the tracer in the defined ROI, in counts per second
Fa = volume of the sample aliquant, (L)
A = correction factor for decay of the tracer from its reference date and
time to the midpoint of the counting period
Z)a = correction factor for decay of the analyte from the time of sample
collection (or other reference time) to the midpoint of the counting
period, if required
/t = probability of a emission in the defined ROI per decay of the tracer
(Table 17.1)
/a = probability of a emission in the defined ROI per decay of the
analyte (Table 17.1)
= combined standard uncertainty of the activity concentration of the
analyte (pCi/L)
= standard uncertainty of the activity of the tracer added to the
sample (pCi)
z/(Fa) = standard uncertainty of the volume of sample aliquant (L)
u(Ra) = standard uncertainty of the net count rate of the analyte in counts
per second
u(R\) = standard uncertainty of the net count rate of the tracer in counts per
second
Note: The uncertainties of the decay-correction factors and of the probability of decay
factors are assumed to be negligible.
Note: The equation for the combined standard uncertainty (wc(y4Ca)) calculation is arranged
to eliminate the possibility of dividing by zero if Ra = 0.
Note: The standard uncertainty of the activity of the tracer added to the sample must reflect
that associated with the activity of the standard reference material and any other significant
sources of uncertainty such as those introduced during the preparation of the tracer solution
(e.g., weighing or dilution factors) and during the process of adding the tracer to the sample.
Note: The alpha spectrum of americium isotopes should be examined carefully and the ROI
reset manually, if necessary, to minimize the spillover of 241Am peak into the 243Am peak.
12.1.1. The net count rate of an analyte or tracer and its standard uncertainty can
be calculated using the following equations:
10/28/2011 12 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
_Cx__Cb
and
where:
Rx = net count rate of analyte or tracer, in counts per second
Cx = sample counts in the analyte or the tracer ROI
ts = sample count time (s)
Cbx = background counts in the same ROI as for x
tb = background count time (s)
z/(7?x) = standard uncertainty of the net count rate of tracer or analyte, in
counts per second1
If the radiochemical yield of the tracer is requested, the yield and its combined
standard uncertainty can be calculated using the following equations:
RY = ^
0.037x4 xDtx!txs
and
where:
RY = radiochemical yield of the tracer, expressed as a fraction
Rt = net count rate of the tracer, in counts per second
AI = activity of the tracer added to the sample (pCi)
A = correction factor for decay of the tracer from its reference date and
time to the midpoint of the counting period
/t = probability of a emission in the defined ROI per decay of the tracer
(Table 17.1)
e = detector efficiency, expressed as a fraction
uc(RY) = combined standard uncertainty of the radiochemical yield
u(Rt) = standard uncertainty of the net count rate of the tracer, in counts
per second
u(At) = standard uncertainty of the activity of the tracer added to the
sample (pCi)
1 For methods with very low counts, MARLAP Section 19.5.2.2 recommends adding one count each to the gross
counts and the background counts when estimating the uncertainty of the respective net counts. This minimizes
negative bias in the estimate of uncertainty and protects against calculating zero uncertainty when a total of zero
counts are observed for the sample and background.
10/28/2011 13 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
u(e) = standard uncertainty of the detector efficiency
12.1.2. If the critical level concentration (Sc) or the minimum detectable
concentration (MDC) are requested (at an error rate of 5%), they can be
calculated using the following equations:
£.=-
x A x Dt L
tsxVaxRtxDax!a
When the Type I decision error rate, a, equals 0.05, z\-a = 1.645, and the constant, d, from the
Stapleton approximation is set to 0.4, the expression above becomes:
S =
0.4x
^-1+ 0.677 x 1 + ^ + 1 .645 x l(Rbatb + 0.4)x ^
b J \ tb ) V tb
x 1 +
x At x Dt x It
tsxVaxRtxDax!a
MDC =
x At x Dt x It
t xV xRt xD xl x2.22
s a i a a
When the Type I decision error rate, a, equals 0.05, z\-a = 1.645, and the Type II decision
error rate, 6, equals 0.05, zi_6 = 1.645, the expression above becomes:
MDC =
2.71x
+3.29x
x Dt x It
t xV xRxD xl
s a i a a
where:
2 The formulations for the critical level and minimum detectable concentrations are as recommended in MARLAP
Section 20A.2.2, Equation 20.54, and Section 20A.3.2, Equation 20.74, respectively. For methods with very low
numbers of counts, these expressions provide better estimates than do the traditional formulas for the critical level
and MDC assuming that the observed variance of the background conforms to Poisson statistics. Consult MARLAP
when background variance may exceed that predicted by the Poisson model or when other decision error rates may
apply.
10/28/2011
14
Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
Rbn = background count rate for the analyte in the defined ROI, in counts
per second
12.2. Results Reporting
12.2.1. The following items should be reported for each result: volume of sample
used; yield of tracer and its uncertainty; and full width at half maximum
(FWHM) of each peak used in the analysis.
12.2.2. The following conventions should be used for each result:
12.2.2.1. Result in scientific notation ± combined standard uncertainty.
12.2.2.2. If solid material was filtered from the solution and analyzed
separately, the results of that analysis should be reported separately
as pCi/L of the original volume from which the solids were filtered
if no other guidance is provided on reporting of results for the
solids. For example:
241 Am for Sample 12-1-99:
Filtrate Result: (1.28 ± 0.15) x 101 pCi/L
Filtered Residue Result: (2.50 ± 0.32) x 10° pCi/L
13. Method Performance
13.1. Method validation results are to be reported as an attachment.
13.1.1. Expected turnaround time per batch of 14 samples plus QC, assuming
microprecipitations for the whole batch are performed simultaneously using
a vacuum box system:
13.1.2. For an analysis of a 200-mL sample aliquant, sample preparation and
digestion should take 3.5 h.
13.1.3. Purification and separation of the americium fraction using cartridges and
vacuum box system should take 2.5 h.
13.1.4. Sample evaporation to near dryness should take ~ 30 minutes.
13.1.5. The last step of source preparation takes ~1 h.
13.1.6. A 1-3 h counting time is sufficient to meet the MQOs listed in 9.3 and 9.4,
assuming detector efficiency of 0.2-0.3, and radiochemical yield of at least
0.5. Longer counting time may be necessary to meet these MQOs if detector
efficiency is lower.
13.1.7. Data should be ready for reduction between 8.5 and 10.5 h after beginning
of analysis.
14. Pollution Prevention: This method utilizes small volume (2-mL) extraction
chromatographic resin columns. This approach leads to a significant reduction in the
volumes of load, rinse and strip solutions, as compared to classical methods using ion
exchange resins to separate and purify the americium fraction.
15. Waste Management
15.1. Types of waste generated per sample analyzed
15.1.1. If Ca3(PC>4)2 coprecipitation is performed, approximately 100-1000 mL of
decanted solution that is pH neutral are generated.
10/28/2011 15 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
15.1.2. Approximately 35 mL of acidic waste from loading and rinsing the two
extraction columns are generated.
15.1.3. Approximately 35 mL of acidic waste from microprecipitation method for
source preparation, contains 1 mL of HF and ~ 8 mL ethanol.
15.1.4. Unless processed further, the UTEVA cartridge may contain isotopes of
uranium, neptunium, and thorium, if any of these were present in the sample
originally.
15.1.5. Unless processed further, the TRU cartridge may contain isotopes of
plutonium if any of them were present in the sample originally.
15.2. Evaluate all waste streams according to disposal requirements by applicable
regulations.
16. References
16.1. ACW03 VBS, Rev. 1.6, "Americium, Plutonium, and Uranium in Water (with
Vacuum Box System)," Eichrom Technologies, Inc., Lisle, Illinois (February 2005).
16.2. G-03, V. 1 "Microprecipitation Source Preparation for Alpha Spectrometry," HASL-
300, 28th Edition, (February 1997).
16.3. ASTM D7282 "Standard Practice for Set-up, Calibration, and Quality Control of
Instruments Used for Radioactivity Measurements," ASTM Book of Standards
11.02, current version, ASTM International, West Conshohocken, PA.
16.4. VBS01, Rev. 1.3, "Setup and Operation Instructions for Eichrom's Vacuum Box
System (VBS)," Eichrom Technologies, Inc., Lisle, Illinois (January 2004).
16.5. U.S. Environmental Protection Agency (EPA). 2009. Method Validation Guide for
Radiological Laboratories Participating in Incident Response Activities. Revision
0. Office of Air and Radiation, Washington, DC. EPA 402-R-09-006, June.
Available at: www.epa.gov/narel/incident guides.html and
www.epa.gov/erln/radiation.html.
16.6. Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP).
2004. EPA 402-B-1304 04-001A, July. Volume I, Chapters 6, 7, 20, Glossary;
Volume II and Volume III, Appendix G. Available at: www.epa.gov/radiation/
marlap/index.html.
16.7. ASTM Dl 193, "Standard Specification for Reagent Water" ASTM Book of
Standards 11.01, current version, ASTM International, West Conshohocken, PA.
10/28/2011 16 Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
17. Tables, Diagrams, Flow Charts, and Validation Data
17.1. Tables [including major radiation emissions from all radionuclides separated]
Table 17.1 Alpha Particle Energies and Abundances of Importance
[i]
Nuclide
241Am
243Am
Half-Life
(Years)
432.6
7.37xl03
>,
(s")
5.077x10""
2.98xlO~12
Abundance
0.848
0.131
0.0166
0.871
0.112
0.0136
a Energy
(MeV)
5.486
5.443
5.388
5.275
5.233
5.181
llJOnly the most abundant particle energies and abundances have been noted here.
10/28/2011
17
Revision 0.1
-------
Americium-241 in Water: Rapid Method for High-Activity Samples
17.2. Ingrowth Curves and Ingrowth Factors
This section intentionally left blank
17.3. Spectrum from a Processed Sample
110 •
100 •
90 -
80 -
» 70 •
1
8 60 -
50 •
40 -
30 -
20 •
10 -
0 •
Arn-243
|
/
Am-241
I
1
1 |—'f"' |" | — | — !*— | — | '' |""f — | — I — !— 1 — 1 — Hi — t 1 '~T I — 1 — 1 — 1 — 1 : — I 1 — 1 i 1 i i i i i i c i i i i i i
3011 3311 3611 3911 4211 4511 4811 5111 5411 5711 6011 6311 6611 6911 7211 7511 7811
Energy (keV)
17.2 Decay Scheme
241Am and 243Am Decay Scheme
^=433y
10/28/2011
18
Revision 0.1
-------
Americium-241 in Water- Rapid Method for High-Activity Samples
17.4. Flowchart
Sample preparation (Step 11.1)
1. Add 243Am tracer
2. Digestion or calcium phosphate
co-precipitation (2—3 hours)
Preparation for cartridge (Step 11.2.1)
1. Dissolve phosphate
2. Add sulfamate, thiocyanate, ascorbic
acid (5 minutes)
Set up of UTEVA and TRU cartridges
in tandem using VBS (Step 11.2.2)
1. Assembly
2. Prep with 5 ml 3 M HNO3 @ 1 mL/min
Load the cartridge (Step 11.2.3)
Sample: 20 ml @ 1 mL/min
Rinse: 5 ml 3 M HNO3 @ 3 mL/min
2ndrinse:5mL3MHNO3
(~ 25 minutes)
Separate cartridges (Step 11.2.3.4)
I
UTEVA cartridge to waste
Effluent to waste
(Step 11.2.3.4)
TRU cartridge for processing
Attach fresh funnel to the cartridge
Elapsed
time
-3.5 hours
~6 hours
Separation scheme and timeline for determination of Am in water samples
Parti
10/28/2011
19
Revision 0.1
-------
Americium-241 in Water- Rapid Method for High-Activity Samples
i
Discard load and rinse
effluents (Step 11. 2. 4. 5)
+
Discard TRU cartridge
(Step 11. 2. 4.1 5)
Caution: may contain Pu
+
Discard filtrates and washes
(Step 11. 3. 15)
Convert Pu '3 to Pu*4 (Steps 11.2.4.1-3)
1 . 5 rnL 2 M HNO , @ 3 mUnin
2. 5 ml_ 2M HN03+0.1 M NalMO 2 @ 1 mUmin
3. 5 ml 0.5 M HNO 3 @ 1 mLJrnin
1
I
>
Strip Am+3 from the cartridge (Steps 11.2.4.6-14
1 . Add 3 ml 9 M HCI @ 1 rnUmin
2. Add 20 rnL 4 M HCI @ 1 mUrnin
3. Evaporate eluate and redissolve
~1 hour
I
1
Microprecipitation (Step 11.3)
1 . Add NdF 3 carrier and wait 30 rnin
2. Filter, dry, mount
(1 hour)
I
3
f Sfrp if Pu "]
> "of
•^ present j
\
Count sample test source (STS)
\ For 1-3 hours ^
-6.5 hours hours
-7.5 hours
8.5 to 10.5 hours
Separation scheme and timeline for determination of2il1 Am in water samples
Part 2
10/28/2011
20
Revision 0.1
------- |