EPA 402-R-10-001 e
www.epa.gov/narel
October 2011
Revision 0.1
Rapid Radiochemical Method for
Isotopic Uranium 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
-------
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.
Add pH paper to list of equipment and supplies (6.7).
Edited Section 8 to conform syntax and layout to other methods.
Added equations in 12.1.2 that allow theoretical calculation of the MDA
and critical level for different decision error rates.
Updated footnote 9 to further clarify origin of critical value and
minimum detectable concentration formulations.
Updated rounding example in 12.2.2.2 for clarity.
Deleted Appendix A (composition of Atlanta tap water) 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.
-------
ISOTOPIC URANIUM IN WATER:
RAPID METHOD FOR HIGH-ACTIVITY SAMPLES
Scope and Application
1.1. The method will be applicable to samples where the source of the contamination is
either known or unknown sample sources. 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 238U, 235U, and 2 4U in drinking water and other aqueous
samples.
1.3. This method uses rapid radiochemical separations techniques for determining alpha-
emitting uranium isotopes in water samples following a nuclear or radiological
incident. Although the method can detect concentrations of 238U, 235U, and234U on the
same order of magnitude as methods used for the Safe Drinking Water Act (SDWA),
this method is not a substitute for SDWA-approved methods for isotopic uranium.
OQQ 9^S
1.4. The method is capable of satisfying a required method uncertainty for U, U, or
234U of 2.6 pCi/L at an analytical action level of 20 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 uranium 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).
1.6. Multi-radionuclide analysis using sequential separation may be possible using this
method in conjunction with other rapid methods.
1.7. This method is applicable to the determination of soluble uranium. This method is not
applicable to the determination of uranium isotopes contained in highly insoluble
particulate matter possibly present in water samples contaminated as a result of a
radiological dispersion device (ROD) event.
Summary of Method
2.1. This method is based on the sequential elution of interfering radionuclides as well as
other components of the matrix by extraction chromatography to isolate and purify
uranium in order to prepare the uranium for counting by alpha spectrometry. The
method utilizes vacuum assisted flow to improve the speed of the separations. Prior to
the use of the extraction resins, a water sample is filtered as necessary to remove any
insoluble fractions, equilibrated with 232U tracer, and concentrated by either
10/28/2011 1 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
evaporation or calcium phosphate precipitation. The sample test source (STS) is
prepared by microprecipitation with NdF3. 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 Specification (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 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 Analytical Laboratory Protocol Manual (MARLAP) (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 and can be quantitative
or qualitative. These analytical data requirements serve as measurement performance
criteria or objectives of the analytical process.
3.7. Radiological Dispersal Device (RDD), 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 (MMR)- 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 Analytical Action level.
3.9. Relative Required Method Uncertainty (^R). The relative required method uncertainty
is the MMR divided by the AAL and typically expressed as a percentage. It is applicable
above the AAL.
3.10. Sample Test Source (STS). This is the final form of the sample that is used for nuclear
counting. This form is usually specific for the nuclear counting technique used in the
method such as a solid deposited on a filter for alpha spectrometry analysis.
4. Interferences
4.1. Radiological
4.1.1. Spectral Overlap: Alpha-emitting radionuclides (or their short-lived decay
progeny) with peaks at energies that cannot be adequately resolved from the
tracer or analyte (e.g., for 232U (5320, 5263 keV), 2f°Po (5304 keV), 228Th
(5423, 5340 keV), and 243Am (5275, 5233 keV)) must be chemically separated
to enable radionuclide-specific measurements. This method separates these
radionuclides effectively. The significance of peak overlap will be determined
10/28/2011 2 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
by the 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 uranium (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 reported with the final sample
results.
5.2.2. For samples with detectable activity concentrations of these radionuclides,
labware should be used only once due to potential for cross contamination.
5.3. Procedure-Specific Non-Radiological Hazards:
5.3.1. Particular attention should be paid to the discussion 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 obtained and used in strict accordance
with the laboratory safety program specification.
6. Equipment and Supplies
6.1. Analytical balance with 1 CT4-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 with 250-mL capacity.
6.5. Filter with 0.45-um membrane.
10/28/2011 3 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
6.6. Filter apparatus with a 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.
6.7. pH paper.
6.8. 25-mm polypropylene filter with 0.1-um pore size.
6.9. Stainless steel planchets or other sample mounts that are 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. Vacuum pump or laboratory vacuum system.
6.14. Tips, white inner, Eichrom part number AC-1000-IT, or equivalent.
6.15. Tips, yellow outer, Eichrom part number AC-1000-OT, or equivalent.
6.16. Vacuum Box, such as Eichrom part number AC-24-BOX, or equivalent.
6.17. Vortex mixer.
6.18. Miscellaneous labware, plastic or glass, both 250 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 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 . Ammonium hydrogen oxalate (0. 1M): Dissolve 6.3 g of oxalic acid (H2C2(
and 7.1 g of ammonium oxalate ((NH4)2C2(VH2C)) in 900 mL of water, and dilute to 1
L with water.
7.2. Ammonium hydrogen phosphate (3.2 M): Dissolve 106 g of (NH4)2HPO4 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
and heat to 70 °C. Slowly add 7 g of iron powder (< 100 mesh size) while heating and
stirring (magnetic stirrer should be used) 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
-------
Isotopic Uranium (238U, 235U, and 234U) 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 for
up to six months.
7.13. Neodymium fluoride substrate solution (10 |ig/mL): Pipette 5.0 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 (16M): 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 (3 M) - aluminum nitrate (1.0 M) solution: Dissolve 210 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.
7.16. Phenolphthalein solution: Dissolve 1 g phenolphthalein in 100 mL 95% isopropyl
alcohol and dilute with 100 mL of water.
7.17. Titanium chloride: 20 % solution, stored in an air-tight container and away from light.
7.18. Uranium-232 tracer solution: 6-10 dpm of 232U per aliquant, activity added known to at
least 5 % (combined standard uncertainty of no more than 5 %).
7.19. UTEVA Resin: 2-mL cartridge, 50-100 |ig, Eichrom part number UT-R50-S and UT-
R200-S, or equivalent.
8. Sample Collection, Preservation, and Storage
8.1. Samples should be collected in 1-L plastic containers.
8.2. No sample preservation is required if sample analysis is initiated within 3 days of
sampling date/time.
8.3. If the sample is to be held for more than three days, HNO3 shall be added until the
solution pH is less than 2.0.
8.4. If the dissolved concentration of uranium is sought, the insoluble fraction must be
removed by filtration before preserving with acid.
10/28/2011 5 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) 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 should 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 that produces a
spectrum with the full width at half maximum (FWHM) of 50-100 keV for each peak
in the spectrum (with the exception of 235U). Precipitate reprocessing should be
considered if this range of FWHM cannot be achieved.
9.3. This method is capable of achieving a WMR of 2.6 pCi/L at or below an action level of
20 pCi/L. This may be adjusted if the event-specific MQOs are different.
9.4. This method is capable of achieving a ^MR of 13 % above 20 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 3-8 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 100-200 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. This usually requires adding
about 2 mL of concentrated HNOs per 1000 mL of sample. However, samples
that are initially alkaline, or that may have high carbonate content, may require
10/28/2011 6 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
substantially more acid. It is important that the pH be verified to be below 2.0,
ensuring that all carbonate (a uranium complexing agent) has been removed.
11.1.3. Following the laboratory protocol, add 6-10 dpm of 232U as a tracer.
Note: For a sample approximately 100 mL or less, the evaporation option is recommended.
Proceed to Step 11.1.5. Otherwise continue 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 NH/iOH with a squeeze bottle to reach
the phenolphthalein end point (a persistent pink color) and form
Ca3(PC>4)2 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.
Note: The calcium phosphate precipitation should be completed promptly
following pH adjustment to the phenolphthalein endpoint to minimize
absorption of CO2 and formation of a soluble carbonate complex with U
that will lead to incomplete precipitation of U.
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 goto 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 centrifuge 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
10/28/2011 7 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
evaporation. If this occurs, use the calcium phosphate 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 HNCb.
11.1.5.3. Repeat Step 11.1.5.2 two more times, evaporate to dryness, and go
to Step 11.2.
11.2. Actinide Separations using Eichrom Resins
11.2.1. Redissolve Ca3(PC>4)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 formation 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 persists, then additional ascorbic acid solution is added
drop-wise with mixing until the red color disappears.
Note: If particles are observed suspended in the solution, centrifuge the
sample at 2000 rpm. The supernatant solution will be transferred to the
column in Step 11.2.3.1. The precipitates will be discarded.
11.2.2. Set up the vacuum box with UTEVA cartridges as follows:
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.
10/28/2011 8 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
11.2.2.3. For each sample solution, fit in the UTEVA cartridge on to the
inner white tip.
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.
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 HNO3 to the funnel to precondition the UTEVA
cartridge.
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. U separation from Pu, Am using UTEVA resin
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 the cartridges at a flow rate of ~1
mL/min.
11.2.3.2. Add 5 mL of 3-M HNOs to each beaker 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 HNCb into each funnel as second column rinse
(flow rate ~3 mL/min).
Note: Maintain the flow rate at <3 mL/min in the next several steps.
Note: If a high concentration of 210Po is present in the sample an additional
3 M HNO3 rinse is necessary to eliminate 210Po. Add 30 mL of 3 M HNO3
rinse to each UTEVA cartridge in increments of 10 mL. Continue with Step
11.2.3.4.
11.2.3.4. Pipette 5 mL of 9-M HC1 into each UTEVA cartridge and allow it
to drain. Discard this rinse.
Note: This rinse converts the resin to the chloride system. Some Np may be
removed here.
11.2.3.5. Pipette 20 mL of 5-M HC1 - 0.05 M oxalic acid into each UTEVA
cartridge and allow it to drain. Discard this rinse.
Note: This rinse removes neptunium and thorium from the cartridge. The
9-M HC1 and 5-M HC1 - 0.05 M oxalic acid rinses also remove any residual
10/28/2011 9 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
ferrous ion that might interfere with micoprecipitation.
11.2.3.6. Ensure that clean, labeled tubes are placed in the tube rack.
11.2.3.7. Pipette 15 mL of 1-M HC1 into each cartridge to strip the uranium.
Allow to drain.
11.2.3.8. Transfer the eluate containing uranium to a 50-mL beaker. Rinse
the tube with a few milliliters of water and add to the same beaker.
11.2.3.9. Evaporate samples to near soft dryness. If a slight white residue
appears, wet-ash by adding a few mL of HNOs, heating till near
dryness and repeating the process 2-3 times. Once wet-ashing is
complete, convert the sample to the chloride form by treating it 2-
3 times with 1-2-mL portions of HC1 and evaporating to near
dryness.
Note: Do not bake the residue.
11.2.3.10. Allow the beaker to cool slightly and then add a few drops of
concentrated HC1 followed by 1 mL of water.
11.2.3.11. Transfer the solution to a 10-mL plastic culture tube. Rinse the
original sample vessel twice with 1-mL washes of 1-M HC1,
transferring the rinses to a culture tube. Mix by gently swirling the
solution in the tube.
11.2.3.12. Proceed to neodymium fluoride microprecipitation, Step 11.3.
11.2.3.13. Discard the UTEVA 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 (Step 7.12) to the culture tube
with a micropipette. Gently swirl the tube to mix the solution.
11.3.2. Add four drops of 20% TiCb solution to the tube and mix gently. A strong
permanent violet color should appear. If the color fails to appear, add a few
more drops of the TiCb solution to provide the permanent violet color.
11.3.3. Add 1 mL of concentrated HF to the tube and mix well by gently swirling.
11.3.4. Cap the tube and place it a cold-water ice bath for at least 30 minutes.
11.3.5. Insert the polysulfone filter stem in the 250-mL vacuum flask. Place the
stainless steel screen on top of the fitted plastic filter stem.
11.3.6. 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.
11.3.7. Lock the filter chimney firmly in place on the filter screen and wash the filter
with additional filtered Type I water wash.
10/28/2011 10 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
11.3.8. Pour 5.0 mL of neodymium substrate solution (Step 7.13) 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.
11.3.9. Repeat Step 11.3.8 with an additional 5.0 mL of the substrate solution.
11.3.10. Pour the sample from Step 11.3.4 down the side of the filter chimney and
allow the vacuum to draw the solution through.
11.3.11. 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.
11.3.12. Repeat rinse using 2-mL filtered Type I water once.
11.3.13. Repeat rinse using 2-mL 80% ethyl alcohol once.
11.3.14. Wash any drops remaining on the sides of the chimney down toward the filter
with a few mL 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.
11.3.15. Without turning off the vacuum, remove the filter chimney.
11.3.16. Turn off the vacuum to remove the filter. Discard 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.
11.3.17. 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.
11.3.18. Let the sample air dry for a few minutes and when dry, place in a container
suitable for transfer and submit for counting.
11.3.19. Count the sample on an alpha spectrometer.
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. Equations for determination of final result, combined standard uncertainty and
radiochemical yield (if required).
The activity concentration of an analyte and its combined standard uncertainty are
calculated using the following equations:
ACa = AiXR*xDtXli
a t a a
and
where:
ACa = activity concentration of the analyte at time of count, (pCi/L)
10/28/2011 11 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
At = activity of the tracer added to the sample aliquant at its reference date
and time, (pCi)
^a = 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
Ai = 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)
It = 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)
Uc(ACa) = combined standard uncertainty of the activity concentration of the
analyte (pCi/L)
u(At) = standard uncertainty of the activity of the tracer added to the sample
(pCi)
w(Fa) = standard uncertainty of the volume of sample aliquant (L)
u(Rn) = standard uncertainty of the net count rate of the analyte, in counts per
second
u(Rt) = 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 (uc(ACa)) 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.
12.1.1. The net count rate of an analyte or tracer and the associated standard
uncertainties are calculated using the following equations:
= Cx Cbx
and
where:
10/28/2011 12 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
u(Rx) = standard uncertainty of the net count rate of tracer or analyte, in
counts per second1
Rx = net count rate of analyte or tracer, in counts per second
Cx = sample counts in the analyte or the tracer peak
ts = sample count time (s)
CW = background counts in the same region of interest (ROI) as for x
t\, = background count time (s)
The radiochemical yield and the combined standard uncertainty can be estimated for
each sample, when required, using the following equations:
RY=-
0.037x4 xDtx!txs
and
= radiochemical yield of the tracer, expressed as a fraction
= net count rate of the tracer, in counts per second
At = activity of the tracer added to the sample (pCi)
Dt = correction factor for decay of the tracer from its reference date and
time to the midpoint of the counting period
It = probability of a emission in the defined ROI per decay of the tracer
(Table 17.1)
s = 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)
u(s) = 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:2
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 zero total counts
are observed for the sample and background.
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.2.3, 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
10/28/2011 13 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
S =
rfxM--!
u.
l_a](Rhath
x At x Dt It
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 I —-I + 0.677 x 1 + ^ +1.645 x J(^6+0.4)x^-x 1 + ^
x A x D x I
t t t
tsxVaxRtxDax!a
MDC =
x At x Dt x 7t
tsxVaxRtxDax!ax2.22
When the Type I decision error rate, a, equals 0.05, z\-a = 1.645, and the Type II decision
error rate, ft, equals 0.05, z\-p = 1.645, the expression above becomes:
MDC =
2.71x1
tx I
AtxDtx It
where:
= background count rate for the analyte in the defined ROI, in counts per second
12.2. Results Reporting
12.2.1. The following data should be reported for each result: volume of sample used,
yield of tracer and its uncertainty, and FWHM of each peak used in the
analysis.
12.2.2. The following conventions should be noted 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
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
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
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:
23*U 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.
13.2. Expected turnaround time per batch of 14 samples plus QC, assuming
microprecipitations for the whole batch are performed simultaneously using a vacuum
box system:
13.2.1. For an analysis of a 200 mL sample aliquant, sample preparation and
digestion should take -3.5 h.
13.2.2. Purification and separation of the uranium fraction using cartridges and
vacuum box system should take -1.5 h.
13.2.3. The sample test source preparation takes -1 h (longer if wet-ashing is
necessary).
13.2.4. A 1-h counting time should be 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. A different counting time may be necessary to meet these MQOs if
any of the relevant parameters are significantly different.
13.2.5. Data should be ready for reduction -6 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 uranium.
15. Waste Management
15.1. Types of waste generated per sample analyzed
15.1.1. If calcium phosphate coprecipitation is performed, 100-1000 mL of decanted
solution that is pH neutral is generated.
15.1.2. Approximately 65 mL of acidic waste from loading and rinsing the extraction
column will be generated. The solution may contain unknown quantities of
radionuclides as may be present in the original sample. If presence of other
radionuclides in the sample is suspected, combined effluents should be
collected separately from other rinses to minimize quantity of mixed waste
generated.
15.1.3. Approximately 45 mL of slightly acidic waste, containing 1 mL of HF and - 8
mL ethanol are produced in the microprecipitation step.
15.1.4. UTEVA cartridge - ready for appropriate disposal.
15.2. Evaluate all waste streams to ensure that all local, state, and federal disposal
requirements are met.
16. References
10/28/2011 15 Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
16.1. ACW02, Rev. 1.3, "Uranium in Water," Eichrom Technologies, Inc., Lisle, Illinois
(April 2001).
16.2. G-03, V.I "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, "Setup and Operation Instructions for Eichrom's Vacuum Box System
(VBS)," Eichrom Technologies, Inc., Lisle, Illinois (Rev. 1.3, January 30, 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 04-001 A, 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
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
17. Tables, Diagrams, Flow Charts, and Validation Data
17.1. Nuclide Decay and Radiation Data
Table 17.1 - Decay and Radiation Data
Nuclide
238U
235U
234U
232U
Half-Life
(Years)
4.468xl09
7.038xl08
2.457xl05
68.9
>,
(s-1)
4.916xlO~18
3.121xlO~17
8.940xlO~14
3.19xlO~10
Abundance
0.79
0.21
0.050
0.042
0.0170
0.0070
0.0210
0.55
0.170
0.7138
0.2842
0.002
0.6815
0.3155
a Energy
(MeV)
4.198
4.151
4.596
4.556
4.502
4.435
4.414
4.398
4.366
4.775
4.722
4.604
5.320
5.263
10/28/2011
17
Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) 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
160-
150-
130-
120-
1 100 -
8 80-
.
70-
60-
40-
30-
10-
U-238
1
i
1
\-
I
c
1
i
J'i
'
i
?
3048 3348 3649 3348
t
]'
b-23
5
i
J I
r
K
L.
I
I
h
' •
f
It
1 '
^
i
lt|
/j|u 234
&&
MA W'T'L 1
,-v.
i
1
!.
u-r
/
f
^
2
424S' '4549' 4849 ' 51 W '5449' 5749' 8049 8349 6649 6949 7249 7548 7849
Energy (teV)
10/28/2011
18
Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
17.4. Decay Scheme: Ingrowth is not generally a large concern with this analysis unless one is
running sequential analysis for uranium and plutonium with 236Pu tracer (due to ingrowth
OQO 008
of U tracer) or sequential analyses for uranium and thorium (due to Th tracer
32T
ingrowth in the U tracer).
p
3.3x1 Q4y
231 Pa
1.1 d
P
235y
a
7.04x108 y
231Th
23^
a
2.45x1 05y
a
230Th
III
6
Jh
P
234pa
23811
4.47x1 03
P
24 d
234TH
1 n
a
y
<« —
7.5x10" y
10/28/2011
19
Revision 0.1
-------
Isotopic Uranium (238U, 235U, and 234U) in Water: Rapid Method for High-Activity Samples
17.5. Flowchart
Separation Scheme and Timeline for Determination of
U Isotopes in Water Samples
Sample preparation (Step 11.1)
1. Digestion (Step 11.1.5)
or
2. Calcium phosphate coprecipitation
(Step 11.1.4)
3. Add phenolphthalein (Step 11.1.4.3)
(1-2 hours)
T
Preparation of load solution (Step
11.2.1)
1. Dissolve phosphate.
2. Add sulfamate, thiocyanate and
ascorbic acid
(5 min)
Set-up of UTEVA cartridge
using vacuum box (Step 11.2.2)
1. Assembly
2. Precondition with 5 ml3 M HN03
@ ~3 mL/min
Load sample: @ ~1 mL/min
Rinse: 5 mL 3M H N03, @ ~3 mL/min
2nd rinse: 5 mL3M HN03,@~3 mL/min
Additional 30 mL 3M HNO3 rinse for Po-210 if present
(Step 11.2.3)
25 min)
Discard effluents
|
i
Rinse: 5 mL of 9 M HCI
20 mL of 5 M HCI - 0.05 M oxalic acid
(Step 11.2.3.4-11.2.3.5)
Discard
effluents
|
i i
Discard UTEVA Column
Elute U with 15 mL of 1 M HCI collecting eluent
(Step 11.2.3.7)
Transfer eluent to beaker and evaporate
Add drops of HCL and 1 mL H20 to dissolve
Transfer to culture tube w/2 1-mL rinses of 1M HCI.
(Step 11.2.3.8-11.2.3.11)
(15 min)
Micro precipitation
1. Add NdF3 carrier i
2. Filter, dry, mount
(Step 11.3)
(1 hour 15 min)
Discard filtrates and washes
Count sample test source (STS)
for at least one hour
(Step 11.3.19)
(1 hour)
\
Elapsed Time
1 -2 hours
1-11A hours
hours
hours
10/28/2011
20
Revision 0.1
------- |