www.epa.gov/radiation
May 2017
EPA 402-S17-002
Revision 0
Improved Rapid Radiochemical Method for
Radium-226 in Building Materials for
Environmental Remediation Following
Radiological Incidents
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Radiation and Indoor Air
National Analytical Radiation Environmental Laboratory
Montgomery, AL 36115
Office of Research and Development
National Homeland Security Research Center
Cincinnati, OH 45268
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Improved Rapid Radiochemical Method for Radium-226 in Building Materials for
Environmental Remediation Following Radiological Incidents using DGA Resin
Revision History
Revision 0 Original release. 05-01-2017
This report was prepared for the National Analytical Radiation Environmental Laboratory of the Office of
Radiation and Indoor Air and the National Homeland Security Research Center of the U.S. Environmental
Protection Agency's (EPA) Office of Research and Development. It was prepared by Environmental
Management Support, Inc., of Silver Spring, Maryland, under contract EP-W-13-016, task order 014,
managed by Dan Askren. This document has been reviewed in accordance with EPA policy and approved
for publication. Note that approval does not signify that the contents necessarily reflect the views of the
Agency. Mention of trade names, products, or services does not convey EPA approval, endorsement, or
recommendation.
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Improved Rapid Radiochemical Method for Ra-226 in Building Materials
Improved Rapid radiochemical Method for Radium-226 in Building Materials for
Environmental Remediation Following Radiological Incidents
1. Scope and Application
1.1. The method will be applicable to samples where contamination is either from known
or unknown origins.
1.2. This method uses improved rapid radiochemical separations techniques for the
isotopic determination of 226Ra in building materials such as asphalt, shingles,
limestone and granite following a nuclear or radiological incident. The method has
been validated for asphalt and asphalt shingles. The matrix specific digestion
procedures digest the samples, removing organics if necessary, rapidly pre-
concentrating 226Ra from the digested samples so that this method can purify this
alpha-emitting isotope for measurement.
1.3. This method is a shorter, newer alternative to Rapid Radiochemical Methodfor
Radium-226 in Brick and Concrete for Environmental Remediation Following
Radiological Incidents (Reference 16.5). It combines the final purification of Ra-226
into a single column (Sr Resin + DGA Resin) instead of two separate steps involving
Sr Resin and then Ln Resin. Other solid samples such as soil, brick and concrete can
be digested using the rapid sodium hydroxide fusion procedure as an alternative to
other digestion techniques, but application of this 226Ra procedure to these samples
will have to be validated by the laboratory.
1.4. This method is specific for 226Ra. It uses 50WX8 cation resin to separate radium from
solid matrix constituents, followed by additional separation steps using Sr Resin and
DGA Resin to remove interferences.
1.5. The method is capable of satisfying the following required method uncertainty for
226Ra in each respective matrix. To attain the stated measurement quality objectives
(MQOs), a sample aliquant of approximately 1 g and count time of 8 hours (or
longer) are recommended. Application of the method must be validated by the
laboratory using the protocols provided in Method Validation Guide for Qualifying
Methods Used by Radiological Laboratories Participating in Incident Response
Activities (Reference 16.1). The sample turnaround time and throughput may vary
based on additional project MQOs, the time for analysis of the sample test source, and
initial sample weight/volume.
1.5.1. 0.34 pCi/g at an analytical action level of 2.61 pCi/g in asphalt shingles
1.5.2. 0.67 pCi/g at an analytical action level of 5.16 pCi/g in asphalt
1.5.3. 0.62 pCi/g at an analytical action level of 4.75 pCi/g in limestone
1.6. The rapid 226Ra 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 (Reference 16.1) and
Chapter 6 of Multi-Agency Radiological Laboratory Analytical Protocols Manual
(Reference 16.2).
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2. Summary of Method
225
2.1. A known quantity of Ra is used as the yield tracer in this analysis. The sample is
fused using a digestion procedure specific for the solid sample analyzed.
2.2. The method has been initially validated using pulverized asphalt shingles which are
digested using Rapid Methodfor Sodium Hydroxide Fusion of Asphalt Roofing
Materials Matrices Prior to Americium, Plutonium, Strontium, Radium, and Uranium
Analyses (Reference 16.6) and pulverized asphalt which are digested using Rapid
Methodfor Sodium Hydroxide Fusion of Asphalt Matrices Prior to Americium,
Plutonium, Strontium, Radium, and Uranium Analyses (Reference 16.7). This
method has been applied to the 226Ra method validation process for the limestone
matrix. Alternate matrices must be digested per the appropriate digestion procedure
and validated by the laboratory.
2.3. Radium isotopes are removed from the fusion matrix using a carbonate precipitation
step. The sample is acidified and loaded onto 50WX8 cation resin to remove sample
interferences such as calcium. The radium is eluted from the cation resin with 8M
nitric acid. After evaporation of the eluate, the sample is dissolved and passed
through a stacked Sr Resin +DGA Resin column. Ba is removed using Sr Resin while
DGA Resin is used to remove interferences such as residual calcium and to remove
225
the initial Ac present. The purified eluent is evaporated to dryness and redissolved
in 1.5M HC1. The radium (including 226Ra) is prepared for counting by
microprecipitation with BaSC>4.
2.4. Low-level measurements are performed by alpha spectrometry. The activity measured
in the 226Ra region of interest is corrected for chemical yield based on the observed
activity of the alpha peak at 7.07 MeV (217At, the third progeny of 225Ra). See Table
17.1 for a list of alpha particle energies of the radionuclides that potentially may be
seen in the alpha spectra.
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. Discrete Radioactive Particles (DRPs or "hot particles"). Particulate matter in a
sample of any matrix where a high concentration of radioactive material is present as
a very small particle (
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Improved Rapid Radiochemical Method for Ra-226 in Building Materials
3.6. Radiological Dispersal Device (RDD), i.e., a "dirty bomb." This device 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.
3.7. 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 as an absolute value is applicable at or below an AAL.
3.8. Relative Required Method Uncertainty ((Pmr)- The relative required method
uncertainty is the Wmr divided by the AAL and is typically expressed as a percentage.
It is applicable above the AAL.
3.9. 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 in
the method, such as a solid deposited on a filter for alpha spectrometry analysis.
4. Interferences
4.1. Radiological
4.1.1. Unless other radium isotopes are present in concentrations greater than
approximately three times the 226Ra activity concentration, interference from
other radium alphas will be resolved when using alpha spectrometry.
Method performance may be compromised if samples contain high levels of
radium isotopes due to ingrowth of interfering decay progeny, but this will
depend on the actual spectral resolution.
229 234
4.1.2. Radionuclides with overlapping alpha energies such as Th, U, and
237
neptunium-23 7 ( Np) will interfere if they are not removed effectively.
The method removes these radionuclides.
225
4.1.3. Decay progeny from the Ra tracer will continue to ingrow as more time
elapses between the separation of radium and the count of the sample.
Delaying the count significantly longer than a day may introduce a possible
positive bias in results near the detection threshold. When MQOs require
measurements close to detection levels, and coordinating sample processing
and counting schedules is not conducive to counting the sample within
approximately 36 hours of the separation of radium, the impact of tracer
progeny tailing into the 226Ra may be minimized by reducing the activity of
the 25Ra tracer that is added to the sample. This will aid in improving the
signal-to-noise ratio for the 226Ra peak by minimizing the amount of tailing
225
from higher energy alphas of the Ra progeny.
4.1.4. There is also a possibility that the higher energy peaks associated with the
225
Ra progeny may result in energy-attenuated counts that show up in the
lower energy 226Ra alpha spectra region so reducing the 225Ra tracer while
217
still achieving enough At counts to minimize tracer uncertainty may be
optimal.
225
4.1.4.1. The amount of Ra added to the samples may be decreased, and
the time for ingrowth between separation and counting increased,
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to ensure that sufficient 225Ac, francium-221 (221Fr), and 217At are
present for yield corrections at the point of the count. Although
this detracts from the rapidity of the method, it does not detract
significantly from the potential for high throughput.
225
4.1.5. A purified Ra tracer solution may be used when performing this method
(see Appendix that follows this method).
225
4.1.5.1. When using a purified source of Ra, the beginning of decay
225
for Ra is the activity reference date established during
225
standardization of the Ra solution.
4.1.6. It is also possible to use 225Ra in equilibrium with thorium-229 (229Th) for
convenience, which may be added to each sample as a tracer.1 This allows
229
use of Th without purification and therefore is a simpler approach. This
approach requires complete decontamination of a relatively high activity of
2 9Th in the later steps in the method, since the spectral region of interest
(ROI) for 229Th slightly overlaps that of 226Ra.
229 225
4.1.7. Th is removed during the cation exchange step (retained) and the Ra is
unsupported from this point on in the method (retained on the cation resin).
If the time delay between the cation exchange step and the DGA Resin
229 225
separation of Th is 6 hours or less the error associated with the Ra
225
reference value is < 1.2% due to Ra decay. A correction for this decay can
also be made by recording the cation exchange elution time, and decaying
225
Ra from this point until the DGA Resin separation time to eliminate this
relatively small bias.
4.1.8. The method provides effective removal of 229Th. Inadequate
229 226
decontamination of Th may lead to high bias in the Ra result especially
when the levels of 226Ra in the sample are below 1 pCi/g. The spectral
226 229
region above Ra corresponding to Th should be monitored routinely to
229
identify samples where Th interference may impact compliance with
229
project MQOs. If problematic levels of Th are identified in spectra,
measures must be taken to address the interference. These might include:
4.1.8.1. Separating 225Ra from 229Th prior to its use as a tracer.
4.1.8.2. Increasing the sample aliquant size without changing the amount
of tracer added will increase the analyte signal and reduce the
relative impact of the interference to levels that may be amenable
with project MQOs.
4.1.8.3. The absolute amount of 229Th added to the samples may be
decreased, as long as the time for ingrowth between separation
and counting is increased to ensure that sufficient 217At is present
for yield corrections at the point of the count. Although this
detracts from the rapidity of the method, it allows more
1 The single-laboratory validation for this method was performed successfully by adding 225Ra in secular equilibrium
with 229Th tracer. See the Appendix of this method for a method for separating (and standardizing) 225Ra tracer from
229Th solution.
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flexibility in the timing of the count and does not detract from
the potential for high throughput.
4.1.8.4. The samples may be counted as early as about 8 hours after
229
separation time with an 8-hour count time if-100 pCi Th is
added, but separation times and counting time midpoints must be
recorded carefully and precisely.
225 229
4.1.9. When a solution containing Ra in equilibrium with Th is used as a
tracer, thorium is removed during the processing of the sample. The
225 229
equilibrium between the Ra and Th is essentially maintained until the
225
cation exchange elution step is performed. At this point, the Ra activity in
the eluate is unsupported and begins to decay. 225Ac is removed during the
DGA Resin separation.
3_i_
4.1.10. Ascorbic acid is added to the sample load solution to reduce Fe present to
2_|_ 3_i_
Fe , which has less retention on cation resin than Fe .
4.1.11. Trace levels of 226Ra may be present in Na2CC>3 used in the 226Ra pre-
concentration step of the fusion method. Adding less 2M Na2CC>3 (<10 mL
used in this method) may reduce 226Ra reagent blank levels, while still
effectively pre-concentrating 226Ra from the fusion matrix. This will need to
be validated by the laboratory.
4.2. Non-radiological
4.2.1. The amount of inherent stable (non-radioactive) barium in the sample that
may be carried through the processes prior to microprecipitation should not
significantly exceed the amount of the barium carrier (50 jag), which is
added for microprecipitation. Microprecipitates on the STS greater than 50
|ig Ba may degrade the resolution of alpha spectra.
4.2.1.1. In this procedure, Ba is removed using Sr Resin and alpha peak
resolution is typically very good. It is important for the total
volume of 4M HNO3 passed through Sr Resin to be kept
relatively small per procedure to remove Ba effectively. It is
likely that Sr Resin can be washed and reused to reduce resin
costs, but this will have to be validated by the laboratory.
4.2.1.2. The removal of Ba allows a larger aliquant size of samples to be
analyzed that could not typically be tolerated in methods that do
not remove Ba, allowing shorter count times and lower minimum
detectable activity levels.
4.2.2. Ca can also cause alpha peak resolution problems and needs to be effectively
removed. Most of the Ca ions are removed using the initial cation exchange
separation. A small amount is removed during the final DGA Resin
purification step.
4.2.3. A smaller sample size may need to be selected when these interferences
cannot be removed adequately.
4.2.4. The DGA Resin step provides a final purification for the Ra-225 tracer. If the
flow rate is too fast (>1.5 drops/second) and Ac-225 is present prior to the
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final separation time breaks through the resin, a high bias in the tracer yield
will occur.
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 your laboratory's chemical hygiene plan for general chemical safety
rules.
5.2. Radiological
5.2.1. Hot Particles (DRPs)
5.2.1.1. Hot particles, also termed "discrete radioactive particles"
(DRPs), will likely be small, on the order of 1 mm or less. DRPs
typically are not evenly distributed in the media and their
radiation emissions are not uniform in all directions
(anisotropic).
5.2.2. For samples with detectable activity concentrations of these radionuclides,
labware should be used only once due to the potential for cross
contamination.
5.3. Procedure-Specific Non-Radiological Hazards:
5.3.1. Solutions of 30% H2O2 can rapidly oxidize organic materials and generate
significant heat. Do not mix large quantities of peroxide solution with
solutions of organic solvents as the potential for conflagration exists.
6. Equipment and supplies
6.1. Alpha spectrometer calibrated for use over the range of-3.5-10 MeV.
6.2. Cartridge reservoirs, 10 or 20 mL syringe style with locking device, or reservoir
columns (empty luer tip, CC-10-M) plus 12 mL reservoirs (CC-06-M), Image
Molding, Denver, Colorado, or equivalent.
6.3. Centrifuge tubes, polypropylene, 50 mL, disposable; or equivalent.
6.4. Chromatography columns, polypropylene, disposable:
6.4.1. 1.5 centimeter (cm) inner diameter x 15 cm; or equivalent (Environmental
Express, Mount Pleasant, South Carolina).
6.4.2. Additional frits for 1.5 cm inner diameter x 15 cm columns (Environmental
Express, Mount Pleasant, South Carolina).
6.5. Filter funnels.
6.6. Filter manifold apparatus with 25 mm diameter polysulfone. A single-use
(disposable) filter funnel/filter combination may be used, to avoid cross-
contamination.
6.7. 100 [j,L, 200 [j,L, 500 [xL and 1 mL pipets or equivalent and appropriate plastic tips.
6.8. 1-10 mL electronic pipet or manual equivalent.
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6.9. Glass beaker, 50 mL, 150 mL and 250 mL capacity.
6.10. Heat lamp.
6.11. Hotplate.
6.12. Graduated cylinders, 500 mL and 1000 mL.
6.13. 25 mm polypropylene filter, 0.1 [j,m pore size, or equivalent.
6.14. pH paper.
6.15. Stainless steel planchets or other adhesive sample mounts (Ex. Environmental
Express, Inc. P/N R2200) able to hold the 25 mm filter.
6.16. Tips, white inner, Eichrom part number AC-1000-IT, or PFA 5/32" x y4" heavywall
tubing connectors, natural, Ref P/N 00070EE, cut to 1 inch , Cole Parmer, or
equivalent
6.17. Tips, yellow outer, Eichrom part number AC-1000-OT, or equivalent.
6.18. Tweezers.
6.19. Vacuum box, such as Eichrom part number AC-24-BOX, or equivalent.
6.20. Vacuum pump or laboratory vacuum system.
6.21. Vortex mixer.
6.22. Heat lamp.
7. Reagents and Standards
Notes:
All reagents are American Chemical Society reagent grade or equivalent unless otherwise specified.
Unless otherwise indicated, all references to water should be understood to mean Type I reagent water
(ASTM D1193, Reference 16.3). For microprecipitation, all solutions used in microprecipitation should
be prepared with water filtered through a 0.45 jim (or smaller) filter.
7.1. Type I reagent water as defined in ASTM Standard D1193 (Reference 16.3).
7.2. Ammonium sulfate, solid (NH4)2S04.
2+
7.3. Barium carrier (1000 |ig/mL as Ba ). May be purchased as an inductively coupled
plasma - atomic emission spectrometry (ICP-AES) standard and diluted, or prepared
by dissolving 0.90 g reagent grade barium chloride, dihydrate (BaCb ¦ 2H20) in water
and diluting to 500 mL with water.
7.4. Calcium nitrate (1.25M): Dissolve 147 g of calcium nitrate tetrahydrate
(Ca(N03)2'4H20) in 300 mL of water and dilute to 500 mL with water.
7.5. Cation Resin, 50WX8, 200-400 [j,m mesh size [available from Eichrom
Technologies, Lisle, IL],
7.6. DGA Resin cartridges, 2 mL, small particle size (50-100 (im), in appropriately sized
column pre-packed cartridges.
7.7. Ethanol, reagent 95% (C2H5OH), available commercially.
7.8. Hydrochloric acid (12M): Concentrated HC1, available commercially.
7.8.1. Hydrochloric acid (6.0M): Add 500 mL of concentrated HC1 to 300 mL of
water and dilute to 1.0 L with water.
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7.8.2. Hydrochloric acid (3.0M): Add 250 mL of concentrated HC1 to 600 mL of
water and dilute to 1.0 L with water.
7.8.3. Hydrochloric acid (1.5M): Add 125 mL of concentrated HC1 to 800 mL of
water and dilute to 1.0 L with water.
7.8.4. Hydrochloric acid (0.5M): Add 41.5 mL of concentrated HC1 to 800 mL of
water and dilute to 1.0 L with water.
7.9. Hydrogen peroxide, H2O2 (30 % weight/weight), available commercially.
7.10. Isopropanol, 2-propanol, (C3H7OH), available commercially.
7.10.1. Isopropanol (2-propanol), 20% (volume/) in water: Mix 20 mL of
isopropanol with 80 mL of water.
7.11. Methanol (CH3OH), available commercially
7.12. Nitric acid (16M): Concentrated HNO3, available commercially.
7.12.1. Nitric acid (8M): Add 506 mL of concentrated HNO3 to 300 mL of water and
dilute to 1.0 L with water.
7.12.2. Nitric acid (4M): Add 253 mL of concentrated HNO3 to 200 mL of water and
dilute to 1.0 L with water.
7.13. Ra-225 tracer in 1M HC1 solution in a concentration amenable to accurate addition of
about 180 dpm per sample (generally about 150-600 dpm/mL).
229 225
7.13.1. Ra-225 may be purified and standardized using a Th/ Ra generator as
described in the appendix of this method.
7.13.2. Th-229 (-70-100 pCi) containing an equilibrium concentration of 225Ra has
225
been successfully used without prior separation of the Ra.
7.14. Sr Resin cartridges, 2 mL, small particle size (50-100 |j,m), in appropriately sized
column pre-packed cartridges.
8. Sample Collection, Preservation, and Storage
Not Applicable.
9. Quality Control
9.1. Batch quality control results shall be evaluated and meet applicable Analytical
Protocol 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 a 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 an acceptable simulant or empty crucible blank
processed through the fusion procedure. If an empty crucible is used to
generate a reagent blank sample, it is recommended that 150 mg Ca be
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added as calcium nitrate to the empty crucible as blank simulant. This
facilitates Ra carbonate precipitations from the alkaline fusion matrix.
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, such as the presence of elemental
barium in the sample, may compromise chemical yield measurements, or
overall data quality.
9.2. Sample-specific quality control measures
9.2.1. Limits and evaluation criteria shall be established to monitor each alpha
spectrum to ensure that spectral resolution and peak separation is adequate
229 225
to provide quantitative results. When Th/ Ra solution is added directly
to the sample, the presence of detectable counts between -5.0 MeV and the
upper boundary established for the 226Ra ROI generally indicates the
229 226
presence of Th in the sample, and in the Ra ROI. If the presence of
229 226
Th is noted and the concentration of Ra is determined to be an order of
magnitude below the action limit or the detection threshold of the method,
take corrective actions to ensure that MQOs have not been compromised
225
(e.g., clean up Ra tracer before adding, or re-process affected samples and
associated QC samples. See interferences sections Steps 4.1.4 - 4.1.5. for
discussion).
9.3. This method is capable of achieving a Wmr of 0.34 and 0.83 pCi/g at or below an
action level of 6.41pCi/g for shingles and a u-Mi of 0.34 pCi/g at or below an action
level of 2.61 pCi/g for asphalt. This may be adjusted in the event specific MQOs are
different. .
9.4. This method is capable of achieving a (p-Mi 13% above 6.41 pCi/g for shingles and
2.61 pCi/g for asphalt. 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-10.5 pCi/g in a counting time of six hours for shingles and -0.21 pCi/g
for asphalt.
10. Calibration and Standardization
10.1. Set up, operate, calibrate and perform quality control for alpha spectrometry units in
accordance with the laboratory's quality manual and standard operating procedures
and consistent with ASTM Standard Practice D7282, Sections 7-13, 18, and 24
(Reference 16.4).
Note: The calibrated energy range for the alpha spectrometer for this method should be from
-3.5 to 10 MeV.
225 229
10.2. If Ra is separated and purified from Th for use as a tracer, the activity reference
225
date established during standardization of the tracer is used as the Ra activity
reference date. (See the appendix of this method.)
229 225
10.3. When using Th containing an equilibrium concentration of Ra, the time of most
229
recent separation/purification of the Th standard solution must be known in order
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229 225
to determine the extent of secular equilibrium between Th and its Ra progeny.
Verify the date of purification by examining the Certificate of Analysis, or other
applicable documentation, for the standard.
229 225 225
10.4. When using Th containing an equilibrium concentration of Ra, Ra is separated
229
from its Th parent in the solution during the cation exchange elution step. This is
225
the beginning of Ra decay and the date and time used for decay correction of the
tracer. This time must be known and recorded precisely.
229
10.4.1. If the purification date of the Th is not documented, at least 100 days must
229
have elapsed between separation and use to ensure that Th, and its
225
progeny Ra are in full secular equilibrium (i.e., >99%. Table 17.3).
11. Procedure
11.1. Initial Sample Preparation for Radium
11.1.1. Ra isotopes are preconcentrated from solid samples using the appropriate
sodium hydroxide (NaOH) fusion procedure, such as Rapid Methodfor
Sodium Hydroxide Fusion of Asphalt Roofing Material Matrices Prior to
Americium, Plutonium, Strontium, Radium, and Uranium Analyses
(Reference 16.6), which fuses the samples using rapid NaOH fusion
followed by carbonate precipitation to preconcentrate Ra isotopes from the
hydroxide matrix. Alternate digestion methods specific to the solid matrix
may also be used, but this will have to be validated by the laboratory.
11.1.2. The carbonate precipitate is dissolved in an HC1 solution and additional
separation steps to purify the radium isotopes are performed using this
procedure.
11.1.3. A smaller volume of the total load solution may be taken and analyzed as
needed for very high activity samples, with appropriate dilution factor
calculations applied.
11.1.4. This separation can be used with other solid sample matrices dissolved in
O.lMto 1.5MHC1.
11.2. Initial Matrix Removal Using 50WX8 Cation Resin
11.2.1. Prepare sample solution
11.2.1.1. Add 3 mL of 1,5M ascorbic acid to each sample solution to
2_|_
reduce any Fe present to Fe . Mix and wait approximately 3
minutes.
11.2.2. Set up vacuum box
Note: More than one vacuum box may be used to increase throughput as needed.
11.2.2.1. For each sample solution, place the empty large columns (15 cm
columns or equivalent) on the vacuum box.
11.2.2.2. Add a water slurry (or weigh out the solid resin) of cation resin
50WX8 (200-400 mesh) into each column equivalent to 5 g of
resin.
11.2.2.3. Turn the vacuum on and ensure proper fitting of the lid.
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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. Alternately,
plastic tape can be used to seal the unused lid holes as well.
11.2.2.4. After the water has passed through, place a frit down on top of
the resin bed.
11.2.2.5. Add additional water (-10-15 mL) to rinse the resin and remove
fine resin particles. Clean resin by adding 15 mL 6M HC1 and
allow to drain at ~2 mL/min, then 15 ml water ~2 mL/min to
rinse each column.
11.2.2.6. Add 10 mL of 0.5M HC1 to the column to precondition the resin.
11.2.2.7. Press frit down tightly on resin bed.
Note: It is important to control flow rates such that they are not too fast.
Gravity flow (no vacuum) may be adequate, although a small amount of
vacuum may be needed to get the flow started.
11.2.2.8. Adjust the vacuum (or use no vacuum) to achieve a flow-rate of
~1 mL/min (~1 drop).
11.2.2.9. Discard column rinses.
11.2.2.10. Load sample solution slowly to each column at ~1 mL/min.
Note: It is likely that the ~1 mL/min, flow rate can be achieved with no
vacuum at all. The frit should be pressed down tightly to prevent too fast
a flow rate.
11.2.2.11. Add 5mL of 1,5M HC1 to rinse each sample solution tube and
add to column at ~l-2 mL/min. Discard eluate.
11.2.2.12. Press frit down on resin bed.
11.2.2.13. Add 30 mL of 3M HC1 to each column at ~l-2 mL/min. Discard
rinse.
Note: The flow rate should not be too fast to ensure effective removal of
Ca and other interferences.
11.2.2.14. Press frit down tightly on resin bed.
11.2.2.15. Place clean 50 mL centrifuge tubes beneath the columns to catch
the eluate.
11.2.2.16. Press frit down tightly on resin bed.
11.2.2.17. Add 20 mL of 8M of HN03 to each column to elute Ra at
~1 mL/min. Record the date and time as the date and time of
225
separation of Ra and thorium to account for the decay of
225
unsupported Ra.
Note: Date and time need only be recorded if the 225Ra was in
equilibrium with 229Th tracer.
11.2.2.18. Transfer the eluate solution to 150 mL glass beakers. Rinse tubes
with ~3 mL of 8M HNO3 and add to beaker.
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11.2.2.19. Add 2 mL of 30 wt% H2O2 to each beaker and evaporate on
medium heat to dryness on a hotplate being very careful not to
bake material into the beaker.
11.2.2.20. Add 5 mL of 4M HNO3 to redissolve each sample, warming
slightly on hotplate as needed.
Note: Barium in the sample can interfere with the 226Ra alpha peak
resolution. Sr Resin is used to remove Ba in the sample. The volume of
4M HNO3 must be kept small to remove Ba effectively. Additional
interferences (Ca, U, Th) are removed using DGA Resin.
11.2.3. Separation of Barium and Radionuclide Interferences
11.2.3.1. Place a stacked column with 2 mL Sr Resin cartridge (top) and 2
mL DGA resin cartridge (bottom) on the vacuum box.
11.2.3.2. Condition each column with 5 mL of 4M HNO3 at 1 mL/min.
Discard rinse.
11.2.3.3. Ensure that clean, labeled plastic tubes are placed in the tube
rack under each cartridge.
11.2.3.4. Transfer each sample solution from Step 11.2.2.20 into the
appropriate column at a flow rate of ~1 mL/min or less.
11.2.3.5. Add 3 mL of 4M HNO3 to each beaker (from Step 11.2.2.20) as
a rinse and transfer each solution into the appropriate column at
~1 mL/min.
11.2.3.6. Add 5 mL of 4M HNO3 into each reservoir as a column rinse
(flow rate -1-2 mL/min).
11.2.3.7. Record the date and time of the last rinse (Step 11.2.3.6) as the
date and time of separation of radium from progeny. This is also
the beginning of ingrowth of 225Ac (and 221Fr and 217At).
Note: If purified 225Ra tracer is added to the sample (see Appendix that
follows this method), the 225Ra activity was unsupported before the tracer
solution was added to the sample. The activity reference date and time
established during standardization of the 225Ra tracer is used as the
reference date for the 225Ra solution.
Note: If 225Ra at some degree of secular equilibrium with 229Th is added
as tracer in the initial step, the activity of 225Ra is dependent upon the
total amount of time between the last 229Th purification and cation
exchange elution step (Step 11.2.2.17). The decay of 225Ra starts at the
229Th removal step and is decayed to the DGA Resin separation time,
where 225Ac is removed, to determine the reference activity of the 225Ra
tracer at that point.
11.2.3.8. Turn off vacuum. Discard Sr Resin plus DGA Resin.
11.2.3.9. Remove tubes and transfer sample solution to 250 mL glass
beakers, rinsing tube with 3 mL of 30 wt% H2O2 and adding to
beaker.
11.2.3.10. Evaporate solutions to dryness on a hotplate using medium heat.
Do not bake.
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11.2.3.11. Add 10 ml 1.5MHC1 to each beaker to redissolve each sample,
warming on a hotplate until hot and transfer to a labeled 50 mL
tube.
11.2.3.12. Rinse each beaker with two 7 mL volumes of 1.5M HC1 and
transfer each rinse to the tube.
11.3. Barium sulfate micro-precipitation of 226Ra
11.3.1. Add -3.0 g of (NH4)2S04 to the purified sample solution. Mix well using a
vortex stirrer to completely dissolve the salt.
11.3.2. Add 50 |ig of Ba carrier (50 |iL of 1000 |ig Ba/mL) into each tube. Cap and
mix well with vortex stirrer.
11.3.3. Add 5.0 mL of isopropanol and mix well using a vortex stirrer.
11.3.4. Place each tube in an ice bath filled with cold tap water for at least 15
minutes, periodically stirring on vortex stirrer (before placing in ice,
midway, and after icing).
11.3.5. Pre-wet a 0.1-micron filter using methanol or ethanol. Filter the suspension
through the filter using vacuum. The precipitate will not be visually
apparent.
11.3.6. Rinse the sample container with 3 mL of 20% isopropanol solution.
11.3.7. Rinse the filter apparatus with about 2 mL of methanol or ethanol to facilitate
drying. Turn off vacuum and discard rinses.
11.3.8. Mount the filter on a labeled adhesive mounting disk (or equivalent) ensuring
that the filter is not wrinkled and is centered on mounting disk.
11.3.9. Place the filter under a heat lamp for approximately 5 minutes or more until it
is completely dry.
217
11.3.10. Store the filter for approximately 24 hours to allow sufficient At (third
progeny of 225Ra) to ingrow into the sample test source allowing a
217
measurement uncertainty for the At of < 5 %.
Note: The filter may be counted immediately if a long enough count time is used to
allow enough tracer counts to accumulate while the sample is being counted. For
example, a longer 1000 minute may be used so the ingrowth of 217At and sample
counting can be done simultaneously. This reduces the overall analytical time
required.
11.3.11. Count by alpha spectrometry. The count times should be adjusted to meet the
uncertainties and detection capabilities identified in Steps 9.3, 9.4, and 9.5.
12. Data Analysis and Calculations
12.1. The final sample test source (filter mounted on a planchet) will likely need to have
225 221 217
approximate ingrowth period of 18 to 24 hours for Ac (and Fr and At) to meet
Analytical Protocol Specifications for chemical yield with a counting time of 4 to 8
hours. At-217 (third progeny of 225Ra) has a single, distinct alpha peak with a centroid
at 7.067 MeV and is used for determining the yield.
12.2. The following equation can be used to calculate the radiochemical yield:
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Rt-Rb
RY= \ (1)
sxAtxIt
where:
225 217
RY = Fractional radiochemical yield based on Ra (from ingrown At
at 7.07 MeV)
Rt = Total count rate beneath the 217At peak at 7.07 MeV, cpm
Rb = Background count rate for the same region, cpm
s = Efficiency for the alpha spectrometer
It = Fractional abundance for the 7.07 MeV alpha peak counted (=
0.9999)
Note: If 225Ra is separated from 229Th for use as a purified tracer, the 225Ra activity is
unsupported and begins to decay at time of prior separation from 229Th. The reference date and
time established when the tracer is standardized is used for decay correction of the 225Ra activity.
If 229Th solution (with 225Ra in full secular equilibrium) is added to the sample, the 225Ra activity
is equal to the 229Th activity added and only begins to decay at the point of separation of 225Ra
from 229Th during the sample preconcentration steps (cation exchange elution step).
217
At = Activity of At at midpoint of the count (the target value that
should be achieved for 100% yield), in dpm
= 3.0408(/tX^225Ra) [e M-e M] (2)
225
^225Ra = Activity in dpm of Ra tracer added to the
sample decay corrected to the date and time of
radium separation in Step 11.3.6.2
225
d = Elapsed ingrowth time for Ac [and the
progeny 21 At], in days from the date and time of Ra
separation to the midpoint of the sample count
= 0.04652 d 1 (decay constant for 225Ra - half-
life = 14.9 days)
= 0.06931 d_1 (decay constant for 225Ac) -
half-life = 10.0 days)
2 Unsupported 225Ra: When separated 225Ra tracer is added to the sample, its initial activity, . I 22^r,.,-imhihi- must be
corrected for decay from the reference date established during standardization of the tracer to the point of separation
of 225Ra and 225Ac as follows:
A225 =(a225 te /"f>')
225Ra \ Ra-initial/\ /
where: ).\ = decay constant for 225Ra (0.04652 d 1): and dt= time elapsed between the activity reference date for the
225Ra tracer solution added to the sample and the separation of 225Ra and 225Ac in Step 11.2.3.6 (days).
229Th/225Ra added in equilibrium: When 229Th containing ingrown 225Ra is added directly to the sample, the
amount of 225Ra ingrown since purification of the 229Th solution up until 229Th removal point during the method is
calculated as:
_ X1 eAi')
where: A229Th = Activity of the 229Th standard on the date of the separation of Th and Ra (cation exchange elution
step); /., = decay constant for 225Ra (0.04652 d '): and d, = time elapsed between the purification of 229Th solution
added to the sample and the separation of 225Ra and 229Th (days). The 225Ra is then corrected for decay to the 225Ac
removal separation time (Step 11.2.3.6) using the first equation above.
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It = Fractional abundance for the 7.07 MeV
alpha peak counted (= 0.9999)
3.0408 - ^2/(^2 + ^1) [a good approximation as the half
221 217
lives of Fr and At are short enough so that
225
secular equilibrium with Ac is ensured]
12.3. The activity concentration of an analyte and its combined standard uncertainty are
calculated using the following equations:
AC = MKi (3)
Wa x Rnt x £>a x /a x 2.22
and
U(AC)= l*(R V: 4 2 (u\At) u\WJ u\Rnt)) (4)
i Wiy.RlxDlxllx2.222 a [ Af ^a2 R2nt )
where:
ACa = activity concentration of the analyte at time of count, (pCi/g)
217
At = activity of At at midpoint of the count (the target value that
should be achieved for 100% yield), in dpm (See Step 12.2 for
detailed calculation of At)
Rna = net count rate of the analyte in the defined region of interest (ROI),
in counts per minute (note that the peaks at 4.784 and 4.602 MeV
are generally included in the ROIfor 226Ra)
Rnt = net count rate of the tracer in the defined ROI, in counts per minute
Wa = weight of the sample aliquant (g)
/Ja = 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
/a = probability of a emission for 226Ra (the combined peaks at 4.78
and 4.602 MeV are generally included in the ROI with an
abundance of 1.00.)
iic(ACa) = combined standard uncertainty of the activity concentration of the
analyte (pCi/g)
u(At) = standard uncertainty of the activity of the tracer added to the
sample (dpm)
u(Ws) = standard uncertainty of the volume of sample aliquant (g)
ii(R,m) = standard uncertainty of the net count rate of the analyte in counts
per minute
u(Rnt) = standard uncertainty of the net count rate of the tracer in counts per
minute
Note: The uncertainties of the decay-correction factors and of the probability of decay factors
are assumed to be negligible.
3
If the individual peak at 4.78 MeV used, and completely resolved from the 4.602 MeV peak, the abundance would
be 0.9445.
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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.
12.3.1. The net count rate of an analyte or tracer and its standard uncertainty can be
calculated using the following equations:
and
C C
D _ X bx
r--T~T
»(7C: ) = ¦
Cx+1 , Cbx + 1
(5)
(6)
where:
Rnx = net count rate of analyte or tracer, in counts per minute
Cx = sample counts in the analyte or the tracer ROI
ts = sample count time (min)
Cbx = background counts in the same ROI as for x (x refers to the
respective analyte or tracer count)
tb = background count time (min)
w(i?nx) = standard uncertainty of the net count rate of tracer or
analyte, in counts per minute
12.3.2. If the critical level concentration (Lc) or the minimum detectable
concentration (MDC) are requested (at an error rate of 5%), they can be
calculated using the following equations.5
L„ =
0.4 x
A
-1
+ 0.677 x
' t ^
1 + ^
v hj
+1.645 x
v^bJb + 0.4) x — x
xA.xD.xI
a a
tsxWaxRtxDaxIa
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.
5 The formulations for the critical level and minimum detectable concentration are based on the Stapleton
Approximation as recommended in MARLAP Section 20A.2.2, Equations 20.54 and 20A.3.2, and Equation 20.74,
respectively. The formulations presented here assume an error rate of a = 0.05, /; = 0.05 (with z, „ = z, = 1.645),
and d = 0.4. For methods with very low numbers of counts, these expressions provide better estimates than do the
traditional formulas for the critical level and MDC.
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2.71x
MDC= ¦
f t ^
1 + ^
V J
+ 3.29x
RbJs*
( t ^
1 + ^
V J
x At
^X^X^txAx/aX2-22
(7)
where:
i?ba = background count rate for the analyte in the defined ROI, in counts
per minute
12.4. Results Reporting
12.4.1. The following data should be reported for each result: weight of sample used;
yield of tracer and its uncertainty; and full width at half maximum of each
peak used in the analysis.
12.4.2. The following conventions should be used for each result:
12.4.2.1. Result in scientific notation ± combined standard uncertainty.
13. Method Performance
13.1. Results of method validation performance are to be archived and available for
reporting purposes.
13.2. Expected sample preparation time for a batch of 15 samples is approximately seven
hours. Total processing time is dependent on actual wait time for 217At ingrowth
(approximately 16-24 hours) and count times (approximately 6 hours).
14. Pollution Prevention
14.1. The use of 50WX8 cation resin, Sr Resin and DGA Resin reduces the amount of
solvents that would otherwise be needed to co-precipitate and purify the final sample
test source.
15. Waste Management
15.1. Nitric acid and hydrochloric acid wastes should be neutralized before disposal and
then disposed of in accordance with local ordinances.
15.2. All final precipitated materials contain tracer and should be dealt with as radioactive
waste and disposed of in accordance with the restrictions provided in the facility's
NRC and/or state license.
15.3. It may be advisable to rinse the cation resin columns with water to remove strong
nitric acid prior to resin disposal.
16. References
Cited References
16.1. EPA 2009. Method Validation Guide for Qualifying Methods Used by Radiological
Laboratories Participating in Incident Response Activities.. Revision 0. Office of Air
and Radiation, Washington, DC. EPA 402-R-09-006, June. Available here.
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16.2. EPA 2004. Multi-Agency Radiological Laboratory Analytical Protocols Manual
(MARLAP). EPA 402-B-1304 04-001A, July. Volume I, Chapters 6, 7, 20, Glossary;
Volume II and Volume III, Appendix G. Available here.
16.3. ASTM D1193, "Standard Specification for Reagent Water," ASTM Book of
Standards 11.02, current version, ASTM International, West Conshohocken, PA.
16.4. 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.
16.5. EPA 2014. Rapid Radiochemical Methodfor Radium-226 in Brick and Concrete for
Environmental Remediation Following Radiological Incidents. Revision 1, EPA 402-
R-14-002. Office of Air and Radiation, Washington, DC. Available here.
16.6. EPA. RapidMethodfor Sodium Hydroxide Fusion of Asphalt Roofing Material
Matrices Prior to Americium, Plutonium, Strontium, Radium, and Uranium Analyses.
Not yet published
16.7. EPA. RapidMethodfor Sodium Hydroxide Fusion of Asphalt Matrices Prior to
Americium, Plutonium, Strontium, Radium, and Uranium Analyses. Not yet published
Other References
16.8. EPA. 2014. Rapid Radiochemical Methodfor Pu-238 and Pu-239/240 in Building
Materials for Environmental Remediation Following Radiological Incidents.
Revision 1, EPA 402-R-14-006. Office of Air and Radiation, Washington, DC.
Available here.
16.9. EPA. 2013. Rapid Radiochemical Methodfor Strontium-90 in Building Materials for
Environmental Remediation Following Radiological Incidents. Office of Air and
Radiation, Washington, DC. Available here.
16.10. EPA 2013. Rapid Radiochemical Methodfor Americium-241 in Building Materials
for Environmental Remediation Following Radiological Incidents. Office of Air and
Radiation, Washington, DC. EPA. Available here.
16.11. EPA. 2014. Rapid Radiochemical Methodfor Isotopic Uranium in Building Materials
for Environmental Remediation Following Radiological Incidents. Revision 1, EPA
402-R-14-005. Office of Air and Radiation, Washington, DC. Available here.
16.12. Koornneef, J.M., Stracke, A, Aciego, S., Renbi, O. and Bourdon, B. 2010. "A new
method for U-Th-Pa-Ra separation and accurate measurement of 234U-230Th-231Pa-
226Ra disequilibria in volcanic rocks by MC-ICPMS." Chemical Geology, Vol. 277,
Issue 1-2, October, 30-41.
16.13. Maxwell, S. and Culligan, B. 2012. "Rapid Determination of Ra-226 in
Environmental Samples," J. Radioanalytical and Nuclear Chemistry, online first
article, February.
16.14. Maxwell, S., Culligan, B, Hutchison, J, Utsey, R, and McAlister, D, "Rapid
Determination of Ra-226 in Urine Samples," J. Radioanalytical and Nuclear
Chemistry, online first article, March. Paper shows new approach using DGA Resin.
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1
2
3
4
17. Tables, Diagrams, and Flow Charts
17.1. Tables [including major radiation emissions from all radionuclides separated]
Table 17.1 - Alpha Particle Energies and Abundances of Importance
Energy
(MeV)
Abundance
(%)
Nuclide
4.601
5.6
Ra -226
4.784
94.5
Ra -226
4.798
1.5
Th -229
4.815
9.3
Th -229
4.838
5.0
Th -229
4.845
56.2
Th -229
4.901
10.2
Th -229
4.968
6.0
Th -229
4.979
3.2
Th -229
5.053
6.6
Th -229
5.434
2.2
Ra -223
5.449
5.1
Ra -224
5.489
99.9
Rn -222
5.540
9.0
Ra -223
5.580
1.2
Ac -225
5.607
25.2
Ra -223
5.609
1.1
Ac -225
5.637
4.4
Ac -225
5.682
1.3
Ac -225
5.685
94.9
Ra -224
5.716
51.6
Ra -223
5.724
3.1
Ac -225
5.732
8.0
Ac -225
5.732
1.3
Ac -225
5.747
9.0
Ra -223
5
6
7
Energy
(MeV)
Abundance
(%)
Nuclide
5.791
8.6
Ac -225
5.793
18.1
Ac -225
5.830
50.7
Ac -225
5.869
1.9
Bi -213
6.002
100.0
Po -218
6.051
25.1
Bi -212
6.090
9.8
Bi -212
6.126
15.1
Fr-221
6.243
1.3
Fr -221
6.278
16.2
Bi -211
6.288
99.9
Rn -220
6.341
83.4
Fr -221
6.425
7.5
Rn -219
6.553
12.9
Rn -219
6.623
83.5
Bi -211
6.778
100.0
Po -216
6.819
79.4
Rn -219
|
1
|
1
7.386
100.0
Po -215
7.450
98.9
Po -211
7.687
100.0
Po -214
8.376
100.0
Po -213
8.525
2.1
Po -212
11.660
96.8
Po -212
217At (3rd progeny of 225Ra tracer)
- Analyte
- 229Th (Check ROI for indications of inadequate clean-up)
Includes only alpha particles with abundance > 1%.
Reference: NUDAT 2.4, Radiation Decay National Nuclear Data Center, Brookhaven National Laboratory;
Available at: WWW,nndc. bill.gov midat2 indx dec. jsp: Queried: November 11, 2007.
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10
11
12
13
14
15
16
17
18
19
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Improved Rapid Radiochemical Method for Ra-226 in Building Materials
217 ,
225.
Time elapsed between
separation of Ra and
midpoint of count
in hours
1
2
3
4
5
6
24
48
Ingrowth Factor*
0.002881
0.005748
0.008602
0.01144
0.01427
0.01708
0.06542
0.1235
Time elapsed between
separation of Ra and
midpoint of count
in hours
72
96
120
144
192
240
360
480
Ingrowth Factor*
0.1748
0.2200
0.2596
0.2940
0.3494
0.3893
0.4383
0.4391
Ra activity present at the date/time ofRa separation. These ingrowth factors may be closely approximated
(within a fraction of a percent) using the expression for A t in Step 12.2.
. 225,
229r,
Time elapsed between
purification of the 229Th
standard and date of Ra
separation
in days
1
5
10
12
15
20
25
27
30
40
Ingrowth Factor*
0.04545
0.2075
0.3720
0.4278
0.5023
0.6056
0.6875
0.7152
0.7523
0.8445
Time elapsed between
purification of the 229Th
standard and date of Ra
separation
in days
50
55
60
70
80
90
100
130
160
200
Ingrowth Factor*
0.9023
0.9226
0.9387
0.9615
0.9758
0.9848
0.9905
0.9976
0.9994
0.9999
Ingrowth Factor represents the fraction Ra activity/ Th activity at the time ofRa separation.
225
Table 17.4 Decay Factors for Unsupported Ra
Time elapsed
between separation
of 229Th and 225Ra
in days
1
5
10
12
15
20
25
27
30
40
Decay Factor*
0.9545
0.7925
0.6280
0.5722
0.4977
0.3944
0.3125
0.2848
0.2477
0.1555
Time elapsed
between separation
of 229Th and 225Ra
in days
50
55
60
70
80
90
100
130
160
200
Decay Factor*
0.09769
0.07741
0.06135
0.03853
0.02420
0.01519
0.00954
0.00236
0.00059
0.00009
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22 17.2. Ingrowth curves and Ingrown factors
23
24
25
Ac-225 In-Growth in Ra-225
1000
100
10
Q.
1
0.1
0
200
400
600
800
1000
Time, Hours
Ra-225
-o- Ac-225
26
27
Ra-225 In-Growth in Th-229
250
200 < > ~ ~
150
E
Q.
T3
100
0
20
40
60
80
100
120
Days
—Th-229, dpm
—B— Ra-225, dpm
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17.3. Example Alpha Spectaim from a Processed Sample
2362 2760 3162 3567 3976 ' 388 48C4 5223 5645 60!
Energy (keV) |
17.4. Decay Schemes for Analyte and Tracer
226Ra Decay Scheme
Secular equilibrium is
established between 226Ra
and 222Rn in about 18 days.
1,600 y
3.8 d
3.1 min
It takes about 4 hours for secular
equilibrium to be established
between 222Rn and 214Po after
fresh 222Rn is separated.
164 ps
22.2 y
27 min
P P
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32 17.5 Flowcharts: Separation Scheme and Timeline for Determination of Ra-226 in
33 Building Materials (Parts 1 and 2)
34 Note: The example timeline below illustrates the sample preparation for asphalt shingles, which
3 5 requires the destruction of organics. The sample preparation times will be shorter when furnace
36 ashing steps to destroy organics prior to the fusion are not required.
Separation Scheme and Timeline for Determination of
Ra-226 in Building Materials
(Part I)
7 Vz hours
8 hours
9 Vz hours
11 hours
Continue to Part
Discard load and
rinse solutions
(Step 11.2.2.9)
Discard Sr
Resin/DGA Resin
(Step 11.2.3.8)
Rapid Fusion (See Separate Procedure)
1. Add 225Ra tracer and fuse with NaOH
2. Ca carbonate precipitation
3. Dissolve in of 20 m L1,5M HCL (column load solution)
4. Add 3m L 1,5M ascorbic acid and mix.
Transfer Ra eluate to 150 mL glass beakers
1. Add 2 mL30wt% H202 to each beaker. Evaporate to dryness
on a hotplate (11.2.2.19)
2. Dissolve in5mL4M HN03, warming slightly on hotplate
(11.2.2.20)
Load sample to cation resin columns
1. Loadsample@1mL/min(11.2.2.10)
2. Beaker/tube rinse: 5m L 1,5M HCL @1 -2 m L/m in (11.2.2.11)
3. Column rinse: 30 mL3M HCL @1 -2 m L/m in (11.2.2.13)
4. Elute Ra with 20 mL8M HN03 @1 m L/min.Transferto 150 m L
beaker and rinse with 3 m L 8M HN03 (11.2.2.17-11.2.2.18)
Vacuum Box Setup
1. Prepare cation column using 5g of 50WX8200-400 mesh resin
on vacuum box. Clean resin with 15 mL6M HCL and allow to
drain @2 m L/m in, then 15 mL water @ 2 m L/m in (11.2.2.2-
11.2.2.5)
2. Conditioncolumnwith 10 mL0.5M HCI @1 m L/m in. (11.2.2.6-
11.2.2.8)
Load sample to Sr Resin+DGA Resin cartridge for Ba
and other interference removal
1. Condition column with 5m L 4M HN03@1 m L/m in. Load sample
@1m L/m in (11.2.3.2-11.2.3.4)
2. Beaker rinse: 3m L4M HN03@1 m L/m in (11.2.3.5)
3. Column rinse: 5mL4M HN03 @ 1-2 m L/m in (11.2.3.6)
4. Record the date and time of last rinse (11.2.3.7)
5. Discard Sr resin plus DGA resin (11.2.3.8)
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Separation Scheme and Timeline for Determination of
Ra-226 in Building Materials
(Part II)
12 hours
13 hours
Count sample test source (STS)
By alpha spec for 1-8 h or as
needed (Step 11.3.11)
14-21 hours
Continued from
Fig. 17.5, Part I
Store filter for 24 hours
(Step 11.3.10)
Transfer Ra eluate to 250 mL glass beakers
1. Transfer solution to 250 mL beaker. Rinse tube with 3
mL 30 wt% H202 (11.2.3.9)
2. Evaporate to dryness on a hotplate with medium heat
(11.2.3.10).
3. Redissolve in 10 mL 1.5M HCI, warming until hot on
hotplateand transferto 50 ml tube(11.2.3.11).
4. Rinse beaker with two 7 mL rinses of 1.5M HCI and
transferto 50 mLtube(11.2.3.12).
M icropreci pitation
1. Add 3g (NhL^SCU to each tube. Cap and mix on
vortex stirrerto dissolvesalt(11.3.1).
2. Add 50 |jg Ba to each tube. Cap and mix well
(11.3.2).
3. Add 5 ml isopropanol to each tube. Cap and mix well
using vortex stirrer (11.3.3)
4. Place in ice/water mixture bath for 15 minutes,
periodically removing and stirring ( 2-3 times ) using
vortex stirrer (11.3.4)
5. Filter and rinse tube with 3mL 20% isopropanol. Add
to filterfunnel (11.3.6)
6. Rinse filter with 2 mL methanol or ethanol. Discard
rinses (11.3.7).
7. Place on mounting disk and warm 5 minutes under
heat lamp (11.3.9)
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Appendix A:
225 229
Preparation and Standardization of Ra Tracer Following Separation from Th
A1. Summary Description of Procedure
This procedure describes a 225Ra generator to make tracer amounts of 225Ra using a 229Th
225
solution. Thorium-229 is separated from Ra using yttrium hydroxide (Y(OH)3) co-
precipitation. Thorium-229 is carried in the precipitate and most of the 2 5Ra remains in solution.
229
Centrifugation to remove Th in the precipitate and filtration of the supernate produces the
225 225
Ra tracer solution. The Ra activity of the tracer solution is standardized by counting sample
225
test sources prepared from at least five replicate aliquants of the Ra solution, each spiked with
a known quantity of a 226Ra standard. This standardized activity concentration, referenced to the
225
date and time of the Ra separation described in Step A4.10.7, is then decay-corrected to the
date and time of subsequent sample analyses.
225
The Y[Th](OH)3 precipitate may be stored and re-used later to generate more Ra tracer
229
solution. Radium-225 ingrows in the Th fraction (Y(OH)3 precipitate) and after 50 days will
be about 90% ingrown. After sufficient ingrowth time 25Ra may be harvested to make a fresh
225 229
Ra tracer solution by dissolving the precipitate and re-precipitating Y(OH)3 to separate Th
from 225Ra.
225 225
Multiple Ra generators may be prepared to ensure that Ra tracer will be continuously
225
available. The Ra tracer solution produced is usable for 2-3 half-lives (approximately 30-45
days). To minimize effort involved with standardization of the 225Ra solution, it is recommended
229
that the laboratory prepare an amount of Th sufficient to support the laboratory's expected
229 229
workload for 3-5 weeks. Since the Th solution is reused, and the half-life of Th is long
229
(7,342 years), the need to purchase a new certified Th solution is kept to a minimum.
A2. Equipment and Supplies
A2.1. Refer to Section 6 of the main procedure.
A3. Reagents and Standards
A3.1. Refer to Section 7 of the main procedure.
A4. Procedure
229
A4.1. Add a sufficient amount of Th solution (that which will yield at least 150-600
dpm/mL of the 225Ra solution) to a 50 mL centrifuge tube.6
A4.2. Add 20 mg yttrium (Y) (2 mL of 10 mg/mL Y metals standard stock solution).
A4.3. Add 1 mg Ba (0.1 mL of 10 mg/mL Ba metals standard stock solution).
A4.4. Add 4 mL of concentrated ammonium hydroxide to form Y(OH)3 precipitate.
A4.5. Centrifuge and decant the supernatant into the open barrel of a 50 mL syringe, fitted
with a 0.45 |im syringe filter. Hold the syringe barrel over a new 50 mL centrifuge
6 For example, if 40 mL of a 229Th solution of 600 dpm/mL is used, the maximum final activity of 225Ra will be ~510
dpm/mL at Step A4.7. This solution would require about 1.4 mL for the standardization process and about 8 mL for
a batch of 20 samples.
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tube while decanting. Insert the syringe plunger and filter the supernatant into the new
centrifuge tube. Discard the filter as potentially contaminated radioactive waste.
A4.6. Cap the centrifuge tube with the precipitate, label clearly with the standard ID,
precipitation date, and the technician's initials and store for future use.
225
A4.7. Properly label the new centrifuge tube with the supernate. This is the Ra tracer
solution.
Add:
well.
Prepa
tracer.
225
A4.8. Add 3 mL of concentrated HC1 to Ra tracer solution. Cap centrifuge tube and mix
225
A4.9. Prepare the following solutions in 10 mL of 4M HNO3 for standardization of Ra
Solution
Standardization
Replicates
(5 replicates)
Blank
Standardization
Control Sample
Spike(s)
-80 dpm of the 225Ra tracer solution, and
~8 dpm of a 226Ra standard traceable to the National
Institute of Standards and Technology (NIST) or
equivalent
-80 dpm of the 225Ra tracer solution (the blank
should be evaluated to confirm that 226Ra is not
225
detected in the Ra tracer solution at levels that
may compromise sample results when used in the
method)
-80 dpm of the 225Ra tracer solution, and
-8 dpm of a second source independent traceable
226Ra standard (the Standardization Control Sample
should be evaluated to confirm that the standardiza-
tion process does not introduce significant bias into
225
the standardized value for the Ra tracer).
A4.10. Process the solutions to prepare sources for alpha spectrometry as follows:
A4.10.1. Place 225Ra aliquots of standard (A4.9) in 10 mL of 4M HNO3 in 50 mL
glass beakers.
A4.10.2. Place a 2 mL DGA Resin cartridge on the vacuum box.
A4.10.3. Add 5 mL of 4M HNO3 into each column to precondition resin at -1
mL/min. Discard rinse.
A4.10.4. Transfer each sample solution from Step A4.10.1 into the appropriate
column reservoir. Allow solution to pass through the DGA Resin cartridge
at a flow rate of-1 mL/min or less.
A4.10.5. Add 5 mL of 4M HNO3 to each beaker (from Step A4.10.1) as a rinse and
transfer each solution into the appropriate reservoir at -1 mL/min.
A4.10.6. Add 5 mL of 4M HNO3 into each column to rinse at -1 mL/min.
A4.10.7. Record the date and time of the last rinse as the date and time of
225
separation of radium (beginning of Ac ingrowth).
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Note: The activity reference date and time established during standardization of
the 225Ra tracer is used as the reference date for the 225Ra solution.
A4.10.8. Remove tubes from vacuum box and evaporate to dryness.
A4.10.9. Remove tubes and transfer sample solution to 250 mL glass beakers,
rinsing tube with 3 mL of 30 wt% H2O2 and adding to beaker.
A4.10.10. Evaporate solutions to dryness on a hotplate using medium heat. Do not
bake.
A4.10.11. Add 10 ml 1,5M HC1 to each beaker to redissolve each sample, warming
on a hotplate until hot and transfer to a labeled 50 mL tube.
A4.10.12. Rinse each beaker with two 7 mL volumes of 1,5M HC1 and transfer each
rinse to the tube.
A4.10.13. Add -3.0 g of (NH4)2S04 to the purified sample solution Mix well to
completely dissolve the salt (dissolves readily).
A4.10.14. Add 75 |ig of Ba carrier (75 |iL of 1000 |ig Ba/mL) into each tube. Cap
and mix well with vortex stirrer.
A4.10.15. Add 5.0 mL of isopropanol and mix well using a vortex stirrer.
A4.10.16. Place each tube in an ice bath filled with cold tap water for at least 20
minutes, periodically stirring on vortex stirrer.
Note: Sonication may be used instead of occasional stirring using a vortex stirrer.
A4.10.17. Pre-wet a 0.1-micron filter using methanol or ethanol. Filter the
suspension through the filter using vacuum. The precipitate will not be
visually apparent.
A4.10.18. Rinse the sample container with 3 mL of 20% isopropanol solution.
A4.10.19. Rinse the filter apparatus with about 2 mL of methanol or ethanol to
facilitate drying. Turn off vacuum.
A4.10.20. Mount the filter on a labeled adhesive mounting disk (or equivalent)
ensuring that the filter is not wrinkled and is centered on mounting disk.
A4.10.21. Place the filter under a heat lamp for ~5 minutes or more until it is
completely dry.
A4.10.22. Count filters for an appropriate period of time by alpha spectrometry.
A4.10.23. Mount the dried filter on a support appropriate for the counting system to
be used.
217
A4.10.24. Store the filter for at least 24 hours to allow sufficient At (third progeny
of 225Ra) to ingrow into the sample test source allowing a measurement
uncertainty for the 217At of < 5 %.
A4.10.25. After allowing about 24-hours ingrowth, count the standardization sources
by alpha spectrometry.
225
A4.11. Calculate the activity of Ra, in units of dpm/mL, in the standardization replicates,
225
at the Ra time of separation as follows:
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N2
'At
Nh
(a226rJx(f226rJ
AC2
'At
Ra
where:
AC
225Ra
N
217At
N
226Ra
Nh
tb
A
226Ra
V„
226Ra
225Ra
d
X\
^2
'At
3.0408 =
(N2
"Ra
Nh
(3.0408)(/,„J (<
ehd -e
V2;
(1)
"Ra
lb J
225
= Activity concentration of Ra, in dpm/mL [at the time of separation from
229
Th, Step A4.10.7]
= Total counts beneath the 217At peak at 7.07 MeV
= Total counts beneath the 226Ra peak at 4.78 MeV
= Background count rate for the corresponding region of interest,
= Duration of the count for the sample test source, minutes
= Duration of the background count, minutes
= Activity of 226Ra added to each aliquant, in dpm/mL
= Volume of 226Ra solution taken for the analysis (mL)
225
= Volume of Ra solution taken for the analysis (mL)
225 217
= Elapsed ingrowth time for Ac [and the progeny At], from separation to
the midpoint of the sample count, days
= 0.04652 d"1 (decay constant for 225Ra - half-life = 14.9 days)
= 0.06931 d"1 (decay constant for 225Ac) - half-life = 10.0 days)
Fractional abundance for the 7.07 MeV alpha peak counted (= 0.9999)
^2/(^2 ~\) [a good approximation as the half lives of 221Fr and 217At
are
225
short enough so secular equilibrium with Ac is ensured]
Note: The activity of the separated A22sra will need to be decay corrected to the point of
separation in the main procedure (Step 11.2.3.6) so that the results can be accurately determined.
225
A4.12. Calculate the uncertainty of the activity concentration of the Ra tracer at the
reference date/time:
"c (AC „SR)~
where:
Nh
C
t;
y AC2 y I2 y V2
A226^_ A 1 226n_ A v 22'
"Ra '"Ra
- + ACI
N„
Nh
X [3.0408 X lmM x (*
u2(AC">RJ | u2(v*"pJ | u2(v*»pJ | u2(RiisfJ j
(2)
AC I
x \e " —e
xC
u(AC )
V 225Ra^
N
217At
N
226Ra
Nh
tb
AC
226Ra
225
= Standard uncertainty of the activity concentration of Ra, in dpm/mL
= Total counts beneath the 217At peak at 7.07 MeV,
= Total counts beneath the 226Ra tracer peak at 4.78 MeV
= Background count rate for the corresponding region of interest,
= Duration of the count for the sample test source, minutes
= Duration of the background count, minutes
= Activity of 226Ra added to each aliquant, in dpm/mL
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225
u(AC ) = Standard uncertainty of activity of Ra, in dpm/mL
V226r = Volume of 226Ra solution taken for the analysis (mL)
m(V226r ) = Standard uncertainty of the volume of 226Ra solution taken for the analysis
(mL)
/„, = Fractional abundance for the 226Ra peak at 4.78 MeV (= 1.000)
225
F225r = Volume of Ra solution taken for the analysis (mL)
225
m(V225r ) = Standard uncertainty of volume of Ra solution taken for the analysis
(mL)
225 217
d = Elapsed ingrowth time for Ac [and the progeny At], from separation to
the midpoint of the sample count, days
X\ = 0.04652 d_1 (decay constant for 225Ra-half-life = 14.9 days)
= 0.06931 d_1 (decay constant for 225Ac) - half-life = 10.0 days)
3.0408 = X2d/(X2d - [a good approximation as the half lives of221Fr
and217At
225
are short enough so secular equilibrium with Ac is ensured]
w(R226r ) = Standard uncertainty of net count rate for 226Ra, in cpm
R = Net count rate for 226Ra, in (cpm)
226Ra ' v r '
Note: The uncertainty of half-lives and abundance values are a negligible contributor to the
combined uncertainty and are considered during the evaluation of combined uncertainty.
A4.13. Calculate the mean and standard deviation of the mean (standard error) for the
replicate determinations, to determine the acceptability of the tracer solution for use.
The calculated standard deviation of the mean should be equal to or less than 5% of
the calculated mean value.
A4.14. Store the centrifuge tube containing the Y(OH)3/Th(OH)4 precipitate. After sufficient
225
time has elapsed a fresh Ra tracer solution may be generated by dissolving the
precipitate with 40 mL of 0.5M HNO3 and repeating Steps A4.4 through A4.10 of
this Appendix.
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