www.epa.gov
April 2014
EPA 402-R14-002
Revision 0
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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Rapid Radiochemical Method for Radium-226 in Building Materials
Revision History
Revision 0 | Original release. | 04-16-2014
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 Office of Research
and Development, United States Environmental Protection Agency. It was prepared by Environmental
Management Support, Inc., of Silver Spring, Maryland, under contract EP-W-07-037, work assignments B-
41, 1-41, and 2-43, managed by David Carman and Dan Askren. This document has been reviewed in
accordance with U.S. Environmental Protection Agency (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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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 rapid radiochemical separations techniques for the isotopic
determination of 226Ra in building materials samples following a nuclear or
radiological incident.
1.3. The method is specific for 226Ra. It uses 50WX8 cation resin to separate radium from
concrete or brick matrix constituents, followed by additional separation steps using Sr
Resin and Ln Resin to remove interferences.
oo/r
1.4. The method is capable of satisfying a required method uncertainty for Ra of 0.83
pCi/g at an analytical action level of 6.41 pCi/g. To attain the stated measurement
quality objectives (MQOs) (see Sections 8.3, 8.4, and 8.5), 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 (EPA 2009, 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. 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 (EPA 2009, Reference
16.1) and Chapter 6 of Multi-Agency Radiological Laboratory Analytical Protocols
Manual (MARLAP 2004, Reference 16.2).
1.6. Other solid samples such as soil can be digested using the rapid sodium hydroxide
fusion procedure as an alternative to other digestion techniques, but this procedure
will have to be validated by the laboratory.
2. Summary of Method
2.1. A known quantity of 225Ra is used as the yield tracer in this analysis. The sample is
fused using procedure, Rapid Method for Sodium Hydroxide Fusion of Concrete and
Brick Matrices Prior to Americium, Plutonium, Strontium, Radium, and Uranium
Analyses (Reference 16.3), and then the 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 Sr Resin to remove Ba. This solution is
evaporated to dryness, redissolved in 0.02M HC1 and passed through Ln Resin to
remove interferences such as residual calcium and to remove the initial 225Ac present.
oo/r
The radium (including Ra) is prepared for counting by microprecipitation with
BaSO4.
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Rapid Radiochemical Method for Radium-226 in Building Materials
2.2. 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). Paniculate matter in a sample
of any matrix where a high concentration of radioactive material is contained in a tiny
particle (micron range).
3.4. Multi-Agency Radiological Analytical Laboratory Protocols Manual (MARLAP)
provides guidance for the planning, implementation, and assessment phases of those
projects that require the laboratory analysis of radionuclides (Reference 16.2).
3.5. Measurement Quality Objective (MQO). The analytical data requirements of the data
quality objectives that 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.
3.6. 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 (cpMn). The relative required method
uncertainty is the MMR 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
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Rapid Radiochemical Method for Radium-226 in Building Materials
radium isotopes due to ingrowth of interfering decay progeny, but this will
depend on the actual spectral resolution.
4.1.2. Radionuclides with overlapping alpha energies such as 229Th, 234U, and
237Np will interfere if they are not removed effectively. The method removes
these radionuclides.
4.1.3. Decay progeny from the 225Ra 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 -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 22 Ra 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 from higher energy
alphas of the 225Ra progeny.
4.1.4. There is also a possibility that the higher energy peaks associated with the
225Ra progeny may result in energy-attenuated counts that show up in the
lower energy 226Ra alpha spectra region so reducing the 225Ra tracer while
still achieving enough 217At counts to minimize tracer uncertainty may be
optimal.
ooc
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,
to ensure that sufficient 225 Ac, 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.
4.1.5. A purified 225Ra tracer solution may be used when performing this method
(See Appendix).
4.1.5.1. When using a purified source of 225Ra, the beginning of decay
for 225Ra is the activity reference date established during
standardization of the 225Ra solution.
r\r\ c 99O
4.1.6. It is also possible to use Ra in equilibrium with Th for convenience,
1 99O
which may be added to each sample as a tracer. This allows use of Th
without purification and therefore is a simpler approach. This approach
requires complete decontamination of a relatively high activity of 229Th in
the later steps in the method, since the spectral region of interest (ROI) for
229Th slightly overlaps that of 226Ra.
99Q™, 99S
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 Ln Resin
1 The single-laboratory validation for this method was performed successfully by adding 225Ra in secular equilibrium
with 229Th tracer. See Appendix B of this method for a method for separating (and standardizing) 225Ra tracer from
229Th solution.
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Rapid Radiochemical Method for Radium-226 in Building Materials
separation of 229Th is 6 hours or less the error associated with the 225Ra
reference value is < 1.2% due to 225Ra decay. A correction for this decay can
also be made by recording the cation exchange elution time, and decaying
225Ra from this point until the Ln Resin separation time to eliminate this
relatively small bias.
OOP
4.1.8. The method provides effective removal of Th. Inadequate
decontamination of 229Th may lead to high bias in the 2 6Ra result especially
when the levels of 226Ra in the sample are below 1 pCi/g. The spectral
region above 226Ra corresponding to 229Th should be monitored routinely to
OOP
identify samples where Th interference may impact compliance with
project MQOs. If problematic levels of 229Th are identified in spectra,
measures must be taken to address the interference. These might include:
99S 99O
4.1.8.1. Separating Ra from Th 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.
OOP
4.1.8.3. The absolute amount of Th 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
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
separation time with an 8-hour count time if-100 pCi 229Th is
added, but separation times and counting time midpoints must be
recorded carefully and precisely.
99S 99O
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
equilibrium between the 225Ra and 229Th is essentially maintained until the
cation exchange elution step is performed. At this point, the 225Ra activity in
the eluate is unsupported and begins to decay. 225Ac is removed during the
Ln Resin separation.
4.1.10. Ascorbic acid is added to the sample load solution to reduce Fe3+ present to
Fe2+, which has less retention on cation resin than Fe 3+.
4.1.11. Trace levels of 226Ra may be present in Na2COs used in the 226Ra pre-
concentration step of the fusion method. Adding less 2M Na2COs (<25 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
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Rapid Radiochemical Method for Radium-226 in Building Materials
significantly exceed the amount of the barium carrier (50 ug), which is
added for microprecipitation. Microprecipitates on the STS greater than 50
jig Ba may severely degrade the resolution of alpha spectra.
4.2.1.1. In this procedure, barium is removed using Sr Resin and alpha
peak resolution is typically very good. It is important for the total
volume of 3M HNCb 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 larger aliquant sizes of concrete, brick
or soil 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 (MDA) 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 Ln
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. After initial separations using cation resin and Sr Resin, the sample eluent
solution is evaporated to dryness. This heating to dryness just prior to
redissolution in very dilute HC1 must be performed at very low heat
(removed from hot plate just prior to going to dryness) to avoid formation of
any oxides that may not dissolve well in the very dilute HCL just prior to
loading on Ln Resin. This is important to maximize chemical yields.
4.2.5. It may be possible to skip the HC1/H2O2 evaporation step after evaporating
the 3M HNOs to reduce sample preparation time, but this would have to be
validated by the laboratory.
4.2.6. The Ln 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
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 be small, on the order of 1 mm or less. Typically,
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Rapid Radiochemical Method for Radium-226 in Building Materials
DRPs 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, Co, or equivalent.
6.3. Centrifuge tubes, polypropylene, 50 mL, disposable; or equivalent.
6.4. Chromatography columns, polypropylene, disposable:
6.4.1. 1.5 cm inner diameter x 15 cm; or equivalent (Environmental Express,
Mount Pleasant, SC).
6.4.2. Additional frits for 1.5 cm inner diameter x 15 cm columns (Environmental
Express, Mount Pleasant, SC).
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 uL, 200 uL, 500 uL and 1 mL pipets or equivalent and appropriate plastic tips.
6.8. 1-10 mL electronic pipet or manual equivalent.
6.9. Glass beaker, 50 mL and 150 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 um 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 i/4" heavywall
tubing connectors, natural, Ref P/N 00070EE, cut to 1 inch , Cole Farmer, 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.
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Rapid Radiochemical Method for Radium-226 in Building Materials
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 (ACS) 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 16.4). For microprecipitation, all solutions used in microprecipitation should
be prepared with water filtered through a 0.45 um (or smaller) filter.
7.1. Type I reagent water as defined in ASTM Standard Dl 193 (Reference 16.4).
7.2. Ammonium sulfate, solid (NH/^SO/j.
7.3. Barium carrier (1000 |ig/mL as Ba2+). 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 (BaCh 2H2O) in water
and diluting to 500 mL with water.
7.4. Calcium nitrate (1.25M): Dissolve 147 g of calcium nitrate tetrahydrate
(Ca(NO3)2-4H2O) in 300 mL of water and dilute to 500 mL with water.
7.5. Cation Resin, 50WX8, 200-400 um mesh size (available from Eichrom
Technologies, Lisle, IL).
7.6. Ethanol, reagent 95 % (C2HsOH), available commercially.
7.7. Hydrochloric acid (12M): Concentrated HC1, available commercially.
7.7.1. Hydrochloric acid (3.0M): Add 250 mL of concentrated HC1 to 600 mL of
water and dilute to 1.0 L with water Hydrochloric acid (1.5M): Add 125 mL
of concentrated HC1 to 800 mL of water and dilute to 1.0 L with water.
7.7.2. Hydrochloric acid (1.5M): Add 125 mL of concentrated HC1 to 800 mL of
water and dilute to 1.0 L with water.
7.7.3. Hydrochloric acid (1M): Add 83 mL of concentrated HC1 to 800 mL of
water and dilute to 1.0 L with water.
7.7.4. Hydrochloric acid (0.1M): Add 8.3 mL of concentrated HC1 to 950 mL of
water and dilute to 1.0 L with water.
7.7.5. Hydrochloric acid (0.02M): Add 1.66 mL of concentrated HC1 to 950 mL of
water and dilute to 1.0 L with water
7.8. Hydrogen peroxide, H2O2 (30 % weight/weight), available commercially.
7.9. Isopropanol, 2-propanol, (CsH/OH), available commercially.
7.9.1. Isopropanol (2-propanol), 20% (volume/volume) in water: Mix 20 mL of
isopropanol with 80 mL of water.
7.10. Ln Resin resin cartridges, 2 mL, small particle size (50-100 |j,m), in appropriately
sized column pre-packed cartridges.
7.11. Methanol (CHsOH), available commercially
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Rapid Radiochemical Method for Radium-226 in Building Materials
7.12. Nitric acid (16M): Concentrated HNCb, available commercially.
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).
99Q™, 99S
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
been successfully used without prior separation of the 225Ra.
7.14. Sr Resin 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
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
to provide quantitative results. When 229Th /22 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
99Q 996
presence of Th in the sample, and in the Ra ROI. If the presence of
29Th is noted and the concentration of 226Ra is determined to be an order of
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Rapid Radiochemical Method for Radium-226 in Building Materials
magnitude below the action limit or the detection threshold of the method,
take corrective actions to ensure that MQOs have not been compromised
(e.g., clean-up 225Ra 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 0.83 pCi/L at or below an action level of
6.41 pCi/g. This may be adjusted in the event specific MQOs are different.
9.4. This method is capable of achieving a ^MR 13% above 6.41 pCi/g. 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.
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.
10.2. If 225Ra is separated and purified from 229Th for use as a tracer, the activity reference
date established during standardization of the tracer is used as the 225Ra activity
reference date (see the appendix of this method).
99Q™, 99S
10.3. When using Th containing an equilibrium concentration of Ra, the time of most
recent separation/purification of the 229Th standard solution must be known in order
to determine the extent of secular equilibrium between 229Th and its 225Ra progeny.
Verify the date of purification by examining the Certificate of Analysis, or other
applicable documentation, for the standard.
99Q™, 99S 99S
10.4. When using Th containing an equilibrium concentration of Ra, Ra is separated
from its 229Th parent in the solution during the cation exchange elution step. This is
the beginning of 225Ra decay and the date and time used for decay correction of the
tracer. This time must be known and recorded precisely.
10.4.1. If the purification date of the 229Th is not documented, at least 100 days must
77Q
have elapsed between separation and use to ensure that Th, and its
99S
progeny Ra are in full secular equilibrium (i.e., >99%. See Table 17.3).
11. Procedure
11.1. Initial Sample Preparation for Radium
11.1.1. Ra isotopes are preconcentrated from building material samples using
procedure Rapid Method for Sodium Hydroxide Fusion of Concrete and
Brick 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.
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Rapid Radiochemical Method for Radium-226 in Building Materials
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
reduce any Fe present to Fe 2+. Mix and wait ~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.
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.
11.2.2.6. Add 10 mL of 1M 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 (roughly ~1 drop/sec).
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 ~ 1-2 mL/min. Discard eluate.
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11.2.2.12. Press frit down on resin bed.
11.2.2.13. Add 30 mL of 3M HC1 to each column at ~ 1-2 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 25 mL of 8M of HNCb to each column to elute Ra at
~1 mL/min. Record the date and time as the date and time of
separation of 225Ra and thorium to account for the decay of
unsupported 225Ra.
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.
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. Samples should be taken off
hotplate prior to going dry and allowed to go to dryness as the
beaker cools.
11.2.2.20. Add 5 mL of 3M HNCb 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
3M HNO3 must be kept small to remove Ba effectively.
11.2.3. Sr Resin Separation of Barium
11.2.3.1. Place a 2-mL Sr Resin cartridge on the vacuum box.
11.2.3.2. Condition each Sr Resin cartridge with 5 mL of 3M HNCb 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 Sr Resin cartridge at a flow rate of ~1 mL/min or
less.
11.2.3.5. Add 3 mL of 3M 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 3 mL of 3M HNCb into each reservoir as a column rinse
(flow rate -1-2 mL/min).
11.2.3.7. Turn off vacuum. Discard Sr Resin.
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11.2.3.8. Remove tubes and transfer sample solution to 100-mL glass
beakers.
11.2.3.9. Add 2 mL of 30 wt% H2O2 and evaporate solutions on medium
heat to dryness on a hot plate being very careful not to bake
material into the beaker. Samples should be taken off the hotplate
prior to going dry and allowed to go to dryness as the beaker
cools
NOTE: The method has been performed in some labs without the
following evaporation step with HC1 and H2O2 to save time but this will
have to be validated by the laboratory.
11.2.3.10. Add 2 mL of 1M-HC1 and 2 mL of 30% H2O2 and evaporate
solutions carefully to dryness on low heat and evaporate
solutions on medium heat to dryness on a hot plate being very
careful not to bake material into the beaker. Samples should be
taken off the hotplate prior to going dry and allowed to go to
dryness as the beaker cools.
NOTE: Heating to dryness on very low heat and allowing to dry just after
coming off the hotplate with low heat is very important to prevent oxide
formation, which can be difficult to redissolve in low acid and cause
lower yields.
11.2.3.11. Add 2 mL of 0.1M HC1 to each beaker, warming on a hotplate to
dissolve.
11.2.3.12. Add 8 mL water and swirl to mix. Warm to ensure sample is
dissolved.
11.2.4. Final Purification Using Ln Resin.
11.2.5. Place a 2 mL Ln Resin cartridge on the vacuum box.
11.2.6. Add 5 mL of 0.02M HC1 into each column to precondition resin at ~1
mL/min. Discard rinse.
11.2.7. Ensure that clean, labeled plastic tubes are in the tube rack below each
cartridge.
11.2.8. Transfer each sample solution from Step 11.2.3.12 into the appropriate
column at -1-1.5 mL/min.
NOTE: It is important to load sample rapidly enough (1-1.5 mL/min) to avoid any
retention of Ra on Ln Resin.
11.2.9. Add5 mL of 0.02MHC1 to each beaker (from Step 11.2.3.12) as a rinse and
transfer each solution into the appropriate reservoir at -1-2 mL/min).
11.2.10. Add 5 mL of 0.02M HC1 into each column to rinse at -1-2 mL/min.
11.2.11. Record the date and time of the last rinse (Step 11.3.6) 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), 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.
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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 Ln Resin
separation time, where 225Ac is removed, to determine the reference activity of the
225Ra tracer at that point.
1 1 .2.12. Remove tubes from vacuum box and add 3 mL concentrated HC1 to each
tube. Cap and mix.
11.2.13. Discard Ln Resin.
99^
1 1.3. Barium sulfate micro-precipitation of Ra
11.3.1. Add ~3 .0 g of (NH4)2SO4 to the purified sample solution. Mix well using a
vortex stirrer to completely dissolve the salt.
1 1.3.2. Add 50 jig of Ba carrier (50 jiL of 1000 jig Ba/mL) into each tube. Cap and
mix well with vortex stirrer.
1 1.3.3. Add 5.0 mL of isopropanol and mix well using a vortex stirrer.
1 1 .3 .4. Place each tube in an ice bath filled with cold tap water for at least 1 5
minutes, periodically stirring on vortex stirrer (before placing in ice,
midway, and after icing).
1 1.3.5. 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.
1 1.3.6. 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 ~ 5 minutes or more until it is
completely dry.
1 1.3.10. Store the filter for ~ 24 hours to allow sufficient 217At (third progeny of
225Ra) to ingrow into the sample test source allowing a measurement
uncertainty for the 217At of < ~5 %.
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
99S 99 1 917
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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RY= R'~Rb
sxAtx!t ,jx
Where:
RY = Fractional radiochemical yield based on 225Ra (from ingrown 217At
at 7.07 MeV)
917
Rt = Total count rate beneath the At peak at 7.07 MeV, cpm
Rb = Background count rate for the same region, cpm
e = Efficiency for the alpha spectrometer
/t = 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).
917
A\ = Activity of At at midpoint of the count (the target value that
should be achieved for 100% yield), in dpm
= 3.0408(/t^225Ra)[ex'd-eX2d]
99S
^225Ra = Activity in dpm of Ra tracer added to the sample decay
r\
corrected to the date and time of radium separation in Step 11.3.6.
d = Elapsed ingrowth time for 225Ac [and the progeny 217At], in days
from the date and time of Ra separation to the midpoint of the
sample count
Ai = 0.04652 d"1 (decay constant for 225Ra - half-life = 14.9 days)
A2 = 0.06931 d"1 (decay constant for 225Ac) - half-life = 10.0 days)
/t = Fractional abundance for the 7.07 MeV alpha peak counted (=
0.9999)
2 Unsupported 225Ra: When separated 225Ra tracer is added to the sample, its initial activity, ^sna-mmd, 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:
where: ^ = decay constant for 225Ra (0.04652 d :); 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 11.3.6 (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:
,
where : A229ih = Activity of the 229Th standard on the date of the separation of Th and Ra (cation exchange elution
step); A! = decay constant for 225Ra (0.04652 d"1); and d1 = 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 1 1.3.6) using the first equation above.
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3.0408 = ^2/(^2 + A) [a g°°d approximation as the half lives of 221Fr and
917 99S
At are short enough so that 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:
ACt=-
and
u(AC)- u*
c( J
where:
ACn = activity concentration of the analyte at time of count, (pCi/g)
917
A\ = 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)
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 ROI for 226Ra)
Rat = net count rate of the tracer in the defined ROI, in counts per minute
Wo. = weight of the sample aliquant (g)
DH = 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.}
uc(ACa) = combined standard uncertainty of the activity concentration of the
analyte (pCi/L)
u(A\) = standard uncertainty of the activity of the tracer added to the
sample (dpm)
u(Wa) = standard uncertainty of the volume of sample aliquant (g)
u(Rna) = 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.
NOTE: The equation for the combined standard uncertainty (wc(y4Ca)) calculation is arranged to
eliminate the possibility of dividing by zero if Ra = 0.
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 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:
12.3.2.
and
where:
Rnx
Cx
t\,
r C
x bx
C+l
(4)
(5)
= net count rate of analyte or tracer, in counts per minute4
= sample counts in the analyte or the tracer ROI
= sample count time (min)
= background counts in the same ROI as for x (x refers to the
respective analyte or tracer count)
= background count time (min)
u(Rnx) = standard uncertainty of the net count rate of tracer or
analyte, in counts per minute
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
0.4xM--l + 0.677 x
+ 1.645 x
A
tsxWaxRtxDax!a
(7)
2.71
+ 3.29x
(8)
4 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, ft = 0.05 (with zi-a = zi-p = 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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Rapid Radiochemical Method for Radium-226 in Building Materials
where:
Rba = 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
(FWHM) 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 ~9 hours. Total
processing time is dependent on actual wait time for 217At ingrowth (-16-24 hours)
and count times (~6 hours).
14. Pollution Prevention
14.1. The use of 50WX8 cation resin, Sr Resin and Ln 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 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. 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.
16.2. 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.
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Rapid Radiochemical Method for Radium-226 in Building Materials
16.3. U.S. Environmental Protection Agency (EPA). 2014. Rapid Method for Sodium
Hydroxide Fusion of Concrete and Brick Matrices Prior to Americium, Plutonium,
Strontium, Radium, and Uranium Analyses. Revision 0, EPA 402-R14-004. Office of
Air and Radiation, Washington, DC. Available at: www.epa.gov/narel.
16.4. ASTM Dl 193, "Standard Specification for Reagent Water," ASTM Book of
Standards 11.02, current version, ASTM International, West Conshohocken, PA.
16.5. 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.
16.6. U.S. Environmental Protection Agency (EPA). 2014. Rapid Radiochemical Method
for Americium-241 in Building Materials for Environmental Remediation Following
Radiological Incidents. Revision 0, EPA 402-R14-007. Office of Air and Radiation,
Washington, DC. Available at: www.epa.gov/narel.
Other References
16.1. U.S. Environmental Protection Agency (EPA). 2014. Rapid Radiochemical Method
for Pu-238 and Pu-239/240 in Building Materials for Environmental Remediation
Following Radiological Incidents. Revision 0, EPA 402-R14-006. Office of Air and
Radiation, Washington, DC. Available at: www.epa.gov/narel.
16.8. U.S. Environmental Protection Agency (EPA). 2014. Rapid Radiochemical Method
for Radium-226 in Building Materials for Environmental Remediation Following
Radiological Incidents. Revision 0, EPA 402-R14-002. Office of Air and Radiation,
Washington, DC. Available at: www.epa.gov/narel.
16.9. U.S. Environmental Protection Agency (EPA). 2014. Rapid Radiochemical Method
for Total Radiostrontium (Sr-90) in Building Materials for Environmental
Remediation Following Radiological Incidents. Revision 0, EPA 402-R14-001.
Office of Air and Radiation, Washington, DC. Available at: www.epa.gov/narel.
16.10. U.S. Environmental Protection Agency (EPA). 2014. Rapid Radiochemical Method
for Isotopic Uranium in Building Materials for Environmental Remediation
Following Radiological Incidents. Revision 0, EPA 402-R14-005. Office of Air and
Radiation, Washington, DC. Available at: www.epa.gov/narel.
16.11. Koornneef, J.M., Stracke, A, Aciego, S., Renbi, O. and Bourdon, B. 2010. "A new
OQ/i 9^0™, 9^ 1
method for U-Th-Pa-Ra separation and accurate measurement of U- Th- Pa-
226Ra disequilibria in volcanic rocks by MC-ICPMS." Chemical Geology, Vol. 277,
Issue 1-2, October, 30-41.
16.12. Maxwell, S. and Culligan, B. 2012. "Rapid Determination of Ra-226 in
Environmental Samples," J. Radioanalytical and Nuclear Chemistry, online first
article, February.
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Rapid Radiochemical Method for Radium-226 in Building Materials
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)
4.601
4.784
4.798
4.815
4.838
4.845
4.901
4.968
4.979
5.053
5.434
5.449
5.489
5.540
5.580
5.607
5.609
5.637
5.682
5.685
5.716
5.724
5.732
5.732
5.747
Abundance
(%)
5.6
94.5
1.5
9.3
5.0
56.2
10.2
6.0
3.2
6.6
2.2
5.1
99.9
9.0
1.2
25.2
1.1
4.4
1.3
94.9
51.6
3.1
8.0
1.3
9.0
Nuclide
Ra-226
Ra-226
Th -229
Th -229
Th -229
Th -229
Th -229
Th -229
Th -229
Th -229
Ra-223
Ra-224
Rn-222
Ra-223
Ac -225
Ra-223
Ac -225
Ac -225
Ac -225
Ra-224
Ra-223
Ac -225
Ac -225
Ac -225
Ra-223
-Analyte
Energy
(MeV)
5.791
5.793
5.830
5.869
6.002
6.051
6.090
6.126
6.243
6.278
6.288
6.341
6.425
6.553
6.623
6.778
6.819
£^&^
7.386
7.450
7.687
8.376
8.525
11.660
Abundance
(%)
8.6
18.1
50.7
1.9
100.0
25.1
9.8
15.1
1.3
16.2
99.9
83.4
7.5
12.9
83.5
100.0
79.4
^&^
100.0
98.9
100.0
100.0
2.1
96.8
Nuclide
Ac -225
Ac -225
Ac -225
Bi-213
Po -218
Bi-212
Bi-212
Fr-221
Fr-221
Bi-211
Rn-220
Fr-221
Rn-219
Rn-219
Bi-211
Po -216
Rn-219
^^^
Po -215
Po-211
Po -214
Po -213
Po-212
Po-212
217
At (3rd progeny of 225Ra tracer)
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. bnl.gOV/nildat2/indxdec.Jsp; Queried: November 11, 2007.
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17.2. Ingrowth curves and Ingrowth factors
1000
E
Q.
TJ
Ac-225 In-Growth in Ra-225
200
400 600
Time, Hours
800 1000
20
Ra-225 In-Growth in Th-229
40
60
Days
•Th-229, dpm
-Ra-225, dpm
80 100 120
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Table 17.2 - Ingrowth Factors for 217At in 225Ra
Time elapsed between
separation of Ra and
midpoint of count
in hours
Ingrowth Factor*
Time elapsed between
separation of Ra and
midpoint of count
in hours
Ingrowth Factor*
1
0.002881
72
0.1748
2
0.005748
96
0.2200
3
0.008602
120
0.2596
4
0.01144
144
0.2940
5
0.01427
192
0.3494
6
0.01708
240
0.3893
24
0.06542
360
0.4383
48
0.1235
480
0.4391
'ingrowth Factor represents the fraction of Ac activity at the midpoint of the sample count relative to the 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 At in Step 12.2.
Table 17.3 - Ingrowth Factors for 225Ra in 229Th
Time elapsed between
purification of the 229Th
standard and date of Ra
separation
in days
Ingrowth Factor*
Time elapsed between
purification of the 229Th
standard and date of Ra
separation
in days
Ingrowth Factor*
1
0.04545
50
0.9023
5
0.2075
55
0.9226
10
0.3720
60
0.9387
12
0.4278
70
0.9615
15
0.5023
80
0.9758
20
0.6056
90
0.9848
25
0.6875
100
0.9905
27
0.7152
130
0.9976
30
0.7523
160
0.9994
40
0.8445
200
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
of229Thand225Ra
in days
Decay Factor*
Time elapsed
between separation
of229Thand225Ra
in days
Decay Factor*
1
0.9545
50
0.09769
5
0.7925
55
0.07741
10
0.6280
60
0.06135
12
0.5722
70
0.03853
15
0.4977
80
0.02420
20
0.3944
90
0.01519
25
0.3125
100
0.00954
27
0.2848
130
0.00236
30
0.2477
160
0.00059
40
0.1555
200
0.00009
Decay Factor represents the fraction Ra activity remaining as calculated using the equation in Footnote 2.
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Rapid Radiochemical Method for Radium-226 in Building Materials
17.3. Example Alpha Spectrum from a Processed Sample
388 48(4 5223 5645 60
2362 2760 3162 3567 3976
Energy (keV)
i3 7369
17.4. Decay Schemes for Analyte and Tracer
a
164
22 2 y
P
226Ra Decay Scheme
Secular equilibrium is
established between 22BRa
and 222Rn in about 18 days.
1 h
3.1 min
a
27 min
1,600y
a
3.8 d
a
It takes about 4 hours for secular
equilibrium to be established
between 222Rn and 214Po after
fresh 222Rn is separated.
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Rapid Radiochemical Method for Radium-226 in Building Materials
225Ra (Including Parent) Decay Scheme
4.8 min
45.6min
a
a
p 7.3x103a
14.9 d
a
10.0d
a
Secular Equilibrium between
229Thand225Rais achieved
after about 70 days.
The short half-lives of 221Fr and217At allow the
32ms 21?At actlvityto be calculated from 225Ac activity
based on secular equilibrium with 225Ac.
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17.5. Flowchart
Separation Scheme and Timeline for Determination of
Ra-226in Building Materials Samples
(Parti)
Discard load and
rinse solutions
(Step 11.2.2.13)
Discard Sr resin
(Step 11.2.3.7)
Rapid Fusion (See Separate Procedure)
1. Add 225Ra tracer and fuse with NaOH.
2. Ca carbonate precipitation.
3. Dissolve in of 20 ml_ 1.5M HCL (column load solution).
v
Vacuum Box Setup (Step 11.2.2)
1. Prepare cation column using 5 g of 50WX8 200-400
mesh resin on vacuum box.
2. Condition column with 10 mL 1M HCI @ 1 mL/min.
Load sample to cation resin columns (Step 11.2.2.10)
1. Load sample @ 1 mL/min.
2. Beaker/tube rinse: 5 mL 1.5M HCI @ 1-2 mL/min.
3. Column rinse: 30 mL 3M HCI @ 1-2 mL/min.
4. Elute Ra with 25 mL 8M HNO3 @ 1 mL/min.
Transfer Ra eluate to 150 mL glass beakers
(Step 11.2.2.19)
1. Add 2 mL 30 wt% H2O2 to each column.
2. Evaporate eluate to dryness on a hotplate.
3. Dissolve in 5 mL 3M HNO3, warming slightly on
hotplate.
v
Load sample to Sr Resin cartridge for Ba removal
(Step 11.2.3.4)
1. Load sample @ 1 mL/min.
2. Beaker rinse: 3 mL 3M HNO3 @ 1 mL/min.
3. Column rinse: 3 mL 3M HNO3 @ 1-2 mL/min.
4. Collect load and rinse solution containing Ra.
Elapsed Time
3 hours
31/2 hours
5 hours
53/4 hours
61/4 hours
Continue to Part II
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Rapid Radiochemical Method for Radium-226 in Building Materials
Discard Ln resin
(Step 11.2.13)
Discard filtrates
and rinses
(Step 11.3.7)
Separation Scheme and Timeline for Determination of
Ra-226in Building Materials Samples
(Part II)
Elapsed Time
Continued from
Fig. 17.5, Part I
v
Transfer Ra eluate to 100 mL glass beakers
(Step 11.2.3.8)
1. Add 2 mL 30 wt% H2O2 to each.
2. Evaporate to dryness on a hotplate with high heat.
3. Add 2 mL 30 wt% H2O2 to each and evaporate to
dryness on a hotplate.
4. Dissolve in 2 mL 0.1 M HCI, warming.
5. Add 8 mL water to each, swirl and warm.
V
Load sample to Ln Resin cartridge (Step 11.2.5)
1. Condition Ln Resin with 5 mL 0.02M HCI @1mL/min.
2. Load sample @ 1-2 mL/min or less.
3. Beaker rinse: 5 mL 0.02M HCI @ 1-2 mL/min.
4. Column rinse: 5 mL0.02M HCI @ 1-2 mL/min.
5. Collect load and rinse solution containing Ra.
6. Add 3 mL concentrated HCI to each eluate. Cap and
mix.
Microprecipitation (Step 11.3)
1. Add 3 g ammonium sulf ate to each tube
2. Cap and mix on vortex stirrer to completely dissolve
ammonium sulf ate
3. Add 50 ug barium to each tube. Cap and mix well.
4. Add 5 mL isopropanol to each tube. Cap and mix well
using vortex stirrer
5. Place in ice/water mixture bath for 15 minutes,
periodically removing and stirring ( 2-3 times ) using
vortex stirrer.
6. Filter and rinse tube with 3 mL 20% isopropanol. Add
to filterfunnel.
7. Rinse filter with methanol orethanol.
8. Place on mounting disk and warm 5 minutes under
heat lamp.
Count sample test source (STS)
alphaspectrometry forSh or as
needed (Step 11.4.11)
71/2 hours
8 hours
9 hours
13-22 hours
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Appendix:
Preparation and Standardization of 225Ra Tracer Following Separation from 229Th
Al. Summary Description of Procedure
This procedure describes a 225Ra generator to make tracer amounts of 225Ra using a 229Th
99Q™, v/S 99Q™,
solution. Th is separated from Ra using Y(OH)3 co-precipitation. Th is carried in the
99S 99O
precipitate and most of the Ra remains in solution. Centrifugation to remove Th in the
precipitate and filtration of the supernate produces the 225Ra tracer solution. The 225Ra activity of
the tracer solution is standardized by counting sample test sources prepared from at least five
replicate aliquants of the 225Ra solution, each spiked with a known quantity of a 226Ra standard.
This standardized activity concentration, referenced to the date and time of the 225Ra separation
described in Step A4.10.9 below, is then decay-corrected to the date and time of subsequent
sample analyses.
ooc
The Y[Th](OH)3 precipitate may be stored and re-used later to generate more Ra tracer
solution. 22 Ra ingrows in the 229Th fraction (Y(OH)3 precipitate) and after 50 days will be about
90% ingrown. After sufficient ingrowth time 225Ra may be harvested to make a fresh 225Ra tracer
99Q™, 99S
solution by dissolving the precipitate and re-precipitating Y(OH)3 to separate Th from Ra.
Multiple 225Ra generators may be prepared to ensure that 225Ra tracer will be continuously
available. The 2 5Ra tracer solution produced is usable for 2-3 half-lives (-30-45 days). To
minimize effort involved with standardization of the 225Ra solution, it is recommended that the
OOP
laboratory prepare an amount of Th sufficient to support the laboratory's expected workload
99Q™, 99O
for 3-5 weeks. Since the Th solution is reused, and the half-life of Th is long (7,342 years),
the need to purchase a new certified 229Th 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
•229n
A4.1. Add a sufficient amount of Th solution (that which will yield at least 150-600
99S 1
dpm/mL of the Ra solution) to a 50 mL centrifuge tube.
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
tube while decanting. Insert the syringe plunger and filter the supernatant into the new
centrifuge tube. Discard the filter as potentially contaminated radioactive waste.
1 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 B4.8. 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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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.
A4.7. Properly label the new centrifuge tube with the supernate. This is the 225Ra tracer
solution.
99S
A4.8. Add 3 mL of concentrated HC1 to Ra tracer solution. Cap centrifuge tube and mix
well.
A4.9. Prepare the following solutions in 10 mL of 2M HC1 for standardization of 225Ra
tracer.
Solution Spike(s)
Standardization -80 dpm of the 225Ra tracer solution, and
Replicates ~8 dpm of a 226Ra standard traceable to the National
(5 replicates) Institute of Standards and Technology (NIST) or
equivalent
Blank -80 dpm of the 225Ra tracer solution (the blank
should be evaluated to confirm that 226Ra is not
detected in the 225Ra tracer solution at levels that
may compromise sample results when used in the
method)
Standardization -80 dpm of the 225Ra tracer solution, and
Control Sample -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
the standardized value for the 225Ra tracer).
A4.10. Process the solutions to prepare sources for alpha spectrometry as follows:
A4.10.1. Evaporate aliquants in 50 mL glass beakers on a hot plate.
A4.10.2. Add 2 mL of 0.1M HC1 to each beaker, warming on hot plate to dissolve.
A4.10.3. Add 8 mL water and swirl to mix. Warm to ensure sample is dissolved.
A4.10.4. Place a 2 mL Ln Resin cartridge on the vacuum box.
A4.10.5. Add 5 mL of 0.02M HC1 into each column to precondition resin at -1
mL/min. Discard rinse.
A4.10.6. Transfer each sample solution from Step A4.10.3 into the appropriate
reservoir. Allow solution to pass through the Ln Resin cartridge at a flow
rate of-1 mL/min.
A4.10.7. Add 5 mL of 0.02M HC1 to each beaker (from Step A4.10.3) as a rinse
and transfer each solution into the appropriate reservoir at -1 mL/min.
A4.10.8. Add 5 mL of 0.02M HC1 into each column to rinse at -1 mL/min.
A4.10.9. Record the date and time of the last rinse as the date and time of
99S
separation of radium (beginning of Ac ingrowth).
NOTE: The activity reference date and time established during standardization of
the 225Ra tracer is used as the reference date for the 225Ra solution.
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A4.10.10. Remove tubes from vacuum box and add 3 mL concentrated HC1 to each
tube. Cap and mix.
A4.10.11. Add -3.0 g of (NH4)2SO4 to the purified sample solution Mix well to
completely dissolve the salt (dissolves readily).
A4.10.12. Add 75 |ig of Ba carrier (75 |iL of 1000 |ig Ba/mL) into each tube. Cap
and mix well with vortex stirrer.
A4.10.13. Add 5.0 mL of isopropanol and mix well using a vortex stirrer.
A4.10.14. 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.
A4.10.15. 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.
A4.10.16. Rinse the sample container with 3 mL of 20% isopropanol solution.
A4.10.17. Rinse the filter apparatus with about 2 mL of methanol or ethanol to
facilitate drying. Turn off vacuum.
A4.10.18. Mount the filter on a labeled adhesive mounting disk (or equivalent)
ensuring that the filter is not wrinkled and is centered on mounting disk.
A4.10.19. Place the filter under a heat lamp for ~ 5 minutes or more until it is
completely dry.
A4.10.20. Count filters for an appropriate period of time by alpha spectrometry.
A4.10.21. Mount the dried filter on a support appropriate for the counting system to
be used.
A4.10.22. Store the filter for at least 24 hours to allow sufficient 217At (third progeny
of 225Ra) to ingrow into the sample test source allowing a measurement
uncertainty for the 217At of < ~5 %.
A4.10.23. After allowing about 24-hours ingrowth, count the standardization sources
by alpha spectrometry.
A4.11. Calculate the activity of 225Ra, in units of dpm/mL, in the standardization replicates,
at the 225Ra time of separation as follows:
A -
^ (N-Ra *>\.
where:
A225 = Activity concentration of 225Ra, in dpm/mL [at the time of separation from
229Th, StepB4.4.10]
7V217 = Total counts beneath the 217At peak at 7.07 MeV
N = Total counts beneath the 226Ra peak at 4.78 MeV
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Rapid Radiochemical Method for Radium-226 in Building Materials
4
tb
A
226
V
2
V
2
d
26Ra
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
99^
Activity of Ra added to each aliquant, in dpm/mL
Volume of 226Ra solution taken for the analysis (mL)
J \ J
Volume of 225Ra solution taken for the analysis (mL)
J \ J
Elapsed ingrowth time for 225Ac [and the progeny 217At], from separation to
the midpoint of the sample count, days
AI = 0.04652 d"1 (decay constant for 225Ra - half-life = 14.9 days)
X2 = 0.0693 1 d"1 (decay constant for 225Ac) - half-life = 10.0 days)
/t = Fractional abundance for the 7.07 MeV alpha peak counted (= 0.9999)
3 .0408 = }i2d/(}i2d - \d) [a good approximation as the half lives of 221Fr and 217At are
short enough so secular equilibrium with 225Ac is ensured]
NOTE: The activity of the separated /422SRa will need to be decay corrected to the point of
separation in the main procedure (Step 11.3.6) so that the results can be accurately determined.
A4. 12. Calculate the uncertainty of the activity concentration of the
reference date/time:
99S
Ra tracer at the
; [3.0408x7,,^
V"''
V'a'Ra
where:
u(AC225 ) = Standard uncertainty of the activity concentration of
= Total counts beneath the 217At peak at 7.07 MeV,
225-
Ra, in dpm/mL
217
N
226Ra
Nb
4
tb
AC
z/(
V,,,
226Ra
w(V
/
oo/r
26
226
26
)
z/(V )
225Ra'
d
25
___
= Total counts beneath the Ra tracer peak at 4.78 MeV
F
= 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
= Activity of 225Ra, in dpm/mL
= Volume of 226Ra solution taken for the analysis (mL)
J \ J
99^
= Volume of Ra solution taken for the analysis (mL)
= Fractional abundance for the 226Ra peak at 4.78 MeV (= 1 .000)
99S
= Volume of Ra solution taken for the analysis (mL)
= Volume of 225Ra solution taken for the analysis (mL)
J \ /
= Elapsed ingrowth time for 225Ac [and the progeny 217At], from separation to
the midpoint of the sample count, days
= 0.04652 d"1 (decay constant for 225Ra - half-life = 14.9 days)
= 0.0693 1 d"1 (decay constant for 225Ac) - half-life = 10.0 days)
= Fractional abundance for the 7.07 MeV alpha peak counted (= 0.9999)
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Rapid Radiochemical Method for Radium-226 in Building Materials
3.0408 = ,42 d/(A2 d - \ d) fa good approximation as the half lives of 221Fr and 217At
are short enough so secular equilibrium with 225Ac is ensured]
u(R ) = Standard uncertainty of net count rate for 226Ra, in cpm
22°Ra
99^
= Net count rate for Ra, in (cpm)
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
time has elapsed a fresh 225Ra tracer solution may be generated by dissolving the
precipitate with 40 mL of 0.5M HNCb and repeating Steps A4.4 through A4.10 of
this Appendix.
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