www.epa.gov
April 2014
EPA 402-R14-001
Revision 0
Rapid Radiochemical Method for
Total Radiostrontium (Sr-90) 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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Total Radiostrontium ( Sr) in Water: Rapid Method for High-Activity Samples
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 TOTAL RADIOSTRONTIUM (SR-90)
IN BUILDING MATERIALS
FOR ENVIRONMENTAL REMEDIATION FOLLOWING RADIOLOGICAL INCIDENTS
1. Scope and Application
1.1. The method will be applicable to samples where the source of the contamination is
either from known or unknown origins. The method provides a very rapid screen for
total radiostrontium (89Sr + 90Sr) in building materials samples.
1.2. This method is specific for beta-emitting isotopes of strontium in building materials
such as concrete and brick. It uses rapid digestion and precipitation steps to
preconcentrate strontium isotopes, followed by final purification using Sr Resin (see
footnote 1 on next page) to remove interferences.
1.3. This method uses rapid radiochemical separations techniques for the determination of
beta-emitting strontium radioisotopes in concrete or brick samples following a
nuclear or radiological incident.
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1.4. The method is capable of satisfying a required method uncertainty for Sr (total as
90Sr) of 0.31 pCi/g at an analytical action level of 2.4 pCi/g. To attain the stated
measurement quality objectives (MQOs) (see Step 9.2), a sample weight of 1.5 g and
a count time of approximately 1.5 hours are recommended. The sample turnaround
time and throughput may vary based on additional project MQOs, the time for
analysis of the final counting form, and initial sample volume. The method must be
validated prior to use following the protocols provided in Method Validation Guide
for Qualifying Methods Used by Radiological Laboratories Participating in Incident
Response Activities (Reference 16.1).
1.5. This method is intended to be used for building materials. The rapid 90Sr 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 (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. Strontium is collected and purified from the building materials sample matrix using
sodium hydroxide fusion (Reference 16.3) and purified from potentially interfering
radionuclides and matrix constituents using a strontium-specific, rapid chemical
separation method. The sample is equilibrated with strontium carrier, and
preconcentrated by Sr/CaCOs coprecipitation from the alkaline fusion matrix. The
carbonate precipitate is dissolved in HC1 and strontium is precipitated with calcium
fluoride to remove silicates. The precipitate is dissolved in strong nitric acid and the
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
solution is passed through a Sr Resin extraction chromatography column1 that
selectively retains strontium while allowing most interfering radionuclides and matrix
constituents to pass through to waste. If present in the sample, residual plutonium and
several interfering tetravalent radionuclides are stripped from the column using an
oxalic/nitric acid rinse. Strontium is eluted from the column with 0.05M HNCb and
taken to dryness in a tared, stainless steel planchet. The planchet containing the
strontium nitrate precipitate is weighed to determine the strontium yield.
2.2. The sample test source is promptly counted on a gas flow proportional counter to
determine the beta emission rate, which is used to calculate the total radiostrontium
activity.
2.2.1. The same prepared sample test source can be recounted after -10 days to
XQ QO
attempt to differentiate Sr from Sr. If the initial and second counts agree
(based on the expected ingrowth of 90Y), this is an indication that 89Sr is not
present in significant amounts relative to 90Sr (within the uncertainty of the
measurement).
2.2.2. Computational methods are available for resolving the concentration of 89Sr
and 9 Sr from two sequential counts of the sample. An example of an
approach that has been used successfully at a number of laboratories is
presented in Appendix B to this method. It is the responsibility of the
laboratory, however, to validate this approach prior to its use.
2.2.3. It is also possible to determine 89Sr more rapidly using Cerenkov counting if
significant amounts of 89Sr are suspected; this method must be validated
independently. The minimum detectable activity (MDA) levels with
Cerenkov counting, however, will be higher than of determination with gas
proportional counting and may or may not meet measurement quality
objectives.
3. Definitions, Abbreviations, and Acronyms
3.1. Analytical Protocol Specification (APS). The output of a directed planning process
that contains the project's analytical data needs and requirements in an organized,
concise form.
3.2. Analytical Action Level (AAL). The term analytical action level is used to denote the
value of a quantity that will cause the decision-maker 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 (um range).
1 Sr-Resin™ is a proprietary extraction chromatography resin consisting of octanol solution of 4,4'(5')-bis (t-butyl-
cyclohexanol)-18-crown-6-sorbed on an inert polymeric support. The resin can be employed in a traditional
chromatography column configuration (gravity or vacuum) or in a flow cartridge configuration designed for use
with vacuum box technology. Sr-Resin™ is available from Eichrom Technologies, Lisle, IL. Throughout the
remainder of the method, the terms Sr-Resin or Sr-cartridge will be used for Sr-Resin.™
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
3.4. Laboratory Control Sample (LCS). A standard material of known composition or an
artificial sample (created by fortification of a clean material similar in nature to the
sample), which is prepared and analyzed in the same manner as the sample. In an
ideal situation, the result of an analysis of the laboratory control sample should be
equivalent to (give 100 percent of) the target analyte concentration or activity known
to be present in the fortified sample or standard material. The result normally is
expressed as percent recovery.
3.5. Matrix Spike (MS). An aliquant of a sample prepared by adding a known quantity of
target analytes to specified amount of matrix and subjected to the entire analytical
procedure to establish if the method or procedure is appropriate for the analysis of the
particular matrix.
3.6. Multi-Agency Radiological Analytical Laboratory Protocols (MARLAP) Manual
provides guidance for the planning, implementation, and assessment phases of those
projects that require the laboratory analysis of radionuclides (Reference 16.2).
3.7. Measurement Quality Objective (MQO). MQOs are the analytical data requirements
of the data quality objectives and are project- or program-specific. They can be
quantitative or qualitative. MQOs serve as measurement performance criteria or
objectives of the analytical process.
3.8. 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.
3.9. Required Method Uncertainty (WMR). The required method uncertainty is a target value
for the individual measurement uncertainties and is an estimate of uncertainty (of
measurement) before the sample is actually measured. The required method
uncertainty is applicable below an AAL.
3.10. Relative Required Method Uncertainty (
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
4.1.1. Count results should be monitored for detectable alpha activity and
appropriate corrective actions taken when observed. Failure to address the
presence of alpha emitters in the sample test source may lead to high result
bias due to alpha-to-beta crosstalk.
Elevated levels of radioisotopes of tetravalent plutonium, neptunium,
cerium, and ruthenium in the sample may hold up on the column and co-
elute with strontium. The method employs an oxalic acid rinse that should
address low to moderate levels of these interferences in samples.
The resin has a higher affinity for polonium than strontium at low nitric acid
concentrations but only minimal retention in 8M HNCb.
If there were any residual Po (IV) retained, it would likely be removed using
the 3M HNOs-O.OSM oxalic acid rinse
4. 1 .2. Significant levels of 89Sr in the sample will interfere with the total
radiostrontium analysis.
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4.1.2.1. The absence of higher activities of interfering Sr may be
detected by counting the sample test source quickly after initial
separation (minimizing ingrowth of 90Y), and then recounting the
sample test source after 1-21 days to verify that the calculated
activity (based on the expected ingrowth of 90Y) does not change
significantly. The presence of only 89Sr may be indicated when
the calculated activity of the second count is less than that of the
first count by an amount greater than that which can be attributed
to statistical variation in the two analyses. However, the second
OQ
count activity is a complex function of the amount of the Sr
on on
present, the ingrowth of the Y from Sr and the time between
the first and second counts.
4. 1 .2.2. Alternatively, Appendix B provides a numerical approach for the
isotopic determination 89Sr and 90Sr from two sequential counts
of the sample, one immediately following separation, and one
on °>Q
after a delay to allow for ingrowth of Y and decay of Sr.
910
4.1.3. High levels of Pb may interfere with low-level strontium analysis due to
910
ingrowth of short-lived Bi during chemical separations, where Pb is
retained by Sr Resin but is not eluted. If 210Pb is known to be present in
samples, minimizing the time between the final rinse and the elution of
strontium to less than 15 minutes will maintain levels of interfering 210Bi to
910 ___
less than 0.1% of the Pb activity present. The presence or absence of
interfering 210Bi may be determined by recounting the sample test source to
verify the half-life of the nuclide present. Bi-214 also can grow in during the
elution step if 214Pb (half life-26.8 minutes) makes it to the Sr Resin. In this
case, holding the samples until the 214Bi decays (~2 hours) may be
advisable.
99/1 919
™, /
4. 1 .4. High levels of Th or its decay progeny Ra and Pb may interfere with
low-level strontium determinations due to ingrowth of short-lived decay
products during chemical separations. Monitoring count data for alpha
activity may provide indications of interferences. Minimizing the time
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
between the final rinse and the elution of strontium from the column to 5
minutes should maintain levels of interfering 212Pb and 208T1 to less than 2%
of the parent nuclide activity. The presence or absence of 212Pb may be
determined by recounting the sample test source to verify the half-life of the
nuclide present.
4.1.5. Levels of radioactive cesium or cobalt in excess of approximately 103 times
the activity of strontium being measured may not be completely removed
and may interfere with final results. Column rinsing to remove interferences
may be increased to minimize interference if high levels of cesium or cobalt
are known to be present. Changing cartridge connector tips and/or column
reservoirs prior to final elution of strontium from Sr Resin can facilitate
removal of sample matrix interferences. It may also be possible to increase
the nitric acid in the eluted Sr fraction to 8M HNCb and reprocess the
sample through the column separation method again.
4.2. Non-Radiological
4.2.1. Stable strontium present in the concrete, brick or other solid sample at levels
that are significant relative to the stable Sr carrier added will increase the
apparent gravimetric yield and cause a negative bias in the final results. If
the quantity of native strontium in the sample aliquant exceeds -5% of the
expected strontium carrier mass, chemical yield measurements will be
affected unless the native strontium is accounted for in the yield
calculations.
4.2.2. The native strontium content in the sample may be determined by an
independent spectrometric measurement (such as inductively coupled
plasma - atomic emission spectroscopy [ICP-AES], etc.) or by taking an
aliquant and processing the sample without the addition of strontium carrier
to obtain an estimate of the native strontium content of the sample.
4.2.3. Sr Resin has a greater affinity for lead than for strontium. Lead will
quantitatively displace strontium from the column when the two are present
in combined amounts approaching or exceeding the capacity of the column.
If the combined quantity of lead and strontium carrier in the sample exceeds
the capacity of the column, decreased strontium yields will be observed.
High lead levels are not typically seen in concrete samples. However,
decreasing the sample size will help address samples with elevated levels of
lead.
4.2.4. High levels of calcium, barium or potassium may compete slightly with
strontium for uptake on the resin, possibly leading to low chemical yield. If
these interfering matrix constituents are present in the final sample test
source, yield results will overestimate the true strontium yield and cause a
low result bias.
4.2.5. Rinsing Sr Resin with 8M HNCb minimizes retention of Ba, K ions which
have more retention at lower nitric acid levels to optimize removal of
interferences.
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
4.2.6. The final solids on the planchets containing strontium nitrate should be
white to very light brown. A significant brown color could indicate
formation of iron oxide solids from the stainless steel planchets. This can
cause a positive bias in the gravimetric chemical yields. Annealing the
planchets properly minimizes the formation of iron oxide solids (Step 6.8).
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,
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 potential for cross contamination.
5.3. Procedure-Specific Non-Radiological Hazards
None noted.
6. Equipment and supplies
6.1. Analytical balance with 10^ g readability or better.
6.2. Centrifuge able to accommodate 225 mL and 50 mL centrifuge tubes.
6.3. Centrifuge tubes, 50 mL and 225 mL.
6.4. Hot plate.
6.5. Low-background gas flow proportional counter.
6.6. 100 uL, 200 uL, 500 uL and 1 mL pipets or equivalent and appropriate plastic tips.
6.7. 1-10 mL electronic pipet.
6.8. Stainless steel planchets or other sample mounts: ~2-inch diameter, annealed at 530-
550 °C or higher in a furnace for -3.5 to 4 hours with a volume of ~5 mL. Planchets
annealed properly will typically have a bronze/brown color. Do not overheat or this
will make the planchets more susceptible to acid degradation and iron oxide
formation.
6.9. 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.
6.10. Tips, yellow outer, Eichrom part number AC-1000-OT, or equivalent.
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
6.11. Vacuum box, such as Eichrom part number AC-24-BOX, or equivalent.
6.12. Vacuum pump or laboratory vacuum system.
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 16.5). All solutions used in microprecipitation should be prepared with water
filtered through a 0.45 um (or better) filter.
7.1. Type I reagent water as defined in ASTM Standard Dl 193 (Reference 16.5).
7.2. Aluminum nitrate (A1(NO3)3' 9H2O)
7.2.1. Aluminum nitrate solution, 2M (A1(NO3)3): Add 750 g of aluminum nitrate
(A1(NO3)3' 9H2O) to -700 mL of water and dilute to 1 L with water.
7.3. Ethanol, reagent 95% (C2HsOH), available commercially.
7.4. Nitric Acid, HNO3 (15.8M), concentrated, available commercially.
7.4.1. Nitric acid (8M): Add 506 mL of concentrated HNO3 to 400 mL of water
and dilute to 1 L with water.
7.4.2. Nitric acid (3M): Add 190 mL of concentrated HNO3 to 800 mL of water
and dilute to 1 L with water.
7.4.3. Nitric acid (0.1M): Add 6.4 mL of concentrated HNO3 to 900 mL water.
Dilute to 1 L with water.
7.4.4. Nitric acid (0.05M): Add 3.2 mL of concentrated HNO3 to 900 mL water.
Dilute to 1 L with water.
7.5. Nitric acid (3M)/oxalic acid solution (0.05M): Add 190 mL of concentrated HNO3
(7.3) and 6.3 g of oxalic acid dihydrate (C2H2O4 2H2O), to 800 mL of demineralized
water and dilute to 1 L with de-ionized water.
7.6. Sr Resin columns, -1.00 g resin, 3 mL, small particle size (50-100 um), in
appropriately sized column or stacked 2 mL+ 1 mL pre-packed cartridges. (Available
from Eichrom Technologies, Inc., Lisle IL.)
7.7. Strontium carrier solution, 7 mg/mL in 0.1M HNO3, traceable to a national standards
body such as NIST or standardized at the laboratory by comparison to independent
standards.
7.7.1. Option 1: Dilute elemental strontium standard to a concentration of 7.00
mg/mL (or mg/g) in 0.1 M HNO3. Verify per Step 7.7.3.
7.7.2. Option 2: To -200 mL de-ionized water, add 6.3 mL HNO3 and
approximately 16.90 g of strontium nitrate (Sr(NO3)2 dried to constant mass
and the mass being determined to at least 0.001 g). Dilute to 1000 mL with
water. Calculate the amount of strontium nitrate/mL actually present and
verify per Step 7.7.3.
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7.7.3. Prior to use, verify the strontium carrier solution concentration by
transferring at least five 1.00-mL portions of the carrier to tared stainless
steel planchets. Evaporate to dryness on a medium heat on a hotplate using
the same technique as that used for samples (Ex. Heat 5 minutes after
dryness is reached to ensure complete dryness). Allow to cool and weigh as
the nitrate to the nearest 0.1 mg. The relative standard deviation for
replicates should be less than 5% and the average residue mass within 5% of
the expected value.
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7.8. Sr standard solution (carrier free), traceable to a national standards body such as
NIST, in 0.5M HNO3 solution.
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 fused using the
procedure Rapid Method for Sodium Hydroxide Fusion of Concrete and
Brick Matrices Prior to Americium, Plutonium, Strontium, Radium, and
Uranium Analyses (Reference 16.3). If analyte-free blank material is not
available and an empty crucible is used to generate a reagent blank sample,
it is recommended thatlOO mg calcium be added as calcium nitrate to the
empty crucible as blank simulant. This facilitates strontium 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
strontium in the sample, may compromise chemical yield measurements, or
overall data quality.
9.2. This method is capable of achieving a WMR of 0.31 pCi/g at or below an action level of
2.4 pCi/g. This may be adjusted if the event-specific MQOs are different.
9.3. This method is capable of achieving a required relative method uncertainty, (pMR, 13%
above 2.4 pCi/g. This may be adjusted if the event-specific MQOs are different.
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
9.4. This method is capable of achieving a required minimum detectable concentration
(MDC)of0.41 pCi/g.
10. Calibration and Standardization
10.1. The effective detection efficiency for total radiostrontium (referenced to 90Sr) is
calculated as the weighted sum of the 90Sr and 90Y efficiencies that reflects the
relative proportions of 90Y and 90Sr based on the 90Y ingrowth after 90Sr separation.
10.2. Set up, operate, and perform quality control for gas-flow proportional counters (GPC)
in accordance with the laboratory's quality manual and standard operating
procedures, and consistent with ASTM Standard Practice D7282, Sections 7-13
(Reference 16.4).
on
10.3. See Appendix A for details on calibration/standardization of the GPC specific to Sr
and 90Y.
11. Procedure
11.1. Initial Sample Preparation for 89Sr + 90Sr
11.1.1. 89'90Sr may be preconcentrated from building material samples using the
separate procedure (Reference 16.3), which fuses the samples using rapid
NaOH fusion followed by carbonate and fluoride precipitations to
QQ Q(-\
preconcentrate ' Sr from the hydroxide matrix.
NOTE: The fusion procedure provides a column load solution for each sample
(consisting of 20 mL of 8M HNOs-O.SM Al(NOs)3), ready for column separation on Sr
Resin.
11.1.2. This separation can be used with other solid sample matrices if the initial
sample preparation steps result in a column load solution containing ~8M
HNO3- 0.5M A1(NO3)3 is used.
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.
11.2. Rapid Sr Separation using Sr Resin
11.2.1. Set up vacuum box
11.2.1.1. Place the inner tube rack (supplied with vacuum box) into the
vacuum box with the centrifuge tubes in the rack. Place the lid
onto the vacuum box system.
11.2.1.2. Place the yellow outer tips into all 24 openings of the lid of the
vacuum box. Fit in the inner white tip into each yellow tip.
11.2.1.3. For each sample solution, place the Sr Resin cartridges (2 mL+1
mL cartridges) on to the inner white tip.
11.2.1.4. Place reservoirs on the top end of the Sr Resin cartridge.
11.2.1.5. Turn the vacuum on (building vacuum or pump) 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.
11.2.1.6. Add 5 mL of 8M HNCb to the column reservoir to precondition
the Sr Resin cartridges.
11.2.1.7. Adjust the vacuum to achieve a flow-rate of ~1 mL/min.
NOTE: Unless otherwise specified in the procedure, use a flow rate of ~ 1
mL/min for load and strip solutions and ~ 2-3 mL/min for rinse solutions.
11.2.2. Sr Resin Separation
11.2.2.1. Transfer each sample solution from the fusion procedure
(Reference 16.3) into the appropriate reservoir. Allow solution to
pass through the Sr Resin cartridge at a flow rate of ~1 mL/min.
11.2.2.2. Add 5 mL of 8M HNO3 to each beaker/tube (from Step 11.2.2.1)
as a rinse and transfer each solution into the appropriate reservoir
(the flow rate can be adjusted to ~2 mL/min).
11.2.2.3. Add 15 mL of 8M HNOs into each reservoir as second column
rinse (flow rate -3-4 mL/min).
11.2.2.4. Turn off vacuum and discard rinse solutions.
11.2.2.5. Add- 5 mL 3M HNO3 - 0.05M oxalic acid solution to each
column (flow rate -1-2 mL/min).
11.2.2.6. Add 5 mL of 8M HNCb into each reservoir as second column
rinse (flow rate -3 mL/min).
11.2.2.7'. Discard column rinses.
11.2.2.8. Record time and date of the end of last rinse to the nearest 15
minutes as t\, "time of strontium separation."
11.2.2.9. Place clean 50 mL centrifuge tubes beneath the columns to catch
the strontium eluate before proceeding to the next step.
11.2.2.10. Elute strontium from the columns by adding 15 mL of 0.05M
HNO3 at~l mL/min.
11.2.2.11. Discard Sr Resin cartridges.
11.2.3. Preparation of the STS and determination of chemical yield
11.2.3.1. Clean and label a stainless steel planchet for each STS.
11.2.3.2. Weigh and record the tare mass of each planchet to the nearest
0.1 mg.
Transfer the strontium eluate from Step 11.2.2.10 to the planchet
and take to dryness on a hotplate (medium heat) to produce a
uniformly distributed residue across the bottom of the planchet.
NOTE: A few mL at a time typically is added to the planchet during
evaporation. Do not evaporate all the way to dryness to prevent
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splattering. After adding all 15 mL, take the planchet all the way to
dryness.
11.2.3.4. Rinse tubes with ~ 2 mL 0.05M HNO3 and add to the planchet.
11.2.3.5. Heat on hot plate for -5-10 minutes after initial dryness is
reached.
11.2.3.6. Allow planchets to cool.
11.2.3.7. Weigh and record the gross mass of each planchet to the nearest
0.1 mg.
NOTE: If gravimetric yields are unusually high with the possibility of
moisture present, additional heating and reweighing should be
performed.
11.2.3.8. Calculate the chemical yield as presented in Step 12 of this
method.
11.3. Counting the Sample Test Source
11.3.1. On a calibrated gas-flow proportional detector that has passed all required
daily performance and background checks, count the STS for a period as
needed to satisfy MQOs.
11.3.1.1. If the presence of 89Sr cannot be excluded, and total
radiostrontium is being determined as a screen for the presence
OQ Qf\
of Sr or Sr, count the STS as soon as practicable after
QH
preparation to minimize the ingrowth of Y into the STS.
OQ
11.3.1.2. If the presence of Sr can be excluded, total radiostrontium will
on
provide isotopic Sr results and the STS may be counted at any
time after preparation (taking into account the appropriate
on
increase in activity due to Y ingrowth).
on
11.3.2. Calculate the total radiostrontium ( Sr) sample results using calculations
presented in Step 12.
11.3.3. Hold planchets for recounting as needed.
12. Data Analysis and Calculations
12.1. Calculation of Total Radiostrontium
on
12.1.1. When a sample is analyzed for total radiostrontium (equivalent Sr), the
effective efficiency is calculated as follows:
^Total Sr = SSr9Q + " ~ Q ^ 2 ' JX ^¥90 (1)
where
£iotai sr = effective detection efficiency for total radiostrontium
on
referenced to Sr
on
£sr90 = final Sr detection efficiency
QO
= final Y detection efficiency
= decay constant for 90Y, 3.005x 10~6 seconds (s)"1
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t\ = date and time of the Sr/Y separation (s)
t2 = date and time of the midpoint of the count (s)
NOTE: The elapsed time between the sample count and the reference date must be
calculated using the same time units as the decay constant.
12. 1 .2. The standard uncertainty of the effective efficiency is calculated as follows:
9°(^
(2)
where
NOTE: The terms M(£Sr9o» £y9o) and r(sSr90, sV90) are derived during calibrations as
shown in Appendix A, Step A4.
90 c
12.1.3. The total radiostrontium activity concentration (/4Cr0tai sr) equivalent to Sr
is calculated as follows:
R3 ~Rb m
Total Sr ^> ^> ^> iT TTr T^T^ \ '
AC
222xsTot3lSlxYxWxDF
where
and where
sr
7
W
DF
t\
beta gross count rate for the sample (counts per minute
[cpm])
beta background count rate (cpm)
effective efficiency of the detector for total strontium
referenced to 90Sr
fractional chemical yield for strontium
weight of the sample aliquant (g)
correction factor for decay of the sample from its
reference date until the midpoint of the total strontium
count
decay constant for 90Sr, 7.642xlO~10 s"1
reference date and time for the sample (s)
date and time of the Sr/Y separation (s)
NOTE: The elapsed time between the sample count and the reference date must be
calculated using the same time units as the decay constant
12. 1 .4. The standard counting uncertainty of the total radiostrontium activity
concentration, ucc(ACi0\a\ sr) is calculated as follows:
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K
2.22xsToi3lSixYxWxDF
(4)
where:
4 = Duration of the sample count (min)
tb = Duration of the background subtraction count (min)
12.1.5. The combined standard uncertainty (CSU) for the total radiostrontium
activity concentration, uc(ACi0\z\ sr), is calculated as follows:
f ..2.
Mc (^Qbtal Sr ) - 1 McC (^Qbtal Sr ) + ^Qbtal Sr
where:
Total Sr
Y2
(5)
w(Y) = standard uncertainty of fractional chemical yield for strontium
w(W) = standard uncertainty of the weight of the sample aliquant (g)
12.1.6. 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:2
0.4x —-1 +0.677x
^ +1.645x l(Rbtb+OA)x^x 1 + ^
tb} V tb {_ tb ^
ts x 2.22 x £Total Sr x Y x F x DF
(6)
MDC =
2.71x
+3.29
2.22x£Ttls xYxWxDF
i oiai or
(7)
12.2. Chemical Yield for Strontium
12.2. 1 . Calculate the chemical yield for strontium using the gravimetric data
collected in Step 11.2.3:
_ m^
ceVe+cnW
where:
Y = strontium yield, expressed as a fraction
TOS = mass of Sr(NO3)2 recovered from the sample (mg)
^sr(No3)2 = gravimetric factor for strontium weighed as the nitrate,
0.414
(8)
2 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 assume a = 0.05, ft = 0.05 (with z\-a = ZJ_P = 1.645), and d = 0.4.
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cc = Sr mass concentration in the strontium carrier solution
(mg/mL)
Fc = volume of strontium carrier added to the sample (mL)
cn = Sr mass concentration native to the sample - if
determined (mg/g)
W = weight of sample aliquant (g)
12.2.2. Calculate the standard uncertainty of the yield as follows:
standard uncertainty of the quantity in parentheses,
relative standard uncertainty of the quantity in parentheses.
12.3. Results Reporting
12.3.1. Unless otherwise specified in the APS, the following items should be
reported for each result:
12.3.1.1. Result for total radiostrontium in scientific notation ±1 combined
standard uncertainty.
12.3.1.2. Weight of sample aliquant and any dilutions used.
12.3.1.3. Yield of tracer and its uncertainty.
12.3.1.4. Case narrative.
13. Method Performance
13.1. Results of method validation performance are to be archived and available for
reporting purposes.
13.2. Expected turnaround time per sample or per batch (See Step 17.5 for typical
processing times (assumes samples are not from ROD).
13.2.1. Preparation and chemical separations for a batch of 20 samples can be
performed by using a vacuum box system (24 ports each) simultaneously,
assuming 24 detectors are available. For an analysis of a 1-g sample
aliquant, sample preparation and digestion should take -2.5 h.
13.2.2. Purification and separation of the strontium fraction using cartridges and
vacuum box system should take -2.5 h.
13.2.3. Sample test source preparation takes -1.5 h.
13.2.4. A 60-90-minute counting time is sufficient to meet the MQO in Step 9.2,
assuming 1.5-g aliquant, a background of 1 cpm, detector efficiency of 0.4-
0.5, and radiochemical yield of at least 0.5.
13.3. Total radiostrontium (89Sr+90Sr) data reduction should be achievable between 5 and
8.5 hours after the beginning of the analysis, depending on batch size and count time.
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13.4. The sample may be recounted following a delay of 10-21 days to differentiate the
QQ (V\ Q(-\
Sr and Sr activities. If the source contains pure Sr, the total radiostrontium
activity calculated from the two counts should agree within the uncertainty of the
measurements. Minimizing the time between the chemical separation of Sr and the
initial count, longer count times, and increasing the delay between the two counts,
will minimize the overall uncertainty of the data and provide more sensitive and
reliable measures of the radiochemical purity of the STS.
NOTE: The 89Sr and 90Sr may be determined from two consecutive counts of the source -
calculations are presented in Appendix B. This approach must be validated prior to use.
14. Pollution Prevention
14.1. The use of Sr Resin reduces the amount of acids and hazardous metals that would
otherwise be needed to co-precipitate and purify the sample and prepare the final
counting form.
15. Waste Management
15.1. Nitric acid and hydrochloric acid wastes should be neutralized before disposal and
then disposed in accordance with prevailing laboratory, local, state and federal
requirements.
15.2. Final precipitated materials may contain radiostrontium and should be treated as
radioactive waste and disposed in accordance with the restrictions provided in the
facility's radioactive materials license and any prevailing local restrictions.
15.3. Used resins and columns should be considered radioactive waste and disposed of in
accordance with restriction provided in the facility's radioactive materials license and
any prevailing local restrictions.
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.
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 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.
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
16.5. ASTM Dl 193, "Standard Specification for Reagent Water," ASTM Book of
Standards 11.02, current version, ASTM International, West Conshohocken, PA.
Other References
16.6. Maxwell, S. 2006. "Rapid Column Extraction Method for Actinides and 89/90Sr in
Water Samples,"/. RadioanalyticalandNuclear Chemistry. 267(3): 537-543.
16.7. Maxwell, S., Culligan, B. and Noyes, G. 2010. Rapid method for actinides in
emergency soil samples, Radiochimica Ada. 98(12): 793-800.
16.8. Maxwell, S., Culligan, B., Kelsey-Wall, A. and Shaw, P. 2011. "Rapid
Radiochemical Method for Actinides in Emergency Concrete and Brick Samples,"
AnalyticaChimicaActa. 701(1): 112-8.
16.9. SR-04, "Radiochemical Determination of Radiostrontium in Water, Sea Water, and
Other Aqueous Media," Eastern Environmental Radiation Facility (EERF)
Radiochemistry Procedures Manual, Montgomery, AL, EPA 520/5-84-006 (August
1984).
16.10. SRW04-11, "Strontium 89, 90 in Water," Eichrom Technologies, Inc., Lisle, Illinois
(February 2003).
16.11. Nuclear data from NUDAT 2.3 and the National Nuclear Data Center at Brookhaven
National Laboratory; available at: www.nndc.bnl.gov/nudat2/indx dec.jsp, database
version of 6/30/2009.
16.12. 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.
16.13. 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.
16.14. 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.
16.15. 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.
16.16. 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.
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
17. Tables, Diagrams, Flow Charts and Validation Data
17.1. Validation Data
This section intentionally left blank.
17.2. Nuclide Decay and Radiation Data
Table 17.2 - Decay and Radiation Data
Nuclide
90Sr
90y
89Sr
Half-life
(days)
1.052E+04
2.6667
50.53
X
(s-1)
7.642xlO"10
3.005xlO"6
1.587X10'7
Abundance
1.00
1.00
1.00
Pmax
(MeV[11)
0.546
2.280
1.495
Pavg
(MeV)
0.196
0.934
0.585
[1] MeV - mega electron volts
17.3. Ingrowth and Decay Curves and Factors
In-Growth Curve for 90Y in 90Sr
200 300 400 500
Time Elapsed After Sr-90 Separation (h)
^^^»Y'-SO Sr-90- • • Beta Activity
000
700
Total Beta Activity Ingrowth Factors for 90Y in 90Sr
Ingrowth time elapsed (hours)
Factor
Ingrowth time elapsed (hours)
Factor
0.25
0.003
144
0.790
2
0.021
192
0.875
4
0.042
240
0.926
12
0.122
320
0.969
24
0.229
400
0.987
48
0.405
480
0.994
72
0.541
560
0.998
96
0.646
640
0.999
Factor = (90 Y activity/90Sr activity at zero hours of ingrowth)
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Rapid Radiochemical Method for Total Radiostrontium ( Sr) in Building Materials
o 0.5-
89 £
Decay Curve for Sr
100 200 300 400
Time Elapsed since collection (h)
— Sr-89 Activity
500
600
700
89 c
Decay Factors for avSr
Decay time elapsed (hours)
Factor
Decay time elapsed (hours)
Factor
0.25
1.000
144
0.921
2
0.999
192
0.896
4
0.998
240
0.872
12
0.993
320
0.833
24
0.986
400
0.796
48
0.973
480
0.760
72
0.960
560
0.726
96
0.947
640
0.694
Factor = (89Sr activity/89Sr activity at zero hours of ingrowth)
17.4. Decay Schemes for 89Sr and 90Sr
89Sr and 90Sr Decay Scheme
= l.l5MeV
= 50.53 d
f«=2.67 d
p = 0.55 MeV
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17.5. Process Flow with Typical Processing Times
Separation Scheme and Timeline for Determination of
Strontium Isotopes in Building Materials Samples
Discard load and
rinse solutions
(Step 11.2.2.7)
Discard Sr Resin
(Step 11.2.2.11)
Rapid Fusion (See Separate Procedure)
1. Add Sr carrier and fuse with NaOH
2. Ca carbonate and Ca fluoride precipitations
3. Dissolve in nitric acid and aluminum nitrate (column
load solution)
Vacuum Box Setup (Step 11.2.1.3)
1. Place Sr cartridges (2mL+1mL) on box
2. Condition columns with 5mL 8M HNO3@1 mL/min
v
Load Sample to Sr Resin Cartridges (Step 11.2.2.1)
1. Load sample @1 mL/min
2. Beaker/tube rinse: 5mL 8M HNO3 @ ~2 mL/min
3. Column rinse: 15 mL 8M HNO3 @ 3^ mL/min
4. Column rinse: 5 mL 3M HNO3-0.05 oxalic acid @ 1-2
mL/min
5. Column rinse: 5 mL 8M HNO3 @ ~3 mL/min
v
EluteSrfrom Resin (Step 11.2.2.10)
1. Add 15mL0.0.05M HNO3 @ 1 mL/min
2. Remove tubes for planchet mounting
v
Planchet Mounting (Step 11.2.3.3)
1. Add Sr eluate to planchet on hot plate, drying to low
volume, and adding more eluate
2. Rinse tubes with ~2 mL 0.0.05M HNO3 and add to
planchet
3. Heat to dryness on hotplate
4. Cool and weigh planchets
v
Count sample test source (STS)
by gas proportional counting as
needed (Step 11.3)
Elapsed Time
21/2 hours
23/4 hours
41/4 hours
5 hours
61/2 hours
71/2-81/2 hours
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Total Radiostrontium ( Sr) in Building Material Samples: Rapid Method for High-Activity Samples
Appendix A:
Method and Calculations for Detector Calibration
on
Al. The effective detection efficiency for total radiostrontium (referenced to Sr) is calculated
on on
as the weighted sum of the Sr and Y efficiencies that reflects the relative proportions of
90Y and 90Sr based on the 90Y ingrowth after strontium separation.
NOTE: While 89Sr efficiency calibration is not needed unless 89Sr analysis will be performed,
instructions for preparation are provided to support the two count approach should this option be
desired.
ALL Due to the low mass of carrier used for this method, self-absorption effects may be
assumed to be constant. Calibrate each detector used to count samples according to
ASTM Standard Practice D7282, Section 16, "Single Point Efficiency or Constant
Test Mass for a Specific Radionuclide" and the instructions below.
Al .2. Prepare a blank and at least three working calibration sources (WCS) for 90Sr and
90Y, and 89Sr (if needed) as follows:
on RQ
Al .2.1. The Sr and Sr radioactive standard solutions used to prepare WCSs
shall be traceable to a national standards body such as NIST and shall
originate from a standards supplier (or lot) different from standards used
for calibration verification and batch quality controls. The standards
should be diluted in nitric acid.
Al.2.2. The planchets used for the sources shall be of the same size, materials and
type as those used for the analysis of STSs.
Al.2.3. Preparation of 89Sr WCSs (if needed): 89Sr standard solution (in 0.5M
HNOs) is evaporated to dryness in a stainless steel planchet as follows:
OQ
Al.2.3.1. For each Sr WCS to be prepared, and for the associated
blank, add strontium carrier to 15 mL of 0.05M HNOs in a
disposable 50 mL centrifuge tube. The amount of carrier
should be adjusted to approximate the amount expected to be
recovered from routine samples.
NOTES:
If the average recovery has not been determined, the laboratory may
assume 85% chemical yield for determining the amount of carrier to
use in Step Al.2.3.1.
If the 89Sr standard contains residual chloride, it will attack the surface
of the planchet and compromise the quality of the calibration standard.
In such cases, convert the aliquant of standard solution to a nitrate
system by adding 1 mL concentrated HNOs and taking to dryness 2
times prior to quantitatively transferring the solution to the planchet.
Al.2.3.2. For each WCS, add a precisely known amount of traceable 89Sr
solution to a 50 mL centrifuge tube. Sufficient activity must be
present at the point of the count to permit accumulation of
greater than 10,000 net counts in a counting period deemed to
be reasonable by the laboratory. The minimum activity used,
however, should produce WCS count rates at least 20 times the
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background signal but not greater than 5000 counts per second
(cps).
Al .2.3.3. Mix the solution and quantitatively transfer each WCS and the
blank to respective clean stainless steel counting planchets
using three rinses of 0.05M FDSTCb.
Al .2.3 .4. Evaporate to dryness using the same techniques used for
sample test sources.
on
Al.2.3.5. For each detector to be calibrated, count three Sr WCSs for
sufficient time to accumulate at least 10,000 net counts.
Al .3 . Preparation of 90Sr and 90Y WCSs: Separate WCSs for 90Sr and 90Y are prepared by
chemically separating 90Y from a standard solution of 90Sr.
Al .3 . 1 . For each 90Sr WCS to be prepared, and for the associated blank, add 1 mL
of 7 mg/mL strontium carrier to a disposable 50-mL centrifuge tube
containing 10 mL 8M FINOs. The amount of carrier added should
correspond to that expected to be recovered from a routine sample.
Note: If the average recovery has not been determined, the laboratory may assume
85% chemical yield for determining the amount of carrier to use for Step Al.3.1.
3M HNO3 may be used instead of 8M HNO3, however Sr yields may be slightly less.
on on
Al.3.2. For each Sr WCS, add a precisely known amount of traceable Sr
solution to a 50-mL centrifuge tube containing 10 mL of 8M
Sufficient activity should be present at the point of the count to permit
accumulation of greater than 10,000 90Sr and 10,000 90Y net counts in the
respective sources in a counting period deemed to be reasonable by the
laboratory. The minimum activity used, however should produce WCS
count rates at least 20 times the background signal but not greater than
5000 cps.
Al.3.3. Set up one (2+lmL)Sr Resin column for each 90Sr WCS and for the
associated blank. Condition each column with 5 mL of 8M FDSTCb.
Column effluents are discarded to waste.
Al .3 .4. Place a clean centrifuge tube under each column to catch all combined 90Y
effluents.
Note: Unless otherwise specified in the procedure, use a flow rate of ~ 1 mL/min for
load and strip solutions and ~ 3 mL/min for rinse solutions.
Al.3.5. Load the 90Sr solution onto the column at 1 drop/second or less (~1
on
mL/min). The load solution effluent containing Y is retained.
Al .3 .6. Rinse the centrifuge tube with three successive 2-mL portions of 8M
FINOs adding each of the rinses to the column after the previous rinse has
___ on
reached the upper surface of the resin. These effluents also contain Y
and are retained.
A 1.3. 7. Rinse the column with 10 mL of 8M FESTOs and retain the column
effluents containing 90Y. Record the date and time that the final rinse
solution leaves the column to the nearest 5 minutes as t\, "Time of 90Y
on
Separation." Remove the centrifuge tube that has the combined Y
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effluents. Place a clean tube under the column to catch the strontium
eluate in subsequent steps.
NOTE: From this point, 90Sr must be eluted, and the 90Sr WCS must be prepared
and counted as expeditiously as possible to minimize 90Y ingrowth and necessary
corrections to the efficiency. Counting of the 90Sr WCS should be completed, if
possible, within 3-5 hours but no longer than 10 hours from the time of 90Y
separation. If processing or counting capacity is limited, concentrate resources on
90Sr WCS and counting first. The 90Y WCS are not compromised by ingrowth but
must only be counted promptly enough to minimize decay and optimize counting
statistics.
Al.3.8. Strip strontium from each column by adding 15 mL of 0.05-M HNOs to
each column, catching the effluents containing 90Sr in the centrifuge tube.
on on
Al .3 .9. Quantitatively transfer Sr and Y fractions to respective tared planchets
using three portions of 0.05-M
Al.3.10. Evaporate to dryness using the same techniques for sample test sources,
with the same heat time applied after dryness is reached.
Note: Gravimetric measurements may be performed following the counting to
minimize elapsed time between separation and counting.
on on
Al .4. Weigh the Sr and Y WCS sources and calculate the net residue mass.
Al .4. 1 . The net mass of the strontium nitrate precipitate shall indicate near
quantitative yield of strontium of 95-103%. If strontium yield falls outside
this range, determine and address the cause for the losses and repeat the
___ on
process. The known activity of Sr in the standard is corrected for losses
based on the measured chemical yields of the strontium carrier.
Note that no correction shall be applied for values greater than 100% because this
will produce a negative bias in the calibrated efficiency.
Al .4.2. The net residue mass of the 90Y should be low. Higher residue mass may
indicate the breakthrough of strontium and will result in high bias in the
on
Y efficiency, but it may simply be the result of corrosion of the stainless
planchet during evaporation of 8M HNOs, forming a small amount of iron
oxide. Lower Sr carrier yields on the Sr planchet would indicate the
present of Sr breakthrough.
NOTE: Formation of a small amount of iron oxide on the planchet during
evaporation may result in a slight mass on the 90Y planchet (~1 mg) but does not
affect the 90Y counting significantly.
Al .4.3 . Count three 90Sr WCS on each detector to be calibrated, for sufficient time
to accumulate at least 10,000 net counts.
Al .4.4. Count three 90Y WCS on each detector to be calibrated, for sufficient time
to accumulate at least 10,000 net counts.
Al .4.5. Count the associated blanks as a gross contamination check on the
process. If indications of contamination are noted, take appropriate
corrective actions to minimize spread and prevent cross-contamination of
other samples in the laboratory.
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Al .5. Verify the calibration of each detector according to ASTM Standard Practice
D7282, Section 16, and the laboratory quality manual and standard operating
procedures.
Al .6. Calculations and data reduction for 90Sr and 90Y calibrations and calibration
verifications are presented in Sections A2, A3, and A4. Calculations for total
radiostrontium are in Section 12 of the method.
on
A2. Calculation of Detection Efficiency for Sr
A2. 1 . Calculate the following decay and ingrowth factors for each WCS:
DFS = Q-^^-'O'' (Al)
//V90=l-e-A™fe-'l) (A2)
where
on
DFS = decay factor for decay of the Sr standard from its reference date
until the 90Sr/90Y separation
7FY9o = ingrowth factor for ingrowth of 90Y after the 90Sr/90Y separation
Asr90 = decay constant for 90Sr, 7.642x 1(T10 s"1
AY90 = decay constant for 90 Y, 3 .005 x 1 (T6 s"1
QO
to = reference date and time for the Sr standard (s)
t\ = date and time of the Sr/Y separation (s)
on
h = date and time of the midpoint of the Sr count (s)
NOTE: The elapsed time between the sample count and the reference date must be calculated
using the same time units as the decay constant
A2.2. Calculate the 90Sr detection efficiency for each WCS:
T r^r
ACSl90 std x V^ x DFSI
where
£sr9o,i
_
§"Y90 = average Y detection efficiency (from Step A3. 2)
9°Sr detection efficiency for the /' WCS
Rs,i = beta gross count rate for the f WCS (cpm)
Rb = background count rate, in cpm
Rn,i = beta net count rate for the f WCS (cpm)
d = activity concentration of the 90Sr standard solution on its
reference date (cpm/mL or cpm/g)
= amount (volume or mass) of the standard solution added to the
/thwcs
A2.3. Average the efficiencies determined in Step A2.2 for all the WCSs to obtain the
ffic
on
final detection efficiency for Sr.
(A4)
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where
eSr9o,z = 9°Sr detection efficiency determined for the/* WCS in A2.2,
n = number of WCSs prepared and counted.
A2.4. Calculate the standard uncertainty of the average 90Sr detection efficiency as
follows:
Y90
^O^ (ACS
Sr90 std
o, = average value of Y ingrowth factors
standard uncertainty of the value in parentheses,
relative standard uncertainty of the value in parentheses.
A3 . Detection Efficiency for 90Y
A3 . 1 . Calculate the 90Y detection efficiency, £Y9o,z, for each WCS,
(A6)
(A7)
where
and
std
on
Y detection efficiency determined for the WCS
beta gross count rate for the f WCS (cpm)
background count rate, in cpm
beta net count rate for the f WCS (cpm)
Qj-\
activity concentration of the Sr standard solution on its reference
date (disintegrations per minute [dpm]/mL or dpm/g)
'*
= amount of the standard solution added to the/' WCS (mL or g)
DFS
'*
combined correction factor for decay of the 90Sr standard in the /'
Q«"|
WCS from its reference date until Y separation, and for the decay
on
of Y from its separation until the midpoint of the count
90
= decay constant for Sr, 7.642x 1(
10 ~f
90
6 "1
= decay constant for Y, 3.005x 1(T s
QO
= reference date and time for the Sr standard (s)
t\
t2
on
= date and time of the Y separation (s)
9
= date and time at the midpoint of the Y count (s)
NOTE: The elapsed time between the sample count and the reference date must be calculated using
the same time units as the decay constant
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Total Radiostrontium ( Sr) in Building Material Samples: Rapid Method for High-Activity Samples
A3. 2. Average the efficiencies determined in Step A3. 1 to obtain the final detection
efficiency for 90Y.
1 "
^¥90 ~~ ^¥90 ~~ /j^Ygcu (A")
nli
where
eY9o,; = 9°Y detection efficiency determined for the f WCS in Step A3.1
n = number of WCS prepared and counted
A3. 3. The combined standard uncertainty of the average efficiency for 90Y including
uncertainty associated with the preparation of the calibration standards is calculated
as follows:
n _ y ut, 90.J (A10)
where
u(x) = standard uncertainty of the value in parentheses,
wr(x) = relative standard uncertainty of the value in parentheses.
NOTE: The uncertainty of the net count rate, uRn^ includes the uncertainty of the background or
u2(Rn,i) = U2(RS) + u2(R6) = (Rs/ts) -
A4. Calculate the covariance and correlation coefficient for the 90Sr efficiency and the 90Y
efficiency:
u(Ssm^Y90) = ssmsYgou^(ACsmsJ-(u\sY90)-s^(ACsmsj)lF^ (All)
and
where
u(x,x) = estimated covariance of the two quantities in parentheses,
r(x,x) = estimated correlation coefficient of the two quantities in
parentheses,
u(x) = standard uncertainty of the quantity in parentheses,
ur(x) = relative standard uncertainty of the quantity in parentheses.
A5. Detection Efficiency for 89Sr (if needed for Appendix B Calculations)
A5.1. Calculate the detection efficiency, esr89,z, for each WCS as follows:
SSr$9,, = = ~ (A13)
where
|J (A14)
and
"9Sr detection efficiency for the /th WCS
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R^i = beta gross count rate for the f WCS (cpm)
Rb = background count rate, in cpm
^4Csr89 std = activity concentration of the 89Sr standard solution on the reference
date (dpm/mL or dpm/g)
Fs,z = amount (volume or mass) of the standard solution added to the f
WCS (mL or g)
DFs,i = correction factor for decay of the 89Sr standard for the /* WCS
from its reference date until the midpoint of the sample count
ASr89 = decay constant for 89Sr, 1.58?x 10~7 s"1
OQ
^o = reference date and time for the Sr standard (s)
t\ = date and time at the midpoint of the 89Sr count (s)
A5.1.1. Average the efficiencies determined in Step A5.1 to obtain the final
^ncy for 89Sr.
1 "
SrS9 = %89 = V %89i (Al5)
OQ
detection efficiency for Sr.
where
£Sr
n = number of WCSs prepared and counted
£sr89,z = 89Sr detection efficiency determined for the f WCS in Step A5.1,
A5.1.2. The combined standard uncertainty of the average efficiency for Sr
including uncertainty associated with the preparation of the calibration
standards is calculated as follows:
n j=\ ^4(_-<3,gQot^K0
+ £Sr89Mr (^QrSgstd) (A16)
oToy r V oioy SIQ s \ /
where
w(x) = standard uncertainty of the value in parentheses,
wr(x) = relative standard uncertainty of the value in parentheses.
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Total Radiostrontium ( Sr) in Building Material Samples: Rapid Method for High-Activity Samples
Appendix B:
OQ Q|-|
Calculations for Isotopic Sr and Sr Results
OQ Q|"\
A numerical approach for determining Sr and Sr activity from a single sample is performed
by a number of laboratories. This presentation, however, allows a more rigorous evaluation of
uncertainties than commonly employed. Lacking this treatment, many labs have found that the
traditional approach (evaluating counting uncertainty for a single count only) has led to
overestimation of the quality of results, and to poor decisions regarding the presence or absence
of low activities of one radioisotope of strontium in the presence of elevated activities of the
second.
___ OQ Qf\
These calculations may be valuable to laboratories who wish to determine isotopic Sr and Sr
in a large number of samples with a minimum of additional effort beyond the initial preparation
and counting of total radiostrontium. Specifically, it involves performing a second count of the
same radiostrontium sample test source (STS) and mathematically resolving the activity of the
two isotopes. Although the STS may be recounted as soon as 1-2 days after the initial count,
resolution is optimized if the two counts span as large a range of the 90Y ingrowth as practicable.
The time elapsed between the chemical separation and the first count should be minimized, while
on on
the second count should optimally proceed as Y approaches secular equilibrium with Sr but
before significant decay of 89Sr has occurred, for example, after 3-5 half-lives of 90Y have
elapsed (1-2 weeks).
This section may not be employed without complete validation of the approach by the
on °>Q
laboratory, including testing with samples containing ratios of Sr relative to Sr varying from
pure 90Sr to pure 89Sr.
___ on °>Q
B 1 . The equations in this section are used to calculate the Sr and Sr activity of a sample
from data generated from two successive counts of the same radiostrontium sample test
source.
B 1 . 1 . For each of the two counting measurements (/'=!, 2), calculate the following decay
and ingrowth factors:
o) (B2)
E1 _ ~^Si9o(*sei)~*o)fl _ ~-*y9o(*i~*sep) I /"R^
/Y90,z ~ C \ ' \DJ)
where:
decay factor for decay of 89Sr from the collection date to the
midpoint of the f count of the STS
decay factor for decay of 90Sr from the collection date to the
midpoint of the /'th count of the STS
on
combined decay and ingrowth factor for decay of Sr from the
collection date to the Sr/Y separation and ingrowth of 90Y from the
separation to the midpoint of the f count of the STS
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= decay constant for 89Sr = 1 .58?x 1(T7 s"1
= decay constant for 90Sr = 7.642x 10~10 s"1
to = collection date and time for the sample (s)
4ep = date and time of the Sr/Y separation (s)
ti = date and time of the midpoint of the f count of the STS (s)
NOTE: The elapsed time between the sample count and the reference date must be calculated
using the same time units as the decay constant
B1.2. For i = 1,2, use the results from Section A5.1 in Appendix A to calculate the
following sensitivity factors:
9Jes*9j (B4)
" ~ -
0,iSr90,i Y90,!' Y90,i
where
a, = sensitivity of the count rate in the f measurement to 89Sr activity
hi = sensitivity of the count rate in the f measurement to 90Sr activity
= 90Y efficiency of the detector for the /'th count of the STS
= 9°Sr efficiency of the detector for the /'* count of the STS
B1.3. Calculate the standard uncertainties of the sensitivity factors using the equations:
u(at) = DFsa9J «0Sr89>! ) (B6)
(B7)
where the estimated covariance of the 90Sr and 90Y efficiencies is calculated as
follows:
«(eSi9eY90,i) = r(eSr90^eY90,;)M(eSr90,!)M(eY90,!) (B8)
and where the estimated correlation coefficient r(eSr9o,*, £Y9o,0 was determined during
the calibration.
B1.4. Calculate the covariances u(a\,ai} and u(b\,l>i} as follows:
u(al)u(a2), if only one detector is used
u(al:,a2) = \ i, Ar, -^ -c ^ j* * A (B9)
1 2 ala2uI (ACSlg9sid), it two detectors are used
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\ Sr90,l Y90.2 Sr90,2 Y-90,1 / ^V^Sr90,l' ^Y90,l /
sr902u'fciwoi) + ^Y9oi^Vso2 "'(^oiX using only one detector (BIO)
!&2 wr2 (^4CSr90 std ), using two detectors
where
= activity concentration of the Sr standard used for calibration
on
Csr90 std = activity concentration of the Sr standard used for calibration
Mr(-) = relative standard uncertainty of the quantity in parentheses
B1.5. For i = 1,2, calculate the net beta count rates, RDJ, and their standard uncertainties:
K,=^-^ (BH)
= ARi + 7i (B12)
Y a,i b,i
where:
.Rn^ = net beta count rate for the /* count of the STS (cpm)
R^i = beta gross count rate for the f count of the STS (cpm)
Rbj = beta background count rate for the f count of the STS (cpm)
4;, = sample count time for the /'th count of the STS (min)
fb,z = background count time for the /'th count of the STS (min)
OQ Qf\
B1.6. Using the values calculated in A5.1 - A5.5, calculate the Sr and Sr activity
concentrations:
ACSIS9= *Ai~Vl2 (B13)
Sr89 2.22xXxVxY ^ }
ACSI90= a^~a^ (B14)
Sr9° 222xXxVxY
where:
X = alb2-a2bl (B15)
and where:
2.22 = conversion factor from dpm to pCi
Y = chemical yield for strontium
W = sample weight (g)
B2. The standard counting uncertainties for 89Sr (wcC(;4CSr89)) and 90Sr (ucC(ACSl90)) are
calculated in units of pCi/g as follows:
u 2(Rn2)
(B16)
2.22xXxWxY
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Total Radiostrontium ( Sr) in Building Material Samples: Rapid Method for High-Activity Samples
222xXxWxY
B3. The combined standard uncertainties (CSU) for 89Sr and 90Sr are calculated as follows:
(B17)
040*89) =
+ ,
+
2 fv\ z.2 If
u2(Y) b2u (a,
,2,.2,
b2u2(b2)-2blb2u(bl,b2)
Y2
(B18)
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