EPA 402-R-10-001 c
                                       www.epa.gov/narel
                                           October 2011
                                            Revision 0.1
     Rapid Radiochemical  Method for
             Radiurn-226 in Water
for Environmental Remediation Following
         Homeland Security Events
            U.S. Environmental Protection Agency

                Office of Air and Radiation
              Office of Radiation and Indoor Air
        National Air and Radiation Environmental Laboratory
                  Montgomery, AL 36115

             Office of Research and Development
          National Homeland Security Research Center
                  Cincinnati, OH 45268

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         Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples
                                    Revision History
Revision 0
Revision 0.1
Original release.
• Corrected typographical and punctuation errors.
• Improve wording consistency with other methods.
• Added pH paper to list of equipment and supplies (6.9).
• Added 225Ra decay diagram to Section 17.4.
• Added Section 12.2.1 header (no change to process).
• Updated equations in sections 12.2.1 (At), 12.3 (ACa), and 12.3.2 (Sc),
to consistently apply factor for It (no impact on calculations).
• Updated equation objects in section 12.2.1 (equation for At) since
MSWord Equation Editor ensure that minus signs would be displayed).
• Updated footnote 9 to further clarify origin of critical value and
minimum detectable concentration formulations.
• Updated values in Table 17.2 to reflect 217At concentration (no impact
on calculations in 12.2.1).
• Updated rounding example in 12.4.2.2 for clarity.
• Deleted Appendix A (composition of Atlanta tap water) as irrelevant.
Redesignated Appendix B ("Preparation and Standardization of 225Ra
Tracer Following Separation from 229Th") as Appendix A.
02/23/2010
10/28/2011
This  report was prepared for the National Air and Radiation Environmental Laboratory of the Office of
Radiation and Indoor Air and the National Homeland Security Research Center of the Office of Research
and Development, United States Environmental Protection Agency.  It was prepared by  Environmental
Management Support, Inc., of Silver Spring, Maryland, under contracts 68-W-03-038, work assignment 43,
and EP-W-07-037, work assignments B-41  and 1-41,  all managed by David Carman. Mention of trade
names or specific applications does not imply endorsement or acceptance by EPA.

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                                 RADiUM-226 IN WATER:
                 RAPID METHOD TECHNIQUE FOR HIGH-ACTIVITY SAMPLES

1.   Scope and Application
    1.1.  The method will be applicable to samples where contamination is either from known or
         unknown origins. If any filtration of the sample is performed prior to starting the
         analysis, filterable solids should be analyzed separately. The results from the analysis
         of these solids should be reported separately (as a suspended activity concentration for
         the water volume filtered), but identified with the filtrate results.
    1.2.  This method uses rapid radiochemical separations techniques for the isotopic
         determination of 226Ra in water samples following a nuclear or radiological incident.
         Although the method can detect 226Ra concentrations on the same order of magnitude as
         methods used for the Safe Drinking Water Act (SDWA), this method is not a substitute
         for SDWA-approved methods for 26Ra.
    1.3.  The method is specific for 226Ra and uses MnO2 fixed on a resin bed (MnO2 resin) to
         separate radium from interfering radionuclides and matrix constituents with additional
         separation using Diphonix® resin1 to improve selectivity by removing radioactive
         impurities.
    1.4.  The method is capable of satisfying a required method uncertainty for 226Ra of 0.65
         pCi/L at an analytical action level of 5 pCi/L. To attain the stated measurement quality
         objectives (MQOs) (see Sections 9.3, 9.4, and 9.5), a sample volume of approximately
         200 mL and count time of 4 hours 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 16.3). 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.
    1.5.  This method is intended to be used for water samples that are similar in composition to
                                996
         drinking water. The rapid  Ra 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 16.3) and Chapter 6 of Multi-Agency Radiological Laboratory Analytical
         Protocols Manual (MARLAP 2004, reference 16.4). Multi-radionuclide analysis using
         sequential separation techniques may be possible.

2.   Summary of Method
    2.1.  A known quantity of 225Ra is  used as the yield determinant in this analysis. Since the
         source of the suspected contamination may not be known,  the sample is initially
         digested using concentrated nitric acid, followed by volume reduction and conversion
         to the chloride salt using concentrated hydrochloric acid. The solution is adjusted to a
         neutral pH and batch equilibrated with MnC>2 resin to separate radium from some
         radioactive and non-radioactive matrix constituents. Further selectivity is achieved
1 A polyfunctional cation exchange resin containing diphosphonic and sulfonic acid functional groups bonded to a
polystyrene/divinylbenzene spherical bead. (Available commercially from Eichrom Technologies, LLC, Lisle, IL,
60561).


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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


        using a column which contains Diphonix® resin. The radium (including 226Ra) eluted
        from the column is prepared for counting by microprecipitation with BaSO/i.
   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
                                             917                      99S         	
        activity of the alpha peak at 7.07 MeV (  At, the third progeny of  Ra). 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. Analytical Decision Level (ADL). The analytical decision level refers to the value that
        is less than the AAL based  on the acceptable error rate and the required method
        uncertainty.
   3.4. Discrete Radioactive Particles (DRPs or Hot Particles). Particulate matter in a sample
        of any matrix where a high concentration of radioactive material is contained in a tiny
        particle (micron range).
   3.5. Multi-Agency Radiological Analytical Laboratory Protocols Manual (MARLAP) (see
        Reference 16.4).
   3.6. 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.
   3.7. Radiological Dispersal Device (RDD), i.e., a "dirty bomb." This is an unconventional
        weapon constructed to distribute radioactive material(s) into the environment either by
        incorporating them into a conventional bomb or by using sprays, canisters, or manual
        dispersal.
   3.8. Required Method Uncertainty  (MMR)- The required method uncertainty is a target value
        for the individual measurement uncertainties and is an estimate of uncertainty (of
        measurement) before  the sample is actually measured. The required method uncertainty
        as an absolute value is applicable at or below an AAL.
   3.9. Relative Required Method  Uncertainty (^MR)- The relative required method uncertainty
        is the WMR divided by  the AAL and is typically expressed as a percentage. It is
        applicable above the action level.
   3.10. Sample Test Source (STS). This is the final form of the  sample that is used for nuclear
        counting. This form is usually specific for the nuclear counting technique in the
        method, such as a solid deposited on a filter for alpha spectrometry analysis.
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


4.  Interferences
    4.1.  Radiological:
         4.1.1. All radium isotopes in addition to 226Ra are retained on MnC>2, as are thorium
               isotopes. Unless other radium isotopes are present in concentrations greater than
               approximately three times the 226Ra activity concentration, interference from
               other radium alphas will be resolved when using alpha spectrometry. Method
               performance may be compromised if samples contain high levels of radium
               isotopes due to ingrowth of interfering decay progeny. Samples should be pre-
               screened prior to aliquanting and appropriate limits established to control the
               amount of activity potentially present in the aliquant.2
         4.1.2. 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 225Ra 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.
               4.1.2.1.  The amount of 225Ra added to the samples may be decreased, and the
                        time for ingrowth between separation and counting increased, to
                        ensure that sufficient 225Ac,  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 from the potential for high
                        throughput.
               4.1.2.2.  The size of the sample aliquant can be increased without changing the
                        amount of tracer added.
                                    99S                 ^
         4.1.3. Optimally, a purified   Ra tracer  solution should be used when performing this
               method.
               4.1.3.1.  When using a purified source of 225Ra, the beginning of decay for
                        225Ra is the activity reference date established during standardization
                              99S
                        of the   Ra solution.
               4.1.3.2.  When a purified 225Ra tracer solution is not available, a solution
                        containing 225Ra in equilibrium with 229Th may be used as a tracer. In
                        this case, the 225Ra activity is supported only until thorium is removed
                        using Diphonix® resin during processing of the sample. When using
                        this variation of the method, the beginning of 225Ra decay is the point
                        when the sample has passed through the Diphonix® column.
2 For very elevated levels of radium isotopes, it is recommended that laboratories use "The Determination of
Radium-226 and Radium-228 in Drinking Water by Gamma-ray Spectrometry Using HPGE or Ge(Li) Detectors,"
Revision 1.2, December 2004. Available from the Environmental Resources Center, Georgia Institute of
Technology, 620 Cherry Street, Atlanta, GA 30332-0335, USA, Telephone: 404-894-3776.
3 Using a purified 225Ra tracer is the approach recommended for this method.  See Appendix B for a method for
purification and standardization of 225Ra tracer from 229Th solution.


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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


                        NOTE: Recording the point in time of the beginning of 225Ra decay to within Vz
                        hour will introduce a maximum bias of 0.1% for this measurement.

         4.1.4.  Every effort should be made to use the purified 225Ra as a tracer. It is also
                possible to use 225Ra in equilibrium with 229Th, which may be added to each
                sample as  a tracer.4 This approach requires complete  decontamination  of a
                relatively high activity of 229Th by the Diphonix® column later in the method,
                however, since the spectral region of interest (ROI) for 229Th slightly overlaps
                that of 226Ra. Inadequate decontamination of 229Th will lead to high bias in the
                99^                                    99^
                  Ra result especially when the levels of   Ra in the sample are below 1 pCi/L.
                	                       oo/r                   99O	
                The spectral region above   Ra corresponding to   Th should be monitored as
                a routine measure to identify samples where 2 9Th 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:
                4.1.4.1.  Separating 225Ra from 229Th prior to its use as a tracer. Using purified
                        225Ra tracer is the default approach recommended for running this
                        method since it will completely address any potential for interference
                        by  removing the source of the problem.
                4.1.4.2.  Increasing the sample aliquant size without  changing the amount of
                        tracer added will increase analyte signal and reduce the relative impact
                        of the interference to levels that may be amenable with project MQOs.
                4.1.4.3.  The absolute amount of 229Th added to the samples may be decreased,
                        as long as the time for ingrowth between separation and counting is
                        increased to ensure that sufficient 217At is  present for yield corrections
                        at the point of the count. Although this detracts from the rapidity of the
                        method, it allows more flexibility in the timing of the count and does
                        not detract from the potential for high throughput.
                4.1.4.4.  Developing spill-down factors (peak overlap corrections) to correct for
                        the interference  and account for additional uncertainty in the  analytical
                        results. This is not a trivial determination and should be validated prior
                        to use.
                                          99S                      99O	
         4.1.5.  When a solution containing  Ra in equilibrium with  Th is used as a tracer,
                thorium is removed later in the processing of the sample. The equilibrium
                between the 225Ra and 229Th is maintained only until the sample is loaded onto
                the Diphonix® column. At this point, thorium and actinium are retained on the
                column and the 225Ra activity in the eluate is unsupported and begins to decay.
    4.2.  Non-radiological:
         4.2.1.   Low conductivity water (<100 uS cm l) may  cause low-yield issues with some
                samples. This may be partially corrected for by increasing the conductivity with
                calcium standard solution.
4 The single-laboratory validation for this method was performed successfully by adding 225Ra in secular equilibrium
with 229Th tracer. Using purified 225Ra will provide better method performance since it will eliminate any concern
about breakthrough of the high levels of 229Th added to each sample. See Appendix B of this method for a method
for separating (and standardizing) 225Ra tracer from 229Th solution.


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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


        4.2.2.  Concentrations of non-radioactive barium present significantly in excess of the
               amount of barium carrier added for microprecipitation may severely degrade the
               resolution of alpha spectra. The quality of spectra should be monitored for
               evidence of decreased resolution. A decreased sample size (i.e., smaller) may
               need to be selected or the barium carrier decreased or omitted if the presence of
               these interferences leads to unacceptably degraded method performance.
        4.2.3.  High concentrations of non-radioactive calcium, magnesium or strontium in the
               sample may not only overwhelm the ability of the MnO2 resin to effectively
               exchange radium isotopes but also may degrade the alpha spectrometry peaks
               and increase analytical uncertainty. A decreased sample size (i.e., smaller) may
               need to be selected when the presence of these interferences leads to degraded
               method performance. If it is anticipated that these elements or barium (see Step
               4.2.2) are present in  quantities exceeding a small fraction of the mass of calcium
               or barium added in Steps 11.2.3 and 11.1.3, respectively, an analytical
               determination may need to be performed separately so that the interference can
               be accommodated.

5.   Safety
    5.1. General
        5.1.1.  Refer to your safety  manual for concerns of contamination control, personal
               exposure monitoring and radiation dose monitoring.
        5.1.2.  Refer to the laboratory chemical hygiene plan 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). Filtration using a 0.45-um or finer filter
                        will minimize the presence of these particles.
               5.2.1.2.  Care should be taken to provide suitable containment for filter media
                        used in the pretreatment of samples that may have DRPs, because the
                        particles become highly statically charged as they dry out and will
                        "jump" to other surfaces causing contamination.
               5.2.1.3.   Filter media should be individually surveyed for the presence of these
                        particles, and this information reported with the final sample results.
        5.2.2.  For samples with detectable activity concentrations of these radionuclides,
               labware should be used only once due to 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.   Centrifuge tubes,  polypropylene, 50 mL, disposable; or equivalent.
    6.3.   Chromatography columns, polypropylene, disposable:
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


          6.3.1.   1.5 cm ID.  x 15 cm, with funnel reservoir; or equivalent.
          6.3.2.   0.8 cm ID.  x 4 cm; or equivalent.
    6.4.   Filter stand and filter funnels.
    6.5.   Filter, 0.1 micron, ~25-mm diameter (suitable for microprecipitation).
    6.6.   Membrane filter, 0.45 micron, ~47-mm diameter.
    6.7.   Vacuum filtration apparatus.
    6.8.   Heat lamp, 250-300 watt, with reflectors mounted -25 cm above the base.
    6.9.   pH paper.
    6.10.  Petri dish or other suitable container for storing sample test sources.
    6.11.  Stainless steel planchets or suitable holders/backing for sample test sources - able to
          accommodate a 25-mm diameter filter.
    6.12.  Glass beaker, 600-mL capacity.
    6.13.  Stirring hot plate.
    6.14.  Magnetic stir bar (optional).
    6.15.  Centrifuge bottle, polypropylene, 250 mL, disposable; or equivalent (optional).

7.  Reagents and Standards

   Note: All reagents are American Chemical Society (ACS) reagent grade or equivalent unless otherwise
   specified.

   Note: Unless otherwise indicated, all references to water should be understood to mean Type I Reagent
   water (ASTM D1193). For microprecipitation, all solutions used in microprecipitation should be
   prepared with water filtered through a 0.45 um (or smaller) filter.

    7.1.   Ammonium sulfate, solid (NH/^SO/t, available commercially.
    7.2.   Barium carrier (nominally 0.5 mg/mL as Ba2+). May be purchased as an atomic
          absorption standard and diluted, or prepared by dissolving 0.45 g reagent grade
          barium chloride,  dihydrate (BaCb^FbO) in water and diluting to 500 mL with water.
    7.3.   Bromthymol blue indicator solution: Dissolve 0.1 g of bromthymol blue in 16 mL of
          0.01 M NaOH. Dilute to 250 mL with water.
    7.4.   Calcium nitrate solution (1000 ppm as calcium). May be purchased as an atomic
          absorption standard and diluted or prepared by dissolving 2.5 g of calcium carbonate
          (CaCOs) in 70 mL of concentrated nitric acid and diluting to 1  L with water.
    7.5.   Diphonix® resin, 100-200-um mesh size [available from Eichrom Technologies,
          Lisle, IL].
    7.6.   Ethanol, reagent 95 % (C2H5OH), available commercially.
    7.7.   Hydrochloric acid (12 M): Concentrated HC1, available commercially.
          7.7.1.  Hydrochloric acid (2M): Add 170 mL of concentrated HC1 to 800 mL of
                 water and dilute to 1.0 L with water.
          7.7.2.  Hydrochloric acid (1M): Add 83 mL of concentrated HC1 to 800 mL of water
                  and dilute to 1.0 L with water.
    7.8.   Hydrogen peroxide, H2O2 (30 % w/w), available commercially.
    7.9.   Isopropanol,  2-propanol, (CsHyOH), available commercially.
          7.9.1.  Isopropanol (2-propanol), 20 % (v/v) in water: Mix 20 mL of isopropanol
                 with 80 mL of water.
    7.10.  Methanol (CH3OH), available commercially.
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


    7.11.  MnO2 resin, 75-150 |j,m MnO2 particle size on non-functionalized polystyrene resin
          beads of 100-200 mesh [available commercially from Eichrom Technologies, Lisle,
          IL].
    7.12.  MnO2 stripping reagent: Add 2 mL of 30 % H2O2 per 100 mL of 2 M HC1. Prepare
          fresh for each use.
    7.13.  Nitric acid (16 M): Concentrated HNCb, available commercially.
    7.14.  Sodium hydroxide (1 M): Dissolve 4 g of sodium hydroxide (NaOH) in 50 mL of
          water and dilute the solution to 100 mL.
    7.15.  Ra-225 tracer in 1-M HC1 solution in a concentration amenable to accurate addition
          of about 180 dpm per sample (generally about 150-600 dpm/mL).
          7.15.1.  Ra-225 may be purified and standardized using a 229Th / 225Ra generator as
                  described in Appendix A of this method.
          7.15.2.  Th-229 containing an equilibrium concentration of 225Ra has been
                  successfully used without prior separation of the 225Ra. However, this
                  approach may be problematic due to the risk of high result bias (see
                  discussion in Steps 4.1.4 - 4.1.5).

8.  Sample Collection, Preservation and Storage
   8.1.     Samples  should be collected in 1-L plastic containers.
   8.2.     No sample preservation is required if sample analysis is initiated within 3 days of
           sampling date/time.
   8.3.     If the sample is to be held for more than three days, HNCb shall be added until the
           solution pH is less than 2.0.
   8.4.     If the dissolved concentration of radium is sought, the insoluble fraction must be
           removed by filtration before preserving with acid.

9.  Quality Control
   9.1.     Batch quality  control results shall be evaluated and meet applicable  Analytical
           Project Specifications (APS) prior to release of unqualified data. In  the absence of
           project-defined APS or a project-specific quality assurance project plan (QAPP), the
           quality control sample acceptance criteria defined in the laboratory quality manual
           and procedures shall be used to determine acceptable performance for this method.
            9.1.1.  A laboratory control sample (LCS) shall be run with each batch of samples.
                  The concentration of the LCS should be at or near the action level or 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 demineralized water.
            9.1.3.  One laboratory duplicate shall be run with each batch of samples. The
                  laboratory duplicate is prepared by removing an aliquant from the original
                  sample container.
            9.1.4.  A matrix spike sample may be included as a batch quality control sample if
                  there is concern that matrix interferences, 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
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


            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 / 225Ra solution is added directly
                   to the sample, the presence of detectable counts between -5.0 MeV and the
                                                   996
                   upper boundary established for the   Ra ROI generally indicates the
                   presence of 229Th in the sample, and in the 226Ra ROI. If the presence of
                   229Th is noted and the concentration of 226Ra is determined to be an order of
                   magnitude below the action limit or the detection threshold of the method,
                   take corrective actions to ensure that MQOs have not been compromised
                   (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 0.65 pCi/L at or below an action level of
          5.0 pCi/L. This may be adjusted in the event  specific MQOs are different.
    9.4.   This method is capable of achieving a 99%. See Table 17.3).

11. Procedure
   11.1.   Initial Sample Treatment
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


          11.1.1.  For each sample in the batch, aliquant 0.2 L of raw or filtered water into a
                   beaker.

                   Note: Smaller or larger aliquants may be used if elevated sample activity is present or
                   as needed to meet detection requirements or MQOs. Method validation must be
                   conducted using approximately the same volume as that to be used in sample analysis^

          11.1.2.  To each aliquant, add 10 mL of concentrated nitric acid per 100 mL of
                   sample.
          11.1.3.  To each sample aliquant, add 100 uL of 0.5 mg/mL (nominal) barium carrier
                   solution and approximately 180 dpm of 225Ra tracer solution. The initial
                   amount of 225Ra added as a tracer should be high enough so that the
                   resultant counting uncertainty of the 217At activity ingrown from the tracer is
                   five  percent (5 %) or less during the allotted sample count  time.

                   Note: The activity of 217At present at the midpoint of the count is used to calculate the
                   chemical yield for radium by back-calculating the activity of 225Ra recovered. The
                   initial amount of 225Ra added as tracer may need to be varied to accommodate
                   planned differences in the time that has elapsed between chemical separation and the
                   count, but the activity should be sufficient, and the count time long enough, to  ensure
                   that the resultant counting uncertainty for the 217At peak is five (5 %) percent  or less.
                   See the calculation for At, in Step 12.2 for calculation of ingrowth factor for 217At and
                   Table 17.2 for typical ingrowth factors for a series of ingrowth times.

          11.1.4.  Reduce the sample volume to -20% of the original volume by bringing the
                   solution to a gentle boil and evaporating.
          11.1.5.  Following this digestion, add 10 mL of concentrated hydrochloric acid, and
                   carefully evaporate the solution to incipient dryness.
          11.1.6.  Reconstitute the sample by adding 100 mL of 1-M HC1. The sample may be
                   gently heated  if necessary to facilitate dissolution of residual salts.
    11.2.  Water Sample Preparation and Pre-concentration of Radium on MnO2 resin:
          11.2.1.  Add 100 mL of 1-M NaOH to each sample.
          11.2.2.  If particulate material is visible  at this time, filter the sample through  a 0.45-
                   |im filter. (Do not rinse the filter). The filter should be saved for possible
                   analysis for DRPs.
          11.2.3.  Add enough 1000 ppm calcium solution  to the filtrate from Step 11.2.2 to
                   ensure that the final calcium concentration is about 10 ppm. For waters that
                   naturally have calcium in them above 10 ppm this step will be unnecessary.
          11.2.4.  Add a few drops of bromthymol blue indicator solution and adjust each
                   sample to neutral pH by  carefully adding 1-M NaOH until  the color changes
                   from yellow to blue-green.

                   Note: Adding too much base will overshoot the blue-green endpoint (indicated by blue
                   color). The amount of NaOH added in Step 11.2.4 may be adjusted by carefully
                   adding a small quantity of 1-M HC1 and 1-M NaOH as needed to reach a blue-green
                   endpoint.

          11.2.5.  The  sample is equilibrated with -1.0 g MnC>2 resin for 0.5-1.5 hours.  Two
                   options are provided:
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                    11.2.5.1. Option 1: Add -1.0 g MnO2 resin to a beaker containing the
                            neutralized sample. Cover with a watch glass and gently stir on a
                            magnetic  stirrer for at least 30 minutes.
                    11.2.5.2. Option 2: Transfer the neutralized sample to a 250 mL centrifuge
                            bottle which contains -1.0 g MnO2 resin. Agitate the bottle gently
                            on a shaker or in a tumbler for at least 30 minutes.

                            Note: Two options are provided for contacting the sample with MnO2 resin.
                            The contact time noted above (30 minutes) is to be understood as a
                            minimum.  Higher radium yields may be obtained with somewhat longer
                            contact times (up to 90 minutes).

                            Note: Excessive agitation of the resin may lead to abrasion and loss of some
                            MnO2 from the resin and result in degraded chemical yields. Although
                            sample quantitation is not significantly impacted since a 225Ra yield tracer is
                            used, uptake on the resin during this step should be reasonably optimized
                            by evaluating the process and time used and choosing a default optimal
                            conditions  corresponding to a minimum of 80-85% uptake from a clean
                            water matrix.

           11.2.6.   Pour the suspension into a 1.5-cm ID. x 15-cm column fitted with a
                    reservoir funnel. Allow sample to pass through column. Rinse the walls of
                    the funnel  reservoir and column with demineralized water. The combined
                    column effluent from this step may be discarded.
           11.2.7.   Place a clean  50 mL centrifuge tube under each MnO2 column. Add 10 mL
                    of freshly made MnO2 Stripping Reagent to the MnO2 column to elute
                    radium and other elements. Catch the column eluate containing radium and
                    retain for subsequent processing.

                    Note: Effervescence will be noted upon addition of the MnO2 Stripping Reagent.
                    Gently tapping the column to dislodge any bubbles that form will help minimize
                    channeling and may improve radium recovery. The resin bed will become light pink in
                    color as MnO2 dissolves.

    11.3.    Actinium and Thorium Removal Using Diphonix® resin:
             11.3.1. Prepare a Diphonix® resin column for each sample to be processed as
                    follows:5
                    11.3.1.1. Slurry -1.0-g Diphonix® resin per column  in water.
                    11.3.1.2. Transfer the resin to the 0.8-cm ID. x 4-cm columns to obtain a
                            uniform resin bed of-1.4-1.6 mL (bed height -26-30 mm). A top
                            column barrier (e.g., frit, glass wool, beads) may be used to
                            minimize turbulence that may disrupt the resin bed when adding
                            solution to the column.
             11.3.2. Precondition the column by passing 20 mL of 2-M HC1 through the column
                    discarding the column effluent.
             11.3.3. Place a clean  50-mL centrifuge tube under each Diphonix® column.
5 Commercially supplied pre-packed columns may be used here. When packing columns using bulk resin, excessive
resin fines should be removed by rinsing the resin one or more times with an excess of water and decanting the
water containing the fines prior to transferring the material to the column.


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            11.3.4. Swirl the solution retained in Step 11.2.7 to remove bubbles and carefully
                   load onto the column taking care to minimize disturbing the resin bed.
                   Collect column effluents in the 50-mL centrifuge tube. Allow the solution to
                   flow by gravity.
            11.3.5. When the load solution has stopped flowing (or is below the top of the resin
                   bed), rinse the column with two 5-mL volumes of 2-M HC1. Collect the
                   rinse solutions in the same 50-mL centrifuge tube (the total volume will be
                   approximately 20 mL).
            11.3.6. Record the date and time of the last rinse (Step 11.3.5) as the date and time
                   of separation of radium from parent and 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 Step 10.2 and Appendix A),
                   the 225Ra activity was unsupported before the tracer solution was added to the sample.
                   The activity reference date and time established during standardization of the 225Ra
                   tracer is used as the reference date for the 225Ra solution.

                   Note: If 225Ra at some degree of secular equilibrium with 229Th is added as tracer in
                   the initial step, the activity of 225Ra is dependent upon the total amount of time
                   between the last 229Th purification and Stepll.3.6. The decay of 225Ra starts at Step
                   11.3.6.
                                   ®
                   Note: The Diphonix  resin contains thorium, actinium and possibly other
                   radionuclides present in the sample and should be disposed of according to applicable
                   laboratory procedures.
                                              99^
    11.4.  Barium sulfate micro-precipitation of   Ra
          11.4.1.   Add ~3.0 g of (NH4)2SO4 to the 20 mL of 2M HC1 solution collected from
                   the Diphonix  column in Steps 11.3.3 - 11.3.5. Mix gently to completely
                   dissolve  the salt (dissolves readily).
          11.4.2.   Add 5.0  mL of isopropanol and mix gently (to avoid generating bubbles).
          11.4.3.   Place in  an ultrasonic bath filled with cold tap water (ice may be added) for
                   at least 20 minutes.
          11.4.4.   Pre-wet a 0.1 -micron filter using methanol or ethanol. Filter the suspension
                   through the filter using vacuum. The precipitate will not be visually
                   apparent.
          11.4.5.   Rinse the sample container and filter apparatus with three 2-mL portions of
                   20% isopropanol solution to dissolve residual (NFL^SO/i. Allow each rinse
                   to completely pass through filter before adding the subsequent rinse.
          11.4.6.   Rinse the filter apparatus with about 2 mL of methanol or ethanol to
                   facilitate drying. Turn off vacuum.
          11.4.7.   Carefully remove the filter and place it face-side up in a Petri dish. Carefully
                   dry under a heating lamp for few minutes. Avoid excessive heat which may
                   cause the filter to curl or shrink.
          11.4.8.   Mount the dried filter on a support appropriate for the counting system to be
                   used.
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                                                                        917
           11.4.9.   Store the filter for at least 24 hours to allow sufficient   At (third progeny
                    of 225Ra) to ingrow into the sample test source allowing a measurement
                    uncertainty for the 217At of < ~5 %.
           11.4.10.  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 need to have at least a
           24-hour ingrowth for 225Ac (and 221Fr and 217At) to meet Analytical Protocol
           Specifications for chemical yield with a counting time of 4 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.

           Note: Actinium 225 and other decay progeny from the 225Ra (e.g., 217At) tracer will continue to
           ingrow as  time elapses between separation 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 sample counting will be delayed longer than 36 hours, and MQOs foresee
           decisions being made close to detection levels, the impact of tracer progeny tailing should be
           minimized. Possible approaches for accomplishing this may include improving the signal to noise
           ratio by: 1) Processing a larger sample aliquant; 2) Decreasing the tracer activity added to a level
           that will still provide adequate statistics ~400-1500 net counts at the time of the analysis but will
           minimize spilldown into the 226Ra ROI.

     12.2. While the radiochemical yield is not directly used to determine the 226Ra activity of
           the sample, the following equation can be used to calculate the radiochemical yield
           (see Reference 16.6), if required:
                        R -Rh
                  RY=    '   b
                       sxAtx!t
           Where:
                                                                   99S                   917
              RY      =    Fractional radiochemical yield based on    Ra (from ingrown   At
                             at 7.07 MeV)
              Rt       =     Total count rate beneath the 217At peak at 7.07 MeV, cpm
              Rb       =    Background count rate for the same region, cpm
              e        =    Efficiency for the alpha spectrometer
              /t        =    Fractional abundance for the 7.07 MeV alpha peak counted (=
                             0.9999)
                                              917
              A\       =    Activity (dpm) of   At at midpoint of the count (see step 12.2.1)

           Note: If 225Ra is separated from 229Th for use as a purified tracer, the 225Ra activity is
           unsupported and begins to decay at the point of separation from 229Th, and not in Step 11.3.6.
           Instead, 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 in Step 11.3.6.

           12.2.1.   Activity of 217Ac at the midpoint of the count interval.
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                             	             917
              A\       =    The activity of  At at midpoint of the count (the target value that
                             should be achieved for 100% yield), in dpm.
                             = 3.0408(^225RJ  [e-Xld-e-M]
                                                99S         f\
              ^225Ra    =    Activity in dpm of  Ra tracer  added to the sample in Step 11.1.3
                             decay 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)
              X2        =    0.06931 d'1 (decay constant for 225Ac) - half-life = 10.0 days)
              3.0408   =   /12 /(/12 - /^ ) [a good 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:
                              ACa  =

           and
                                     Fax^ntxJDax/ax2.22
           where:
              ^4Ca        =  activity concentration of the analyte at time of count, (pCi/L)
              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)
6 When separated 225Ra tracer is added to the sample, its initial activity, ^sRa-mitmi, must be corrected for decay from
 he refen
follows:
the reference date established during standardization of the tracer to the point of separation of 225Ra and225 Ac as
where: k\ = decay constant for 225Ra (0.04652 d"1); and dt = time elapsed between the activity reference date for the
225Ra tracer solution added to the sample and the separation of 225Ra and 225Ac in Step 11.3.6 (days).

When 229Th containing ingrown 225Ra is added directly to the sample, the amount of 225Ra ingrown since purification
of the 229Th solution is calculated as:
where: A229ih = Activity of the 229Th standard on the date of the separation of Th and Ra (Step 11.3.6); ^ = decay
constant for 225Ra (0.04652 d"1); and d, = time elapsed between the purification of 229Th solution added to the sample
and the separation of 225Ra and 229Th/225Ac in Step 1 1.3.6 (days).


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                                          917
              A\         =   the activity of   At at midpoint of the count that should be
                             achieved for 100% yield, in dpm (see Step 12.2 for detailed
                             calculation)
              /t       =     Fractional abundance for the 7.07 MeV alpha peak counted (=
                             0.9999)
              Rnt        =   net count rate of the tracer in the defined ROI, in counts per minute
              Va         =   volume of the sample aliquant (L)
              Da         =   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 LOO.)1
              uc(ACz)    =   combined standard uncertainty of the activity concentration of the
                             analyte (pCi/L)
              u(Ai)      =   standard  uncertainty of the activity of the tracer added to the
                             sample (dpm)
              z/(Fa)      =   standard  uncertainty of the volume of sample aliquant (L)
              w(Rna)     =   standard  uncertainty of the net count rate of the analyte in counts
                             per minute
              u(RDt)     =   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(^4Ca)) calculation is arranged to
           eliminate the possibility of dividing by zero if Ra = 0.
           Note: The standard uncertainty of the activity of the tracer added to the sample must reflect that
           associated with the activity of the standard reference material and any other significant sources
           of uncertainty such as those introduced during the preparation of the tracer solution (e.g.,
           weighing or dilution factors) and during the process of adding the tracer to the sample.

           12.3.1    The net count rate of an analyte  or tracer and its standard uncertainty can be
                    calculated using the following equations:
                                   r    r
                             n   _ *-"x   *-b
                                         tb
                    and
                    where:

                                                                                        o
                       Rnx    =    net count rate of analyte or tracer, in counts per minute
7 If only the individual peak at 4.78 MeV is used, and completely resolved from the 4.602 MeV peak, the abundance
would be 0.9445.
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                        Cx     =    sample counts in the analyte or the tracer ROI
                        ts      =    sample count time (min)
                        Cbx    =    background counts in the same ROI as for x (x refers to the
                                     respective analyte or tracer count)
                        tb      =    background count time (min)
                        w(^nx) =    standard uncertainty of the net count rate of tracer or
                                     analyte, in counts per minute

           12.3.2   If the critical level concentration (Sc) or the minimum detectable
                    concentration (MDC) are requested (at an error rate of 5%), they can be
                    calculated using the following equations.9
          (1
          u
            Stapleton
--1  +^x 1 + f- +z:_ a](Rbatb+dstapleton]
                                     X At X  /,
    When the Type I decision error rate, a, equals 0.05, z\.a = 1.645, and the constant, dstapieton,
    from the Stapleton approximation is set to 0.4, the expression above becomes:
    S  =
          0.4x ^-1  + 0.677x  1 + ^ +1.645x  l(Rbatb + 0.4)x^x  1
               Vb   )           \   tb}          V              tb   {_
                                       tsxVaxRntxDax!a
    MDC =
                                                                       x At x 7t
8 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.
9 The formulations for the critical level and minimum detectable concentrations are as recommended in MARLAP
Section 20A.2.2, Equation 20.54, and Section 20A.3.2, Equation 20.74, respectively. For methods with very low
numbers of counts, these expressions provide better estimates than do the traditional formulas for the critical level
and MDC assuming that the  observed variance of the background conforms to Poisson statistics.  Consult MARLAP
when background variance may exceed that predicted by the Poisson model or when other decision error rates may
apply.
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   When the Type I decision error rate, a, equals 0.05, zi_a = 1.645, and the Type II decision
   error rate, /?, equals 0.05, z\-p = 1.645, the expression above becomes:
   MDC =
 2.71 x
                           3.29xjft  t. x
                                                   x 4 x /t
where:
   Rba
    i_a
                         background count rate for the analyte in the defined ROI, in counts
                         per minute
                         the 1-a quantile of the normal standard distribution
                         the 1-6 quantile of the normal standard distribution
    12.4   Results Reporting
          12.4. 1    The following data should be reported for each result: volume of sample
                   used; yield of tracer and its uncertainty; and full width at half maximum
                   (FWHM) of each peak used in the analysis.
          12.4.2    The following conventions should be used for each result:
                   12.4.2.1 Result in scientific notation ± combined standard uncertainty.
                   12.4.2.2 If solid material was filtered from the solution and analyzed
                           separately, the results of that analysis should be reported separately
                           as pCi/L of the original volume  from which the solids were filtered
                           if no other guidance is provided on reporting of results for the
                           solids. For example:
                           226Ra for Sample 12-1-99:
                                   Filtrate Result:            (1.28 ± 0.15) x 101 pCi/L
                                   Filtered Residue Result:    (2.50 ± 0.32) x 10° pCi/L

13 Method Performance
   13.1   Results of method validation performance are to be archived and available for
          reporting purposes.
   13.2   Expected turnaround time for an individual sample is -35 hours and per batch is -38
          hours.
                           ®
14 Pollution Prevention
   14. 1   The use of MnO2 and Diphonix  resin reduces the amount of solvents that would
          otherwise be needed to co-precipitate and purify the final sample test source.
1 5 Waste Management
   15.1   Nitric acid and hydrochloric acid wastes should be neutralized before disposal and
          then disposed of in accordance with local ordinances.
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


   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.

16 References
   16.1   RAW04-10,  "Radium-226/228 in Water (MnO2 Resin and DGA Resin Method),"
          Eichrom Technologies, Lisle Illinois (June 2006).
   16.2   A Rapid Method For Alpha-Spectrometric Analysis of Radium Isotopes in Natural
          Waters Using Ion-Selective Membrane Technology; S. Purkl and A. Eisenhauer.
          Applied Radiation and Isotopes 59(4):245-54 (Oct 2003).
   16.3   U.S. Environmental Protection Agency (EPA). 2009. Method Validation Guide for
          Radiological Laboratories Participating in Incident Response Activities. Revision 0.
          Office of Air and Radiation, Washington, DC. EPA 402-R-09-006, June. Available
          at: www.epa.gov/narel/incident guides.html and www.epa.gov/erln/radiation.html.
   16.4   Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP).
          2004. EPA 402-B-1304  04-001 A, July. Volume I, Chapters 6, 7, 20, Glossary;
          Volume II and Volume III, Appendix G. Available at: www.epa.gov/radiation/
          marlap/index.html.
   16.5   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   S. Purkl and  A. Eisenhauer (2003).  "A Rapid Method for Alpha-Spectrometric
          Analysis of Radium Isotopes in Natural Waters Using Ion-Selective Membrane
          Technology." Applied Radiation and Isotopes 59(4):245-54.
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples

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
7.067
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
99.99
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
At -217
Po -215
Po-211
Po -214
Po -213
Po -212
Po -212
                                                  217
       At (3rd progeny of 225Ra tracer)
      I             I -  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/nudat2/mdx dec.jsp; Queried: November 11, 2007.
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         Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples
   17.2  Ingrowth curves and Ingrowth factors
         1000
                       Ac-225 In-Growth in Ra-225
              0      200
400     600
Time, Hours
800     1000
ocn _,
onn t

•i^n -
Q.
"° inn -
en
Op
c
Ra-225 In-Growth in Th-229



jT
f
I
} 20 40 60 80 100 V.
Days




—»— Th-229, dpm
— B — Ra-225, dpm


10
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           Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples
                        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

0.002867

72

0.1748

2

0.005734

96

0.2200

3

0.008588

120

0.2596

4

0.01143

144

0.2940

5

0.01425

192

0.3494

6

0.01707

240

0.3893

24

0.06540

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 12.2.1.

                        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 6.
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples
    17.3   Example Alpha Spectrum from a Processed Sample
   100-.
                    5000
                                               218PoV21W
                                                                         — background
                                                                          - 1  I ground water
                                                                          o  Th-series
                                                                          e  Np-series
                                                                          :  U-Ra-series
                                                                            Ac-series
6000
7000
8000
9000
                                           Energy/keV
   Reference: Purkl, Stefan, Dissertation: Entwicklung und Anwendung neuer analytischer Methoden zur
   schnellen Bestimmung von kurzlebigen Radiumisotopen und Radon im Grundwasserbeeinflussten Milieu der
   Ostsee; Chapter 2, Figure 3; Christian-Albrechts Universitaet, Kiel, Germany, 2003.
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   17.4   Decay Schemes for Analyte and Tracer
               a
               164
     22.2 y

       P
                          226Ra Decay Scheme
                                 Secular equilibrium is
                                 established between 228Ra
                                 and 222Rn in about 18 days.
                1 h
                     3.1 min
                      a
                     27 min

                         P
                                                        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.
              225Ra (Including Parent)  Decay Scheme
 45.6 min
P
                        4.8 min
                  a
                                        a
                                        10.0 d
                       a
                                                               7.3x103a
                                                      14.9 d
                                 Secular Equilibrium between
                                 229Thand225Rais achieved
                                 after about 70 days.
          The short half-lives of 221Fr and 217At allow the
32 ms     217 At activity to be calculated from 225Ac activity
          based on secular equilibrium with 225Ac.
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            Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples
    17.5    Flowchart
                         Note: Shaded figures are associated with the timeline.
    11.1.1 to 11.1.5
   Aliquant sample.
    Add nitric acid,
   tracer and barium
   carrier and digest.
   Reduce volume.
                      Separation Scheme and Timeline for 226Ra
 11.3.1 to 11.3.2
 Prepare and pre-
condition Diphonix
    column.
11.1.6
Reconstitute with
with 1 00 ml
oflMHCL


                           11.2.5.1 or 11.2.5.2
                           Equilibrate sample
                           with MnO2 resin for
                              30-90 min.
        11.2.1 to 11.2.4
      Add NaOH and filter
     to remove particulates.
      Add calcium nitrate.
     Add indicator and adjust
         pH to neutral.
                                     11.2.6
                                  Transfer MnO2
                                resin to a column.
                                   Rinse with
                               demineralized water.
                                  Discard eluent.
      11.3.3to 11.3.4
Load solution from MnO2 onto
   Diphonix® column and
    allow to gravity drain.
  Elute with two more 5-mL
    aliquantsof 2M HCI.
          11.2.7
        Add 10 ml
     2M HCI/0.6% H2O2
    to strip analytefrom
      MnO2 resin into
      centrifuge tube.
                                  11.3.5
                           Collect, load, and rinse
                             eluates containing
                                 radium.
                    11.4.1 to 11.4.6
                 Add ammonium sulfate,
                    isopropanol.and
                     ultrasonicate
                   to ppt Ra/BaSO4.
                                                                           11.4.7to 11.4.10
                                                                            Filter, dry and
                                                                          mount precipitate.
                                                                             Start count.
   1     2.5
                                   Timeline (Hours)
                           7.
            30
34
37
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples
                                     Appendix A:
 Preparation and Standardization of   Ra 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
solution. Th-229 is separated from 225Ra using Y(OH)3 co-precipitation. Th-229 is carried in the
precipitate and most of the 225Ra remains in solution. Centrifugation to remove 229Th in the
                                                 99S                  	   90S
precipitate and filtration of the supernate produces the  Ra tracer solution. The   Ra 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 4.11.7 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. 225Ra ingrows in the 229Th fraction (Y(OH)3 precipitate) and after 50 days will be about
90% ingrown. After sufficient ingrowth time 22 Ra may be harvested to make a fresh 225Ra tracer
solution by dissolving the precipitate and re-precipitating Y(OH)3 to separate 229Th from 225Ra.
Multiple 225Ra generators may be prepared to ensure that 225Ra tracer will be continuously
available. The 225Ra 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
laboratory staff prepare an amount of 229Th sufficient to support the laboratory's expected
workload for 3-5 weeks. Since the 229Th solution is reused, and the half-life of 229Th is long
                                              OOP	
(7,342 years), the need to purchase a new certified   Th solution is kept to a minimum.

A2.Equipment and Supplies
   A2.1.  Refer to Section 6 of the main procedure.

A3.Reagents and Standards
   A3.1.  Refer to Section 7 of the main procedure.

A4. Procedure
   A4.1.  Add a sufficient amount of 229Th  solution (that which will yield at least 150-600
          dpm/mL of the 225Ra solution) to  a 50-mL centrifuge tube.10
   A4.2.  Add 20 mg 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 rad waste.
10 For example, if 40 mL of a 229Th solution of 600 dpm/mL is used, the maximum final activity of 225Ra will be
-510 dpm/mL at Step A4.8. 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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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


   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 2-M 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 NIST or
           (5 replicates)       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)

                                           99S
           Standardization    -80 dpm of the  Ra 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. Add 75 |ig Ba (0.075 mL of 1000 |ig/mL Ba) to all solutions.
   A4.11. Process the solutions to prepare sources for alpha spectrometry as follows:
          A4.11.1.   Slurry -1.0 g of Diphonix® resin per column in water.
          A4.11.2.   Transfer the resin to 0.8 cm (ID.) x 4 cm columns to obtain a uniform
                    resin bed.
          A4.11.3.   Precondition the columns by passing 20 mL 2 M HC1 through the
                    columns. Discard the effluent.
          A4.11.4.   Place clean 50-mL centrifuge tubes under the columns.
          A4.11.5.   Load the solutions from Step A4.10 onto the columns. Collect the
                    effluents in the 50-mL centrifuge tubes. Allow the solutions to flow by
                    gravity.
          A4.11.6.   When the load solutions have  stopped flowing, rinse columns with two 5-
                    mL volumes of 2-M HC1. Collect the rinse solutions in the same 50-mL
                    centrifuge tubes (the total volume will be about 20 mL).
          A4.11.7.   Record the  date and time of the last rinse as the date and time of
                    separation of radium  (beginning of 225Ac ingrowth).
          A4.11.8.   Add -3.0 grams of (NH4)2SO4 to the solutions from Step A4.11.6. Mix
                    gently to dissolve.
          A4.11.9.   Add 5.0 mL of isopropanol and mix gently.
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples


          A4.11.10. Place in an ultrasonic bath filled with cold tap water for at least 20
                    minutes.
          A4.11.11. Filter the suspensions through pre-wetted (using methanol or ethanol) 0.1-
                    um filters.
          A4.11.12. Rinse the filters with three 2-mL portions of 20% isopropanol. Allow each
                    rinse to completely pass through filter before adding the next rinse.
          A4.ll.13. Rinse each filter with about 2 mL of methanol or ethanol.
          A4.11.14. Carefully place each filter face-side up on a labeled stainless steel
                    planchet, or other suitable source mount, which has previously been
                    prepared with an appropriate adhesive (e.g., double stick tape).
          A4.11.15. Dry under a heat lamp for a few minutes.
          A4.11.16. After allowing about 24-hours ingrowth, count the  standardization sources
                    by alpha spectrometry.
   A4.12. Calculate the activity of 225Ra, in units of dpm/mL,  in the standardization replicates,
          at the 225Ra time of separation as follows:
          A7

(N*»At ^b]
V tmAt *b ,
X(A™Ra
)x(^J
                                 [(3.0408)(/() (e 2ld -e ^l
   where:
                                          99S
      A       =   Activity concentration of   Ra, in dpm/mL [at the time of separation from
                  229Th, Step A4.11.7]
       217     =   Total counts beneath the 217At peak at 7.07 MeV

              =   Total counts beneath the 226Ra peak at 4.78 MeV

      Nb      =   Background count rate for the corresponding region of interest,
      4       =   Duration of the count for the sample test source, minutes
      tb       =   Duration of the background count, minutes
      A       =   Activity of 226Ra added to  each aliquant, in dpm/mL
       226Ra
                            99^
      V226     =   volume of   Ra solution taken for the analysis (mL)
                            99S
      F225     =   volume of   Ra solution taken for the analysis (mL)
                                           ooc                   917
      d       =   Elapsed ingrowth time for   Ac [and the progeny   At], from separation to
                  the midpoint of the sample count, days
      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)
      3.0408  =   X2d/(X2d - \d) [a good approximation as the half lives  of 221Fr and 217At are
                                                        99S
                  short enough so secular equilibrium with  Ac 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.
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          Radium-226 in Water: Rapid Radiochemical Method for High-Activity Samples
                                                                  225T
   A4.13. Calculate the uncertainty of the activity concentration of the   Ra tracer at the
          reference date/time:
   where:
       226Ra
      Nb
      4
      tb
V,

/,
V

d
       226Ra
         ,™  )
         226Ray
        25Ra
       225Ra
      3.0408

                   '^AL + ^t_
                -^M xfe.CMOgx/,,,,
                  j    L        A
                                               - + ACl,  x
                                                   225 Ra
=  Standard uncertainty of the activity concentration of 225Ra, in dpm/mL
=  Total counts beneath the 217At peak at 7.07 MeV,
   	                     99^
=  Total counts beneath the   Ra tracer peak at 4.78 MeV
=  Background count rate for the corresponding region of interest,
=  Duration of the count for the sample test source, minutes
=  Duration of the background count, minutes
             99^
=  Activity of  Ra added to each aliquant, in dpm/mL
=  Activity of 225Ra, in dpm/mL
=  Volume of 226Ra solution taken for the analysis (mL)
=  Volume of 226Ra 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)
             99S
=  Volume of  Ra solution taken for the analysis (mL)
=  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)
=  0.06931 d"1 (decay constant for 225Ac) - half-life = 10.0 days)
=  Fractional  abundance for the 7.07 MeV alpha peak counted (= 0.9999)
=  h2d/(h2d - \d] [a good approximation as the half lives of221Fr and 217At
   are short enough so secular equilibrium with 225Ac is ensured]
=  Standard uncertainty of net count rate for 226Ra, in cpm
=  Net count rate for 226Ra, 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.
   A4.14. 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.
   A4.15. Store the centrifuge tube containing the Y(OH)3/Th(OH)4precipitate. After sufficient
          time has elapsed a fresh 225Ra tracer solution may be generated by dissolving the
          precipitate with 40 mL of 0.5-M HNOs and repeating Steps B4.3 through B4.9 of this
          Appendix.
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