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3.4.2 Method G–2, Low Resolution Gamma Spectrometry.
Principle: The sample is counted with a low resolution gamma detector, a thallium activated sodium iodide crystal. The detector is coupled to a photomultiplier tube and connected to a multichannel analyzer. The gamma emitting radionuclides in the sample are measured from the gamma count rates in the energy regions characteristic of the individual radionuclides. Corrections are made for counts contributed by other radionuclides to the spectral regions of the radionuclides of interest. Radiochemical separation may be used prior to counting to obtain less complex gamma spectra if needed.
Applicability: This method is applicable to the measurement of gamma emitting radionuclides with energies greater than 100 keV. It can be applied only to relatively simple mixtures of gamma emitting radionuclides. The samples counted may be in the form of particulate filters, absorbers, liquids or gas. The method can be applied to the analysis of gaseous radionuclides directly in an effluent stream by passing the gas stream through a chamber or cell containing the detector. ASTM–D–2459(12), EMSL–LV–0539–17(19).
3.4.3 Method G–3, Single Channel Gamma Spectrometry.
Principle: The sample is counted with a thallium activated sodium iodide crystal. The detector is coupled to a photomultiplier tube connected to a single channel analyzer. The activity of a gamma emitting radionuclide is determined from the gamma counts in the energy range for which the counter is set.
Applicability: This method is applicable to the measurement of a single gamma emitting radionuclide. It is not applicable to mixtures of radionuclides. The samples counted may be in the form of particulate filters, absorbers, liquids or gas. The method can be applied to the analysis of gaseous radionuclides directly in an effluent stream by passing the gas stream through a chamber or cell containing the detector.
3.4.4 Method G–4, Gross Gamma Counting.
Principle: The sample is counted with a gamma detector usually a thallium activated sodium iodine crystal. The detector is coupled to a photomultiplier tube and gamma rays above a specific threshold energy level are counted.
Applicability: Gross gamma measurements may be used to measure emissions of specific radionuclides only when it is known that the sample contains a single radionuclide or the identity and isotopic ratio of the radionuclides in the effluent stream are well known. When gross gamma measurements are used to determine emissions of specific radionuclides periodic measurements using Methods G–1 or G–2 should be made to demonstrate that the gross gamma measurements provide reliable emission data. This method may be applied to analysis of gaseous radionuclides directly in an effluent stream by placing the detector directly in or adjacent to the effluent stream or passing an extracted sample of the effluent stream through a chamber or cell containing the detector.
3.5 Counting Methods. All of the above methods with the exception of Method A–5 involve counting the radiation emitted by the radionuclide. Counting methods applicable to the measurement of alpha, beta and gamma radiations are listed below. The equipment needed and the counting principles involved are described in detail in ASTM–3648(8).
3.5.1 Alpha Counting:
• Gas Flow Proportional Counters. The alpha particles cause ionization in the counting gas and the resulting electrical pulses are counted. These counters may be windowless or have very thin windows.
• Scintillation Counters. The alpha particles transfer energy to a scintillator resulting in a production of light photons which strike a photomultiplier tube converting the light photons to electrical pulses which are counted. The counters may involve the use of solid scintillation materials such as zinc sulfide or liquid scintillation solutions.
• Solid-State Counters. Semiconductor materials, such as silicon surface-barrier p-n junctions, act as solid ionization chambers. The alpha particles interact which the detector producing electron hole pairs. The charged pair is collected by an applied electrical field and the resulting electrical pulses are counted.
• Alpha Spectrometers. Semiconductor detectors used in conjunction with multichannel analyzers for energy discrimination.
3.5.2 Beta Counting:
• Ionization Chambers. These chambers contain the beta-emitting nuclide in gaseous form. The ionization current produced is measured.
• Geiger-Muller (GM) Counters-or Gas Flow Proportional Counters. The beta particles cause ionization in the counting gas and the resulting electrical pulses are counted. Proportional gas flow counters which are heavily shielded by lead or other metal, and provided with an anti-coincidence shield to reject cosmic rays, are called low background beta counters.
• Scintillation Counters. The beta particles transfer energy to a scintillator resulting in a production of light photons, which strike a photomultiplier tube converting the light photon to electrical pulses which are counted. This may involve the use of anthracene crystals, plastic scintillator, or liquid scintillation solutions with organic phosphors.
• Liquid Scintillation Spectrometers. Liquid scintillation counters which use two photomultiplier tubes in coincidence to reduce background counts. This counter may also electronically discriminate among pulses of a given range of energy.
3.5.3 Gamma Counting:
• Low-Resolution Gamma Spectrometers. The gamma rays interact with thallium activated sodium iodide or cesium iodide crystal resulting in the release of light photons which strike a photomultiplier tube converting the light pulses to electrical pulses proportional to the energy of the gamma ray. Multi-channel analyzers are used to separate and store the pulses according to the energy absorbed in the crystal.
• High-Resolution gamma Spectrometers. Gamma rays interact with a lithium-drifted (Ge(Li)) or high-purity germanium (HPGe) semiconductor detectors resulting in a production of electron-hole pairs. The charged pair is collected by an applied electrical field. A very stable low noise preamplifier amplifies the pulses of electrical charge resulting from the gamma photon interactions. Multichannel analyzers or computers are used to separate and store the pulses according to the energy absorbed in the crystal.
• Single Channel Analyzers. Thallium activated sodium iodide crystals used with a single window analyzer. Pulses from the photomultiplier tubes are separated in a single predetermined energy range.
3.5.4 Calibration of Counters. Counters are calibrated for specific radionuclide measurements using a standard of the radionuclide under either identical or very similar conditions as the sample to be counted. For gamma spectrometers a series of standards covering the energy range of interest may be used to construct a calibration curve relating gamma energy to counting efficiency.
In those cases where a standard is not available for a radionuclide, counters may be calibrated using a standard with energy characteristics as similar as possible to the radionuclide to be measured. For gross alpha and beta measurements of the unidentified mixtures of radionuclides, alpha counters are calibrated with a natural uranium standard and beta counters with a cesium-137 standard. The standard must contain the same weight and distribution of solids as the samples, and be mounted in an identical manner. If the samples contain variable amounts of solids, calibration curves relating weight of solids present to counting efficiency are prepared. Standards other than those prescribed may be used provided it can be shown that such standards are more applicable to the radionuclide mixture measured.
3.6 Radiochemical Methods for Selected Radionuclides. Methods for a selected list of radionuclides are listed in Table 1. The radionuclides listed are those which are most commonly used and which have the greatest potential for causing doses to members of the public. For radionuclides not listed in Table 1, methods based on any of the applicable “principles of measurement” described in section 3.1 through 3.4 may be used.
3.7 Applicability of Gross Alpha and Beta Measurements to Unidentified Mixtures of Radionuclides. Gross alpha and beta measurements may be used as a screening measurement as a part of an emission measurement program to identify the need to do specific radionuclide analyses or to confirm or verify that unexpected radionuclides are not being released in significant quantities.
Gross alpha (Method A–4) or gross beta (Methods B–2 or B–4) measurements may also be used for the purpose of comparing the measured concentrations in the effluent stream with the limiting “Concentration Levels for Environmental Compliance” in table 2 of appendix E. For unidentified mixtures, the measured concentration value shall be compared with the lowest environmental concentration limit for any radionuclide which is not known to be absent from the effluent stream.
Table 1_List of Approved Methods for Specific Radionuclides
------------------------------------------------------------------------
Radionuclide Approved methods of analysis
------------------------------------------------------------------------
Am-241.................................... A-1, A-2, A-3, A-4
Ar-41..................................... B-1, B-2, G-1, G-2, G-3, G-4
Ba-140.................................... G-1, G-2, G-3, G-4
Br-82..................................... G-1, G-2, G-3, G-4
C-11...................................... B-1, B-2, G-1, G-2, G-3, G-4
C-14...................................... B-5
Ca-45..................................... B-3, B-4, B-5
Ce-144.................................... G-1, G-2, G-3, G-4
Cm-244.................................... A-1, A-2, A-3, A-4
Co-60..................................... G-1, G-2, G-3, G-4
Cr-51..................................... G-1, G-2, G-3, G-4
Cs-134.................................... G-1, G-2, G-3, G-4
Cs-137.................................... G-1, G-2, G-3, G-4
Fe-55..................................... B-5, G-1
Fe-59..................................... G-1, G-2, G-3, G-4
Ga-67..................................... G-1, G-2, G-3, G-4
H-3 (H2O)................................. B-5
H-3 (gas)................................. B-1
I-123..................................... G-1, G-2, G-3, G-4
I-125..................................... G-1
I-131..................................... G-1, G-2, G-3, G-4
In-113m................................... G-1, G-2, G-3, G-4
Ir-192.................................... G-1, G-2, G-3, G-4
Kr-85..................................... B-1, B-2, B-5, G-1, G-2, G-
3, G-4
Kr-87..................................... B-1, B-2, G-1, G-2, G-3, G-4
Kr-88..................................... B-1, B-2, G-1, G-2, G-3, G-4
Mn-54..................................... G-1, G-2, G-3, G-4
Mo-99..................................... G-1, G-2, G-3, G-4
N-13...................................... B-1, B-2, G-1, G-2, G-3, G-4
O-15...................................... B-1, B-2, G-1, G-2, G-3, G-4
P-32...................................... B-3, B-4, B-5
Pm-147.................................... B-3, B-4, B-5
Po-210.................................... A-1, A-2, A-3, A-4
Pu-238.................................... A-1, A-2, A-3, A-4
Pu-239.................................... A-1, A-2, A-3, A-4
Pu-240.................................... A-1, A-2, A-3, A-4
Ra-226.................................... A-1, A-2, G-1, G-2
S-35...................................... B-5
Se-75..................................... G-1, G-2, G-3, G-4
Sr-90..................................... B-3, B-4, B-5
Tc-99..................................... B-3, B-4, B-5
Te-201.................................... G-1, G-2, G-3, G-4
Uranium (total alpha)..................... A-1, A-2, A-3, A-4
Uranium (Isotopic)........................ A-1, A-3
Uranium (Natural)......................... A-5
Xe-133.................................... G-1
Yb-169.................................... G-1, G-2, G-3, G-4
Zn-65..................................... G-1, G-2, G-3, G-4
------------------------------------------------------------------------
4. Quality Assurance Methods
Each facility required to measure their radionuclide emissions shall conduct a quality assurance program in conjunction with the radionuclide emission measurements. This program shall assure that the emission measurements are representative, and are of known precision and accuracy and shall include administrative controls to assure prompt response when emission measurements indicate unexpectedly large emissions. The program shall consist of a system of policies, organizational responsibilities, written procedures, data quality specifications, audits, corrective actions and reports. This quality assurance program shall include the following program elements:
4.1 The organizational structure, functional responsibilities, levels of authority and lines of communications for all activities related to the emissions measurement program shall be identified and documented.
4.2 Administrative controls shall be prescribed to ensure prompt response in the event that emission levels increase due to unplanned operations.
4.3 The sample collection and analysis procedures used in measuring the emissions shall be described including where applicable:
4.3.1 Identification of sampling sites and number of sampling points, including the rationale for site selections.
4.3.2 A description of sampling probes and representativeness of the samples.
4.3.3 A description of any continuous monitoring system used to measure emissions, including the sensitivity of the system, calibration procedures and frequency of calibration.
4.3.4 A description of the sample collection systems for each radionuclide measured, including frequency of collection, calibration procedures and frequency of calibration.
4.3.5 A description of the laboratory analysis procedures used for each radionuclide measured, including frequency of analysis, calibration procedures and frequency of calibration.
4.3.6 A description of the sample flow rate measurement systems or procedures, including calibration procedures and frequency of calibration.
4.3.7 A description of the effluent flow rate measurement procedures, including frequency of measurements, calibration procedures and frequency of calibration.
4.4 The objectives of the quality assurance program shall be documented and shall state the required precision, accuracy and completeness of the emission measurement data including a description of the procedures used to assess these parameters. Accuracy is the degree of agreement of a measurement with a true or known value. Precision is a measure of the agreement among individual measurements of the same parameters under similar conditions. Completeness is a measure of the amount of valid data obtained compared to the amount expected under normal conditions.
4.5 A quality control program shall be established to evaluate and track the quality of the emissions measurement data against preset criteria. The program should include where applicable a system of replicates, spiked samples, split samples, blanks and control charts. The number and frequency of such quality control checks shall be identified.
4.6 A sample tracking system shall be established to provide for positive identification of samples and data through all phases of the sample collection, analysis and reporting system. Sample handling and preservation procedures shall be established to maintain the integrity of samples during collection, storage and analysis.
4.7 Regular maintenance, calibration and field checks shall be performed for each sampling system in use by satisfying the requirements found in Table 2: Maintenance, Calibration and Field Check Requirements.
Table 2_Maintenance, Calibration and Field Check Requirements
------------------------------------------------------------------------
Sampling system components Frequency of activity
------------------------------------------------------------------------
Cleaning of thermal anemometer elements As required by application.
Inspect pitot tubes for contaminant At least annually.
deposits.
Inspect pitot tube systems for leaks... At least annually.
Inspect sharp-edged nozzles for damage. At least annually or after
maintenance that could cause
damage.
Check nozzles for alignment, presence Annually.
of deposits, or other potentially
degrading factors.
Check transport lines of HEPA-filtered Annually.
applications to determine if cleaning
is required.
Clean transport lines.................. Visible deposits for HEPA-
filtered applications. Mean
mass of deposited material
exceeds 1g/m\2\ for other
applications.
Inspect or test the sample transport At least annually.
system for leaks.
Check mass flow meters of sampling At least quarterly.
systems with a secondary or transfer
standard.
Inspect rotameters of sampling systems At the start of each sampling
for presence of foreign matter. period.
Check response of stack flow rate At least quarterly.
systems.
Calibration of flow meters of sampling At least annually.
systems.
Calibration of effluent flow At least annually.
measurement devices.
Calibration of timing devices.......... At least annually.
------------------------------------------------------------------------
4.8 Periodic internal and external audits shall be performed to monitor compliance with the quality assurance program. These audits shall be performed in accordance with written procedures and conducted by personnel who do not have responsibility for performing any of the operations being audited.
4.9 A corrective action program shall be established including criteria for when corrective action is needed, what corrective actions will be taken and who is responsible for taking the corrective action.
4.10 Periodic reports to responsible management shall be prepared on the performance of the emissions measurements program. These reports should include assessment of the quality of the data, results of audits and description of corrective actions.
4.11 The quality assurance program should be documented in a quality assurance project plan that should address each of the above requirements.
5. References
(1) American National Standards Institute “Guide to Sampling Airborne Radioactive Materials in Nuclear Facilities”, ANSI–N13.1–1969, American National Standards Institute, New York, New York (1969).
(2) American Public Health Association, “Methods of Air Sampling”, 2nd Edition, Method 605, “Tentative Method of Analysis for Plutonium Content of Atmospheric Particulate Matter”. American Public Health Association, New York, NY (1977).
(3) Ibid, Method 601, “Tentative Method of Analysis for Gross Alpha Radioactivity Content of the Atmosphere”.
(4) Ibid, Method 602, “Tentative Method of the Analysis for Gross Beta Radioactivity Content of the Atmosphere”.
(5) Ibid, Method 608, “Tentative Method of Analysis for Strontium-90 Content of Atmospheric Particulate Matter”.
(6) Ibid, Method 609, “Tentative Method of Analysis for Tritium Content of the Atmosphere”.
(7) Ibid, Method 603, “Tentative Method of Analysis for Iodine-131 Content of the Atmosphere”.
(8) American Society for Testing and Materials, 1986 Annual Book ASTM Standards, Designation D–3648–78, “Standard Practices for the Measurement of Radioactivity”. American Society for Testing and Materials, Philadelphia, PA (1986).
(9) Ibid, Designation D–3649–85, “Standard Practice for High Resolution Gamma Spectrometry”.
(10) Ibid, Designation D–1943–81, “Standard Test Method for Alpha Particle Radioactivity of Water”.
(11) Ibid, Designation D–1890–81, “Standard Test Method for Beta Particle Radioactivity of Water”.
(12) Ibid, Designation D–2459–72, “Standard Test Method for Gamma Spectrometry of Water”.
(13) Ibid, Designation D–3972–82, “Standard Test Method for Isotopic Uranium in Water by Radiochemistry”.
(14) Ibid, Designation D–2907–83, “Standard Test Methods for Microquantities of Uranium in Water by Fluorometry”.
(15) Ibid, Designation E–318, “Standard Test Method for Uranium in Aqueous Solutions by Colorimetry”.
(16) Ibid, Designation D–3084–75, “Standard Practice for Alpha Spectrometry of Water”.
(17) Corley, J.P. and C.D. Corbit, “A Guide for Effluent Radiological Measurements at DOE Installations”, DOE/EP–0096, Pacific Northwest Laboratories, Richland, Washington (1983).
(18) Department of Energy, “RESL Analytical Chemistry Branch Procedures Manual”, IDO–12096, U.S. Department of Energy, Idaho Falls, Idaho (1982).
(19) Environmental Protection Agency, “Radiochemical Analytical Procedures for Analysis of Environmental Samples”, EMSL–LV–0539–17, U.S. Environmental Protection Agency, Environmental Monitoring and Support Laboratory, Las Vegas, Nevada (1979).
(20) Environmental Protection Agency, “Radiochemistry Procedures Manual”, EPA 520/5–84–006, Eastern Environmental Radiation Facility, Montgomery, Alabama (1984).
(21) National Council on Radiation Protection and Measurements, NCRP Report No. 50, “Environmental Radiation Measurements”, National Council on Radiation Protection and Measurement, Bethesda, Maryland (1976).
(22) Ibid, Report No. 47, “Tritium Measurement Techniques”. (1976).
(23) Ibid, Report No. 58 “A Handbook of Radioactivity Measurement Procedures” (1985).
(24) Environmental Protection Agency, “Indoor Radon and Radon Decay Product Measurement Protocols”, EPA 520/1–89–009, U.S. Environmental Protection Agency, Washington, DC (1989).
Method 115—Monitoring for Radon-222 Emissions
This appendix describes the monitoring methods which must be used in determining the radon-222 emissions from underground uranium mines, uranium mill tailings piles, phosphogypsum stacks, and other piles of waste material emitting radon.
1. Radon-222 Emissions from Underground Uranium Mine Vents
1.1 Sampling Frequency and Calculation of Emissions. Radon-222 emissions from underground uranium mine vents shall be determined using one of the following methods:
1.1.1 Continuous Measurement. These measurements shall be made and the emissions calculated as follows:
(a) The radon-222 concentration shall be continuously measured at each mine vent whenever the mine ventilation system is operational.
(b) Each mine vent exhaust flow rate shall be measured at least 4 times per year.
(c) A weekly radon-222 emission rate for the mine shall be calculated and recorded weekly as follows:
Aw= C1Q1T1 + C2Q2T2 + . . . CiQiTi
Where:
Aw=Total radon-222 emitted from the mine during week (Ci)
Ci=Average radon-222 concentration in mine vent i(Ci/m 3 )
Qi=Volumetric flow rate from mine vent i(m 3 /hr)
Ti=Hours of mine ventilation system operation during week for mine vent i(hr)
(d) The annual radon-222 emission rate is the sum of the weekly emission rates during a calendar year.
1.1.2 Periodic Measurement. This method is applicable only to mines that continuously operate their ventilation system except for extended shutdowns. Mines which start up and shut down their ventilation system frequently must use the continuous measurement method describe in Section 1.1.1 above. Emission rates determined using periodic measurements shall be measured and calculated as follows:
(a) The radon-222 shall be continuously measured at each mine vent for at least one week every three months.
(b) Each mine vent exhaust flow rate shall be measured at least once during each of the radon-222 measurement periods.
(c) A weekly radon-222 emission rate shall be calculated for each weekly period according to the method described in Section 1.1.1. In this calculation T=168 hr.
(d) The annual radon-222 emission rate from the mine should be calculated as follows:
Where:
Ay=Annual radon-222 emission rate from the mine(Ci)
Awi=Weekly radon-222 emission rate during the measurement period i (Ci)
n=Number of weekly measurement periods per year
Ws=Number of weeks during the year that the mine ventilation system is shut down in excess of 7 consecutive days, i.e. the sum of the number of weeks each shut down exceeds 7 days
1.2 Test Methods and Procedures
Each underground mine required to test its emissions, unless an equivalent or alternative method has been approved by the Administrator, shall use the following test methods:
1.2.1 Test Method 1 of appendix A to part 60 shall be used to determine velocity traverses. The sampling point in the duct shall be either the centroid of the cross section or the point of average velocity.
1.2.2 Test Method 2 of appendix A to part 60 shall be used to determine velocity and volumetric flow rates.
1.2.3 Test Methods A–6 or A–7 of appendix B, Method 114 to part 61 shall be used for the analysis of radon–222. Use of Method A–7 requires prior approval of EPA based on conditions described in appendix B.
1.2.4 A quality assurance program shall be conducted in conformance with the programs described for Continuous Radon Monitors and Alpha Track Detectors in EPA 520/1–89–009. (2)
2. Radon–222 Emissions from Uranium Mill Tailings Piles
2.1 Measurement and Calculation of Radon Flux from Uranium Mill Tailings Piles.
2.1.1 Frequency of Flux Measurement. A single set of radon flux measurements may be made, or if the owner or operator chooses, more frequent measurements may be made over a one year period. These measurements may involve quarterly, monthly or weekly intervals. All radon measurements shall be made as described in paragraphs 2.1.2 through 2.1.6 except that for measurements made over a one year period, the requirement of paragraph 2.1.4(c) shall not apply. The mean radon flux from the pile shall be the arithmetic mean of the mean radon flux for each measurement period. The weather conditions, moisture content of the tailings and area of the pile covered by water existing at the time of the measurement shall be chosen so as to provide measurements representative of the long term radon flux from the pile and shall be subject to EPA review and approval.
2.1.2 Distribution of Flux Measurements. The distribution and number of radon flux measurements required on a pile will depend on clearly defined areas of the pile (called regions) that can have significantly different radon fluxes due to surface conditions. The mean radon flux shall be determined for each individual region of the pile. Regions that shall be considered for operating mill tailings piles are:
(a) Water covered areas,
(b) Water saturated areas (beaches),
(c) Dry top surface areas, and
(d) Sides, except where earthen material is used in dam construction.
For mill tailings after disposal the pile shall be considered to consist of only one region.
2.1.3 Number of Flux Measurements. Radon flux measurements shall be made within each region on the pile, except for those areas covered with water. Measurements shall be made at regularly spaced locations across the surface of the region, realizing that surface roughness will prohibit measurements in some areas of a region. The minimum number of flux measurements considered necessary to determine a representative mean radon flux value for each type of region on an operating pile is:
(a) Water covered area—no measurements required as radon flux is assumed to be zero,
(b) Water saturated beaches—100 radon flux measurements,
(c) Loose and dry top surface—100 radon flux measurements,
(d) Sides—100 radon flux measurements, except where earthern material is used in dam construction.
For a mill tailings pile after disposal which consists of only one region a minimum of 100 measurements are required.
2.1.4 Restrictions to Radon Flux Measurements. The following restrictions are placed on making radon flux measurements:
(a) Measurements shall not be initiated within 24 hours of a rainfall.
(b) If a rainfall occurs during the 24 hour measurements period, the measurement is invalid if the seal around the lip of the collector has washed away or if the collector is surrounded by water.
(c) Measurements shall not be performed if the ambient temperature is below 35 °F or if the ground is frozen.
2.1.5 Areas of Pile Regions. The approximate area of each region of the pile shall be determined in units of square meters.
2.1.6 Radon Flux Measurement. Measuring radon flux involves the adsorption of radon on activated charcoal in a large-area collector. The radon collector is placed on the surface of the pile area to be measured and allowed to collect radon for a time period of 24 hours. The radon collected on the charcoal is measured by gamma-ray spectroscopy. The detailed measurement procedure provided in appendix A of EPA 520/5–85–0029(1) shall be used to measure the radon flux on uranium mill tailings, except the surface of the tailings shall not be penetrated by the lip of the radon collector as directed in the procedure, rather the collector shall be carefully positioned on a flat surface with soil or tailings used to seal the edge.
2.1.7 Calculations. The mean radon flux for each region of the pile and for the total pile shall be calculated and reported as follows:
(a) The individual radon flux calculations shall be made as provided in appendix A EPA 86 (1). The mean radon flux for each region of the pile shall be calculated by summing all individual flux measurements for the region and dividing by the total number of flux measurements for the region.
(b) The mean radon flux for the total uranium mill tailings pile shall be calculated as follows.
Where:
Js=Mean flux for the total pile (pCi/m 2 -s)
Ji=Mean flux measured in region i (pCi/m 2 -s)
Ai=Area of region i (m 2 )
At=Total area of the pile (m 2 )
2.1.8 Reporting. The results of individual flux measurements, the approximate locations on the pile, and the mean radon flux for each region and the mean radon flux for the total stack shall be included in the emission test report. Any condition or unusual event that occurred during the measurements that could significantly affect the results should be reported.
3.0 Radon-222 Emissions from Phosphogypsum Stacks.
3.1 Measurement and Calculation of the Mean Radon Flux. Radon flux measurements shall be made on phosphogypsum stacks as described below:
3.1.1 Frequency of Measurements. A single set of radon flux measurements may be made after the phosphogypsum stack becomes inactive, or if the owner or operator chooses, more frequent measurements may be made over a one year period. These measurements may involve quarterly, monthly or weekly intervals. All radon measurements shall be made as described in paragraphs 3.1.2 through 3.1.6 except that for measurements made over a one year period, the requirement of paragraph 3.1.4(c) shall not apply. For measurements made over a one year period, the radon flux shall be the arithmetic mean of the mean radon flux for each measurement period.
3.1.2 Distribution and Number of Flux Measurements. The distribution and number of radon flux measurements required on a stack will depend on clearly defined areas of the stack (called regions) that can have significantly different radon fluxes due to surface conditions. The mean radon flux shall be determined for each individual region of the stack. Regions that shall be considered are:
(a) Water covered areas,
(b) Water saturated areas (beaches),
(c) Loose and dry top surface areas,
(d) Hard-packed roadways, and
(e) Sides.
3.1.3 Number of Flux Measurements. Radon flux measurements shall be made within each region on the phosphogypsum stack, except for those areas covered with water. Measurements shall be made at regularly spaced locations across the surface of the region, realizing that surface roughness will prohibit measurements in some areas of a region. The minimum number of flux measurements considered necessary to determine a representative mean radon flux value for each type of region is:
(a) Water covered area—no measurements required as radon flux is assumed to be zero,
(b) Water saturated beaches—50 radon flux measurements,
(c) Loose and dry top surface—100 radon flux measurements,
(d) Hard-packed roadways—50 radon flux measurements, and
(e) Sides—100 radon flux measurements.
A minimum of 300 measurements are required. A stack that has no water cover can be considered to consist of two regions, top and sides, and will require a minimum of only 200 measurements.
3.1.4 Restrictions to Radon Flux Measurements. The following restrictions are placed on making radon flux measurements:
(a) Measurements shall not be initiated within 24 hours of a rainfall.
(b) If a rainfall occurs during the 24 hour measurement period, the measurement is invalid if the seal around the lip of the collector has washed away or if the collector is surrounded by water.
(c) Measurements shall not be performed if the ambient temperature is below 35 °F or if the ground is frozen.
3.1.5 Areas of Stack Regions. The approximate area of each region of the stack shall be determined in units of square meters.
3.1.6 Radon Flux Measurements. Measuring radon flux involves the adsorption of radon on activated charcoal in a large-area collector. The radon collector is placed on the surface of the stack area to be measured and allowed to collect radon for a time period of 24 hours. The radon collected on the charcoal is measured by gamma-ray spectroscopy. The detailed measurement procedure provided in appendix A of EPA 520/5–85–0029(1) shall be used to measure the radon flux on phosphogypsum stacks, except the surface of the phosphogypsum shall not be penetrated by the lip of the radon collector as directed in the procedure, rather the collector shall be carefully positioned on a flat surface with soil or phosphogypsum used to seal the edge.
3.1.7 Calculations. The mean radon flux for each region of the phosphogypsum stack and for the total stack shall be calculated and reported as follows:
(a) The individual radon flux calculations shall be made as provided in appendix A EPA 86 (1). The mean radon flux for each region of the stack shall be calculated by summing all individual flux measurements for the region and dividing by the total number of flux measurements for the region.
(b) The mean radon flux for the total phosphogypsum stack shall be calculated as follows.
Where:
Js=Mean flux for the total stack (pCi/m 2 -s)
Ji=Mean flux measured in region i (pCi/m 2 -s)
Ai=Area of region i (m 2 )
At=Total area of the stack
3.1.8 Reporting. The results of individual flux measurements, the approximate locations on the stack, and the mean radon flux for each region and the mean radon flux for the total stack shall be included in the emission test report. Any condition or unusual event that occurred during the measurements that could significantly affect the results should be reported.
4.0 Quality Assurance Procedures for Measuring Rn–222 Flux
A. Sampling Procedures
Records of field activities and laboratory measurements shall be maintained. The following information shall be recorded for each charcoal canister measurement:
(a) Site
(b) Name of pile
(c) Sample location
(d) Sample ID number
(e) Date and time on
(f) Date and time off
(g) Observations of meteorological conditions and comments
Records shall include all applicable information associated with determining the sample measurement, calculations, observations, and comments.
B. Sample Custody
Custodial control of all charcoal samples exposed in the field shall be maintained in accordance with EPA chain-of-custody field procedures. A control record shall document all custody changes that occur between the field and laboratory personnel.
C. Calibration Procedures and Frequency
The radioactivity of two standard charcoal sources, each containing a carefully determined quantity of radium-226 uniformly distributed through 180g of activated charcoal, shall be measured. An efficiency factor is computed by dividing the average measured radioactivity of the two standard charcoal sources, minus the background, in cpm by the known radioactivity of the charcoal sources in dpm. The same two standard charcoal sources shall be counted at the beginning and at the end of each day's counting as a check of the radioactivity counting equipment. A background count using unexposed charcoal should also be made at the beginning and at the end of each counting day to check for inadvertent contamination of the detector or other changes affecting the background. The unexposed charcoal comprising the blank is changed with each new batch of charcoal used.
D. Internal Quality Control Checks and Frequency
The charcoal from every tenth exposed canister shall be recounted. Five percent of the samples analyzed shall be either blanks (charcoal having no radioactivity added) or samples spiked with known quantities of radium-226.
E. Data Precision, Accuracy, and Completeness
The precision, accuracy, and completeness of measurements and analyses shall be within the following limits for samples measuring greater than 1.0 pCi/m 2 -s.
(a) Precision: 10%
(b) Accuracy: ±10%
(c) Completeness: at least 85% of the measurements must yield useable results.
5.0 References
(1) Hartley, J.N. and Freeman, H.D., “Radon Flux Measurements on Gardinier and Royster phosphogypsum Piles Near Tampa and Mulberry, Florida,” U.S. Environmental Protection Agency Report, EPA 520/5–85–029, January 1986.
(2) Environmental Protection Agency, “Indoor Radon and Radon Decay Product Measurement Protocols”, EPA 520/1–89–009, U.S. Environmental Protection Agency, Washington, DC. (1989).
[38 FR 8826, Apr. 6, 1973]
Editorial Notes: 1. For Federal Register citations to appendix B see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed volume and on GPO Access.
2. At 65 FR 62161, Oct. 17, 2000, appendix B to part 61 was amended by revising Methods 101, 101A, 102, 103, 104, 105, 106, 107, 107A, 108, 108A, 108B, 108C, and 111. However, because the amendment contains no revised text for Method 107A, this part of the revision could not be incorporated.
Appendix C to Part 61—Quality Assurance Procedures
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Procedure 1—Determination of Adequate Chromatographic Peak Resolution
In this method of dealing with resolution, the extent to which one chromatographic peak overlaps another is determined.
For convenience, consider the range of the elution curve of each compound as running from -2s to +2s. This range is used in other resolution criteria, and it contains 95.45 percent of the area of a normal curve. If two peaks are separated by a known distance, b, one can determine the fraction of the area of one curve that lies within the range of the other. The extent to which the elution curve of a contaminant compound overlaps the curve of a compound that is under analysis is found by integrating the contaminant curve over the limits b-2ss to b+2ss, where ss is the standard deviation of the sample curve.
This calculation can be simplified in several ways. Overlap can be determined for curves of unit area; then actual areas can be introduced. Desired integration can be resolved into two integrals of the normal distribution function for which there are convenient calculation programs and tables. An example would be Program 15 in Texas Instruments Program Manual ST1, 1975, Texas Instruments, Inc., Dallas, Texas 75222.
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In judging the suitability of alternate GC columns or the effects of altering chromatographic conditions, one can employ the area overlap as the resolution parameter with a specific maximum permissible value.
The use of Gaussian functions to describe chromatographic elution curves is widespread. However, some elution curves are highly asymmetric. In cases where the sample peak is followed by a contaminant that has a leading edge that rises sharply but the curve then tails off, it may be possible to define an effective width for tc as “twice the distance from the leading edge to a perpendicular line through the maxim of the contaminant curve, measured along a perpendicular bisection of that line.”
Procedure 2—Procedure for Field Auditing GC Analysis
Responsibilities of audit supervisor and analyst at the source sampling site include the following:
A. The audit supervisor verifies that audit cylinders are stored in a safe location both before and after the audit to prevent vandalism.
B. At the beginning and conclusion of the audit, the analyst records each cylinder number and pressure. An audit cylinder is never analyzed when the pressure drops below 200 psi.
C. During the audit, the analyst performs a minimum of two consecutive analyses of each audit cylinder gas. The audit must be conducted to coincide with the analysis of source test samples, normally immediately after GC calibration and prior to sample analyses.
D. At the end of audit analyses, the audit supervisor requests the calculated concentrations from the analyst and compares the results with the actual audit concentrations. If each measured concentration agrees with the respective actual concentration within ±10 percent, he directs the analyst to begin analyzing source samples. Audit supervisor judgment and/or supervisory policy determine action when agreement is not within ±10 percent. When a consistent bias in excess of 10 percent is found, it may be possible to proceed with the sample analysis, with a corrective factor to be applied to the results at a later time. However, every attempt should be made to locate the cause of the discrepancy, as it may be misleading. The audit supervisor records each cylinder number, cylinder pressure (at the end of the audit), and all calculated concentrations. The individual being audited must not under any circumstance be told actual audit concentrations until calculated concentrations have been submitted to the audit supervisor.
Field Audit Report
Part A— To be filled out by organization supplying audit cylinders.
1. Organization supplying audit sample(s) and shipping address
____________________
2. Audit supervisor, organization, and phone number
____________________
____________________
3. Shipping instructions: Name, Address, Attention
____________________
____________________
____________________
4. Guaranteed arrival date for cylinders____________________
5. Planned shipping date for cylinders____________________
6. Details on audit cylinders from last analysis
------------------------------------------------------------------------
Low conc. High conc.
------------------------------------------------------------------------
a. Date of last analysis........................ .......... ..........
b. Cylinder number.............................. .......... ..........
c. Cylinder pressure, psi....................... .......... ..........
d. Audit gas(es)/balance gas.................... .......... ..........
e. Audit gas(es), ppm........................... .......... ..........
f. Cylinder construction........................ .......... ..........
------------------------------------------------------------------------
Part B—To be filled out by audit supervisor.
1. Process sampled____________________
____________________
2. Audit location____________________
____________________
3. Name of individual audit____________________
4. Audit date____________________
5. Audit results:
------------------------------------------------------------------------
Low High
conc. conc.
cylinder cylinder
------------------------------------------------------------------------
a. Cylinder number.................................. ........ ........
b. Cylinder pressure before audit, psi.............. ........ ........
c. Cylinder pressure after audit, psi............... ........ ........
d. Measured concentration, ppm Injection #1* ........ ........
Injection #2* Average..............................
e. Actual audit concentration, ppm (Part A, 6e)..... ........ ........
f. Audit accuracy:\1\
Low Conc. Cylinder................................ ........ ........
High Conc. Cylinder............................... ........ ........
Percent \1\ accuracy=
Measured Conc.-Actual Conc.
________________ x100
Actual Conc.
g. Problems detected (if any)....................... ........ ........
------------------------------------------------------------------------
\1\ Results of two consecutive injections that meet the sample analysis
criteria of the test method.
[47 FR 39178, Sept. 7, 1982]
Appendix D to Part 61—Methods for Estimating Radionuclide Emissions
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1. Purpose and Background
Facility owners or operators may estimate radionuclide emissions to the atmosphere for dose calculations instead of measuring emissions. Particulate emissions from mill tailings piles should be estimated using the procedures listed in reference re num;2. All other emissions may be estimated by using the “Procedures” listed below, or using the method described in reference #1.
2. Procedure
To estimate emissions to the atmosphere:
(a) Determine the amount (in curies) used at facilities for the period under consideration. Radioactive materials in sealed packages that remain unopened, and have not leaked during the assessment period should not be included in the calculation.
(b) Multiply the amount used by the following factors which depend on the physical state of the radionuclide. They are:
(i) 1 for gases;
(ii) 10-3 for liquids or particulate solids; and
(iii) 10-6 for solids.
If any nuclide is heated to a temperature of 100 degrees Celsius or more, boils at a temperature of 100 degrees Celsius or less, or is intentionally dispersed into the environment, it must be considered to be a gas.
(c) If a control device is installed between the place of use and the point of release, multiply emissions from (b) by an adjustment factor. These are presented in Table 1.
Table 1_Adjustment to Emission Factors for Effluent Controls
----------------------------------------------------------------------------------------------------------------
Types of radionuclides Adjustment factor to
Controls controlled emissions Comments and conditions
----------------------------------------------------------------------------------------------------------------
HEPA filters..................... Particulates............. 0.01.................... Not applicable to
gaseous radionuclides;
periodic testing is
prudent to ensure high
removal efficiency.
Fabric filter.................... Particulates............. 0.1..................... Monitoring would be
prudent to guard
against tears in
filter.
Sintered metal................... Particulates............. 1....................... Insufficient data to
make recommendation.
Activated carbon filters......... Iodine gas............... 0.1..................... Efficiency is time
dependent; monitoring
is necessary to ensure
effectiveness.
Douglas bags: Held one week or Xenon.................... 0.5/wk.................. Based on xenon half-life
longer for decay. of 5.3 days;
Douglas bags: Released within one Xenon.................... 1....................... Provides no reduction of
week. exposure to general
public.
Venturi scrubbers................ Particulates............. 0.05.................... Although venturis may (continued)