AIR SAMPLING PROGRAM/METHODS RCT STUDY GUIDE State the three primary objectives of an airborne radioactivity sampling program.

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1 LEARNING OBJECTIVES: State the three primary objectives of an airborne radioactivity sampling program Describe the three physical states of airborne radioactive contaminants List the two primary considerations to ensure a representative air sample is obtained For purposes of appropriate air sampling, state the relationship between sample function and location Define the term "isokinetic sampling" as associated with airborne radioactivity sampling Identify the six general methods for obtaining samples or measurements of airborne radioactivity concentrations and describe the principle of operation for each method. a. Filtration b. Volumetric c. Impaction/impingement d. Adsorption e. Condensation/dehumidification f. In-line/flow-through detection Using the air sample calculation, calculate an air sample concentration List the factors that affect the accuracy of airborne radioactivity measurements State the purpose of the five types of airborne radioactivity samplers/monitors: a. Personal air samplers (breathing zone) b. High volume/flow rate air samplers c. Low volume/flow rate air samplers d. Movable continuous air monitors e. Installed continuous air monitoring systems Describe the general considerations for selection of an air sampling method. -1- FH 05/2003

2 Define a "General Area" air sample Define a "Breathing Zone" air sample Define upwind and downwind as applied to air sampler location Describe the responsibilities of an RCT should an air sample result show greater than 10% of DAC on the initial calculation Describe the process for evaluating an air sample for Radon/Thoron Define the criteria for the placement of a portable CAM in a room (area) Calculate CAM Alarm Set Point (ASP) and state the maximum ASP value allowed State the requirements for taking a CAM out-of-service if it fails an operational or performance test State the beta and alpha CAM efficiency parameter criteria Define Protection Factor (PF) as it applies to respirators INTRODUCTION Characterizing the airborne hazard is necessary so we can prescribe controls to keep our employees from receiving unnecessary exposures to radioactive material. Additionally, airborne radioactivity measurements are necessary to ensure that the control measures assigned are effective and continue to be effective. Air monitoring equipment should be used in situations where airborne radioactivity levels can fluctuate and early detection of airborne radioactivity could prevent or minimize inhalation of radioactivity by personnel. Selection of air monitoring equipment should be based on the specific job being monitored. Air monitoring equipment includes portable and fixed air sampling equipment and continuous air monitors. Air sampling equipment shall be used in occupied areas where, under normal operating conditions, a person is likely to receive an annual intake of 2 percent or more of the specified Annual Limit of Intake (ALI) values (40 Derived Air Concentration (DAC) hours). An annual intake of 2 percent of a specified ALI generally represents a committed effective dose equivalent to a person of approximately 100 mrem. -2- FH 05/2003

3 Continuous air monitoring equipment shall be installed in occupied areas where a person without respiratory protection is likely to be exposed to a concentration of radioactivity in air exceeding 40 DAC-hrs in one week, or where there is a need to alert potentially exposed workers to unexpected increases in the airborne radioactivity levels. One DAC breathed for 40 hrs (1 work week) = 40 DAC-hrs. ( 40 DAC-hrs = approximately 100 mrem CEDE.) PURPOSE AND OBJECTIVES OF AIRBORNE RADIOACTIVITY SAMPLING Airborne radioactive contaminants are of concern to the radiological control organization due to the biological effects of the ionizing radiation emitted by those contaminants. Airborne radioactive material can become an internal hazaw4d as well as an external hazard (source of exposure). Regulations govern the allowable or limiting effective dose equivalent to an individual. The effective dose equivalent of an individual is determined by combining the external and internal dose equivalent values. Typically, airborne radioactivity levels are maintained well below allowable levels to keep the internal dose equivalent contribution to the total effective dose equivalent small. Confirmation that airborne radioactivity levels are maintained low is accomplished by the airborne radioactivity sampling program. It is important to note that the individual dose equivalent from internal sources is not normally determined from air sampling analysis data, unless other information, such as bioassay data, is unavailable. Airborne radioactivity sampling is performed to determine the radiological conditions of the air that workers breathe during radiological work, that generally exists in specific areas, rooms or buildings, and that is exhausted to the outside environment State the three primary objectives of an airborne radioactivity sampling program. The primary objectives of an airborne radioactivity sampling program are: to measure the concentration of the radioactive contaminant(s) in the air by collection and analysis; to identify the type and physical characteristics of the radioactive contaminant to help evaluate the hazard potential to the worker; -3- FH 05/2003

4 and to evaluate the performance of airborne radioactivity control measures. The primary goal of the airborne radioactivity sampling program is to determine if the level of protection provided to the worker is sufficient to minimize the internal dose equivalent. Allowable concentration values, such as DACs, are used as an index of the degree of control needed and achieved. Documented measurements of the airborne radioactivity concentrations are required to demonstrate that satisfactory control is achieved and maintained. The relationship between airborne concentration and internal dose equivalent is considered to be 2.5 mrem per DAC-hr. (Standard thumb rule) Additionally, the airborne radioactivity sampling program must demonstrate that airborne radioactivity released to the general environment is maintained as low as possible and below the allowable limits established by regulatory agencies. THE NATURE OF AIRBORNE RADIOACTIVITY Describe the three physical states of airborne radioactive contaminants. Particulates Gases Airborne radioactive contaminants are generally divided into three categories, based on the physical state of the contaminant. Particulate contaminates are solid and liquid particles, ranging upward from molecular sizes (approximately 10-3 Φm,(.001 micron)), in an airborne suspension. Solids may be subdivided into fumes, dusts, and smokes, which are distinguished mainly by their mode of generation. Liquids are subdivided into mists and fogs, depending on the dispersion of the liquid particulates. The term "aerosols" is used to collectively refer to airborne suspensions of solid and liquid particulates. Generally, particulates are more readily retained in the lungs than are gases, but retention is highly dependent on particle size and charge. Particulates are found in a distribution of sizes and the retention and deposition in the body varies with the size distribution of the particulates. While this suggests that particulate airborne contaminant sampling should measure particle size, this is not practically accomplished on a routine basis. Particulate size is utilized in certain sampling instruments to separate larger particles from smaller particles (e.g., impactors). Gases are substances that, under normal conditions of temperature and pressure, exist in the gaseous phase. The retention of the gases in the body from inhalation is poor and -4- FH 05/2003

5 Vapors usually radioactive gases are treated as an external source of exposure. Radioactive gases typically found are the fission product gases, such as xenon and krypton, and naturally occurring radon. While the gases contribute primarily to external exposure, the particulate progeny to which they decay, can contribute to internal exposure. Vapors are considered the gaseous phase of a substance that is normally a solid or liquid under normal conditions of temperature and pressure. Airborne vapor sampling is most commonly done for radioiodine and tritium. The contaminant may be dispersed in vapor form at abnormal conditions of temperature and pressure. However, as the temperature and pressure conditions return to "normal," the contaminant will return to its normal solid or liquid form, or become a particulate. Sampling methods for vapors should isolate or measure the contaminant regardless of whether the vapor or particulate form is present. REPRESENTATIVE AIR SAMPLES List the two primary considerations to ensure a representative air sample is obtained. There are two primary considerations to ensure that the sample is representative of the actual conditions. The airborne radioactivity concentration entering the sample line must be representative of the airborne radioactivity concentration in the air near the sampling device. The airborne radioactivity concentration entering the sampling device must be representative of the airborne radioactivity concentration at the point of concern, or the air that is breathed. When obtaining an air sample, care must be taken to ensure that the sample obtained is representative of the air around the sampling device. This is particularly important for sample lines that directly sample an air flow, such as a stack or duct monitor. To ensure the sample is representative, the velocity in the sample line or orifice must be the same as the velocity in the system, such as the duct or stack. -5- FH 05/2003

6 For purposes of appropriate air sampling, state the relationship between sample function and location. The appropriate placement of air samplers depends upon the purpose of the sample. Refer to Table 1, Air Sampling Purposes (NUREG 1400). In general, air samplers positioned to evaluate the effectiveness of a containment or confinement system should be placed near (downstream from) the potential release point. When monitoring to determine the workers potential intake the sampler should be located near the workers breathing zone (nose and mouth). Purpose of Sampling/Monitoring General Placement of Samplers/Monitors Estimate worker s intake for calculating internal dose Identify area needing confinement control Provide early warning of elevated airborne release Sampler located in worker s breathing zone, near nose and mouth Sampler in airflow pathway near actual or potential release point Continuous air monitor(s) placed between worker(s) and release point(s) Test for leakage of radioactive materials from sealed confinement system Determine total concentration from many potential release points Determine airborne radioactivity area status or respiratory protection adequacy Samplers placed downstream of confinementcontrol area Downstream at exhaust point Samplers at worker s location Special purposes, e.g., determining particle size Case-by-case depending on airflow patterns Table 1 - Air Sampling Purposes - NUREG FH 05/2003

7 ISOKINETIC SAMPLING Define the term "isokinetic sampling" as associated with airborne radioactivity sampling. When the sample line velocity is equal to the system velocity at the sample point, it is called isokinetic sampling. Figure 1 - Isokinetic Sampling If the velocities are not the same, (Figure 1) then discrimination can occur for smaller or larger particles. This occurs because the inertia of the more massive particles prevents them from following an airstream that makes an abrupt directional change. If the velocity of the sample airstream is > the velocity of the system airstream, then the larger particles can not make the abrupt change and are discriminated against in the sample. If the velocity of the sample airstream is < the velocity of the system airstream, then -7- FH 05/2003

8 the small particles do make the abrupt change and are discriminated against in the sample. Sampling lines should be as short and straight as possible to avoid depositing of the sample along the walls of the tube. When possible, sample lines should be vertical instead of horizontal. When obtaining an air sample, care must be taken to ensure that the sample obtained is representative of the air at the point of interest (the breathing zone). Depending on the source of the airborne contaminant, the concentrations within a work area can vary. The sample taken must be representative of the air entering the nose and mouth of the individual workers. The best method to ensure a representative breathing zone sample is to sample the air at the individual's nose and mouth. This sampling method is typically not practical and general work area sampling may be the alternative. Care must be exercised in the selection of the number and placement of the general area air samplers to ensure that the sample is as representative as possible. BASIC SAMPLING METHODS AND DEVICES Basically, three types of samples are collected: 1. A volumetric sample in which part of the atmosphere is isolated in a suitable container, providing the original concentration of the contaminant at a particular place and time. 2. An integrated sample which concentrates the contaminant on some collecting medium, providing an average concentration over the collection time. (Sometimes called a "grab" sample if collected in a short period of time.) 3. The sample air flow is directed past or through a detection device providing a measurement of the activity per unit volume of air. The sampling method selected for a particular situation is determined by several factors including the physical and chemical state of the contaminant, the analysis methods available and the type of information required. The physical and chemical characteristics of the contaminant will determine the type of collection method and medium that should be used. The analysis methods available may dictate the volume and flow rate of the sample, based on the sensitivity of the analysis equipment. If immediate readout of information is needed, then collection and analysis are done at the same time. If not, then samples may be taken and removed to a central analysis location. -8- FH 05/2003

9 Identify the six general methods for obtaining samples or measurements of airborne radioactivity concentrations and describe the principle of operation for each method. a. Filtration b. Volumetric c. Impaction/impingement d. Adsorption e. Condensation/dehumidification f. In-line/flow-through detection. Filtration Filter samplers employ filtration of the air as the method of concentrating the airborne radioactive particulate (aerosol) contaminants. Filtration is the most common sampling method employed for particulates because it is relatively simple and efficient, but is ineffectual as a sampling method for gases and vapors. The filter sampling technique employs some sort of air mover, such as a vacuum pump, to draw air through the removable filter medium at a known flow rate for a known length of time. If the flow rate and sample time are known, the total volume sampled can be calculated. After analysis of the filter medium to determine the amount of radioactive material collected on the filter at the time of the sample, and with knowledge of the filters collection efficiency the airborne concentration can also be calculated. The filtration medium selected for a sample depends on several factors: the collection efficiency required, the flow resistance of the medium, and the mechanical strength of the filter. A wide choice of filters are available. The most common types are: Cellulose-asbestos filters Glass fiber (GF) filters Membrane filters are manufactured with various pore sizes and can be dissolved in organic solvents. -9- FH 05/2003

10 Volumetric Volumetric samplers employ a sample container into which the sample is drawn, by some method, and isolated for analysis. Several methods are employed to draw the sample into the container. The container may be evacuated by a vacuum pump and isolated away from the sample location. The container is opened at the sample location to draw the air into the container. The sample is located in the container and removed for analysis. An air mover, such as a vacuum pump, may be employed at the sample location to draw a representative atmospheric sample into the container. The container could be filled with water, isolated and taken to the sample location. The water is poured out of the container, drawing the air sample into the container as the water pours out. This method can be employed for particulates, gases, and vapors. Impaction/Impingement Impingers or impactors concentrate particulate contaminants on a prepared surface by abruptly changing the direction of the sample air flow at some point in the sampler. Particles are collected on a selected surface as the airstream is sharply deflected. Due to their inertia, the particles are unable to follow abrupt changes in airstream direction. The surface on which the particles are collected must be able to trap the particles and retain them after impaction. Several methods are commonly used to trap the particles, such as: Coating the collection surface with a thin layer of grease or adhesive. Immersing the collection surface in a fluid, such as water or alcohol, which is then analyzed. Impingers and impactors may utilize several stages or impingement distances to discriminate for or against different particle sizes. Impactors are frequently used to isolate particles larger than the undesired smaller particles, such as transuranics over radon progeny, or radon progeny over fission products FH 05/2003

11 Adsorption Adsorber sampling devices concentrate the contaminants by causing them to adhere to the surface of the adsorption medium. Adsorption is the adhesion of a substance to the surface of another substance through a bonding process. The adsorption medium is granulated or porous to increase the surface area available for trapping of the contaminant. The technique employs an air mover to draw and collect the sample through the adsorption media. Adsorbers, such as activated charcoal, silica gel, and silver zeolite, are commonly used to collect organic vapors and non-reactive gases and vapors. Charcoal is used primarily for radioiodine sampling, but does trap some noble gases, such as xenon, krypton and argon. Silica gel is primarily used for tritium oxide vapor sampling. Silver zeolite is used for radioiodine sampling when trapped noble gases would interfere with the radioiodine analysis. Particulates would be "filtered" by the adsorption media and must be filtered out before the adsorption process to prevent interference during the analysis of the media. Condensation/dehumidification Condensation or dehumidifier sampling devices employ a "cold trap" to condense water vapors in the sampled atmosphere and provide a liquid sample for further analysis. Some means, such as liquid nitrogen or a refrigeration unit is employed to cool the condensation surface and cause condensation of the water vapor as it passes over the cold surface. The collected water is frequently analyzed using a liquid scintillation counter. Calculations must include the relative humidity and temperature of the air at the time the sample is taken to determine the concentration of water vapor per unit volume of air. This technique is normally only applied for tritium oxide vapor (HTO or T 2 O). In-line/flow-through detection In-line or flow-through samplers employ an air mover to direct the sample air flow through or past the detection device. This method is employed for radionuclides which are difficult to collect or detect by other means. Because the air flow passes directly inside the detector or actually through the inside of the detector, the air must be filtered for particulates or vapors that could accumulate on or in the detector. In-line detectors are used to measure gaseous activity after filtration and adsorption have been accomplished. Flow-through detectors are employed where the radionuclide emits low FH 05/2003

12 energy radiation, such as tritium, which could not otherwise pass through the detector window. These various techniques may be combined into one sampler or monitor. Some samplers employ the filtration technique for particulates, the adsorption technique for vapors and the volumetric grab-sample technique for gases (in that order). One vacuum pump supplies the air flow for all the samples. All the samples are drawn at the same time to minimize the amount of time spent by the technician drawing samples. Some monitors employ the filtration techniques for particulates, the adsorption technique for vapors and the volumetric grab-sample technique for gases. In addition, the monitor has detectors installed to monitor each sample and provide an immediate readout as well as other capabilities, such as alarms, data records, and trending. BASIC AIR SAMPLE CALCULATIONS (Practice problems at the end of the lesson) Using the air sample calculation, calculate an air sample concentration. Once the air sample is collected and analyzed, calculations must be performed to determine the amount of activity per unit volume. The specific calculations for particular sampling methods are not covered in this lesson; however, some basics are necessary for each calculation. The analysis of the sample provides the activity of the sample at the time of the sample analysis. This value may be corrected for decay for the time period between when the sample was taken to when it was analyzed. This is especially true for short-lived radionuclides. This correction is typically not necessary because we often work with very long-lived radionuclides. The volume of the sample must be determined from the sample data recorded, such as flow rates at the beginning and end of the sample, and sample time period. The basic calculation listed below for long-lived radionuclides would also include the conversions -12- FH 05/2003

13 necessary for the desired units such as dpm/liter to µci/cc (HNF 13536, Section ). Activity (μci / ml) = N K Cf V E Ef N : Net Count Rate (cpm) k : 1.6E-11 (conversion factor [µci*ft 3 ]/[dpm*ml]) V : Sample Volume in cubic feet E: Instrument detection efficiency (fractional) cpm/dpm Cf: Geometry correction factor for reading 4" filter with EGM pancake probe=3, with 50 cm 2 PAM = 1.5 Ef: Filter collection efficiency (fractional assuming silver zeolite cartridge at some known airflow) is 1 if # 5 cfm and.85 if >5 cfm. Derivation of k conversion factor (HNF 13536, Section 5.2.2]) The conversion factor k is derived as follows: 1 µci = 2.22E6 dpm 1 ft 3 = 2.83E4 ml k 3 3 1μCi 1 ft μci ft = ( ) ( ) = 1.59E E6dpm 2.83E4ml dpm ml k is rounded to 1.6E-11 for simplicity. The calculation would also include correction factors, as necessary, for: Interference of other radionuclides, such as radon progeny Collection efficiency Counter efficiency Self-absorption by the sample media Counter background FH 05/2003

14 FACTORS AFFECTING AIRBORNE RADIOACTIVITY MEASUREMENTS Many errors are inherent or induced in the sampling analysis process and affect the accuracy of the resulting data. The operator of the sampling and analysis equipment must be aware of these points of error to ensure the resulting data is as accurate as possible List the factors that affect the accuracy of airborne radioactivity measurements. Factors affecting the accuracy of airborne radioactivity measurements: Sample is not representative of the atmosphere being sampled Sample is not representative of the air being breathed by the worker Incorrect or improperly installed sampling media for the selected sampler, causing filter by-pass leaks or improper flow rates Malfunctioning or miscalibrated sampling device, causing errors in flow rates Accuracy and operation of the timing device, causing errors in the time value Accuracy and operation of the flow rate measuring device, causing errors in the flow rate value Mishandling of the sample media causing cross-contamination or removal of sample material Changes in the collection efficiency of the medium due to sample loading, humidity, improper flow rate, and other factors Improper use or selection of analysis equipment Inherent errors in the counting process due to sample geometry, self-absorption, resolving time, backscatter and statistical variations Mathematical errors during calculations due to rounding of numbers and simple mistakes Mismarking of samples and inaccurate recording of data -14- FH 05/2003

15 Changes in collection efficiency of the sampler and/or sample lines (exclusive of filter media changes) due to improper selection of sample flow rate. It is important that the personnel performing the sample collection and analysis minimize the magnitude of these errors to ensure that accurate and reliable data is obtained for the assignment of internal exposure control methods, and confirm the effectiveness of methods already in place. Occupied areas with airborne concentrations of radioactivity that are > or, potentially > 10 % of a DAC shall be posted as Airborne Radioactivity Area IAW Project Hanford Radiological Control Manual (HNF-5173/HNF-5183) Art When respiratory protective equipment is being worn the associated Protection Factor will also be considered when determining the adequacy of this equipment. PRIMARY TYPES OF AIR SAMPLERS State the purpose of the five types of airborne radioactivity samplers/monitors: a. Personal air samplers (breathing zone) b. High volume/flow rate air samplers c. Low volume/flow rate air samplers d. Movable continuous air monitors e. Installed continuous air monitoring systems. Personal Air Samplers Personal air samplers (PAS) provide an estimate of the airborne radioactivity concentration in the air the worker is breathing during the sampling period. The PAS may also be used to determine if the protection factor for respiratory equipment is exceeded, to compare with other workplace air samples, and to verify the effectiveness of engineered and administrative controls. Personal air samplers are small portable batterypowered devices which sample the air in the breathing zone of the worker's nostrils and mouth. Also known as "Lapel" air samplers FH 05/2003

16 The device contains a small battery-powered pump that is calibrated to a flow rate similar to the breathing rate of a worker. The sampling line terminates in a filter cassette which contains the filtration medium for the radioactive particulate contaminants. The sample filter cassette is attached close to the nose and mouth of the individual. High Volume/Flow Rate Samplers (Figure 2) High volume/flow rate samplers provide an estimate of the airborne radioactivity concentration at a particular location in a short period of time. Portable high flow rate samplers are used to collect airborne aerosols on a filter paper (filtration) or on a greased planchet (impaction). Portable high flow rate samplers can also be used to collect radioiodine samples using Silver Zeolite cartridges (adsorption) as long as the maximum flow rate of the cartridge is not exceeded or a correction factor is used. These samplers do not have installed detectors and the sample must be removed from the sampler and analyzed on separate analysis equipment. High Volume Samplers air flow is typically > 2 cfm. The high volume/flow rate samplers may be used to: Provide a routine "slice of time" estimate of the area airborne radioactivity related to a specific work activity Verify boundaries of areas posted for airborne radioactivity Emergency Response-Quick estimates of airborne activity levels Figure 2 Staplex High Volume Air Sampler -16- FH 05/2003

17 Low Flow Rate Samplers (Figure 3) Low flow rate samplers (# 2cfm), provide an estimate of airborne radioactivity concentrations averaged over a longer period of time at a particular location. Portable low flow rate samplers are used to collect samples for aerosols on filter paper (filtration) and radioiodine on an adsorption medium, such as an activated charcoal cartridge. Low flow rate samplers may be used to provide average airborne radioactivity estimates over a period of time for: Commonly traversed areas that normally have a low probability of airborne problems Areas not commonly traversed with a higher probability of airborne problems Backup samples in areas where airborne problems are discovered by other means Work maintenance activities normally characterized by low airborne concentrations. Figure 3 - Low Volume Sampler -17- FH 05/2003

18 Movable Continuous Air Monitors Movable continuous air monitors (CAMs) provide an estimate of airborne radioactivity concentrations averaged over time at a particular location, and provide immediate readout and alarm capabilities for present concentrations. These air monitors are movable low flow rate sampling systems, containing the necessary sampling devices and built-in detection systems to monitor the activity on the filters, cartridges, planchettes and/or chambers in the system. The system may provide a visual readout device for each type of sample medium, a recording system for data, and computer functions such as data trending, preset audible and visual alarms/warning levels and alerts for system malfunctions. Typical CAMs provide information on alpha and/or beta/gamma particulates (filtration), radioiodine activity (adsorption) and noble gas activity (volumetric chamber or in-line detector). Movable CAMs can be utilized as: Low volume general area monitors (typically not a good sampler due to poor collection efficiency of most CAM sampler designs) Monitors with alarm capabilities for areas where airborne radioactivity conditions may quickly degrade Trending devices in selected areas Devices to locate system leaks, if used with the appropriate length hose or tubing. Installed Continuous Air Monitors Installed continuous air monitoring systems (CAMs) provide an estimate of airborne radioactivity concentrations averaged over time at a fixed, designated location, and provides immediate local and remote readout and alarm capabilities for preset concentrations. These air monitors are fixed low flow rate sampling systems, and contain the necessary sampling devices and built-in detection systems to monitor the activity of selected areas or airstreams. The system may provide a local and remote visual readout device, a recording system for data, and computer functions such as data trending, preset audible and visual alarms/warning levels and alerts for system malfunctions. Generally, three types of installed CAMs are used: Fixed installations capable of monitoring several locations through valved sample lines. Stack monitors -18- FH 05/2003

19 Duct monitors Workplace air monitor SELECTION OF THE AIR SAMPLING METHOD It is critical that the proper air sampling method and equipment be selected because: The data obtained must be meaningful and accurate to adequately assign radiological control measures The air sampler must be selected based on the requirement/regulations that define why the measurement is taken. Proper sensitivity, location, frequency, testing, and calibration Improper selection and use may incorrectly indicate a safe environment where an airborne radiological hazard exists or leads to unneeded postings where no hazard exists Describe the general considerations for selection of an air sampling method. The environmental conditions in the area where the sample is to be obtained. Humid conditions may preclude the use of some methods, such as paper filtration devices or charcoal canisters, because water vapor loading of the medium will change the collection efficiency and flow rate. High temperature environments may cause some samplers to overheat if run for long periods of time. Explosive gases may be present which could present an explosion hazard for samplers with electric motors not designed for such environments. Dusty areas could cause excessive sample loading which will reduce sampler flow rates causing errors in measurement and potentially overheat the sampler. The physical characteristics of the area in which the sample is to be obtained. An electrical outlet may not be available or close, and a battery powered sampler would be better suited. Close spaces or passages may preclude the use of movable CAMs or heavy samplers. The energy and type radiation will dictate the type of CAM or analysis equipment require to determine the airborne radioactivity concentration. The expected concentration level will determine the length of sample time and -19- FH 05/2003

20 type of sampler required. Low-level concentrations will require large volumes to reduce statistical errors and meet minimum sensitivity levels of the analysis equipment. Large volume samples obtained over a long time period are best obtained by samplers designed to run for long periods. In addition, the DAC for the isotope of concern and the sampler flow rate will be considered when determining the minimum sample collection time. The physical state of the airborne contaminant, whether gas, vapor or aerosol, will dictate the type of sampler and sample medium that is required. The type of survey required also determines the type of equipment that is selected, such as breathing zone samples, routine general area samples, general work area samples, general area trending over time, etc. Procedural requirement may dictate a particular type of sample method and/or sample medium for a given application. o Check the appropriate procedures prior to sampler selection. o Ask supervision and experienced technicians. Sample duration - (How long should the sample be drawn?) HNF , SECTION provides the formula for determining the minimum sample collection time to estimate respiratory protection effectiveness. RCT input: Lab input: Limiting radionuclide Purpose of sample Flow rate of sampler PF of respiratory equipment (if sample for respiratory protection efficiency) Current MDA -20- FH 05/2003

21 Formula: t = k MDA 0.1 DAC PF F where: t = time in minutes k = 1.6E-11 (conversion factor [μci x ft 3 ] / [dpm x ml] MDA = instrument MDA in dpm DAC = DAC value for isotope of concern PF = protection factor for respirator F = flow rate in cubic feet per minute (typically the maximum possible calibrated flow rate of the sampler) The MDA at a 95% confidence level for the GM probe is 1,000 dpm for general beta/gamma activity (radionuclide specific values are 625 dpm for 137 Cs and 560 dpm for 90 Sr 90 Y) based upon listening to the audible output count rate for 5 seconds. Activity is detected when the measurement is perceived to be above background. Background is limited to 150 cpm and the probe should be placed on contact with the filter. The MDA at a 95% confidence level for the PAM probe is 180 dpm for general alpha activity based upon listening to the audible output count rate for 5 seconds or 90 dpm based upon listening to the audible output count rate for 10 seconds. These levels are based upon listening to the audible output count rate for the time period specified. When a count is detected, reevaluate, the filter for an additional time period (5 or 10 seconds). If no additional counts are detected, the activity on the filter is below the detection limit. The background is assumed to be zero and a maximum background of 3 cpm will allow efficient operation. The probe should be placed on contact with the filter. DACs: 239 Pu = 2E-12 µci/ml 90 Sr = 2E-9 µci/ml 137 Cs = 7E-8 µci/ml 131 I = 2E-8 µci/ml -21- FH 05/2003

22 Example problem 01 An air sample needs to be drawn to verify the adequacy of a full-face respirator. The limiting radionuclide is 239 Pu and the maximum calibrated flow rate on the sampler is 4 cfm. The lab indicates the counting instrument s MDA is 15 dpm, for a one minute count. Calculate the minimum time to adequately draw the sample. Given: k = 1.6E-11 µci ft 3 /dpm ml MDA = 15 dpm DAC = 2E-12 µci/ml PF = 100 F = 4 cfm t = 3 μci ft 1.6E 11 15dpm dpm ml 3 μci ft 0.1 2E ml min = 3min Sample Problem 01 An air sample needs to be drawn to determine the airborne radioactivity status for posting purposes. The limiting radionuclide is 241 Am (same DAC as Pu) and the maximum calibrated flow rate on the sampler is 4 cfm. The lab indicates the counting instrument s MDA is 13 dpm, for a one minute count. Calculate the minimum time to adequately draw the sample. (Answer: 260 minutes) Sample Problem 02 It has been determined the sampling time for the job described in above problem is too long. The lab indicates that the MDA, for a 10 minute count, is 3.2 dpm. With the revised MDA, what is the minimum time for drawing the sample? (Answer: 64 min) -22- FH 05/2003

23 AIR SAMPLER PLACEMENT CONSIDERATIONS Define a "General Area" air sample. General area air samples are typically low volume samples drawn in routinely entered or occupied spaces which are either known to have airborne radioactivity or potentially have airborne radioactivity. They are typically defined as: "a representative sample of the air which an individual would inhale while in that room, or space providing the individual was not performing an evolution which had potential for causing an increase in airborne contaminates" Define a Breathing Zone air sample. Breathing zone air samples are more straight forward -- they are typically defined as: "an air sample taken in the immediate area of the job-specific work site and is drawing in the same air as that which the worker(s) of concern is/are breathing" Define upwind and downwind as applied to air sampling location. Upwind-based on the airflow current in the workplace, upwind refers to sampling air prior to the contamination source. Downwind-based on the airflow current in the workplace, samples taken after the contamination source are downwind. Placement factors: - NUREG 1400 Purpose/type of sample Location of workers in the field Identification of release points of source material Exhaust of air Air flow patterns -23- FH 05/2003

24 Presence of loose surface contamination Placement considerations: - NUREG 1400 Samplers should be placed where it cannot be bumped by the worker or interfere with the progress of work Samplers should not be influenced by supply airflow, otherwise the sampler would sample the supply air and not the workplace air Samplers should be placed for easy access Samplers should be positioned such that exhaust is pointed down wind Samplers on a horizontal surface should not have the discharge air directed at the surface, where it may increase levels by resuspension -24- FH 05/2003

25 Example One: Room 30 - Given: Sample purpose: Release points: Supply air: Identify area needing confinement control (confirm room concentration) Hoods 4 & 5 - high activity sample preparation and Hoods 1, 2, & 3 - low activity sample preparation Ceiling panels providing a uniform distribution Indicate, with an X on the map, where a grab air sampler(s) should be placed FH 05/2003

26 Example Two: Room 30 additional information: Supply air: Ceiling panels and Corridor A Exhaust Air: Hoods and Corridor B - airflow to the east (arrows) With this additional information, indicate where a grab air sampler(s) should be placed FH 05/2003

27 Example Three: Room 31 - Given: Sample purpose: Supply air: Exhaust air: Test for leakage of radioactive materials from confinement systems South corridor and ceiling air vents Hoods and north-east wall exhaust airflow is to the north (arrows) 1. List potential release points 2. Indicate with an X on the map, the location(s) you would place a grab air sampler FH 05/2003

28 SAMPLE CONCENTRATIONS GREATER THAN 10% DAC Describe the responsibilities of an RCT should an air sample result show greater than 10 percent of DAC on the initial calculation. If an air sample result shows greater than 10 percent of the DAC during the initial calculation, the RCT has some responsibilities to fulfill. They are: Post the room and inform HP First Line Manager. Note if work is in progress Note if there are workers in the effected area/room Note if workers are using respiratory protection Note if RWP is adequate for the changed (new) radiological conditions Stop work if necessary Recount the sample after a 30 minute decay period. Record the results on the Radiation Survey Report and the HP Field Log. Recount the sample after a 24 hour decay period. If the sample is still greater than 10% of the DAC limit, send the sample to the lab for isotopic analysis. ESTABLISHING RADON PROGENY INDICATORS Describe the process for evaluating an air sample for Radon/Thoron. The concentration of radon progeny in air is affected by a number of environmental factors including temperature, humidity, atmospheric pressure, soil constituency, and local building materials. Temperature inversions commonly give rise to elevated radon concentrations. Each facility on site should have established procedures for identifying radon progeny in the workplace FH 05/2003

29 RCTs may need to collect and analyze grab air samples from an area known to be free of the airborne radioactive material of concern, when radon progeny are suspected of interfering with air sampling and monitoring equipment or to document elevated background levels. The RCT may collect the sample from an area where radon levels are known, or expected, to be similar to the area of interest. No single indicator is used as an absolute indication that the activity is solely radon. The approach is to use multiple indicators (such as the alpha/beta ratio, half-life, or weather conditions) to make accurate decisions. Alpha to Beta (:) Ratios Establish alpha to beta (:) ratios for radon progeny as follows: Measure the : ratio within the workplace by simultaneously analyzing air samples for alpha and beta emissions. o Collect and analyze two "identical" samples in parallel when no simultaneous alpha/beta counting instruments are available OR analyze one sample and evaluate for alpha and beta contamination in series. o When a single sample is analyzed in series, use the same analysis process when evaluating unknowns as follows: If beta emission is analyzed first for five minutes and alpha analysis immediately follows for five minutes, analyze any unknown for beta emissions first (five minutes) followed immediately by a five-minute alpha analysis. o Fully document analytical methods and ensure that they are reproduced in facility-specific radon progeny mitigation procedures. As needed, analyze many samples to address variations in the : ratio. o Document the : ratio as a function of the time between collection (removing the sample from the sampling apparatus) and analysis for each sample FH 05/2003

30 Use the same time interval between counting for each sample (if your first sample was analyzed at five minute intervals starting ten minutes after collection, then each subsequent sample must be analyzed in this same manner to achieve comparable data). o Generate a decay curve (: ratio vs. time) from collected data, as needed. If necessary to generate an accurate curve, repeat analysis at short intervals (every few minutes). Fit a curve to the collected data, and plot curve and data together to document that the fit is representative. o Compile data from all samples to produce a range of acceptable ratios (e.g., 2 ± 0.3, at 95 percent confidence within 2 hours of collection, 1.5 ± 0.5, at 95 percent confidence between 2 and 4 hours of collection, where 95 percent confidence is achieved by using a sigma factor of 1.96) or to establish the uncertainty (error bars) in a fitted curve. Establish the absence of long-lived radioactive material by analyzing collected air samples after allowing sufficient decay time (up to seven days). Repeat this process, as needed, to identify : ratios for different levels within a building, for different buildings, for outdoor locations, and perform ratio measurements periodically throughout the year to address seasonal variation. Characteristic Decay Curve (effective rate of decay) Establish the rate of decay associated with radon progeny by analyzing air samples for alpha and beta emissions. Measure the decay rate by systematically analyzing air samples as follows: (Repeat analysis frequently and document sample activity over time, as needed.) Generate a decay curve (activity vs. time) from collected data. NOTE: Repeat analysis at extraordinarily short intervals, every few minutes if necessary to generate accurate curves. Fit a curve to the collected data and plot curve and data together to document that the fit is representative FH 05/2003

31 Generate a table, as needed, to identify the measured reduction in activity for corresponding time intervals. As necessary, analyze many samples to address variations in the observed rate of decay. Document the sample activity as a function of time following collection (removing the sample from the collection apparatus). Analyze each sample using the same time interval between counting (if your first sample was analyzed at five minute intervals starting ten minutes after collection, then each subsequent sample must be analyzed in the same manner to achieve comparable data). Compile the data to produce a range of acceptable reduction rates (e.g., 50 percent reduction every 35 ± 6 minutes at 95 percent confidence within 2 hours of collection, or a 50 percent reduction every 50 ± 9 minutes at 95 percent confidence between 2 and 4 hours of collection, where 95 percent confidence is achieved by using a sigma factor of 1.96) or to identify the uncertainty (error bars) in a fitted curve. Establish the absence of long-lived radioactive material by analyzing collected air samples after allowing sufficient decay time (up to seven days). Repeat this process, as needed, to identify decay rates for different levels within a building, for different buildings, and perform ratio measurements periodically throughout the year to address seasonal variation. CONTINUOUS AIR MONITORS (CAM) Define the criteria for the placement of a portable CAM in a room (area). The following materials are excerpted from the Work Place Air Monitoring procedure (HNF 13536, Section 5.2.1). Perform real-time air monitoring using continuous air monitors (CAMs) installed where unexpected increases in airborne radioactivity levels, should they occur, are likely to result in an exposure exceeding 40 DAC-hrs in one week or where there is a need to alert potentially exposed individuals to unexpected increases in airborne radioactivity levels FH 05/2003

32 Use the compilation of items below when determining the need for continuous air monitoring: Air sample data NOTE: Use a value of 2.5 mrem/dac-h to estimate internal dose. Occupancy time (as needed to estimate exposure) Apply eight hour time averaging to airborne concentrations as needed. One DAC averaged over a single eight hour shift is equivalent to 8 DAC-h. Base decisions on using CAMs on the air actually breathed by workers; apply respiratory protection factors when estimating worker exposure if all workers in the area are wearing respiratory protection devices. RWP constraints Increase CAM alarm set points, according to procedure, by including the respiratory protection factor, or fraction of, when all workers in the affected area are wearing respiratory protection devices. Use portable CAMs to monitor infrequently occupied areas when cost effective. If potentially significant (40 DAC-hours exposure in one week) airborne concentrations are possible but the probability of initiating airborne is remote, then facilities may perform a risk analysis by comparing the calculated risk against the requirement to perform air monitoring with CAMs. NOTE: Calculate risk by multiplying potential airborne concentration (converted to dose through stay time, as needed) by the probability of material release. Assess the likelihood of exposure within the facility design and RWP constraints. Document, in the WAM technical basis document, criteria involving the use of CAMs and include an assessment for potential unexpected increases and the need to notify occupants of increases FH 05/2003

33 CAM ALARM SET POINT (HNF 13536, Section 5.5.4) Calculate CAM Alarm Set Point (ASP) and state the maximum ASP value allowed. The following materials are excerpted from the Establishing CAM ASP section. The CAM ASP should be set at the lowest possible level without resulting in a significant number (one per month per CAM) of false alarms. The ASP, as set on a CAM, can be determined as the background count rate measured with a radiologically clean filter paper and no flow + the calculated ASP. Applying a sticker to the CAM identifying the ASP provides a convenient method for communicating the current ASP to other RCTs. Calculate ASPs using the following equation: ASP( cpm) = min ( DAC) (60 ) ( E) ( F) ( PF) hr 1.6E FH 05/2003

34 Where: DAC = Derived Air Concentration for the isotope of concern (uci/ml) NOTE: ASP Maximum Level - at no time should the CAM ASP exceed 40 DAC-h, after accounting for any applicable respiratory protection factor (i.e., Maximum hour value = 40). hr = Ideally 8 or less; no greater than 24 unless prevented by radon progeny interference 60 min/hr = Conversion factor E = CAM counting efficiency in decimal form (e.g., if the instrument efficiency is 12%, use 0.12 NOT 12) F= CAM Flow rate in ft 3 /min (as measured on the CAM OR the flow rate that will be used when the instrument is placed into service) 1.6E-11 = conversion constant (uci ft 3 /dpm ml) PF = Respiratory protection factor (1 if not wearing respirators) REMOVING A CAM FROM SERVICE (HNF-13536, Section 5.2.4) State the requirements for taking a CAM out-of-service if it fails an operational or performance test. The following materials are excerpted from Removing CAM From Service section. Sometimes a CAM will have to be taken out-of-service. One of the reasons it may be taken out of service is failure of an operability, source, or function test. If the happens, the RCT shall: 1. Tag the CAM out-of-service with an appropriate service tag. 2. Notify facility management of the need for CAM repair, replacement, and/or calibration FH 05/2003