ML003739616

Regulatory Guide 8.25, Revision 1 (Drfat Was Issued as DG-8003), Air Sampling in Workplace

ML003739616
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Issue date:	06/30/1992
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Reg Guide 8.25, Rev 1
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U.S. NUCLEAR REGULATORY COMMISSION Revision 1 June 1992 REGULATORY GUIDE OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 8.25 (Draft was issued as DG-80)

AIR SAMPLING IN THE WORKPLACE A. INTRODUCTION In addition, this guide does not apply to activities conducted under 10 CFR Part 50 at reactor facilities.

Air sampling in the workplace is an acceptable Although the provisions of 10 CFR Part 20 apply method for meeting certain of the survey and dose equally to nuclear reactors and to other facilities, the assessment requirements of 10 CFR Part 20, 'Stan- air sampling programs of reactor licensees are well es-dards for Protection Against Radiation." For exam-tablished, and the NRC is satisfied that the quality of ple, 10 CFR 20.1204 allows estimates of worker in-air sampling at nuclear reactors is adequate. There-takes of radioactive materials based on air sampling fore, no further guidance on air sampling is needed at and allows adjustments of derived air concentrations this time for reactor licensees.

(DACs) and annual limits on intake (ALIs) based on the particle size distribution; 10 CFR 20.1501 re- Any information collection activities mentioned quires radiation surveys necessary to comply with the in this regulatory guide are contained as requirements regulations and to evaluate potential radiological haz- in 10 CFR Part 20, which provides the regulatory ba-ards; 10 CFR 20.1703 requires assessment of air- sis for this guide. The information collection require-borne radioactive material concentrations when respi- ments in 10 CFR Part 20 have been cleared under rators are used; 10 CFR 20.1902 requires posting of OMB Clearance No. 3150-0014.

airborne radioactivity areas; 10 CFR 20.2103 requires records of radiation surveys; and 10 CFR 20.2202 and 10 CFR 20.2203 require reporting of excessive B. DISCUSSION concentrations of or exposure to airborne radioactive Air sampling can be used to determine whether materials. the confinement of radioactive materials is effective, This guide provides guidance on air sampling in to measure airborne radioactive material concentra-restricted areas (as defined in 10 CFR Part 20) of the tions in the workplace, to estimate worker intakes, to workplace. In this guide, the term "air sampling" in- determine posting requirements, to determine what cludes the collection of samples for later analysis as protective equipment and measures are appropriate, well as real-time monitoring in which samples are and to warn of significantly elevated levels of airborne analyzed as they are collected. The guide does not radioactive materials. If bioassay measurements are cover environmental or effluent sampling or the used to determine worker doses of record, air sam-analysis of samples. pling may be used to determine time of intake and to USNRC REGUlATORY GUIDES The guides are issued in the following ten broad divisions:

Regulatory Guides are Issued to describe and make available to the pub-lic methods acceptable to the NRC staff of implementing specific parts 1. Power Reactors 6. Products of the Commission's regulations, to delineate techniques used by the 2. Research and Test Reactors 7. Transportation staff in evaluating specific problems or postulated accidents, or to pro- 3. Fuels and Materials Facilities 8. Occupational Health vide guidance to applicants. Regulatory Guides are not substitutes for Environmental and Siting 9. Antitrust and Financial Review regulations, and compliance with them is not required. Methods and 4.

5. Materials and Plant Protection 10. General solutions different from those set out in the guides will be acceptable if they provide a basis for the findings requisite to the issuance or continu-ance of a permit or license by the Commission. Copies of Issued guides may be purchased from the Government Printing This guide was Issued after consideration of comments received from Office at the current GPO price. Information on current GPO prices may the public. Comments and suggestions for Improvements In these be obtained by contacting the Superintendent of Documents, U.S.

guides are encouraged at all times, and guides will be revised, as ap- Government Printing Office, Post Office Box 37082, Washington, DC propriate, to accommodate comments and to reflect new information or 20013-7082, telephone (202)275-2060 or (202)275-2171.

experience.

Written comments may be submitted to the Regulatory Publications Issued guides may also be purchased from the National Technical Infor-Branch, DRIPS, ADM, U.S. Nuclear Regulatory Commission, Washing- mation Service on a standing order basis. Details on this service may be ton, DC 20555. obtained by writing NTIS. 5285 Port Royal Road, Springfield, VA 22161.

determine which workers should have bioassay meas- material is used, the need for air sampling should be urements. determined by whether the sum of the quantities of General guidance on air sampling for specific each divided by each respective ALI exceeds 10,000.

types of facilities is also discussed in several other When quantities handled in a year are less than regulatory guides, including: 10,000 times the ALI, air sampling generally is not needed. (The basis for this value is that experience I

• Regulatory Guide 8.21, "Health Physics Sur- has shown that worker intakes are unlikely to exceed veys for Byproduct Material at NRC- one one-millionth of the material being handled or Licensed Processing and Manufacturing processed, as discussed in NUREG-1400.)

Plants"

• Regulatory Guide 8.23, "Radiation Safety 1.2 Air Sampling Based on Potential Intakes Surveys at Medical Institutions" and Concentrations

• Regulatory Guide 8.24, "Health Physics Sur- The extent of air sampling may be based on esti-veys During Enriched Uranium-235 Process- mates of worker intakes and on estimated airborne ing and Fuel Fabrication" concentrations of radioactive materials as shown in Table 1. Estimates of potential intakes and concen-

• Regulatory Guide 8.30, "Health Physics Sur- trations should be based on historical air sampling or veys in Uranium Mills" bioassay data if these data are available. If the data These facility-specific guides cover air sampling are not available, potential intakes and concentra-in general terms, while this guide discusses air sam- tions should be estimated. Estimates of intakes and pling in more depth. Thus, the guides are comple- concentrations should be based on a consideration of mentary. (1) the quantity of radioactive material being han-dled, (2) the ALI of the material, (3) the release This guide provides recommendations on air fraction for the radioactive material based on its sampling to meet the requirements of 10 CFR physical form and use, (4) the type of confinement Part 20. Draft NUREG-1400, "Air Sampling in the for the material, and (5) other factors appropriate for Workplace, 1 provides examples, methods, and tech-the specific facility. The estimated prospective intake niques that the licensee may find useful for imple-provides only a guide to the appropriate types of air menting the recommendations in this guide. How-sampling. The radiation safety officer should use pro-ever, NUREG-1400 does not establish regulatory fessional judgment and experience to perform air positions or recommendations and should not be sampling appropriate for the specific situation.

used as a compliance document to establish the ade-quacy of licensee programs. 1.3 Grab vs. Continuous Air Sampling Air sampling may be continuous during work C. REGULATORY POSITION hours or intermittent (grab samples taken during part of the work). When continuous sampling during the

1. EVALUATING THE NEED FOR AIR work day is performed for continuous processes, a SAMPLING weekly sample exchange period is generally accept-The implementation of some sections in 10 CFR able (except for very short-lived radionuclides).

Part 20 may require air sampling. This section of the Longer sample exchange periods may be appropriate guide provides recommendations on when and what if airborne radioactive material concentrations and type of air sampling is acceptable to meet the Part 20 nuisance dust concentrations are both relatively low.

requirements. When grab sampling is performed for continuous processes, a weekly sampling frequency is generally 1.1 When To Evaluate the Need for Air acceptable; however, monthly or quarterly sampling Sampling may be acceptable for areas in which concentrations As a general rule, any licensee who handles or of airborne radioactive material are expected to aver-processes unsealed or loose radioactive materials in age below a few percent of the DAC. Grab sampling quantities that during a year will total more than would also be appropriate when operations are con-10,000 times the ALI for inhalation should evaluate ducted on an intermittent basis.

the need for air sampling. (If the same material is used repeatedly, multiply the quantity used by the 1.4 Air Sampling When Respiratory Protective number of times used.) If more than one radioactive Equipment Is Used

'Single copies of draft NUREG-1400 are available free, to Air sampling is required by 10 CFR the extent of the supply. Submit a written request to the Office 20.1703(a)(3)(i) to evaluate airborne hazards when-of Administration, Distribution and Mail Services Section, U.S. Nuclear Regulatory Commission, Washington, DC ever respiratory protective equipment is used to limit 20555. A final version of NUREG-1400 is being developed intakes pursuant to 10 CFR 20.1702. Air samplers and should be published in 1993. that are located to determine worker intake are I

8.25-2

Table 1 Air Sampling Recommendations Based on Estimated Intakes and Airborne Concentrations Worker's estimated Estimated airborne annual intake as a concentrations as a fraction of ALI fraction of DAC Air sampling recommendations

< 0.1 < 0.01 Air sampling is generally not necessary. However, monthly or quarterly grab samples or some other measurement may be appropriate to confirm that airborne levels are indeed low.

> 0.01 Some air sampling is appropriate. Intermittent or grab samples are appropriate near the lower end of the range. Continuous sampling is appropriate if concen-trations are likely to exceed 0.1 DAC averaged over 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> or longer.

> 0.1 < 0.3 Monitoring of intake by air sampling or bioassay is required by 10 CFR 20.1502(b).

> 0.3 A demonstration that the air samples are representa-tive of the breathing zone air is appropriate if (1) intakes of record will be based on air sampling and (2) concentrations are likely to exceed 0.3 DAC averaged over 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> (i.e., intake more than 12 DAC-hours in a week).

Any annual intake > 1 Air samples should be analyzed before work resumes the next day when potential intakes may exceed 40 DAC-hours in 1 week. When work is done in shifts, results should be available before the next shift ends. (Credit may be taken for protection factors if a respiratory protection program is in place.)

>5 Continuous air monitoring should be provided if there is a potential for intakes to exceed 40 DAC-hours in 1 day. (Credit may be taken for protection factors if a respiratory protection program is in place.)

acceptable for this purpose. If the worker's job activ- nonroutine operations, an attempt should be made to ity will be the main source of airborne radioactive have analysis results available within one hour.

material, the sampling should be done during the ac-tivity, not prior to the activity. 1.6 Continuous Air Monitoring In situations in which there is a potential for ac-1.5 Prompt Analysis of Certain Samples cidents to cause intakes exceeding 40 DAC-hours in a day, continuous air monitoring should be done.

In situations in which there is a potential for in- When continuous air monitors with automatic alarms takes to exceed 40 DAC-hours in a week, air samples are used, the alarm set points should be set as low as should be analyzed promptly on a daily basis. (In practical for the work being conducted without caus-evaluating the need for prompt analysis, credit may ing excessive false alarms (e.g., more than once per be taken for respirator protection factors if a respira- quarter).If continuous air monitors with automatic tory protection program is in place.) Sample results alarms are used, check sources should be used should be available before work resumes the follow- weekly to check that the monitor responds and ing day. When work is done in shifts, results should causes an alarm. Continuous check sources may also be available before the next shift ends, preferably be used, provided there is no interference with the during the first half of the next shift. For special or radionuclide of interest. If the response is not within 8.25-3

+/- 20 percent of the normal response, the monitor 2.1 Purpose of the Measurement should be repaired or recalibrated. Before selecting a sampling location, the licensee should decide on the purpose of the measurement.

1.7 Establishing Airborne Radioactivity Areas Examples of purposes are (1) estimating worker in-Air sampling with samplers located to determine takes, (2) verifying that the confinement of radioac- I tive materials is effective, (3) providing warning of worker intake may be used to determine whether an abnormally high concentrations, (4) determining area is an airborne radioactivity area. Any room, en-whether there is any leakage of radioactive materials closure, or area must be posted as an airborne radio-from a sealed confinement system, and (5) determin-activity area if (1) concentrations of airborne radio-ing whether an airborne radioactivity area exists.

active materials are in excess of the DAC or (2) a worker in the area would be exposed to more than 12 2.2 Determination of Airflow Patterns DAC-hours in a week (10 CFR 20.1902 and 20.1003). To determine whether the concentration Airflow patterns should be determined in order to locate air samplers appropriately. The locations of exceeds the DAC over the short term, the sample ventilation air inlets and exhausts and of sources of collection time should not exceed 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Shorter airborne radioactive materials should be noted in or-sample collection times may be used if desired, but they are not required. der to determine the predominant airflow patterns and likely radioactive material transport routes.

Areas should not be posted as airborne radioac- When sampling air in rooms with complex airflow tivity areas on the basis of unlikely accidents that patterns, it may be useful to use smoke tubes or might cause the DAC to be exceeded. An airborne neutrally buoyant markers to determine airflow pat-radioactivity area should be established based on the terns.

radioactivity levels normally encountered or on levels When sampling air in an airborne radioactivity ihat can reasonably be expected to occur when work area to determine the intakes of workers whose in-is being performed. take must be monitored under 10 CFR 20.1502(b),

smoke tubes or neutrally buoyant markers should be 1.8 Air Sampling vs. Bioassay for Determining used to determine airflow patterns from the source to Intakes the worker's breathing zone. In some instances, the If sufficient data to determine a worker's intake use of larger smoke sources or neutrally buoyant are available from both air sampling and bioassay marker sources to observe airflow patterns is desir-measurements and the results are significantly differ- able. However, observations of airflow patterns ent, the licensee should base the worker's intake esti- should be omitted in areas of high external radiation mate on the data considered by the radiation protec- exposure if making the observations would result in tion staff to be the most accurate. total worker doses (internal plus external) that are not as low as is reasonably achievable.

1.9 Substitutes for Air Sampling The airflow pattern determinations should be re-If experience indicates that worker intakes are peated if there are changes at the facility, including generally low, it may be acceptable to substitute other changes in locations of the individual work locations techniques in place of air sampling. For example, and seasonal variations that might change airflow pat-when working with tritium, iodine, or other materials terns, or if there is a reason to suspect problems. The that are easily and effectively detected by bioassay, it radiation protection staff should be aware of facility could be appropriate to eliminate all air sampling and characteristics, operations, and changes that might rely completely on bioassays to measure intakes and change airflow patterns. In addition, the location of verify confinement. at least 10 percent of the fixed-location samplers should be evaluated annually to confirm that their lo-

2. LOCATION OF AIR SAMPLERS cations are still appropriate.

Concentrations of airborne radioactive materials 2.3 Selecting Sampler Locations in a room are generally not uniform. Concentrations Air samples should be collected in airflow path-usually vary greatly from one location to another, ways downstream of sources of airborne radioactive sometimes by orders of magnitude even for locations material.

that are relatively close. Therefore, the location of air When the purpose of the sample is to verify the samplers is important because inappropriately placed samplers can give misleading results. effectiveness of confinement or to provide warning of elevated concentrations, the sampling point should be This section applies only to fixed-location and located in the airflow pathway near the release point.

portable samplers. It does not-apply to personal (la- These samplers do not have to be placed near the pel) samplers. worker's breathing zone, and thus concentrations 8.25-4

might be considerably different from the concentra- 3.2 Demonstration that Air Sampling Is tions in the breathing zone. If the room has several Representative widely spaced sources of airborne radioactive mate- Four methods may be used to demonstrate rial, more than one sampling point may be needed. representativeness of the results from samplers that are not located within about 1 foot of the worker's When the purpose of sampling is to determine head: (1) comparison with lapel sampler results (for worker intakes, each frequently occupied work loca-this comparison, lapel samplers may be equipped with tion should have its own sampler. The air samplers cyclones with an efficiency of at least 50 percent for should be placed as close to the breathing zone of the particles with an aerodynamic equivalent diameter of worker as practical without interfering with the work 4 micrometers if the particles sampled are solubility or the worker. In addition, air flow patterns in the class W or Y),2 (2) comparison with bioassay results, area should be considered in placing samplers so that (3) comparison using multiple measurements near the the sampler is likely to be in the airflow downstream breathing zone, and (4) comparison with quantitative of the source and prior to or coincident with the loca-airflow tests.

tion of the worker. An estimate should be made of the time the worker spends at the work location (un- Table 2 describes the application of each of the less personal air samplers are being used). methods and includes acceptance criteria for deter-mining whether sampling results may be considered For hoods, glove boxes, and other similar enclo- representative.

sures used to contain radioactive material, air sam-plers may be installed slightly above head height and 3.3 Corrective Actions if Sampling Results Are in front of the worker or they may be installed on the Not Representative front face of the enclosure. If the method used to demonstrate representa-Normally, air samplers intended to measure tiveness does not show that the sampling results are workplace concentrations should not be located in or representative, the licensee should analyze the situ-near exhaust ducts, because concentrations there will ation, determine the likely cause of the problem, and usually be diluted compared to concentrations in fix the problem. The licensee should also correct work areas. However, samplers may be located in intake estimates made within the last year and subse-ducts if their purpose is to detect leakage from sys- quent to the previous demonstration of representa-tems that do not leak during normal operation and if tiveness. To fix the problem, it may be appropriate to quantitative measurements of workplace airborne relocate samplers to be more representative, apply concentrations are not needed. correction factors to correct sampling results, switch to lapel sampling, or use bioassay measurements to

3. DEMONSTRATION THAT AIR SAMPLING determine intakes.

IS REPRESENTATIVE OF INHALED AIR

4. ADJUSTMENTS TO DERIVED AIR Section 20.1502(b) of 10 CFR Part 20 requires CONCENTRATIONS monitoring of the intake of any worker whose intake NRC regulations in 10 CFR 20.1204(c) permit, is likely to exceed 0.1 ALI. Section 20.1204 allows upon prior approval of the NRC, the adjustment of the use of air sampling, bioassay, or a combination of DACs to reflect the actual physical and chemical both to determine a worker's intake. characteristics of airborne radioactive materials.

3.1 Need To Demonstrate that Air Sampling Is 4.1 Adjusting DACs Based on Measurements of Representative of Breathing Zone Air Particle Size It should be demonstrated that the air sampled If the licensee elects to request approval to ad-is representative of breathing zone air if all four of just DACs based on measured activity median aero-the following conditions are met: (1) monitoring of dynamic diameters of airborne particles, the following intake is required by 10 CFR 20.1502(b) because an- information should be submitted:

nual intake is likely to exceed 0.1 ALI, (2) the intake of record will be based on air sampling rather than 1. The need for the adjustment.

bioassay, and (3) the exposure will occur in an air- 2. The radioactive materials involved and borne radioactivity area where airborne concentra- either their chemical form (if the chemical tions are likely to exceed 12 DAC-hours in a week, and (4) lapel samplers or samplers located within 2 American Conference of Governmental Industrial Hygien-about 1 foot of the worker's head are not used. (The ists, Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices, Notice of results from lapel samplers or samplers that are lo- Intended Changes: Appendix D-Particle Size Selective Sam-cated within about 1 foot of the worker's head may pling Criteria for Airborne Particulate Matter, 1991. The 4-micrometer criterion is also in the process of being adopted be accepted as representative without further demon- by the International Standards Organization (ISO) and the stration that the results are representative.) European Standardization Committee (CEN).

8.25-5

Table 2 Methods To Demonstrate the Representativeness of Air Sampling Method Description I

1. Comparison with Include: Workers whose annual intakes must be monitored under 10 CFR lapel samplers 20.1502(b) because intakes are likely to exceed 10% of an ALI and whose dose of record will be based primarily on air sampling.

Comparison: Compare intakes measured by air sampling with intakes meas-ured by lapel samplers for at least 1 week for continuous operations or for several operations for repeated short-duration operations.

Acceptance criteria: The ratio of the intakes calculated from air sampling divided by the intakes calculated from lapel samplers should exceed 0.7 when averaged for all workers included in the comparison. The ratio for each individual worker should exceed 0.5. (The values of 0.7 and 0.5 were selected so that the accuracy of intakes based on air sampling would be com-patible with the accuracy expected of external radiation dosimeters.)

2. Comparison with Include: Workers whose annual intakes must be monitored under 10 CFR bioassay results 20.1502(b) because intakes are likely to exceed 10% of an ALI and whose dose of record will be based primarily on air sampling.

Comparison: Compare the sum of the intakes determined from air sampling with the sum of the intakes calculated from those bioassay measurements.

Acceptance criteria: The ratio of the sum of the intakes calculated from air sampling divided by the sum of the intakes calculated from bioassay meas-urements should exceed 0.7 when averaged for all workers included in the comparison. The ratio for each individual worker should exceed 0.5 for each individual worker.

3. Comparison with Include: Work locations at which airborne concentrations are likely to multiple samplers exceed 0.3 DAC and that are generally occupied by workers whose intakes must be monitored and whose dose of record will be based on air sampling.

Comparison: Use multiple samplers to take measurements at four or more locations around the worker's head.

Acceptance criteria: The concentration determined by the fixed-location sampler divided by the concentration averaged for all the multiple samplers should exceed 0.7 for the work location.

4. Comparison with Include: Work locations at which airborne concentrations are likely to quantitative airflow exceed 0.3 DAC that are generally occupied by workers whose intakes must measurements be monitored and whose dose of record will be based on air sampling.

Comparison: Release a tracer material near the source release point. Meas-ure its concentration with the fixed-location sampler and with another sam-pler placed closed to the worker's head.

Acceptance criteria: The concentration measured by fixed-location sampler divided by the concentration of the sampler placed close to the worker's head should exceed 0.7.

8.25-6

compounds are listed in Appendix B of Part 2. The radioactive materials involved and

20) or their solubility classes (D, W, or Y). their chemical form (relative to the chemi-Describe how the chemical forms or solubil- cal forms listed in Appendix B to Part 20) ity classes were determined. or solubility class (D, W, or Y).

3. A graph of the adjusted DAC vs. activity 3. A description of how the chemical form or median aerodynamic diameter. solubility class was determined.

4. The type of cyclone, the type of sampler,

4. The method by which the activity median the air flow rate, and the collection effi-aerodynamic diameter will be measured.

ciency of 4 micrometer particles at the flow

5. The locations at which the measurements rate that will be used.

will be made. 5. A list of locations or worker areas that will be sampled using cyclones.

6. The frequency of measurements.

In general, this method is suitable for solubility

7. Methods or techniques that will be used to class W and Y compounds but not solubility class D average results by location or time. compounds. Cyclones should have an efficiency of at least 50 percent for particles with an aerodynamic di-The following locations and frequency of meas- ameter of 4 micrometers. 2 urements are acceptable to the NRC. For an initial determination of the adjustment, the licensee should 4.3 Adjusting DACs for Solubility take the average of three measurements of the activ- NRC regulations in 10 CFR 20.1204(c) permit, ity median aerodynamic diameter at or near each upon prior approval of the NRC, the adjustment of work location or process. The licensee should then the DAC based on chemical characteristics. If the li-determine whether the entire area or room can be censee elects to request approval to adjust DACs represented by a single activity median aerodynamic based on particle solubility in the human body, the diameter or whether the area or room should be di- following information should be submitted:

vided into areas with different particle sizes. After the initial determination of median diameter in each area 1. The need for adjustment.

of the workplace has been made, the licensee should 2. A description of how the solubility of the reassess the median diameters by making another material was determined.

measurement at approximately one-quarter of the work locations at 6-month intervals, selecting differ- 3. A description of how the adjusted DAC was ent locations each time. However, if two consecutive determined.

reassessments do not show a substantial change in the

4. The number and frequency of measure-median diameter, reassessments may be annual.

ments. (A frequency of at least annually is Reassessments should also be done after there have recommended.)

been process changes likely to affect the size distribu-tion of particles. If the activity median aerodynamic 5. MEASURING THE VOLUME OF AIR diameter has changed, the median diameter for the SAMPLED area should either be reassessed or replaced with a The accuracy of air sampling measurements and default value of 1 micrometer. the calibration of air sampling instruments is not ex-If the licensee elects to adjust the DAC based on plicitly dealt with in Part 20. However, it is implied the size distribution for short-duration operations, that measurements required by-Part 20 must be suit-such as special maintenance jobs, at least one meas- ably accurate. This section of the guide describes ac-urement should be made each time the job is done. ceptable methods to determine the volume of air to In the event of abnormal or accident conditions, the be sampled to ensure suitable accuracy.

median diameter for normal operating conditions 5.1 Means To Determine Volume of Air may be assumed for intake assessments. Sampled 4.2 Using Cyclones To Adjust Measured All air samplers to be used for quantitative Airborne Concentrations measurements should have a means to determine the volume of air sampled. This recommendation applies If the licensee elects to request approval to use to fixed-location samplers, portable samplers, and la-cyclones or other particle size discrimination samplers pel samplers.

to adjust the measured airborne concentrations, the following information should be submitted: 5.2 Calibration Frequency and Methods The licensee should calibrate airflow meters at

1. The need for the adjustment. least annually. Additional calibrations should be 8.25-7

performed after repairs or modifications to the meter collected by the collection media. If penetration of or if the meter is believed to have been damaged. radioactive material into the collection media or self-The methods described in Section F of "Air Sam- absorption of radiation by the material collected pling Instruments" 3 to calibrate airflow meters are would reduce the count rate by more than 5 percent, acceptable to the NRC staff. a correction factor should be used. I 5.3 Uncertainty 6.3 Detection Sensitivity The uncertainty in the volume of air sampled The 10 CFR Part 20 monitoring criteria (i.e., 10 should be less than 20 percent. The uncertainty, U, percent of the limit) do not establish required levels in percent may be calculated from the equation: of detection sensitivity (lower level of detection, mini-mum detectable activity, minimum detectable con-U. = [U2 + u2 + 01/2 centration, etc.). For example, lapel samplers may not be able to detect uranium concentrations of 10 where: U, = the percent uncertainty in reading percent of the DAC, but lapel samplers are still ac-the meter scale ceptable for measuring the uranium intake of work-Uc= the percent uncertainty in deter- ers. The monitoring criteria should not be considered mining the calibration factor requirements on the sensitivity of a particular meas-U, = the percent uncertainty in the urement because when the results of multiple meas-measurement of the sampling urements are summed, the sum will have a greater time. statistical power than the individual measurements.

However, to achieve the greater statistical power, the 5.4 Inleakage licensee should record all numerical values meas-Air samplers and associated sampling lines ured, even values below "minimum detectable should be checked for leakage of air into the sam- amounts" and values that are negative because the pling line upstream of the flow measurement device measured count rate is below the background. Results when they are calibrated for volume of air sampled. should not be recorded as "below MDA" or similar statements.

5.5 Change in Flow Rate If the licensee desires to calculate the minimum If the flow rate changes by more than +/- 10 per- detectable activity of a single sample (MDA), it may cent during collection of a sample, a correction be calculated by use of the following equation:

should be made by averaging the initial and the final flow rates. 2 MDA = 2.71 + 3.29IRbTS(1 + T./Tb)]"

6. EVALUATION OF SAMPLING RESULTS EKT, 6.1 Detecting Changes in Air Concentrations where: Rb = the background count rate Over Time T, = the sample counting time For fixed-location sampling whose purpose is to confirm confinement of radioactive materials for rou- Tb = the background (or blank) count-tine or repeated operations, the results should either ing time (1) be analyzed for trends (for example, by control E = the filter efficiency charts) to determine whether airborne concentrations K = a calibration factor to convert are within the normal range and administrative and counts per minute into activity engineering controls are thus operating properly to (e.g., counts per minute per mi-maintain occupational doses as low as is reasonably crocurie) achievable or (2) be compared with administrative action levels that serve as a basis for determining (The derivation of this equation is described in when confinement is satisfactory. NUREG-1400.)

If the proportion of the total activity of a sample 6.2 Efficiency of Collection Media that is due to a specific radionuclide in a mixture is If the efficiency of the collection media (such as known, the MDA for that radionuclide should be re-filters) for an air sample is less than 95 percent for duced proportionally:

the material being collected, the sample result should be corrected to account for radioactive material not MDAi = Ai/A x MDA 3

7th Edition, American Conference of Governmental Indus-where:

trial Hygienists, 1989. Copies are available for purchase from the ACGIH, 6500 Glenway Avenue, Building D-7, Cincin- At/A = the proportion of the total sample ac-nati, Ohio 45211. tivity from radionuclide i.

8.25-8

6.4 Deposition of Particulates in Sampling 3. Trends: Do trends in air sampling results Lines and worker intakes indicate that confine-If sampling lines are used for collecting airborne ment of radioactive materials remains ade-particulates, the lines should be as short as possible quate? Were prospective estimates of in-and should be made of a material not subject to sig- take reasonably accurate?

nificant static charge effects (e.g., grounded metal).

However, up to several feet of flexible plastic tubing, 4. Posting: Is the posting of airborne radioac-such as tygon, may be used to connect the sampling tivity areas appropriate?

line to the sample collector. The penetration of parti-cles with an aerodynamic equivalent diameter of 10 5. Procedures: Are written procedures still micrometers should be at least 50 percent. DEPOSI- suitable and up to date?

TION 4 software is an acceptable means of calculating penetration. 6. Adjustment of DACs: Were DACs adjusted for particle size or solubility? If so, are the 6.5 Annual Review of Air Sampling original adjustment factors still valid?

Measurements Section 2 0.1101(c) of Part 20 requires that the 7. Correctionfactors: Were correction factors licensee periodically (at least annually) review the applied to air samples to determine worker radiation protection program content and implemen- intakes? If so, are the correction factors still tation. The review of the air sampling component of valid?

the program should determine (1) whether the meas-urements are accurate and reliable and (2) whether 8. False alarms: Was continuous air monitor-changes should be made to improve the measure- ing done? If so, did excessive false alarms ments. The review should be done annually and occur?

should cover the prior year's activities. The annual review of air sampling measurements may be com- 9. Representativeness: For air sampling done bined with reviews of other aspects of the radiation to determine significant intakes, was the protection program. representativeness demonstrated to be ade-quate?

The annual review should include but not neces-sarily be limited to: 10. Changes: Have changes in air sampling pro-cedures or equipment occurred that could

1. Purposes and amount of airsampling: Was affect the quality of the measurements?

the air sampling appropriate for the in- Have changes in the facility operation or tended purposes? Was there too much or equipment occurred that could affect the too little air sampling done? quality of air sampling measurements?

2. Location of Sampling: Were fixed-location air samplers located properly? Were grab D. IMPLEMENTATION samples taken with proper regard to airflow patterns? The purpose of this section is to provide infor-mation to applicants and licensees regarding the NRC 4N.K. Anand and A. R. McFarland, "DEPOSITION: staff's plans for using this regulatory guide.

Software for Characterizing Aerosol Particle Deposition in Sampling Lines," Draft NUREG/GR-0006, October 1991. Except in those cases in which an applicant pro-Single copies are available free, to the extent of supply, upon poses acceptable alternative methods for complying written request to the Office of Information Resources Man- with specified portions of the Commission's regula-agement, Distribution Section, U.S. Nuclear Regulatory Com-mission, Washington, DC 20555. A final version of NUREGf tions, the methods described in this guide will be used GR-0006 is being developed. For information on DEPOSI- in the evaluation of applications for new licenses, TION software contact: Aerosol Technology Laboratory, De-partment of Mechanical Engineering, Texas A&M University, license renewals, and license amendments and for College Station, TX 77843, Attention: Dr. Andrew R. McFar- evaluating compliance with 10 CFR 20.1001-land. Telephone (409) 845-2204.

20.2401.

8.25-9

REGULATORY ANALYSIS A separate regulatory analysis was not prepared A copy of the "Regulatory Analysis for the Revision for this regulatory guide. The regulatory analysis pre- of 10 CFR Part 20" (PNL-6712, November 1988), is pared for 10 CFR Part 20, "Standards for Protection available for inspection and copying for a fee at the I Against Radiation" (56 FR 23360), provides the NRC Public Document Room, 2120 L Street, NW.

regulatory basis for this guide and examines the costs (Lower Level), Washington, DC, as an enclosure to and benefits of the rule as implemented by the guide. Part 20.

8.25-10

J UNITED STATES FIRST CLASS MAIL NUCLEAR REGULATORY COMMISSION POSTAGE AND FEES PAID WASHINGTON, D.C. 20555-0001 USNRC PERMIT NO. G-67 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $300