U.S. NUCLEAR REGULATORY COMMISSION

REGULATORY

Revision 1

June 1992

GUIDE

OFFICE OF NUCLEAR REGULATORY RESEARCH

REGULATORY GUIDE 8.25

(Draft was issued as DG-80)

AIR SAMPLING IN THE WORKPLACE

A. INTRODUCTION

Air sampling in the workplace is an acceptable

method for meeting certain of the survey and dose

assessment requirements of 10 CFR Part 20, 'Standards for Protection Against Radiation." For example, 10 CFR 20.1204 allows estimates of worker intakes of radioactive materials based on air sampling

and allows adjustments of derived air concentrations

(DACs) and annual limits on intake (ALIs) based on

the particle size distribution; 10 CFR 20.1501 requires radiation surveys necessary to comply with the

regulations and to evaluate potential radiological hazards; 10 CFR 20.1703 requires assessment of airborne radioactive material concentrations when respirators are used; 10 CFR 20.1902 requires posting of

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

concentrations of or exposure to airborne radioactive

materials.

This guide provides guidance on air sampling in

restricted areas (as defined in 10 CFR Part 20) of the

workplace. In this guide, the term "air sampling" includes the collection of samples for later analysis as

well as real-time monitoring in which samples are

analyzed as they are collected. The guide does not

cover environmental or effluent sampling or the

analysis of samples.

In addition, this guide does not apply to activities

conducted under 10 CFR Part 50 at reactor facilities.

Although the provisions of 10 CFR Part 20 apply

equally to nuclear reactors and to other facilities, the

air sampling programs of reactor licensees are well established, and the NRC is satisfied that the quality of

air sampling at nuclear reactors is adequate. Therefore, no further guidance on air sampling is needed at

this time for reactor licensees.

Any information collection activities mentioned

in this regulatory guide are contained as requirements

in 10 CFR Part 20, which provides the regulatory basis for this guide. The information collection requirements in 10 CFR Part 20 have been cleared under

OMB Clearance No. 3150-0014.

B. DISCUSSION

Air sampling can be used to determine whether

the confinement of radioactive materials is effective,

to measure airborne radioactive material concentrations in the workplace, to estimate worker intakes, to

determine posting requirements, to determine what

protective equipment and measures are appropriate,

and to warn of significantly elevated levels of airborne

radioactive materials. If bioassay measurements are

used to determine worker doses of record, air sampling may be used to determine time of intake and to

USNRC REGUlATORY GUIDES

Regulatory Guides are Issued to describe and make available to the public methods acceptable to the NRC staff of implementing specific parts

of the Commission's regulations, to delineate techniques used by the

staff in evaluating specific problems or postulated accidents, or to provide guidance to applicants. Regulatory Guides are not substitutes for

regulations, and compliance with them is not required. Methods and

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 continuance of a permit or license by the Commission.

This guide was Issued after consideration of comments received from

the public. Comments and suggestions for Improvements In these

guides are encouraged at all times, and guides will be revised, as appropriate, to accommodate comments and to reflect new information or

experience.

Written comments may be submitted to the Regulatory Publications

Branch, DRIPS, ADM, U.S. Nuclear Regulatory Commission, Washington, DC 20555.

The guides are issued in the following ten broad divisions:

1. Power Reactors

2. Research and Test Reactors

3. Fuels and Materials Facilities

4. Environmental and Siting 5. Materials and Plant Protection

6. Products

7. Transportation

8. Occupational Health

9. Antitrust and Financial Review

10. General

Copies of Issued guides may be purchased from the Government Printing

Office at the current GPO price. Information on current GPO prices may be obtained by contacting the Superintendent of Documents, U.S.

Government Printing Office, Post Office Box 37082, Washington, DC

20013-7082, telephone (202)275-2060 or (202)275-2171.

Issued guides may also be purchased from the National Technical Information Service on a standing order basis. Details on this service may be

obtained by writing NTIS. 5285 Port Royal Road, Springfield, VA 22161.
determine which workers should have bioassay measurements.

General guidance on air sampling for specific

types of facilities is also discussed in several other

regulatory guides, including:

* Regulatory Guide 8.21, "Health Physics Surveys for Byproduct Material at NRCLicensed Processing and Manufacturing

Plants"

* Regulatory Guide 8.23, "Radiation Safety

Surveys at Medical Institutions"

* Regulatory Guide 8.24, "Health Physics Surveys During Enriched Uranium-235 Processing and Fuel Fabrication"

* Regulatory Guide 8.30, "Health Physics Surveys in Uranium Mills"

These facility-specific guides cover air sampling

in general terms, while this guide discusses air sampling in more depth. Thus, the guides are complementary.

This guide provides recommendations on air

sampling to meet the requirements of 10 CFR

Part 20. Draft NUREG-1400, "Air Sampling in the

Workplace, 1 provides examples, methods, and techniques that the licensee may find useful for implementing the recommendations in this guide. However, NUREG-1400 does not establish regulatory positions or recommendations and should not be

used as a compliance document to establish the adequacy of licensee programs.

C. REGULATORY POSITION

1. EVALUATING THE NEED FOR AIR

SAMPLING

The implementation of some sections in 10 CFR

Part 20 may require air sampling. This section of the

guide provides recommendations on when and what

type of air sampling is acceptable to meet the Part 20

requirements.

1.1 When To Evaluate the Need for Air

Sampling

As a general rule, any licensee who handles or

processes unsealed or loose radioactive materials in

quantities that during a year will total more than

10,000 times the ALI for inhalation should evaluate

the need for air sampling. (If the same material is

used repeatedly, multiply the quantity used by the

number of times used.) If more than one radioactive

'Single copies of draft NUREG-1400 are available free, to the extent of the supply. Submit a written request to the Office of Administration, Distribution and Mail Services Section, U.S. Nuclear Regulatory Commission, Washington, DC 20555. A final version of NUREG-1400 is being developed and should be published in 1993.

material is used, the need for air sampling should be

determined by whether the sum of the quantities of

each divided by each respective ALI exceeds 10,000.

When quantities handled in a year are less than

10,000 times the ALI, air sampling generally is not

needed. (The basis for this value is that experience has shown that worker intakes are unlikely to exceed

one one-millionth of the material being handled or

processed, as discussed in NUREG-1400.)

1.2 Air Sampling Based on Potential Intakes

and Concentrations

The extent of air sampling may be based on estimates of worker intakes and on estimated airborne

concentrations of radioactive materials as shown in

Table 1. Estimates of potential intakes and concentrations should be based on historical air sampling or

bioassay data if these data are available. If the data

are not available, potential intakes and concentrations should be estimated. Estimates of intakes and

concentrations should be based on a consideration of

(1) the quantity of radioactive material being handled, (2) the ALI of the material, (3) the release

fraction for the radioactive material based on its

physical form and use, (4) the type of confinement

for the material, and (5) other factors appropriate for

the specific facility. The estimated prospective intake

provides only a guide to the appropriate types of air

sampling. The radiation safety officer should use pro- fessional judgment and experience to perform air

sampling appropriate for the specific situation.

1.3 Grab vs. Continuous Air Sampling

Air sampling may be continuous during work

hours or intermittent (grab samples taken during part of the work). When continuous sampling during the

work day is performed for continuous processes, a

weekly sample exchange period is generally accept- able (except for very short-lived radionuclides).

Longer sample exchange periods may be appropriate

if airborne radioactive material concentrations and

nuisance dust concentrations are both relatively low.

When grab sampling is performed for continuous

processes, a weekly sampling frequency is generally acceptable; however, monthly or quarterly sampling

may be acceptable for areas in which concentrations

of airborne radioactive material are expected to average below a few percent of the DAC. Grab sampling would also be appropriate when operations are conducted on an intermittent basis.

1.4 Air Sampling When Respiratory Protective

Equipment Is Used

Air sampling is required by 10 CFR

20.1703(a)(3)(i) to evaluate airborne hazards whenever respiratory protective equipment is used to limit

intakes pursuant to 10 CFR 20.1702. Air samplers that are located to determine worker intake are

I

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 concentrations are likely to exceed 0.1 DAC averaged over

40 hours 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 representative 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 hours (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 DAChours 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 activity will be the main source of airborne radioactive

material, the sampling should be done during the activity, not prior to the activity.

1.5 Prompt Analysis of Certain Samples

In situations in which there is a potential for intakes to exceed 40 DAC-hours in a week, air samples

should be analyzed promptly on a daily basis. (In

evaluating the need for prompt analysis, credit may

be taken for respirator protection factors if a respiratory protection program is in place.) Sample results

should be available before work resumes the following day. When work is done in shifts, results should

be available before the next shift ends, preferably

during the first half of the next shift. For special or

nonroutine operations, an attempt should be made to

have analysis results available within one hour.

1.6 Continuous Air Monitoring

In situations in which there is a potential for accidents to cause intakes exceeding 40 DAC-hours in

a day, continuous air monitoring should be done.

When continuous air monitors with automatic alarms

are used, the alarm set points should be set as low as

practical for the work being conducted without causing excessive false alarms (e.g., more than once per

quarter).If continuous air monitors with automatic

alarms are used, check sources should be used

weekly to check that the monitor responds and

causes an alarm. Continuous check sources may also

be used, provided there is no interference with the

radionuclide of interest. If the response is not within

8.25-3
± 20 percent of the normal response, the monitor

should be repaired or recalibrated.

1.7 Establishing Airborne Radioactivity Areas

Air sampling with samplers located to determine

worker intake may be used to determine whether an

area is an airborne radioactivity area. Any room, enclosure, or area must be posted as an airborne radioactivity area if (1) concentrations of airborne radioactive materials are in excess of the DAC or (2) a

worker in the area would be exposed to more than 12

DAC-hours in a week (10 CFR 20.1902 and

20.1003). To determine whether the concentration

exceeds the DAC over the short term, the sample

collection time should not exceed 1 hour. Shorter

sample collection times may be used if desired, but

they are not required.

Areas should not be posted as airborne radioactivity areas on the basis of unlikely accidents that

might cause the DAC to be exceeded. An airborne

radioactivity area should be established based on the

radioactivity levels normally encountered or on levels

ihat can reasonably be expected to occur when work

is being performed.

1.8 Air Sampling vs. Bioassay for Determining

Intakes

If sufficient data to determine a worker's intake

are available from both air sampling and bioassay

measurements and the results are significantly different, the licensee should base the worker's intake estimate on the data considered by the radiation protection staff to be the most accurate.

1.9 Substitutes for Air Sampling

If experience indicates that worker intakes are

generally low, it may be acceptable to substitute other

techniques in place of air sampling. For example,

when working with tritium, iodine, or other materials

that are easily and effectively detected by bioassay, it

could be appropriate to eliminate all air sampling and

rely completely on bioassays to measure intakes and

verify confinement.

2. LOCATION OF AIR SAMPLERS

Concentrations of airborne radioactive materials

in a room are generally not uniform. Concentrations

usually vary greatly from one location to another,

sometimes by orders of magnitude even for locations

that are relatively close. Therefore, the location of air

samplers is important because inappropriately placed

samplers can give misleading results.

This section applies only to fixed-location and

portable samplers. It does not-apply to personal (lapel) samplers.

2.1 Purpose of the Measurement

Before selecting a sampling location, the licensee

should decide on the purpose of the measurement.

Examples of purposes are (1) estimating worker intakes, (2) verifying that the confinement of radioactive materials is effective, (3) providing warning of

abnormally high concentrations, (4) determining

whether there is any leakage of radioactive materials

from a sealed confinement system, and (5) determining whether an airborne radioactivity area exists.

2.2 Determination of Airflow Patterns

Airflow patterns should be determined in order

to locate air samplers appropriately. The locations of

ventilation air inlets and exhausts and of sources of

airborne radioactive materials should be noted in order to determine the predominant airflow patterns

and likely radioactive material transport routes.

When sampling air in rooms with complex airflow

patterns, it may be useful to use smoke tubes or

neutrally buoyant markers to determine airflow patterns.

When sampling air in an airborne radioactivity

area to determine the intakes of workers whose intake must be monitored under 10 CFR 20.1502(b),

smoke tubes or neutrally buoyant markers should be

used to determine airflow patterns from the source to

the worker's breathing zone. In some instances, the

use of larger smoke sources or neutrally buoyant

marker sources to observe airflow patterns is desirable. However, observations of airflow patterns

should be omitted in areas of high external radiation

exposure if making the observations would result in

total worker doses (internal plus external) that are

not as low as is reasonably achievable.

The airflow pattern determinations should be repeated if there are changes at the facility, including

changes in locations of the individual work locations

and seasonal variations that might change airflow patterns, or if there is a reason to suspect problems. The

radiation protection staff should be aware of facility

characteristics, operations, and changes that might

change airflow patterns. In addition, the location of

at least 10 percent of the fixed-location samplers

should be evaluated annually to confirm that their locations are still appropriate.

2.3 Selecting Sampler Locations

Air samples should be collected in airflow pathways downstream of sources of airborne radioactive

material.

When the purpose of the sample is to verify the

effectiveness of confinement or to provide warning of

elevated concentrations, the sampling point should be

located in the airflow pathway near the release point.

These samplers do not have to be placed near the

worker's breathing zone, and thus concentrations

I

8.25-4
might be considerably different from the concentrations in the breathing zone. If the room has several

widely spaced sources of airborne radioactive material, more than one sampling point may be needed.

When the purpose of sampling is to determine

worker intakes, each frequently occupied work location should have its own sampler. The air samplers

should be placed as close to the breathing zone of the

worker as practical without interfering with the work

or the worker. In addition, air flow patterns in the

area should be considered in placing samplers so that

the sampler is likely to be in the airflow downstream

of the source and prior to or coincident with the location of the worker. An estimate should be made of

the time the worker spends at the work location (unless personal air samplers are being used).

For hoods, glove boxes, and other similar enclosures used to contain radioactive material, air samplers may be installed slightly above head height and

in front of the worker or they may be installed on the

front face of the enclosure.

Normally, air samplers intended to measure

workplace concentrations should not be located in or

near exhaust ducts, because concentrations there will

usually be diluted compared to concentrations in

work areas. However, samplers may be located in

ducts if their purpose is to detect leakage from systems that do not leak during normal operation and if

quantitative measurements of workplace airborne

concentrations are not needed.

3. DEMONSTRATION THAT AIR SAMPLING

IS REPRESENTATIVE OF INHALED AIR

Section 20.1502(b) of 10 CFR Part 20 requires

monitoring of the intake of any worker whose intake

is likely to exceed 0.1 ALI. Section 20.1204 allows

the use of air sampling, bioassay, or a combination of

both to determine a worker's intake.

3.1 Need To Demonstrate that Air Sampling Is

Representative of Breathing Zone Air

It should be demonstrated that the air sampled

is representative of breathing zone air if all four of

the following conditions are met: (1) monitoring of

intake is required by 10 CFR 20.1502(b) because annual intake is likely to exceed 0.1 ALI, (2) the intake

of record will be based on air sampling rather than

bioassay, and (3) the exposure will occur in an airborne radioactivity area where airborne concentrations are likely to exceed 12 DAC-hours in a week,

and (4) lapel samplers or samplers located within

about 1 foot of the worker's head are not used. (The

results from lapel samplers or samplers that are located within about 1 foot of the worker's head may

be accepted as representative without further demonstration that the results are representative.)

3.2 Demonstration that Air Sampling Is

Representative

Four methods may be used to demonstrate

representativeness of the results from samplers that

are not located within about 1 foot of the worker's

head: (1) comparison with lapel sampler results (for

this comparison, lapel samplers may be equipped with

cyclones with an efficiency of at least 50 percent for

particles with an aerodynamic equivalent diameter of

4 micrometers if the particles sampled are solubility

class W or Y),2 (2) comparison with bioassay results,

(3) comparison using multiple measurements near the

breathing zone, and (4) comparison with quantitative

airflow tests.

Table 2 describes the application of each of the

methods and includes acceptance criteria for determining whether sampling results may be considered

representative.

3.3 Corrective Actions if Sampling Results Are

Not Representative

If the method used to demonstrate representativeness does not show that the sampling results are

representative, the licensee should analyze the situation, determine the likely cause of the problem, and

fix the problem. The licensee should also correct

intake estimates made within the last year and subsequent to the previous demonstration of representativeness. To fix the problem, it may be appropriate to

relocate samplers to be more representative, apply

correction factors to correct sampling results, switch

to lapel sampling, or use bioassay measurements to

determine intakes.

4. ADJUSTMENTS TO DERIVED AIR

CONCENTRATIONS

NRC regulations in 10 CFR 20.1204(c) permit,

upon prior approval of the NRC, the adjustment of

DACs to reflect the actual physical and chemical

characteristics of airborne radioactive materials.

4.1 Adjusting DACs Based on Measurements of

Particle Size

If the licensee elects to request approval to adjust DACs based on measured activity median aerodynamic diameters of airborne particles, the following

information should be submitted:

1. The need for the adjustment.

2. The radioactive materials involved and

either their chemical form (if the chemical

2American Conference of Governmental Industrial Hygienists, Threshold Limit Values for Chemical Substances and

Physical Agents and Biological Exposure Indices, Notice of

Intended Changes: Appendix D-Particle Size Selective Sampling Criteria for Airborne Particulate Matter, 1991. The

4-micrometer criterion is also in the process of being adopted

by the International Standards Organization (ISO) and the

European Standardization Committee (CEN).

8.25-5
Table 2

Methods To Demonstrate the Representativeness of Air Sampling

Method Description

I

1. Comparison with

lapel samplers

Include: Workers whose annual intakes must be monitored under 10 CFR

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 measured 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 compatible with the accuracy expected of external radiation dosimeters.)

2. Comparison with

bioassay results

Include: Workers whose annual intakes must be monitored under 10 CFR

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 measurements 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

multiple samplers

Include: Work locations at which airborne concentrations are likely to

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

quantitative airflow

measurements

Include: Work locations at which airborne concentrations are likely to

exceed 0.3 DAC that are generally occupied by workers whose intakes must

be monitored and whose dose of record will be based on air sampling.

Comparison: Release a tracer material near the source release point. Measure its concentration with the fixed-location sampler and with another sampler 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

20) or their solubility classes (D, W, or Y).

Describe how the chemical forms or solubility classes were determined.

3. A graph of the adjusted DAC vs. activity

median aerodynamic diameter.

4. The method by which the activity median

aerodynamic diameter will be measured.

5. The locations at which the measurements

will be made.

6. The frequency of measurements.

7. Methods or techniques that will be used to

average results by location or time.

The following locations and frequency of measurements are acceptable to the NRC. For an initial

determination of the adjustment, the licensee should

take the average of three measurements of the activity median aerodynamic diameter at or near each

work location or process. The licensee should then

determine whether the entire area or room can be

represented by a single activity median aerodynamic

diameter or whether the area or room should be divided into areas with different particle sizes. After the

initial determination of median diameter in each area

of the workplace has been made, the licensee should

reassess the median diameters by making another

measurement at approximately one-quarter of the

work locations at 6-month intervals, selecting different locations each time. However, if two consecutive

reassessments do not show a substantial change in the

median diameter, reassessments may be annual.

Reassessments should also be done after there have

been process changes likely to affect the size distribution of particles. If the activity median aerodynamic

diameter has changed, the median diameter for the

area should either be reassessed or replaced with a

default value of 1 micrometer.

If the licensee elects to adjust the DAC based on

the size distribution for short-duration operations,

such as special maintenance jobs, at least one measurement should be made each time the job is done.

In the event of abnormal or accident conditions, the

median diameter for normal operating conditions

may be assumed for intake assessments.

4.2 Using Cyclones To Adjust Measured

Airborne Concentrations

If the licensee elects to request approval to use

cyclones or other particle size discrimination samplers

to adjust the measured airborne concentrations, the

following information should be submitted:

1. The need for the adjustment.

2. The radioactive materials involved and

their chemical form (relative to the chemical forms listed in Appendix B to Part 20)

or solubility class (D, W, or Y).

3. A description of how the chemical form or

solubility class was determined.

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

the air flow rate, and the collection efficiency of 4 micrometer particles at the flow

rate that will be used.

5. A list of locations or worker areas that will

be sampled using cyclones.

In general, this method is suitable for solubility

class W and Y compounds but not solubility class D

compounds. Cyclones should have an efficiency of at

least 50 percent for particles with an aerodynamic diameter of 4 micrometers. 2

4.3 Adjusting DACs for Solubility

NRC regulations in 10 CFR 20.1204(c) permit,

upon prior approval of the NRC, the adjustment of

the DAC based on chemical characteristics. If the licensee elects to request approval to adjust DACs

based on particle solubility in the human body, the

following information should be submitted:

1. The need for adjustment.

2. A description of how the solubility of the

material was determined.

3. A description of how the adjusted DAC was

determined.

4. The number and frequency of measurements. (A frequency of at least annually is

recommended.)

5. MEASURING THE VOLUME OF AIR

SAMPLED

The accuracy of air sampling measurements and

the calibration of air sampling instruments is not explicitly dealt with in Part 20. However, it is implied

that measurements required by-Part 20 must be suitably accurate. This section of the guide describes acceptable methods to determine the volume of air to

be sampled to ensure suitable accuracy.

5.1 Means To Determine Volume of Air

Sampled

All air samplers to be used for quantitative

measurements should have a means to determine the

volume of air sampled. This recommendation applies

to fixed-location samplers, portable samplers, and lapel samplers.

5.2 Calibration Frequency and Methods

The licensee should calibrate airflow meters at

least annually. Additional calibrations should be

8.25-7
performed after repairs or modifications to the meter

or if the meter is believed to have been damaged.

The methods described in Section F of "Air Sampling Instruments"3 to calibrate airflow meters are

acceptable to the NRC staff.

5.3 Uncertainty

The uncertainty in the volume of air sampled

should be less than 20 percent. The uncertainty, U,

in percent may be calculated from the equation:

U. = [U2 + u2 + 01/2

where: U, = the percent uncertainty in reading

the meter scale

Uc= the percent uncertainty in determining the calibration factor

U, = the percent uncertainty in the

measurement of the sampling

time.

5.4 Inleakage

Air samplers and associated sampling lines

should be checked for leakage of air into the sampling line upstream of the flow measurement device

when they are calibrated for volume of air sampled.

5.5 Change in Flow Rate

If the flow rate changes by more than ± 10 percent during collection of a sample, a correction

should be made by averaging the initial and the final

flow rates.

6. EVALUATION OF SAMPLING RESULTS

6.1 Detecting Changes in Air Concentrations

Over Time

For fixed-location sampling whose purpose is to

confirm confinement of radioactive materials for routine or repeated operations, the results should either

(1) be analyzed for trends (for example, by control

charts) to determine whether airborne concentrations

are within the normal range and administrative and

engineering controls are thus operating properly to

maintain occupational doses as low as is reasonably

achievable or (2) be compared with administrative

action levels that serve as a basis for determining

when confinement is satisfactory.

6.2 Efficiency of Collection Media

If the efficiency of the collection media (such as

filters) for an air sample is less than 95 percent for

the material being collected, the sample result should

be corrected to account for radioactive material not

3 7th Edition, American Conference of Governmental Industrial Hygienists, 1989. Copies are available for purchase from

the ACGIH, 6500 Glenway Avenue, Building D-7, Cincinnati, Ohio 45211.

collected by the collection media. If penetration of

radioactive material into the collection media or selfabsorption of radiation by the material collected

would reduce the count rate by more than 5 percent,

a correction factor should be used.

6.3 Detection Sensitivity

The 10 CFR Part 20 monitoring criteria (i.e., 10

percent of the limit) do not establish required levels

of detection sensitivity (lower level of detection, minimum detectable activity, minimum detectable concentration, etc.). For example, lapel samplers may

not be able to detect uranium concentrations of 10

percent of the DAC, but lapel samplers are still acceptable for measuring the uranium intake of workers. The monitoring criteria should not be considered

requirements on the sensitivity of a particular measurement because when the results of multiple measurements are summed, the sum will have a greater

statistical power than the individual measurements.

However, to achieve the greater statistical power, the

licensee should record all numerical values measured, even values below "minimum detectable

amounts" and values that are negative because the

measured count rate is below the background. Results

should not be recorded as "below MDA" or similar

statements.

If the licensee desires to calculate the minimum

detectable activity of a single sample (MDA), it may

be calculated by use of the following equation:

MDA = 2.71 + 3.29IRbTS(1 + T./Tb)]" 2

EKT,

where: Rb = the background count rate

T, = the sample counting time

Tb = the background (or blank) counting time

E = the filter efficiency

K = a calibration factor to convert

counts per minute into activity

(e.g., counts per minute per microcurie)

I

(The derivation

NUREG-1400.)

of this equation is described in

If the proportion of the total activity of a sample

that is due to a specific radionuclide in a mixture is

known, the MDA for that radionuclide should be reduced proportionally:

MDAi = Ai/A x MDA

where:

At/A = the proportion of the total sample activity from radionuclide i.

8.25-8
6.4 Deposition of Particulates in Sampling

Lines

If sampling lines are used for collecting airborne

particulates, the lines should be as short as possible

and should be made of a material not subject to significant static charge effects (e.g., grounded metal).

However, up to several feet of flexible plastic tubing,

such as tygon, may be used to connect the sampling

line to the sample collector. The penetration of parti- cles with an aerodynamic equivalent diameter of 10

micrometers should be at least 50 percent. DEPOSITION 4 software is an acceptable means of calculating

penetration.

6.5 Annual Review of Air Sampling

Measurements

Section 2 0.1101(c) of Part 20 requires that the

licensee periodically (at least annually) review the

radiation protection program content and implementation. The review of the air sampling component of

the program should determine (1) whether the measurements are accurate and reliable and (2) whether

changes should be made to improve the measurements. The review should be done annually and

should cover the prior year's activities. The annual

review of air sampling measurements may be combined with reviews of other aspects of the radiation

protection program.

The annual review should include but not necessarily be limited to:

1. Purposes and amount of air sampling: Was

the air sampling appropriate for the intended purposes? Was there too much or

too little air sampling done?

2. Location of Sampling: Were fixed-location

air samplers located properly? Were grab

samples taken with proper regard to airflow

patterns?

4N.K. Anand and A. R. McFarland, "DEPOSITION: Software for Characterizing Aerosol Particle Deposition in Sampling Lines," Draft NUREG/GR-0006, October 1991. Single copies are available free, to the extent of supply, upon written request to the Office of Information Resources Management, Distribution Section, U.S. Nuclear Regulatory Com- mission, Washington, DC 20555. A final version of NUREGf GR-0006 is being developed. For information on DEPOSI- TION software contact: Aerosol Technology Laboratory, De- partment of Mechanical Engineering, Texas A&M University, College Station, TX 77843, Attention: Dr. Andrew R. McFar- land. Telephone (409) 845-2204.

3. Trends: Do trends in air sampling results

and worker intakes indicate that confinement of radioactive materials remains adequate? Were prospective estimates of intake reasonably accurate?

4. Posting: Is the posting of airborne radioactivity areas appropriate?

5. Procedures: Are written procedures still

suitable and up to date?

6. Adjustment of DACs: Were DACs adjusted

for particle size or solubility? If so, are the

original adjustment factors still valid?

7. Correction factors: Were correction factors

applied to air samples to determine worker

intakes? If so, are the correction factors still

valid?

8. False alarms: Was continuous air monitoring done? If so, did excessive false alarms

occur?

9. Representativeness: For air sampling done

to determine significant intakes, was the

representativeness demonstrated to be adequate?

10. Changes: Have changes in air sampling procedures or equipment occurred that could

affect the quality of the measurements?

Have changes in the facility operation or

equipment occurred that could affect the

quality of air sampling measurements?

D. IMPLEMENTATION

The purpose of this section is to provide information to applicants and licensees regarding the NRC

staff's plans for using this regulatory guide.

Except in those cases in which an applicant proposes acceptable alternative methods for complying

with specified portions of the Commission's regula- tions, the methods described in this guide will be used

in the evaluation of applications for new licenses,

license renewals, and license amendments and for

evaluating compliance with 10 CFR 20.1001-

20.2401.

8.25-9
REGULATORY ANALYSIS

A separate regulatory analysis was not prepared

for this regulatory guide. The regulatory analysis prepared for 10 CFR Part 20, "Standards for Protection

Against Radiation" (56 FR 23360), provides the

regulatory basis for this guide and examines the costs

and benefits of the rule as implemented by the guide.

A copy of the "Regulatory Analysis for the Revision

of 10 CFR Part 20" (PNL-6712, November 1988), is

available for inspection and copying for a fee at the

NRC Public Document Room, 2120 L Street, NW.

(Lower Level), Washington, DC, as an enclosure to

Part 20.

I

8.25-10
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