Regulatory Guide 8.25

Calibration and Error Limits of Air Sampling Instruments for Total Volume of Air Sampled

ML12181A384
Person / Time
Issue date:	08/31/1980
Revision:	0
From:	NRC/OSD
To:
References
Task OH 905-4 RG-8.025
Download: ML12181A384 (5)

9W-August 1980U.S. NUCLEAR REGULATORY COMMISSIONF REGULATORY GUIDE,OP OFFICE OF STANDARDS DEVELOPMENTREGULATORY GUIDE 8.25(Task OH 905-4)CALIBRATION AND ERROR LIMITS OF AIR SAMPLING INSTRUMENTS FORTOTAL VOLUME OF AIR SAMPLEDA. INTRODUCTIONParagraph (a)(3) of § 20.103, "Exposure of Individuals toConcentrations of Radioactive Materials in Air in RestrictedAreas," of 10 CFR Part 20, "Standards for ProtectionAgainst Radiation," requires that licensees use suitablemeasurements of concentrations of radioactive materials inair for detecting and evaluating airborne radioactivity inrestricted areas. In addition, paragraph (c)(4) of § 20.106,"Radioactivity in Effluents to Unrestricted Areas," requiresthat licensees provide information as to the highest concen-tration of each radionuclide in an unrestricted area, aprocedure that in many cases requires air monitoringbeyond the restricted area. This guide identifies methodsacceptable to the NRC staff for calibrating air samplinginstruments for total volume of air sampled and providesguidance for ensuring that volumes of air sampled areknown within certain limits.B. DISCUSSIONIn order to accurately assess the air concentration ofradioactive materials in a given location, the volume of airsampled as well as the quantity of contaminant in thesample must be determined. Accurate determination of thevolume of air sampled requires standard, reproducible,and frequent calibration of the air metering devices that areused with air sampling instruments.The American Conference of Governmental IndustrialHygienists has published a manual entitled "Air SamplingInstruments for Evaluation of Atmospheric Contaminants," 15th Edition, 1978. Part II,Section I, "Calibration of AirSampling Instruments," of this manual provides instructionsfor acceptable methods of calibrating air volume andflow rate metering devices. In particular, Tables II, Ill, and1Copies are available from the American Conference of Govern-mental Industrial Hygienists, P.O. Box 1937, Cincinnati, Ohio 45201.IV of this manual provide sources of published, recommended,or standard methods; a summary of recommended standardmethods; and a listing of calibration instruments and theirsuppliers.This guide supplements the instructions in this manualby adding guidance for frequency of calibration, for accept-able error limits in volume measurement, and for documen-tation.C. REGULATORY POSITIONThe publication entitled "Air Sampling Instruments forEvaluation of Atmospheric Contaminants,"1 5th Edition,1978, provides guidance on total air sample volume calibra-tion methods acceptable to the NRC staff, as supplementedbelow:1. FREQUENCY OF CALIBRATIONA licensee committed to a routine or emergency airsampling program should perform an acceptable calibrationof all airflow or volume metering devices at least once every6 months, with the exception of permanently installedeffluent monitors.2 Special calibrations should be performedat any time there is reason to believe that the operatingcharacteristics of a metering device have been changed, byrepair or alteration, or whenever system performance isobserved to have changed significantly. Routine instrumentmaintenance should be performed as recommended by themanufacturer. Primary or secondary standard instrumentsused to calibrate air sampling instruments should be inspectedfrequently for consistency of performance.2See NUREG-0472, "Radiological Effluent Technical Specifica-tions for PWRs," July 1979, and NUREG-0473, "RadiologicalEffluent Technical Specifications for BWRs," July 1979, whichspecify calibration at least once every 18 months.USNRC REGULATORY GUIDESRegulatory Guides are issued to describe and make available to thepublic methods acceptable to the NRC staff of implementingspecific parts of the Commission's regulations, to delineate tech-niques used by the staff In evaluating specific problems or postu-lated accidents or to provide guidance to applicants. RegulatoryGuides are noi substitutes for regulations, and compliance withthem is not required. Methods and solutions different from those setout in the guides will be acceptable if they provide a basis for thefindings requisite to the issuance or continuance of a permit orlicense by the Commission.Comments and suggestions for improvements in these guides areencouraged at all times, and guides will be revised, as appropriate,to accommodate comments and to reflect new information orexperience. This guide was revised as a result of substantive com-ments received from the public and additional staff review.Comments should be sent to the Secretary of the Commission,U.S. Nuclear Regulatory Commission Washington, D.C. 20555,Attention: Docketing and Service Branch.The guides are issued In the following ten broad divisions:1. Power Reactors 6. Products2. Research and Test Reactors 7. Transportation3. Fuels and Materials Facilities 8. Occupational Health4. Environmental and Siting. 9. Antitrust and Financial Review5. Materials and Plant Protection 10. GeneralCopies of issued guides may be purchased at the current GovernmentPrinting Office price. A subscription service for future guides in spe-cific divisions is available through the Government Printing Office.Information on the subscription service and current GPO prices maybe obtained by writing the U.S. Nuclear Regulatory Commission,Washington, D.C. 20555, Attention: Publications Sales Manage . ERROR LIMIT FOR MEASUREMENT OF AIR SAMPLEVOLUMEMost methods of calibrating airflow or air volume meteringdevices require direct comparison to a primary or secondarystandard instrument to determine a calibration curve or acorrection factor. An example 6.f a primary standard is aspirometer that measures total'air volume directly with highprecision by liquid displacement. An example of a secondarystandard is a wet-test meter that has been calibrated againsta primary standard. Primary standards are usually accurateto within 1 percent and secondary standards to within 2percent.The significant errors associated with determining thetotal air volume sampled are:Ec: The error in determining the calibration factor.(An acceptable estimate is the percent errorassociated with the standard instrument used inthe calibration.)3Es: Intrinsic error in reading the meter scale. (Anacceptable estimate is the percent equivalent ofone-half of the smallest scale division compared tothe scale reading.)Et: The percent error in measurement of samplingtime that should be kept within 1 percent.Ev: The most probable value of the cumulative percenterror in the determination of the total air volumesampled.E. can be calculated from the following equation pro-vided there are no additional significant sources of errors:Ev [Es2 +Ec +E2]1/2Air sampling instruments, including those personal(lapel) samplers that have flow rate meters, should haveflow rate or total volume metering devices calibrated sothat the most probable value of the cumulative error Ev, in3The calibration factor should be based on two kinds of deter-minations. First, correction factors should be determined at severalflow rates distributed over the full-scale range. Each flow ratecorrection factor should be determined while adjusting flow ratesupscale and again while adjusting flow rates downscale, and the twosets of data should be compared; Second, subsequent calibrationsshould compare the new correction factors to those determinedduring the previous calibration. If observed differences are signif-icant compared to the overall volume error limit of 20 percent, anadditional error term should be included in the calculation above.the determination of total volume, is less than 20 percent.This analysis assumes a linear change in the flow rate acrossthe sample collector during the sampling period when flowrate meters are used. In turn, this assumption allows simple aaveraging of the initial and final flow rates for a singleWsample.If there are significant differences in pressure and temper-ature between the calibration site and the sampling site,appropriate corrections should be made using the ideal gaslaws as discussed in the previously described manual.A sample calculation of the most probable value of thecumulative error in total volume measured is as follows- Ifaccuracies of the scale reading, the calibration factor, andsample time are +4, 2, and 1 percent, respectively, and thereare no other significant sources of error, the cumulativeerror would be:Ev= [42 +22 + 12]1/2= 4.58%or r,5%3. DOCUMENTATION OF CALIBRATION OF AIRMETERING DEVICESThe licensee should maintain records of all routine andspecial calibrations of airflow or volume metering devices,including the primary or secondary standard used, methodemployed, and estimates of accuracy of the calibratedmetering devices. All instruments should be clearly labeledas to the date and results of the most recent calibration andshould include the appropriate correction factors to beused.D. IMPLEMENTATIONThe purpose of this section is to provide information toapplicants and licensees regarding the NRC staff's plans forusing this regulatory guide.Except in those cases in which an applicant or licenseeproposes an acceptable alternative method for complyingwith § § 20.103 and 20.106 of the Commission's regula-tions, the staff will use the method described herein in theevaluation of ongoing and proposed air monitoring pro-grams after November 15, 1980.If an applicant or licensee wishes to use the methoddescribed in this regulatory guide on or before November 15,1980, the pertinent portions of the application or thelicensee's performance will be evaluated on the basis ofthis guide.8.25-2 VALUE/IMPACT STATEMENT1. PROPOSED ACTION1.1 DescriptionMany NRC licensees are required to maintain radiationand contamination survey programs, including air sampling,to assess concentrations of airborne radionuclides. Regula-tory concentration values are specified in Appendix B to10 CFR Part 20. The proposed action is to provide guidancefor improving air sampling procedures in the form ofacceptable methods of calibrating air sampling instrumentsfor determining total volume of air sampled, frequency ofcalibration, and documentation procedures. Measurement.of the total volume is required in the calculation of theconcentration.1.2 Need for Proposed ActionIn order to accurately characterize the air quality of aworking environment, the volume of air sampled as well asthe quantity of contaminant must be determined. Accurateassessment of the quantity of air sampled requires frequentcalibration of air metering devices by standard, reproduciblemethods. To assess internal exposure resulting from airborneradioactive material and to evaluate working conditions,acceptable standard calibration and measurement methodsmust be developed. The Office of Nuclear Materials Safetyand Safeguards requested the Office of Standards Develop-ment to accelerate the schedule for issuing guidance toNRC licensees on acceptable methods for total volumecalibration and measurement.1.3 Value/Impact of Proposed Action1.3.1 NRC OperationsAcceptable methods for calibrating air sampling instru-ments provide additional criteria for inspection and enforce-ment of NRC radiation protection regulations. Increasedaccuracy in assessing airborne radioactive material concen-trations would provide a more reliable data base for develop-ing additional regulatory action to control and reduceinternal radiation exposure. Impacts of the development ofguidance as described include task completion manpowercost, estimated to be 0.3 man-year, and printing costs ofapproximately $300.1.3.2 Other Government AgenciesCoordination with several governmental agencies (e.g.,NBS, OSHA, EPA) has been necessary to ensure consistencyin cases where respective regulatory and monitoring func-tions interface. Agreement States whose licensing regulationsinclude air sampling requirements may benefit by theavailability of acceptable calibration methods suitable foradoption in their programs.1.3.3 IndustryThe value to industry in providing guidance on airvolume calibration procedures consists of the probableimprovement in worker protection from more accurateassessment of airborne radioactive material hazards. Theimpacts include equipment and manpower costs that do notappear to be excessive in view of the proposed acceptablemethods and frequency of calibration requirements. Thestaff estimates the initial cost of an acceptable calibrationsystem to be less than $300 and approximate man-powerrequirements to be 1 to 2 man-hours per year per instrument.1.3.4 WorkersFor the workers, the values of improved air monitoringinclude more accurate assessments of the quality of theworking environment and a probable reduction in internalradiation exposure. Recent staff discussion with unionrepresentatives indicates that there is an increasing concernabout exposure to airborne radioactive material on the partof workers in the industry. Continued NRC efforts toincrease our understanding of this aspect of radiationhazard and to improve monitoring and control of airborneradioactivity is essential.1.3.5 PublicEnvironmental monitoring to assess the release ofradioactive materials in the vicinity of NRC-licensed facil-ities includes air sampling. Calibration procedures forlow-flow-rate, continuous air sampling instruments will beincluded. The public will benefit from increased reliabilityof environmental measurements.1.4 DecisionThe NRC should develop and provide guidance onacceptable total air volume calibration methods for thosetypes of radiological air sampling instruments used bylicensees.2. TECHNICAL APPROACHThe action proposed here is to provide guidance onacceptable methods of calibrating airflow and air volumemetering devices on radiological air samplers. Surveyprograms and, where appropriate, air monitoring programsare required of many NRC licensees. It is our intent thatacceptable methods of air volume calibration be a required8.25-3 component of licensee monitoring procedures. There are notechnical alternatives- to providing this guidance.3. PROCEDURAL APPROACH3.1 Procedural AlternativesThe proposed action, to publish guidance on calibrationprocedures for radiological air sampling instruments, couldbe accomplished by several methods: publishing an NRCregulation requiring that specific calibration procedures beused by all licensees; preparing or revising a regulatoryguide (based on the existing paragraph 20.201(b) of 10 CFRPart 20) that would provide an acceptable method forcalibration; developing an ANSI standard on calibrationprocedures that could be endorsed by a new regulatoryguide; or publishing a NUREG report or a branch positionpaper.3.2 Value/Impact of Procedural AlternativesAn NRCregulation establishes general legal requirements,is more costly and time consuming to prepare, and is not anappropriate vehicle for the specific and narrow objective pro-posed here. One advantage is that a regulation legally requirescompliance. In general, this approach is not considered costeffective in view of the objective of the proposed action.ANSI standards are generally intended as technicaltreatments of broad areas of concern to industry. An ANSIstandard concerning all aspects of an acceptable monitoringprogram would be appropriate but beyond the narrowerobjective proposed here. Developing an ANSI standard andan endorsing regulatory guide might require several yearsand would be costly. This approach is not considered costeffective in view of the proposed objective.A NUREG report would be an appropriate vehicle forreporting on technical studies of various methods of calibrat-ing air samplers. Regulatory guidance, however, is notestablished through publication of a NUREG report.Since this proposal includes establishing an acceptablemethod for compliance with required surveying programs, aNUREG report is not considered suitable.Branch position statements are intended as interimmeasures to be used when an immediate response is required.They are usually superseded when a more permanent modeof guidance is developed.A regulatory guide can be prepared at reasonable costwithin a reasonable time period. A regulatory guide canestablish acceptable criteria for compliance with a regulatoryrequirement and, if incorporation into a license is requested,is subject to inspection and enforcement.Development of a regulatory guide allows extensive inputfrom all segments of the nuclear industry and the public. Aregulatory guide could reference existing and acceptablestandard calibration methods or adequately describe calibra-tion procedures acceptable to the NRC staff. The staff doesnot consider that revision of any existing regulatory guidescould provide the objectives proposed here.3.3 Decision on Procedural ApproachThe staff concludes that a regulatory guide adoptingacceptable methods for total air volume calibration forradiological air sampling instruments should be published.4. STATUTORY CONSIDERATIONS4.1 NRC Regulatory AuthorityParagraph 20.201 (b) of 10 CFR Part 20 establishes a legalrequirement that each licensee make or cause to be madesuch surveys as may be necessary for him to comply with theregulations. The NRC is thus authorized to provide criteriafor acceptable survey methodology, including calibration ofinstrumentation.4.2 Need for NEPA StatementThe action proposed here is not considered to constitutea major addition or change and would entail no effect onthe environment. The staff does not believe that an environ-mental impact statement is necessary.5. RELATIONSHIP TO OTHER EXISTING OR PROPOSEDREGULATIONS OR POLICIESSeveral regulatory guides concerning health physicssurveys at various types of NRC-licensed facilities such asRegulatory Guide 8.21, "Health Physics Surveys for Bypro-duct Material at NRC-Licensed Processing and Manufactur-ing Plants," are in preparation. These guides would appro-priately reference the guide proposed here. In addition,guides such as Regulatory Guide 1.70, "Standard Formatand Content of Safety Analysis Reports for Nuclear PowerPlants," will include a commitment to acceptable airsampler calibration procedures. When next revised, theseguides should include cross-references to this guide as anacceptable element of a licensee's monitoring program.The proposed guide is consistent with RegulatoryGuide 8.8, "Information Relevant to Ensuring That Occupa-tional Exposures at Nuclear Power Stations Will Be As LowAs Is Reasonably Achievable." When next revised, Regula-tory Guide 8.8 should include a cross-reference to this guide.6. SUMMARY AND CONCLUSIONSIn summary, it is proposed that a regulatory guide bepublished for the purpose of providing guidance on accept-able methods of calibrating radiological air sampling instru-ments for total volume of air sampled.8.25-4 UNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, D. C. 20555OFFICIAL BUSINESSPENALTY FOR PRIVATE USE. $300POSTAGE AND FEES PAIDU.S. NUCLEAR REGULATORYCOMMISSION119406002001 1 DAD8QAQ8US NRC REGION IOFFICE OF INSPECTION & ENFORCER J BORES631 PARK AVENUEREGION IKING OF PRUSSIA PA 19406