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9W- August 1980 U.S. NUCLEAR REGULATORY COMMISSION F REGULATORY GUIDE ,OP OFFIC

9W- August 1980 U.S. NUCLEAR REGULATORY COMMISSION F REGULATORY GUIDE ,OP OFFICE OF STANDARDS DEVELOPMENT REGULATORY GUIDE 8.25 (Task OH 905-4) CALIBRATION AND ERROR LIMITS OF AIR SAMPLING INSTRUMENTS FOR TOTAL VOLUME OF AIR SAMPLED A. INTRODUCTION Paragraph (a)(3) of § 20.103, "Exposure of Individuals to Concentrations of Radioactive Materials in Air in Restricted Areas," of 10 CFR Part 20, "Standards for Protection Against Radiation," requires that licensees use suitable measurements of concentrations of radioactive materials in air for detecting and evaluating airborne radioactivity in restricted areas. In addition, paragraph (c)(4) of § 20.106, "Radioactivity in Effluents to Unrestricted Areas," requires that licensees provide information as to the highest concen- tration of each radionuclide in an unrestricted area, a procedure that in many cases requires air monitoring beyond the restricted area. This guide identifies methods acceptable to the NRC staff for calibrating air sampling instruments for total volume of air sampled and provides guidance for ensuring that volumes of air sampled are known within certain limits. B. DISCUSSION In order to accurately assess the air concentration of radioactive materials in a given location, the volume of air sampled as well as the quantity of contaminant in the sample must be determined. Accurate determination of the volume of air sampled requires standard, reproducible, and frequent calibration of the air metering devices that are used with air sampling instruments. The American Conference of Governmental Industrial Hygienists has published a manual entitled "Air Sampling Instruments for Evaluation of Atmospheric Contaminants," 1 5th Edition, 1978. Part II, Section I, "Calibration of Air Sampling Instruments," of this manual provides instructions for acceptable methods of calibrating air volume and flow rate metering devices. In particular, Tables II, Ill, and 1Copies 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 standard methods; and a listing of calibration instruments and their suppliers. This guide supplements the instructions in this manual by adding guidance for frequency of calibration, for accept- able error limits in volume measurement, and for documen- tation. C. REGULATORY POSITION The publication entitled "Air Sampling Instruments for Evaluation of Atmospheric Contaminants," 1 5th Edition, 1978, provides guidance on total air sample volume calibra- tion methods acceptable to the NRC staff, as supplemented below: 1. FREQUENCY OF CALIBRATION A licensee committed to a routine or emergency air sampling program should perform an acceptable calibration of all airflow or volume metering devices at least once every 6 months, with the exception of permanently installed effluent monitors.2 Special calibrations should be performed at any time there is reason to believe that the operating characteristics of a metering device have been changed, by repair or alteration, or whenever system performance is observed to have changed significantly. Routine instrument maintenance should be performed as recommended by the manufacturer. Primary or secondary standard instruments used to calibrate air sampling instruments should be inspected frequently for consistency of performance. 2 See NUREG-0472, "Radiological Effluent Technical Specifica- tions for PWRs," July 1979, and NUREG-0473, "Radiological Effluent Technical Specifications for BWRs," July 1979, which specify calibration at least once every 18 months. 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 tech- niques used by the staff In evaluating specific problems or postu- lated accidents or to provide guidance to applicants. Regulatory Guides are noi 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. 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. 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. Products 2. Research and Test Reactors 7. Transportation 3. Fuels and Materials Facilities 8. Occupational Health 4. Environmental and Siting. 9. Antitrust and Financial Review 5. Materials and Plant Protection 10. General Copies of issued guides may be purchased at the current Government Printing 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 may be obtained by writing the U.S. Nuclear Regulatory Commission, Washington, D.C. 20555, Attention: Publications Sales Manager. 2. ERROR LIMIT FOR MEASUREMENT OF AIR SAMPLE VOLUME Most methods of calibrating airflow or air volume metering devices require direct comparison to a primary or secondary standard instrument to determine a calibration curve or a correction factor. An example 6.f a primary standard is a spirometer that measures total'air volume directly with high precision by liquid displacement. An example of a secondary standard is a wet-test meter that has been calibrated against a primary standard. Primary standards are usually accurate to within 1 percent and secondary standards to within 2 percent. The significant errors associated with determining the total air volume sampled are: Ec: The error in determining the calibration factor. (An acceptable estimate is the percent error associated with the standard instrument used in the calibration.) 3 Es: Intrinsic error in reading the meter scale. (An acceptable estimate is the percent equivalent of one-half of the smallest scale division compared to the scale reading.) Et: The percent error in measurement of sampling time that should be kept within 1 percent. Ev: The most probable value of the cumulative percent error in the determination of the total air volume sampled. E. can be calculated from the following equation pro- vided there are no additional significant sources of errors: Ev [Es 2 +Ec +E2]½ Air sampling instruments, including those personal (lapel) samplers that have flow rate meters, should have flow rate or total volume metering devices calibrated so that the most probable value of the cumulative error Ev, in 3The calibration factor should be based on two kinds of deter- minations. First, correction factors should be determined at several flow rates distributed over the full-scale range. Each flow rate correction factor should be determined while adjusting flow rates upscale and again while adjusting flow rates downscale, and the two sets of data should be compared; Second, subsequent calibrations should compare the new correction factors to those determined during the previous calibration. If observed differences are signif- icant compared to the overall volume error limit of 20 percent, an additional 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 across the sample collector during the sampling period when flow rate meters are used. In turn, this assumption allows simple a averaging of the initial and final flow rates for a singleW sample. 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 gas laws as discussed in the previously described manual. A sample calculation of the most probable value of the cumulative error in total volume measured is as follows- If accuracies of the scale reading, the calibration factor, and sample time are +4, 2, and 1 percent, respectively, and there are no other significant sources of error, the cumulative error would be: Ev= [42 +22 + 12]½= 4.58%or r,5% 3. DOCUMENTATION OF CALIBRATION OF AIR METERING DEVICES The licensee should maintain records of all routine and special calibrations of airflow or volume metering devices, including the primary or secondary standard used, method employed, and estimates of accuracy of the calibrated metering devices. All instruments should be clearly labeled as to the date and results of the most recent calibration and should include the appropriate correction factors to be used. 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 or licensee proposes an acceptable alternative method for complying with § § 20.103 and 20.106 of the Commission's regula- tions, the staff will use the method described herein in the evaluation of ongoing and proposed air monitoring pro- grams after November 15, 1980. If an applicant or licensee wishes to use the method described in this regulatory guide on or before November 15, 1980, the pertinent portions of the application or the licensee's performance will be evaluated on the basis of this guide. 8.25-2 VALUE/IMPACT STATEMENT 1. PROPOSED ACTION 1.1 Description Many NRC licensees are required uploads/Finance/ regulatory-guide-op-office-of-standards-development.pdf