Regulatory Guide 1.23: Difference between revisions

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{{Adams
{{Adams
| number = ML070350028
| number = ML020360030
| issue date = 03/23/2007
| issue date = 02/17/1972
| title = Meteorological Monitoring Programs for Nuclear Power Plants
| title = Onsite Meteorological Programs
| author name = Harvey B
| author name =  
| author affiliation = NRC/RES
| author affiliation = NRC/RES
| addressee name =  
| addressee name =  
Line 9: Line 9:
| docket =  
| docket =  
| license number =  
| license number =  
| contact person = Harvey Brad, NRO/DSER/RSAC, 415-4118
| contact person =  
| case reference number = DG-1164
| document report number = Reg Guide 1.023
| document report number = RG-1.023, Rev. 1
| package number = ML070310671
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 20
| page count = 6
}}
}}
{{#Wiki_filter:U.S. NUCLEAR REGULATORY COMMISSION                                                                March 2007 Revision 1 REGULATORY GUIDE
{{#Wiki_filter:2/17/72 SAFETY GUIDE 23 ONSITE METEOROLOGICAL PROGRAMS
                                    OFFICE OF NUCLEAR REGULATORY RESEARCH
                                              REGULATORY GUIDE 1.23 (Draft was issued as DG-1164, dated October 2006)
                  METEOROLOGICAL MONITORING PROGRAMS
                                    FOR NUCLEAR POWER PLANTS


==A. INTRODUCTION==
==A. INTRODUCTION==
This revised regulatory guide provides licensees and applicants with improved guidance concerning criteria for an onsite meteorological measurements program that the staff of the U.S. Nuclear Regulatory Commission (NRC) considers acceptable for the collection of basic meteorological data needed to support plant licensing and operation.
Subparagraph 100. 10(c)(2) of 10 CFR Part
100 states that, in determining the acceptability of a site for a power or testing reactor, the Commission will take into consideration meteorological conditions at the site and in the surrounding area.


For stationary power reactor site applications submitted before January 10, 1997, Title 10,
Subparagraph 50.36a(a)(2) of 10 CFR Part
Section 100.10(c)(2), of the Code of Federal Regulations [10 CFR 100.10(c)(2), Ref. 1] states that meteorological conditions at the site and in the surrounding area should be considered in determining the acceptability of a site for a power reactor. As an aid in evaluating a proposed site, 10 CFR 100.11(a)
50 requires nuclear power plant licensees to submit semiannual reports specifying the quantity of each of the principal radionuclides released to unrestricted areas in liquid and in gaseous effluents, and such other information as may be required by the Atomic Energy Commission to estimate maximum potential annual radiation doses to the public resulting from effluent releases.
states that meteorological conditions pertinent to the site should be used, along with an assumed fission product release from the core and the expected containment leak rate, to ensure that prescribed dose limits for the exclusion area and low-population zone, as defined in 10 CFR 50.2, Definitions (Ref. 2), are met.


For stationary power reactor site applications submitted on or after January 10, 1997,
A
10 CFR 100.20(c)(2) requires consideration of the meteorological characteristics of the site that are necessary for safety analysis or that may have an impact upon plant design in determining the acceptability of a site for a nuclear power plant. In addition, 10 CFR 100.21(c) requires the evaluation of site atmospheric dispersion characteristics and the establishment of dispersion parameters such that
knowledge of meteorological conditions in the vicinity of the reactor is important in providing a basis for estimating maximum potential annual radiation doses resulting from radioactive materials eleased in gaseous effluents.
(1) radiological effluent release limits associated with normal operation from the type of facility proposed to be located at the site can be met for any individual located off site, and (2) radiological dose The U.S. Nuclear Regulatory Commission (NRC) issues regulatory guides to describe and make available to the public methods that the NRC staff considers acceptable for use in implementing specific parts of the agencys regulations, techniques that the staff uses in evaluating specific problems or postulated accidents, and data that the staff need in reviewing applications for permits and licenses. Regulatory guides are not substitutes for regulations, and compliance with them is not required. Methods and solutions that differ from those set forth in regulatory guides will be deemed acceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.


This guide was issued after consideration of comments received from the public. The NRC staff encourages and welcomes comments and suggestions in connection with improvements to published regulatory guides, as well as items for inclusion in regulatory guides that are currently being developed.
In order for the Commission to fulfill its responsibilities under the National Environmental Policy Act of 1969. and in accordance with the requirements of Appendix D to 10 CFR Part 50. "Statement of General Policy and Procedure: Implementation of the National Environmental Policy Act of 1969 (Public Law 91-190)," basic meteorological information must be available for use in assessing potentially adverse envircnmental effects of a radiological and nonradiological nature resulting from the construction or operation of a nuclear power plant.


The NRC staff will revise existing guides, as appropriate, to accommodate comments and to reflect new information or experience. Written comments may be submitted to the Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.
Appendix E
to
10
CFR
Part
50,  
"Emergency Plans for Production and Utilization Facilities," requires each applicant for an operating license to include in its final safety analysis report required by § 50.34(b) of  
10 CFR Part
50.


Regulatory guides are issued in 10 broad divisions: 1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities;
plans for coping with radiological emergencies. The plans must include criteria for determining when protective measures should be considered within and outside the site boundary to protect health and fety and prevent damage to propert
4, Environmental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Health; 9, Antitrust and Financial Review;
and 10, General.


Requests for single copies of draft or active regulatory guides (which may be reproduced) should be made to the U.S. Nuclear Regulatory Commission, Washington, DC 20555, Attention: Reproduction and Distribution Services Section, or by fax to (301) 415-2289; or by email to Distribution@nrc.gov.
====y. In this ====
,egard, it is necessary for the applicant to establish and maintain a meteorological program capable of rapidly assessing critical meteorological parameters.


Electronic copies of this guide and other recently issued guides are available through the NRCs public Web site under the Regulatory Guides document collection of the NRCs Electronic Reading Room at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML070350028.
Thus. at each nuclear power plant site there are multiple needs for an onsite program which will adequately measure and document basic meteorological data. These data may be used to develop atmospheric diffusion parameters which. with an appropriate diffusion model,'
may be used to estimate potential radiation doses to the public resulting from actual routine or accidental releases of radioactive materials to the atmosphere or to evaluate the poential dose to the public as a result of hypothetical reactor accidents. This safety guide describes a suitable onsite meteorological program to provide meteorological data needed to estimate these potential radiation doses.


consequences of postulated accidents meet the prescribed dose limits at the exclusion area and low- population zone distances set forth in 10 CFR 50.34(a)(1).
B.
          The General Design Criteria [GDC] for Nuclear Power Plants set forth in Appendix A
to 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities (Ref. 2), establish minimum requirements for the principal design criteria for water-cooled nuclear power plants.


Specifically, GDC 19, Control Room, requires that a control room be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions. Adequate radiation protection must be provided to permit access to and occupancy of the control room for the duration of accident conditions. For plants that use alternate source terms, 10 CFR 50.67(b)(2)(iii) provides similar criteria. Atmospheric dispersion estimates are significant inputs in assessments performed to demonstrate compliance with this requirement.
DISCUSSION
An onsite meteorological measurements program at a nuclear power plant site shouldJhe capable of providing the meteorological information required to make the following assessments:
I.


In 10 CFR Part 50 (Ref. 2), Paragraphs 50.47(b)(4), 50.47(b)(8), and 50.47(b)(9), as well as Section IV.E.2 of Appendix E, Emergency Planning and Preparedness for Production and Utilization Facilities, require each applicant for an operating license or combined license to describe its plans for coping with radiological emergencies. These plans must include provisions for equipment for determining the magnitude and continuously assessing the impact of the release of radioactive materials to the environment. These plans must also include a standard emergency classification and action level scheme for determining minimum initial offsite response measures. In addition, if plant meteorological program parameters (i.e., wind speed, wind direction, and an indicator of atmospheric stability)
A
are available on in-plant computer systems, they must be made available in a digital data stream to the Emergency Response Data System (ERDS) maintained by the NRC, pursuant to Section VI
conservative assessment by the applicant and the regulatory staff of the potential dispersion of radioactive material from, and the radiological consequences of, design basis accidents to aid in evaluating the acceptability of a site and the adequacy of engineered safety features for a nuclear power plant.
of Appendix E to 10 CFR Part 50.1 In this regard, it is necessary for the applicant to establish and maintain a meteorological program capable of rapidly assessing critical meteorological parameters.


In addition, in 10 CFR Part 50, Appendix I, Numerical Guides for Design Objectives and Limiting Conditions for Operation to Meet the Criterion As Low as is Reasonably Achievable for Radioactive Material in Light-Water-Cooled Nuclear Power Reactor Effluents, provides numerical guidance for the design objectives of equipment intended to control releases of radioactive material in effluents from nuclear power reactors. An assessment of the maximum potential annual radiation dose to the public resulting from the routine release of radioactive materials in gaseous effluents is required to assist in demonstrating that operations will be or are being conducted within the limits of 10 CFR Part 20,
2.
Standards for Protection Against Radiation (Ref. 3), and Appendix I to 10 CFR Part 50 and to ensure that effluent control equipment design objectives and proposed operating procedures meet the Commissions requirements for keeping levels of radioactive material in effluents to unrestricted areas as low as practicable.


In addition, 10 CFR 50.36a(a)(2) requires nuclear power plant licensees to submit a report to the Commission annually that specifies the quantity of each of the principal radionuclides released to unrestricted areas in liquid and gaseous effluents during the previous 12 months, including any other information that the Commission may need to estimate maximum potential annual radiation doses to the public resulting from effluent releases. A knowledge of meteorological conditions in the vicinity of the reactor is important to provide the basis for estimating maximum potential annual radiation doses resulting from radioactive materials released in gaseous effluents.
An assessment by both the applicant and the regulatory staff of the maximum potential annual radiation dose to the public resulting from the routine release of radioactive materials in gaseous effluents to assist in demonstrating that operations will be or are being conducted within the limits of 10 CFR Part 20 and to assure that effluent control equipment design objectives and proposed operating procedures meet the Commission's requirements for keeping levels of radioactive material in effluents to
'Safety Guide 3, "Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling Water Reactors."
November 2, 1970: Safety Guide 4. "Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors."
November
2. 1970. "Meteorology and
,t sr-,: -n:.
1r(8" T'D
410"Y.


1 The ERDS is a direct, near-real-time electronic data link between the licensees onsite computer system and the NRC
23.1
          Operations Center that provides for the automated transmission of a limited data set of selected plant parameters in the event of a radiological emergency.


Rev. 1 of RG 1.23, Page 2
unrestricted areas as low as practicable.


In order for the Commission to fulfill its responsibilities under the National Environmental Policy Act of 1969, as amended (Ref. 4), and in accordance with the requirements of Subpart A,
3.
National Environmental Policy Act  Regulations Implementing Section 102(2), of 10 CFR Part 51, Environmental Protection Regulations for Domestic Licensing and Related Regulatory Functions (Ref. 5), basic meteorological information must be available for use in assessing (1) the environmental effects of radiological and nonradiological emissions and effluents resulting from the construction or operation of a nuclear power plant and (2) the benefits of design alternatives.


Thus, each nuclear power plant site has multiple needs for an onsite program to measure and document basic meteorological data. These data may be used to develop atmospheric transport and diffusion parameters that, with appropriate atmospheric dispersion models, may be used to estimate potential radiation doses to the public resulting from actual routine or accidental releases of radioactive materials to the atmosphere or to evaluate the potential dose to the public and control room as a result of hypothetical reactor accidents. These data may also be used to assess nonradiological environmental effects resulting from the construction or operation of a nuclear power plant, such as the impacts of the plants heat dissipation system. This regulatory guide describes a suitable onsite program to provide meteorological data needed to estimate these potential impacts.
A realistic assessment by the applicant and the regulatory staff of the potential dispersion of radioactive materials from, and the radiological consequences of.


This regulatory guide relates to information collections that are covered by the requirements of 10 CFR Parts 50 and 52, which the Office of Management and Budget (OMB) has approved under OMB control numbers 3150-0011 and 3150-0151, respectively. The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number.
a spectrum of accidents to aid in evaluating the environmental risk posed by a nuclear power plant in accordance with Appendix D to 10 CFR Part 50.


==B. DISCUSSION==
4.
The NRC issued the original version of Regulatory Guide 1.23 in February 1972 to describe a suitable onsite meteorological measurements program to collect the basic meteorological data needed to determine the environmental impacts of the plant, perform consequence assessments supporting routine release and design-basis accident evaluations, and support emergency preparedness programs and other applications at power reactor sites.


The NRC subsequently issued a proposed Revision 1 of Regulatory Guide 1.23 for public comment in September 1980 in response to the accident at Three Mile Island. That first proposed Revision 1 of Regulatory Guide 1.23 contained special considerations for emergency planning, which included
A realistic assessment by the applicant and the regulatory staff of other than radiological environmental effects. such as fogging, icing, and salt drift from cooling towers, to aid in evaluating the environmental impact of a nuclear power plant in accordance with Appendix D to 10 CFR Part 50.
(1) provisions for remote interrogation of the meteorological system by the NRC and other emergency response organizations during emergency situations, and (2) a viable backup system to obtain real-time local meteorological data. The NRC never officially adopted its first proposed Revision 1 of Regulatory Guide 1.23.


The NRC issued a second proposed Revision 1 for public comment in April 1986.
5.


That second proposed Revision 1 endorsed, with some minor exceptions, the Standard for Determining Meteorological Information at Nuclear Power Sites, which the American National Standards Institute/American Nuclear Society (ANSI/ANS) promulgated as ANSI/ANS-2.5-1984 (Ref. 6).
A rapid, conservative assessment by the licensee and other appropriate persons of the radiological consequences of an accidental release of radioactive material to the atmosphere.
Although ANSI/ANS-2.5-1984 did not contain the special considerations for emergency planning included in the first proposed Revision 1 of Regulatory Guide 1.23, it did update other provisions of the earlier revision. Nonetheless, the NRC never officially adopted the second proposed Revision 1 of Regulatory Guide 1.23, and ANSI/ANS-2.5-1984 has since been withdrawn and is currently inactive.


Rev. 1 of RG 1.23, Page 3
The assessment should be used to provide early guidance to persons assigned to licensee's emergency organization and to appropriate local. State and Federal agencies with responsibilities for coping with emergencies, for use in determining (i)
the need for notification and participation of local and State agencies and the Commission and other Federal agencies, and (ii)
when appropriate measures should be taken to protect public health and safety and prevent damage to property in accordance with Appendix E to 10
CFR
Part 50. Onsite meterological measurements should provide an adequate basis for short- distance atmospheric diffusion calculations.


The NRC solicited public comment on a third proposed Revision 1 of this guide by publishing Draft Regulatory Guide DG-1164 (Ref. 7) in October 2006.
(Regional meteorological data will be needed in the event it should become necessary to make diffusion estimates for long distances. To assure that the required data are readily available, the applicant should establish and maintain contact with the nearest National Weather Service Focal Point Air Pollution Meteorologist.) 2
2The name and address of the nearest Focal Point Air Pollution Meteorologist may be obtained by contacting the Air Pollution Meteorologist. Weather Analysis and Prediction Division, National Weather Service, National Oceanographic and Atmospheric Administration. Silver Spring. Marvland 20910.


This revised guide replaces the original (February 1972) version of Regulatory Guide 1.23.
Specific guidance for evaluatirig t
potential radiological consequences of desi basis reactor accidents is given in Safety GuidL
3 and 4. The basic diffusion model described in these guides may also be used to estimate the dispersion of radioactive materials in the atmosphere following the routine or accidental release of such materials. When using the model for evaluating short-term releases, the actual meteorological parameters measured during the release period should be used. For long-term releases the observed joint frequency distribution of wind speed and direction and atmospheric stability for the period should be used. In the event of large variations in the rate of release, it may be necessary to subdivide the meteorological data into periods of approximately uniform release rate.


This revision clarifies regulatory requirements and updates regulatory guidance regarding the criteria for an onsite meteorological measurements program to collect the basic meteorological data needed to support plant licensing and operation. In so doing, this revision better reflects current regulatory requirements and best practices, using guidance provided in ANSI/ANS-3.11-2005, Determining Meteorological Information at Nuclear Facilities (Ref. 8), where appropriate, with explicit references to the NRCs regulatory requirements.2 An onsite meteorological measurements program at a nuclear power plant site should be capable of providing the meteorological information needed to make the following assessments:
While there are differences in the specific types of meteorological information required for each of the above assessments, a single set of instruments can generally be used to obtain the basic data needed for all of them. For this reason, when establishing a
*      a conservative assessment by both the applicant and the regulatory staff of the potential dispersion of radioactive material from, and the radiological consequences of, design-basis accidents to aid in evaluating the acceptability of a site and the adequacy of engineered safety features for a nuclear power plant in accordance with 10 CFR Part 100 criteria 3
meteorological program for an initial site survey, careful consideration should be given to the operational need:  
*      an assessment by both the applicant and the regulatory staff of the maximum potential annual radiation dose to the public resulting from the routine release of radioactive materials in gaseous effluents to assist in demonstrating that operations will be or are being conducted within the limits of 10 CFR Part 20 and Appendix I to 10 CFR Part 50, and to ensure that effluent control equipment design objectives and proposed operating procedures meet the Commissions requirements for keeping levels of radioactive material in effluents to unrestricted areas as low as practicable 4
of the plant for meteorological information. In particular, care should be taken to locate the stations at positions where the measurements will accurately represent the overall site meteorology and. if possible. where wind patterns will not be significantly influenced by plant structures.
2 Whereas ANSI/ANS-2.5-1984 (Ref. 6) was primarily intended to support licensing applications of commercial nuclear power plants, ANSI/ANS-3.11-2005 (Ref. 8) has an expanded scope that includes nuclear installations at Federal sites, ranges, and reservations (e.g., U.S. Department of Energy and Department of Defense facilities). Because the nature and extent of the radiological and hazardous chemical materials present at Federal sites can differ significantly from similar materials present at commercial nuclear power plants, ANSI/ANS-3.11-2005 provides additional guidance beyond what the NRC considers to be basic meteorological monitoring program criteria applicable to commercial nuclear power plants.


3 Regulatory Guide 1.145, Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants (Ref. 9), provides specific guidance on atmospheric dispersion modeling for evaluating the potential offsite radiological consequences of design-basis reactor accidents.
The number of locations on a site at which meteorological measurements are necessary will depend largely on the complexity of the terrain in the vicinity of the site. For example. the study of a hill-valley complex, or a site near a large body of water would require a larger number of measuring points to determine air flow patterns and spatial variations of atmospheric stability.


4 Regulatory Guide 1.111, Methods for Estimating Atmospheric Transport and Dispersion of Gaseous Effluents in Routine Releases from Light-Water-Cooled Reactors (Ref. 10), provides specific guidance on atmospheric dispersion modeling for evaluating the potential offsite radiological consequences of routine releases from power reactors.
The minimum amount of meteorological data needed for siting evaluation is considered to be that amount of data gathered on a
continuous basis for a representative consecutive
12 month period. Two full annual cycles of data are desirable.


Rev. 1 of RG 1.23, Page 4
C.


*        a conservative assessment by both the applicant and the regulatory staff of the habitability of the control room during postulated design-basis radiological accidents and hazardous chemical releases to demonstrate that the control room can remain occupied under accident conditions in accordance with GDC 195
REGULATORY POSITION
*        a near-real-time ongoing assessment by the licensee of atmospheric transport and diffusion immediately following an accidental release of airborne radioactive materials to provide input to the evaluation of the consequences of radioactive releases to the atmosphere and to aid in the implementation of emergency response decisions in accordance with the requirements in Appendix E to 10 CFR Part 50
This section describes a suitable onsitf meteorological program to provide meteorological data needed to estimate potential radiation doses to the public as a result of the routine or accidental release of radioactive
*        an assessment by the licensee of natural phenomena being experienced or projected beyond usual levels (e.g., high winds) for the purposes of emergency classification in accordance with
23,2
        10 CFR 50.47(b)(4) and Section IV.B of Appendix E to 10 CFR Part 50
*        a realistic assessment by both the applicant and the regulatory staff of the potential dispersion of radioactive materials from, and the radiological consequences of, a spectrum of accidents to aid in evaluating the environmental risk posed by a nuclear power plant in accordance with Subpart A to 10 CFR Part 51
*        a realistic assessment by both the applicant and the regulatory staff of nonradiological environmental effects, such as fogging, icing, and salt drift from cooling towers or ponds, to aid in evaluating the environmental impact of a nuclear power plant in accordance with Subpart A to 10 CFR Part 51 While the specific types of meteorological information needed differ for each of the above assessments, a single set of instruments can generally be used to obtain the basic data needed for all of them. For this reason, when establishing a meteorological program for an initial site survey, careful consideration should be given to the operational needs for meteorological information. In particular, care should be taken to locate the instrumentation where the measurements will accurately represent the overall site meteorology and, if possible, where singular topographic features and vegetation or the construction of additional structures at a later date will not significantly influence wind patterns.


For cases where a meteorological monitoring system is being upgraded due to age or when any change to the system is warranted, a review of appropriate new technologies should be undertaken to consider whether the meteorological monitoring system should utilize up-to-date technologies that may provide improved data sources.
-!rials to the atmosphere and to assess other ronmental effects.


The minimum amount of onsite meteorological data to be provided at the time of application
1.
(1) for a construction permit is a representative consecutive 12-month period; (2) for an operating license is a representative consecutive 24-month period, including the most recent 1-year period;
and (3) for an early site permit or a combined license that does not reference an early site permit is a consecutive 24-month period of data that is defendable, representative and complete, but not older than
10 years from the date of the application. However, 3 or more years of data are preferable and, if available, should be submitted with the application.


5 Regulatory Guide 1.194, Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants (Ref. 11), provides specific guidance on atmospheric dispersion modeling for design-basis control room radiological habitability assessment. Regulatory Guide 1.78, Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release (Ref. 12), provides guidance on assessing the habitability of the control room during and after a postulated external release of hazardous chemicals.
Meteorological Parameters.


Rev. 1 of RG 1.23, Page 5
To obtain the meteorological information required for a
valid estimate of atmospheric diffusion at a particular site. instrumentation should be provided that is capable of measuring wind direction, wind speed.


==C. REGULATORY POSITION==
and ambient air temperature at a minimum of two levels on at least one tower or mast. At sites where there is a potential for fogging or icing due to an increase in atmospheric moisture content caused by plant operation, instrumentation should be provided for measuring the dew point (or humidity)
This section describes a suitable onsite program to collect the basic meteorological data needed to determine the environmental impacts of the plant, perform consequence assessments supporting routine release and design-basis accident evaluations, and support emergency preparedness programs and other applications at power reactor sites.
on the tower or mast.


1.      Definitions Ambient Temperature: A measure of the hotness or coldness of the ambient air, as measured by a suitable instrument.
2.


Calm: Any wind speed below the starting threshold of the wind speed or direction sensor, whichever is greater.
Siting of Meteorological Instruments.


Channel Check: The qualitative assessment, by observation, of channel behavior during operation. This determination should include, where possible, comparison of the channel indication and status to other indications or status derived from independent instrument channels measuring the same parameter.
The tower or mast should be sited at approximately the same elevation as finished plant grade and in an area where plant structures will have little or no influence on the meteorological measurements.


Dew Point Temperature: The temperature to which a given parcel of air must be cooled at constant pressure and constant water-vapor content in order for saturation to occur.
The lower set of instruments should sense wind speed and direction. termperature, and dew point (where required) at an elevation of 10 meters above the ground and the upper set should sense wind speed and direction and temperature at the height of release of radioactive material (plant vent height) but should be positioned not less than 30 meters above the-lower sensor set. For stack releases, another set of sensors should be located at an elevation such that meteorological conditions at stack height can be represented.


Gaussian Plume Model: A basic atmospheric dispersion model that assumes that the plume spread has a Gaussian distribution in both the horizontal and vertical directions and, therefore, uses the standard deviations of plume concentration distribution in the horizontal ( Fy) and vertical (Fz).
3.
        Precipitation: Any of the forms of water particles, whether liquid or solid, that fall from the atmosphere and reach the ground.


Relative Humidity: The ratio of the vapor pressure to the saturation vapor pressure with respect to water.
Data Recorders Either analog (strip chart) or digital recording of data may be used as a basis for analysis.


Pasquill Stability Class: A classification of atmospheric stability, or the amount of turbulent mixing in the atmosphere and its effect on effluent dispersion.
In lieu of providing redundant digital recorders.


Starting Threshold: The minimum wind speed above which the measuring instrument is performing within its minimum specification.
digital outputs may be supplemented by strip chart recorders to minimize possible loss of data due to instrument malfunction.


System Accuracy: The amount by which a measured variable deviates from a value accepted as true or standard. System accuracy encompasses all the components of the system, from sensors through processors, data recorders, and displays.
Recorders (analog or digital) for wind direction and speed and temperature difference (two temperatures or one temperature difference measurement on a tower or mast) should be located in the reactor control room for use during plant operation.


System Calibration: The process of validating the output of an observing system against known reference observations or standards.
4.


Vertical Temperature Difference ( )T): The measured difference in ambient temperature between two elevations on the same tower. It is defined as the upper level temperature measurement minus the lower level temperature measurement.
Instrument Accuracy a.


Rev. 1 of RG 1.23, Page 6
Wind direction accuracy for instantaneous recorded values +/-5°.
b.


Water Equivalent: The amount of water, in inches, measured at ground level from rain and/or melted frozen precipitation (e.g., snow, freezing precipitation).
Wind speed accuracy for time averaged values +/-0.5 mph. Starting speed of anemometer< 1 mph.
        Wet-Bulb Temperature: The temperature an air parcel would have if cooled adiabatically to saturation at constant pressure by evaporation of water into it, all latent heat being supplied by the parcel.


Wind Direction: The direction from which the wind is blowing. Wind direction is reported in degrees azimuth, measured clockwise from true north and ranging from 0E to 360E (e.g., north is 0E
c.
or 360E, east is 90E, etc.).
        Wind Speed: The rate at which air is moving horizontally past a given point.


2.       Meteorological Parameters This section discusses the criteria for a basic meteorological monitoring system.
Temperature accuracy for time averaged values
+/-0.5'C.


2.1     Wind Speed and Direction Wind speed and direction should be measured on one open-lattice tower or mast measured at heights of approximately 10 meters (33 feet) and 60 meters (197 feet) above ground level.
Temperature difference accuracy from either difference between averaged temperatures or average temperature difference +/-0.1 IC.


A measurement height other than 60 meters (197 feet) may be appropriate for those plants where the most probable atmospheric release height is other than 60 meters (197 feet). A third measurement height should be implemented at a representative level for stack releases that are 85 meters (279 feet) or higher.
d.


2.2      Vertical Temperature Difference Vertical temperature difference ()T) should be measured on the same open-lattice tower or mast as wind speed and wind direction between the 10-meter (33-foot) level and 60-meter (197-foot) levels and, if necessary, between the 10-meter (33-foot) level and a higher level that is representative of diffusion conditions from release points that are 85 meters (279 feet) or higher. Table 1 provides a definition of Pasquill stability classes as a function of )T.
Dew point accuracy for time averaged values +/-0.50C.


Vertical temperature difference is the preferred method for determining Pasquill stability classes at nuclear power plants for licensing purposes because it is an effective indicator for the worst-case stability conditions (e.g., Pasquill stability classes E, F, and G). Also, certain Gaussian plume models endorsed by the NRC (such as the models referenced in Regulatory Guides 1.145 and 1.194, Refs. 9 and 11)
5.
are based on empirically derived plume meander factors from field tracer studies that used )T to classify atmospheric stability. Alternative methods may be used to classify atmospheric stability for licensing purposes if appropriate justification is provided. However, the use of alternative methods to classify atmospheric stability may require modifications of the models described in Regulatory Guides 1.145 and 1.194.


Alternative methods may be appropriate for classifying atmospheric stability for emergency response purposes if these methods can be shown to be compatible with the plants emergency response dose assessment methodology.
Instrument Maintenance and Servicing Schedules Meteorological instruments should be inspected and serviced at a frequency which will assure at least a 907 data recovery and which will minimize extended periods of instrument outage.


Rev. 1 of RG 1.23, Page 7
The use of redundant sensors andlor recorders may be another acceptable means of achieving the
901/ data recovery goal. The instruments should be calibrated at least semiannually.


Table 1. Classification of Atmospheric Stability Stability                          Pasquill                Ambient Temperature Change Classification                  Stability Category                With Height (EC/100m)
6.
          Extremely unstable                          A                              )T # !1.9 Moderately unstable                          B                          !1.9 < )T # !1.7 Slightly unstable                          C                          !1.7 < )T # !1.5 Neutral                              D                          !1.5 < )T # !0.5 Slightly stable                          E                          !0.5 < )T # 1.5 Moderately stable                          F                            1.5 < )T # 4.0
            Extremely stable                          G                              )T > 4.0
2.3      Ambient Temperature Ambient temperature should be monitored at approximately 10 meters (33 feet).
2.4      Precipitation Precipitation should be measured near ground level near the base of the mast or tower.


While routine release or design-basis accident assessments of offsite dose consequences do not typically consider precipitation, the presence or absence of precipitation and its amount are important for severe accident assessments that are included in the applicants environmental report and the staffs environmental impact assessment pursuant to Subpart A of 10 CFR Part 51. Severe accident dose consequence computer codes, such as Version 2 of the MELCOR Accident Consequence Code System (MACCS2) (Ref. 13), account for the efficient removal of particulate radionuclides from the plume by wet deposition. Precipitation information can also be useful as an input to developing emergency response protective action recommendations by indicating the potential for increased ground contamination as a result of wet deposition.
Data Reduction and Compilation a.


2.5      Atmospheric Moisture At sites utilizing cooling towers, cooling lakes and ponds, or spray ponds as the plants normal heat sink, the pre-operational monitoring program should include ambient temperature and atmospheric moisture measurements (e.g., dew point temperature, wet-bulb temperature, or relative humidity) at height(s) representative of water-vapor release. In the case of natural draft cooling towers, ambient temperature and atmospheric moisture measurements may be made at the highest measurement level on the meteorological tower.
Wind. temperature and hurMidit.*
data should be averaged ower a period of at least 15 minutes at least once each hour.


These data are required to assess the physical and aesthetic impacts of vapor plumes from such heat dissipation facilities, including the length and frequency of elevated plumes, increases in ground- level humidity, frequency and extent of ground-level fogging and icing, drift deposition, cloud formation, cloud shadowing, and additional precipitation in the site vicinity as discussed in Section 5.1.4 of Regulatory Guide 4.2, Preparation of Environmental Reports for Nuclear Power Stations(Ref. 14),
b.
and Section 5.3.3.1 of NUREG-1555, Environmental Standard Review Plan(Ref. 15).
These measurements need not be continued during the operational monitoring program, unless specified by the plants Environmental Protection Program pursuant to 10 CFR 50.36b or 10 CFR 51.50.


Rev. 1 of RG 1.23, Page 8
The basic reduced data should be compiled into monthly or seasonal and annual joint frequency distributions of wind speed and wind direction by atmospheric stability class. Table I gives an example of a suitable format for data compilation and reporting purposes. Similar tables of joint frequency distribution should be prepared for each of the other atmospheric stability classe


3.       Siting of Meteorological Instruments To the extent practical, meteorological measurements should be made in locations that can provide data representative of the atmospheric conditions into which material will be released and transported.
====s. Table ====
2 presents a classification of the various atmospheric stability categories.


The tower or mast should be sited at approximately the same elevation as finished plant grade. Factors to be considered in selecting the appropriate measurement locations and installation of the instruments include the prevailing wind direction, topography, and location of manmade and vegetation obstructions.
c.


Whenever possible, wind measurements should be made at locations and heights that avoid airflow modifications by obstructions such as large structures, trees, and nearby terrain. The sensors should be located over level, open terrain at a distance of at least 10 times the height of any nearby obstruction if the height of the obstruction exceeds one-half the height of the wind measurement. 6 Wind sensors should be located on top of the measurement tower or mast or extended outward on a boom to reduce airflow modification and turbulence induced by the supporting structure itself.
To aid in assessing the impact of plant operation on the environment, joint frequency distribution types of data
23.3


Because the tower structure can affect downwind measurements, wind sensors on the side of a tower should be mounted at a distance equal to at least twice the longest horizontal dimension of the tower (e.g., the side of a triangular tower). The sensors should be on the upwind side of the mounting object in areas with a dominant prevailing wind direction. In areas with two distinct prevailing wind directions (e.g., mountain valleys), the sensors should be mounted in a direction perpendicular to the primary two directions.
summaries should be compiled which will permit the description of the frequency and extent of fogging and icing conditions caused by plant operation.


Ambient temperature and atmospheric moisture measurements should be made to avoid air modification by heat and moisture sources (e.g., ventilation sources, cooling towers, water bodies, large parking lots). For this reason, the tower or mast should not be located on or near permanent manmade surfaces, such as concrete or asphalt, or temporary land disturbances, such as coal piles, plowed fields, or storage areas. Temperature sensors should be mounted in fan-aspirated radiation shields to minimize the adverse influences of thermal radiation and precipitation. The aspirated temperature shields should either be pointed downward or laterally towards the north and the shield inlet should be at least 11/2 times the tower horizontal width away from the nearest point on the tower.
d.


Precipitation gauges should be equipped with wind shields to minimize the wind-caused loss of precipitation. Where appropriate, precipitation gauges should also be equipped with heaters or an antifreeze (i.e., ethylene glycol) to melt frozen precipitation. If heaters are used, they should be operated to minimize underestimation attributable to evaporation caused by the heater device.
When evaluating' the acceptability of a site for a nuclear power plant.


4.       Instrument Accuracy and Range The time-average accuracies for digital systems should meet the criteria listed in Table 2.
because of unique meteorological conditions at the site, it is sometimes necessary or desirable to depart from the meteorological assumptions provided in Safety Guides 3 and 4. In these cases, when reducing the data. it is necessary to analyze the joint frequency of persistent wind direction, wind speed, and atmospheric stability to determine appropriately conservative atmospheric diffusion factors (x./Q) for time periods over which the release is assumed to occur (up to 30 days). 
e.


These accuracies are stated in terms of overall system accuracies and should include, where applicable, the errors introduced by sensors, cables, signal conditioners, temperature environments for signal conditioning and recording equipment, recorders, processors, data displays, and the data reduction process.
An analysis of meteorological conditions and atmospheric diffusion factors (x/Q)
for accidental and annual average releases of effluents should be provided and the assumptions and calculation procedures described.


The ambient temperature and atmospheric moisture instrumentation should be capable of operating over the range of expected climatic extremes based on regional climatology.
The probability distributions of x/Q estimates for appropriate time periods should be presented.


6 For example, trees 15 meters (49 feet) in height should be no closer than 150 meters (492 feet) from the tower or mast.
7.


Rev. 1 of RG 1.23, Page 9
Special Considerations At some sites, due to complex flow patterns in nonuniform terrain, additional wind and temperature instrumentation and more comprehensive programs may be necessary.


If the accuracies of the signal conditioning equipment and/or data acquisition system are sensitive to changes in temperature, they should be housed in a climate-controlled environment.
Also, measurements of precipitation and/or solar radiation may be desirable at some locations.


Table 2. Meteorological System Accuracies and Resolutions Measurement Measurement                                      System Accuracy                                        Resolution Wind Speed                    +/-0.2 m/s (+/-0.45 mph) or 5% of observed wind speed                    0.1 m/s or 0.1 mph starting threshold < 0.45 m/s (1 mph)
Occasionally the unique diffusion characteristics of a particular site may warrant use of special meteorological instrumentation and/or studies.
      Wind Direction                                        +/-5 degree                                          1.0 degree starting threshold < 0.45 m/s (1 mph)
  Ambient Temperature                                    +/-0.5 EC (+/-0.9 EF)                                  0.1 EC or 0.1 EF
  Vertical Temperature                                  +/-0.1 EC (+/-0.18 EF)                                0.01 EC or 0.01 EF
        Difference Dew Point Temperature                                  +/-1.5 EC (+/-2.7 EF)                                  0.1 EC or 0.1 EF
  Wet-Bulb Temperature                                  +/-0.5 EC (+/-0.9 EF)                                  0.1 EC or 0.1 EF
    Relative Humidity                                          +/-4%                                                0.1%
        Precipitation                  +/-10% for a volume equivalent to 2.54 mm (0.1 in.)                  0.25 mm or 0.01 in.


(water equivalent)                    of precipitation at a rate < 50 mm/h (<2 in./h)
Proposed studies of this nature should be described in the application for a construction permit.
            Time                                                +/-5 min                                            1 min
5.        Instrument Maintenance and Servicing Schedules Meteorological instruments should be inspected and serviced at a frequency that will ensure data recovery of at least 90 percent on an annual basis. 7 The 90-percent rate applies to the composite of all variables (e.g., the joint frequency distribution of wind speed, wind direction, stability class)
needed to model atmospheric dispersion for each potential release pathway. In addition, the 90-percent rate applies individually to the other meteorological parameters.


Channel checks should be performed daily for operational monitoring programs, and channel calibrations should be performed semiannually for both pre-operational and operational monitoring programs, unless the operating history of the equipment indicates that either more- or less-frequent calibration is necessary. System calibrations should encompass entire data channels, including all recorders and displays (e.g., those local at the meteorological tower and in the emergency response facilities, as well as those used to compile the historical data set). System calibrations may be performed by a series of sequential, overlapping, or total channel steps, such that each channel from sensors to recorders and displays is calibrated. For guyed towers, guyed wires should be inspected annually, and anchors should be inspected once every 3 years in accordance with industry standards.
8.


7 The use of redundant sensors and/or recorders is an acceptable approach to achieve the 90-percent data recovery goal.
Documentation The onsite meteorological measurements program should be fully documented in the safety analysis report, in accordance with subparagraphs
50.34(a)(1)
and
50.34(bX)1) of 10 CFR Part 50.


Rev. 1 of RG 1.23, Page 10
23.4


6.        Data Reduction and Compilation Meteorological monitoring systems should use electronic digital data acquisition systems as the primary data recording system. Data may be recorded and displayed in either English units (e.g., miles per hour, degrees Fahrenheit, inches) or metric units (e.g., meters per second, degrees Celsius, millimeters) and should meet the resolution criteria listed in Table 2.
TABLE 1 Extremely Stable (AT exceeds 4.00 C/100m)  
 
Period of Record:
A backup recording system (either analog or digital) may be used to provide a high assurance of valid data. Where analog data recording systems are used, wind speed and wind direction should be recorded on continuous trace strip charts. Other variables may be recorded on multipoint charts with a sampling rate of at least once per minute.
Wind Direction N  
 
NNE  
The digital sampling of data should be at least once every 5 seconds. The digital data should be
NE  
(1) compiled as 15-minute average values for real-time display in the appropriate emergency response facilities (e.g., control room, technical support center, and emergency operations facility), and (2) compiled and archived as hourly values for use in historical climatic and dispersion analyses. The hourly values may be generated by (1) averaging all the samples taken during the hour, (2) using one 15-minute value per hour (if the same 15-minute period is used each hour), or (3) averaging all of the 15-minute values recorded during the hour.8 For precipitation, the hourly value should represent the total amount of precipitation (water equivalent) measured during the hour. Appendix A shows the format for the electronic copy of the hourly database that should be submitted as a supplement to the application.
ENE  
 
E  
The basic data should also be compiled into annual joint frequency distributions of wind speed and wind direction by atmospheric stability class. Table 3 gives an example of a suitable format for data compilation and reporting purposes. Similar tables of joint frequency distribution should be prepared for each of the other atmospheric stability classes.
ESE  
 
SE  
7.        Special Considerations for Complex Terrain Sites The plants pre-operational meteorological monitoring program should provide an adequate basis for atmospheric transport and diffusion estimates for the exclusion area distance, the outer boundary of the low-population zone, and the hypothetical maximally exposed member of the public [e.g., the site boundary and the nearest resident, vegetable garden, and milk and meat animals within 8 kilometers
SSE  
(5 miles) in each downwind sector].
S  
          At some sites, because of complex flow patterns in nonuniform terrain, additional wind and temperature instrumentation and more comprehensive programs may be necessary. For example, the representation of circulation for a hill-valley complex or a site near a large body of water may need additional measuring points to determine airflow patterns and spatial variations of atmospheric stability.
SSW  
 
SW  
Occasionally, the unique diffusion characteristics of a particular site may also warrant the use of special meteorological instrumentation and/or studies.
WSW  
 
W  
The plants operational meteorological monitoring program should provide an adequate basis for atmospheric transport and diffusion estimates within the plume exposure emergency planning zone
WNW  
[i.e., within approximately 16 kilometers (10 miles)].9
NW  
8 Note that wind direction is a circular function with values between 0 and 360 degrees. The wind direction discontinuity at the beginning/end of the scale requires special processing to compute a valid average value.
NNW  
 
9 For example, if the comparison of the primary and supplemental meteorological systems indicates convergence in a lake breeze setting, then a keyhole protective action recommendation (e.g., evacuating a 2-mile radius and 5 miles downwind) may not be appropriate.
 
Rev. 1 of RG 1.23, Page 11
 
8.      Special Considerations to Support Emergency Preparedness In order to identify rapidly changing meteorological conditions for use in performing emergency response dose consequence assessments, 15-minute average values should be compiled for real-time display in the appropriate emergency response facilities (e.g., control room, technical support center, and emergency operations facility). All the meteorological channels required for manual input to the dose assessment models should be available and presented in a format compatible for input to the models (e.g., wind speed is displayed in the proper units; atmospheric stability is displayed as a )T value versus a Pasquill stability class, etc.). Regulatory Guide 1.97, Criteria for Accident Monitoring Instrumentation for Nuclear Power Plants (Ref. 16), provides additional criteria for the display of meteorological data in control rooms.
 
If the basis for any of the emergency action levels includes the monitoring of onsite meteorological conditions (e.g., the occurrence of measured hurricane-force winds onsite as a basis for declaring an Unusual Event), the tower and its instrumentation should be capable of surviving, monitoring, and displaying the meteorological condition.
 
If the plant computer system collects wind speed, wind direction, and atmospheric stability data, these data should be submitted as inputs to the NRCs ERDS as provided for in Section VI of Appendix E
to 10 CFR Part 50.
 
The applicant should have provisions in place to obtain representative meteorological data
[e.g., wind speed and direction representative of the 10-meter (33-foot) level and an estimate of atmospheric stability that is not necessarily based on )T] from alternative sources during an emergency if the site meteorological monitoring system is unavailable.
 
9.      Documentation The safety analysis report should document the onsite meteorological measurements program, in accordance with 10 CFR 50.34(a)(1) and 50.34(b)(1).
                                          Rev. 1 of RG 1.23, Page 12
 
Table 3. Example Joint Frequency Distribution of Wind Direction, Wind Speed, and Stability Class Site/Plant Name:
                                          Extremely Stable ()T exceeds 4.0 EC/100 m)
                                                    Pasquill Stability Class G
                                                Period of Record:
                                      Wind Speed (m/s) at    Meter Level; )T between    Meters and  Meters Wind                 0.5-      1.1-      1.6-      2.1-    3.1-      4.1-    5.1-      6.1-  8.1- Direction     <0.5      1.0        1.5      2.0      3.0      4.0        5.0      6.0      8.0  10.0 >10.0 TOTAL
      N
    NNE
    NE
    ENE
      E
    ESE
    SE
    SSE
      S
    SSW
    SW
  WSW
    W
  WNW
    NW
    NNW
VARIABLE
VARIABLE
    Total Number of Calms:
Wine Speed (mph) at lore Level
            Number of Missing Hours:
1-3  
Values in this table can be in counts or percent of total valid hours.
4-7  
 
8-12  
Rev. 1 of RG 1.23, Page 13
13-18
 
19-24
==D. IMPLEMENTATION==
>24 Total Periods of calm (hours)  
The purpose of this section is to provide information to licensees regarding the NRC staffs plans for using this regulatory guide. No backfitting is intended or approved in connection with the issuance of this guide.
Hours of missing data -
 
23.5 TOTAL
Except in those cases in which a licensee proposes or has previously established an acceptable alternative method for complying with specified portions of the NRCs regulations, the NRC staff will use the methods described in this guide to evaluate the applicants or licensees onsite meteorological measurements program, as presented in (1) submittals in connection with applications for construction permits, standard plant design certifications, operating licenses, early site permits, and combined licenses;
and (2) submittals from operating reactor licensees who voluntarily propose to initiate system modifications that have a clear nexus with the subject for which guidance is provided herein.
 
REGULATORY ANALYSIS / BACKFIT ANALYSIS
        The regulatory analysis and backfit analysis for this regulatory guide are available in Draft Regulatory Guide DG-1164, Meteorological Monitoring Programs for Nuclear Power Plants (Ref. 7).
The NRC issued DG-1164 in October 2006 to solicit public comment on the draft of this Revision 1 of Regulatory Guide 1.23.
 
Rev. 1 of RG 1.23, Page 14
 
REFERENCES
1. U.S. Code of Federal Regulations, Title 10, Energy, Part 100, Reactor Site Criteria. 10
2. U.S. Code of Federal Regulations, Title 10, Energy, Part 50, Domestic Licensing of Production and Utilization Facilities. 10
3. U.S. Code of Federal Regulations, Title 10, Energy, Part 20, Standards for Protection Against Radiation.10
4. National Environmental Policy Act of 1969, Pub. L. 91-190, 42 U.S.C. 4321-4347, United States Senate and House of Representatives, Washington, DC, January 1, 1970. 11
5. U.S. Code of Federal Regulations, Title 10, Energy, Part 51, Environmental Protection Regulations for Domestic Licensing and Related Regulatory Functions.10
6. ANSI/ANS-2.5-1984, Standard for Determining Meteorological Information at Nuclear Power Sites, American National Standards Institute/American Nuclear Society, 1984. 12
7. Draft Regulatory Guide DG-1164 Meteorological Monitoring Programs for Nuclear Power Plants, U.S. Nuclear Regulatory Commission, Washington, DC, October 2006.13
8. ANSI/ANS-3.11-2005, Determining Meteorological Information at Nuclear Facilities, American National Standards Institute/American Nuclear Society, 2005.12
10
  All NRC regulations listed herein are available electronically through the Public Electronic Reading Room on the NRCs public Web site, at http://www.nrc.gov/reading-rm/doc-collections/cfr/. Copies are also available for inspection or copying for a fee from the NRCs Public Document Room at 11555 Rockville Pike, Rockville, MD;
  the PDRs mailing address is USNRC PDR, Washington, DC 20555; telephone (301) 415-4737 or (800) 397-4209;
  fax (301) 415-3548; email PDR@nrc.gov.
 
11 The National Environmental Policy Act of 1969 is available electronically through the NEPAnet Web site at http://ceq.eh.doe.gov/nepa/regs/nepa/nepaeqia.htm.
 
12 Copies may be purchased from the American National Standards Institute/American Nuclear Society,
  555 North Kensington Avenue, La Grange Park, Illinois 60526; telephone (708)352-6611; or fax (708)352-0499.
 
Purchase information is available through the ANS Web site at http://www.ans.org/store/vc-stnd.
 
13 Draft Regulatory Guide DG-1164 is available electronically under Accession #ML062540408 in the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html.
 
Copies are also available for inspection or copying for a fee from the NRCs Public Document Room (PDR), which is located at 11555 Rockville Pike, Rockville, Maryland; the PDRs mailing address is USNRC PDR, Washington, DC
  20555-0001. The PDR can also be reached by telephone at (301) 415-4737 or (800) 397-4209, by fax at (301) 415-3548, and by email to PDR@nrc.gov.
 
Rev. 1 of RG 1.23, Page 15
 
9.  Regulatory Guide 1.145, Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants, U.S. Nuclear Regulatory Commission, Washington, DC.14
10. Regulatory Guide 1.111, Methods for Estimating Atmospheric Transport and Dispersion of Gaseous Effluents in Routine Releases from Light-Water-Cooled Reactors, U.S. Nuclear Regulatory Commission, Washington, DC.14
11. Regulatory Guide 1.194, Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants, U.S. Nuclear Regulatory Commission, Washington, DC.14
12. Regulatory Guide 1.78, Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release, U.S. Nuclear Regulatory Commission, Washington, DC.14
13. NUREG/CR-6613, A Code Manual for MACCS2, SAND97-0594, D. Chanin and M.L. Young, U.S. Nuclear Regulatory Commission, Washington, DC, May 1998.15
14. Regulatory Guide 4.2, Preparation of Environmental Reports for Nuclear Power Stations ,
    U.S. Nuclear Regulatory Commission, Washington, DC.14
14 All regulatory guides listed herein were published by the U.S. Nuclear Regulatory Commission or its predecessor, the U.S. Atomic Energy Commission. Most are available electronically through the Electronic Reading Room on the NRCs public Web site, at http://www.nrc.gov/reading-rm/doc-collections/reg-guides/. Single copies of regulatory guides may also be obtained free of charge by writing the Reproduction and Distribution Services Section, ADM, USNRC, Washington, DC 20555-0001, by fax to (301) 415-2289, or by email to DISTRIBUTION@nrc.gov.
 
Active guides may also be purchased from the National Technical Information Service (NTIS). Details may be obtained by contacting NTIS at 5285 Port Royal Road, Springfield, Virginia 22161, online at http://www.ntis.gov, by telephone at (800) 553-NTIS (6847) or (703) 605-6000, or by fax to (703) 605-6900. Copies are also available for inspection or copying for a fee from the NRCs Public Document Room (PDR), which is located at 11555 Rockville Pike, Rockville, Maryland; the PDRs mailing address is USNRC PDR, Washington, DC 20555-000
 
===1. The PDR===
    can also be reached by telephone at (301) 415-4737 or (800) 397-4209, by fax at (301) 415-3548, and by email to PDR@nrc.gov.
 
15 NUREG/CR-6613 was developed by Sandia National Laboratories and published by the U.S. Nuclear Regulatory Commission. Copies are available for inspection or copying for a fee from the NRCs Public Document Room at 11555 Rockville Pike, Rockville, MD; the PDRs mailing address is USNRC PDR, Washington, DC 20555;
    telephone (301) 415-4737 or (800) 397-4209; fax (301) 415-3548; email PDR@nrc.gov. In addition, copies are available at current rates from the U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20402-9328 (telephone 202-512-1800); or from the National Technical Information Service (NTIS) by writing NTIS
    at 5285 Port Royal Road, Springfield, Virginia 22161, online at http://www.ntis.gov, by telephone at (800) 553-NTIS
    (6847) or (703)605-6000, or by fax to (703) 605-6900.
 
Rev. 1 of RG 1.23, Page 16
 
15. NUREG-1555, Standard Review Plans for Environmental Reviews for Nuclear Power Plants, Section 5.3.3.1, Heat Dissipation to the Atmosphere, U.S. Nuclear Regulatory Commission, Washington, DC, October 1999.16
16. Regulatory Guide 1.97, Criteria for Accident Monitoring Instrumentation for Nuclear Power Plants, U.S. Nuclear Regulatory Commission, Washington, DC.14
16 Copies are available at current rates from the U.S. Government Printing Office, P.O. Box 37082, Washington, DC
    20402-9328 (telephone 202-512-1800); or from the National Technical Information Service (NTIS) by writing NTIS
    at 5285 Port Royal Road, Springfield, Virginia 22161, online at http://www.ntis.gov, by telephone at (800) 553-NTIS
    (6847) or (703)605-6000, or by fax to (703) 605-6900. Copies are also available for inspection or copying for a fee from the NRCs Public Document Room (PDR), which is located at 11555 Rockville Pike, Rockville, Maryland;
    the PDRs mailing address is USNRC PDR, Washington, DC 20555-0001. The PDR can also be reached by telephone at (301) 415-4737 or (800)397-4209, by fax at (301)415-3548, and by email to PDR@nrc.gov. In addition, NUREG-1555 is available electronically through the Electronic Reading Room on the NRCs Public Web site at http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1555/.
                                            Rev. 1 of RG 1.23, Page 17
 
APPENDIX A
                                    RECOMMENDED FORMAT
                      FOR HOURLY METEOROLOGICAL DATA
                        TO BE PLACED ON ELECTRONIC MEDIA
          Hourly meteorological data should be submitted to the U.S. Nuclear Regulatory Commission (NRC) on mutually agreed-upon media. The file is a formatted, sequential access, ASCII text data file.
 
Comma-delimited or binary data files should not be submitted. The data should be in files that are of a size that are convenient for use and storage. Annual data files are acceptable.
 
At the beginning of each file, use the first five records to give a file description. Include plant name, location (latitude, longitude), dates of data, information explaining data contained in the other fields if they are used, heights of measurements, and any additional information pertinent to the identification of the file (e.g., type of atmospheric moisture measurements). Ensure that all five records are included, even if some are blank. Use 160A1 as the format for the first five records. The remaining records, one per hour, contain the meteorological data in the format A4, I4, I3, I4, 25F5.1, F5.2, 3F5.1.
 
The use of decimal points in the database is not required. Check the file to ensure quality (e.g., compare against the raw data to ensure that the electronic file has been properly formatted, unit conversions are correct, and invalid data are properly identified).
          Provide all data to the tenth of a unit, except solar radiation, which should be provided to a hundredth of a unit. This does not necessarily indicate the accuracy of the data (e.g., wind direction is usually given to the nearest degree). Use all nines in any field to indicate a lost record (99999). Use all sevens in a wind direction field to indicate calm (77777). If there are only two levels of data, use the upper and lower levels. If there is only one level of data, use the upper level.
 
NOTE: The sigma theta, solar radiation, and visibility measurements listed in the following pages are not required measurements but should be provided if they are available. Ambient temperature and atmospheric moisture measurements should be provided at height(s) representative of water-vapor release for those sites utilizing cooling towers, cooling lakes and ponds, or spray ponds as the plants normal heat sink.
 
Appendix A to Rev. 1 of RG 1.23, Page A-1


METEOROLOGICAL DATA ON ELECTRONIC MEDIA
TABLE 2 Classification of Atmospheric Stability Stability Classification Extremel&#xfd; unstable Moderately unstable Slightly unstable Neutral Slightly stable Moderately stable Extremely stable P"Wqill Categor.. 
LOCATION:
A
DATE OF DATA RECORD:
B
A4  Identifier (can be anything)
C
I4  Year I3  Julian Day I4  Hour (on 24-hour clock)
D
                                                                  ACCURACY
E
F5.1 Upper Measurements: Level = _____ meters                      _____
F
F5.1 Wind Direction (degrees)                                     _____
G
F5.1 Wind Speed (meters/second)                                    _____
(dowe.)  
F5.1 Sigma Theta (degrees)                                        _____
25.00
F5.1 Ambient Temperature (EC)                                      _____
20.00
F5.1 Atmospheric Moisture: _____                                  _____
15.00
F5.1 Other: _____                                                  _____
10.00
F5.1 Intermediate Measurements: Level = _____ meters              _____
5.00
F5.1 Wind Direction (degrees)                                     _____
2.50
F5.1 Wind Speed (meters/second)                                    _____
S.70
F5.1 Sigma Theta (degrees)                                        _____
Temperature change with heigt (&deg;ClOOm)  
F5.1 Ambient Temperature (EC)                                      _____
<-1.9
F5.1 Atmospheric Moisture: _____                                  _____
-1.9 to -1.7
F5.1 Other: _____                                                  _____
-1.7 to-1.5
F5.1 Lower Measurements: Level = _____ meters                      _____
-1.5 to -0.5
F5.1 Wind Direction (degrees)                                      _____
-0.5 to 1.5
                            Appendix A to Rev. 1 of RG 1.23, Page A-2
1.5 to 4.0
>4.0
Standard deviation of horizontal wind direction fluctuation over a period of 15 minutes to I hour. The values shown are averages for each stability classification.


METEOROLOGICAL DATA ON ELECTRONIC MEDIA (Continued)
23.6}}
F5.1 Wind Speed (meters/second)                                    _____
F5.1 Sigma Theta (degrees)                                          _____
F5.1 Ambient Temperature (EC)                                      _____
F5.1 Atmospheric Moisture: _____                                    _____
F5.1 Other: _____                                                  _____
F5.1 Temp. Diff. (Upper-Lower) (EC/100 meters)                      _____
F5.1 Temp. Diff. (Upper-Intermediate) (EC/100 meters)              _____
F5.1 Temp. Diff. (Intermediate-Lower) (EC/100 meters)              _____
F5.1 Precipitation (millimeters)                                    _____
F5.2 Solar Radiation (calories/square centimeter/minute)            _____
F5.1 Visibility (kilometers)                                        _____
F5.1 Other: _____                                                  _____
F5.1 Other: _____                                                  _____
                            Appendix A to Rev. 1 of RG 1.23, Page A-3}}


{{RG-Nav}}
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Latest revision as of 01:12, 17 January 2025

Onsite Meteorological Programs
ML020360030
Person / Time
Issue date: 02/17/1972
From:
Office of Nuclear Regulatory Research
To:
References
Reg Guide 1.023
Download: ML020360030 (6)
v • d • e


2/17/72 SAFETY GUIDE 23 ONSITE METEOROLOGICAL PROGRAMS

A. INTRODUCTION

Subparagraph 100. 10(c)(2) of 10 CFR Part

100 states that, in determining the acceptability of a site for a power or testing reactor, the Commission will take into consideration meteorological conditions at the site and in the surrounding area.

Subparagraph 50.36a(a)(2) of 10 CFR Part

50 requires nuclear power plant licensees to submit semiannual reports specifying the quantity of each of the principal radionuclides released to unrestricted areas in liquid and in gaseous effluents, and such other information as may be required by the Atomic Energy Commission to estimate maximum potential annual radiation doses to the public resulting from effluent releases.

A

knowledge of meteorological conditions in the vicinity of the reactor is important in providing a basis for estimating maximum potential annual radiation doses resulting from radioactive materials eleased in gaseous effluents.

In order for the Commission to fulfill its responsibilities under the National Environmental Policy Act of 1969. and in accordance with the requirements of Appendix D to 10 CFR Part 50. "Statement of General Policy and Procedure: Implementation of the National Environmental Policy Act of 1969 (Public Law 91-190)," basic meteorological information must be available for use in assessing potentially adverse envircnmental effects of a radiological and nonradiological nature resulting from the construction or operation of a nuclear power plant.

Appendix E

to

10

CFR

Part

50,

"Emergency Plans for Production and Utilization Facilities," requires each applicant for an operating license to include in its final safety analysis report required by § 50.34(b) of

10 CFR Part

50.

plans for coping with radiological emergencies. The plans must include criteria for determining when protective measures should be considered within and outside the site boundary to protect health and fety and prevent damage to propert

y. In this

,egard, it is necessary for the applicant to establish and maintain a meteorological program capable of rapidly assessing critical meteorological parameters.

Thus. at each nuclear power plant site there are multiple needs for an onsite program which will adequately measure and document basic meteorological data. These data may be used to develop atmospheric diffusion parameters which. with an appropriate diffusion model,'

may be used to estimate potential radiation doses to the public resulting from actual routine or accidental releases of radioactive materials to the atmosphere or to evaluate the poential dose to the public as a result of hypothetical reactor accidents. This safety guide describes a suitable onsite meteorological program to provide meteorological data needed to estimate these potential radiation doses.

B.

DISCUSSION

An onsite meteorological measurements program at a nuclear power plant site shouldJhe capable of providing the meteorological information required to make the following assessments:

I.

A

conservative assessment by the applicant and the regulatory staff of the potential dispersion of radioactive material from, and the radiological consequences of, design basis accidents to aid in evaluating the acceptability of a site and the adequacy of engineered safety features for a nuclear power plant.

2.

An assessment by both the applicant and the regulatory staff of the maximum potential annual radiation dose to the public resulting from the routine release of radioactive materials in gaseous effluents to assist in demonstrating that operations will be or are being conducted within the limits of 10 CFR Part 20 and to assure that effluent control equipment design objectives and proposed operating procedures meet the Commission's requirements for keeping levels of radioactive material in effluents to

'Safety Guide 3, "Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling Water Reactors."

November 2, 1970: Safety Guide 4. "Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors."

November

2. 1970. "Meteorology and

,t sr-,: -n:.

1r(8" T'D

410"Y.

23.1

unrestricted areas as low as practicable.

3.

A realistic assessment by the applicant and the regulatory staff of the potential dispersion of radioactive materials from, and the radiological consequences of.

a spectrum of accidents to aid in evaluating the environmental risk posed by a nuclear power plant in accordance with Appendix D to 10 CFR Part 50.

4.

A realistic assessment by the applicant and the regulatory staff of other than radiological environmental effects. such as fogging, icing, and salt drift from cooling towers, to aid in evaluating the environmental impact of a nuclear power plant in accordance with Appendix D to 10 CFR Part 50.

5.

A rapid, conservative assessment by the licensee and other appropriate persons of the radiological consequences of an accidental release of radioactive material to the atmosphere.

The assessment should be used to provide early guidance to persons assigned to licensee's emergency organization and to appropriate local. State and Federal agencies with responsibilities for coping with emergencies, for use in determining (i)

the need for notification and participation of local and State agencies and the Commission and other Federal agencies, and (ii)

when appropriate measures should be taken to protect public health and safety and prevent damage to property in accordance with Appendix E to 10

CFR

Part 50. Onsite meterological measurements should provide an adequate basis for short- distance atmospheric diffusion calculations.

(Regional meteorological data will be needed in the event it should become necessary to make diffusion estimates for long distances. To assure that the required data are readily available, the applicant should establish and maintain contact with the nearest National Weather Service Focal Point Air Pollution Meteorologist.) 2

2The name and address of the nearest Focal Point Air Pollution Meteorologist may be obtained by contacting the Air Pollution Meteorologist. Weather Analysis and Prediction Division, National Weather Service, National Oceanographic and Atmospheric Administration. Silver Spring. Marvland 20910.

Specific guidance for evaluatirig t

potential radiological consequences of desi basis reactor accidents is given in Safety GuidL

3 and 4. The basic diffusion model described in these guides may also be used to estimate the dispersion of radioactive materials in the atmosphere following the routine or accidental release of such materials. When using the model for evaluating short-term releases, the actual meteorological parameters measured during the release period should be used. For long-term releases the observed joint frequency distribution of wind speed and direction and atmospheric stability for the period should be used. In the event of large variations in the rate of release, it may be necessary to subdivide the meteorological data into periods of approximately uniform release rate.

While there are differences in the specific types of meteorological information required for each of the above assessments, a single set of instruments can generally be used to obtain the basic data needed for all of them. For this reason, when establishing a

meteorological program for an initial site survey, careful consideration should be given to the operational need:

of the plant for meteorological information. In particular, care should be taken to locate the stations at positions where the measurements will accurately represent the overall site meteorology and. if possible. where wind patterns will not be significantly influenced by plant structures.

The number of locations on a site at which meteorological measurements are necessary will depend largely on the complexity of the terrain in the vicinity of the site. For example. the study of a hill-valley complex, or a site near a large body of water would require a larger number of measuring points to determine air flow patterns and spatial variations of atmospheric stability.

The minimum amount of meteorological data needed for siting evaluation is considered to be that amount of data gathered on a

continuous basis for a representative consecutive

12 month period. Two full annual cycles of data are desirable.

C.

REGULATORY POSITION

This section describes a suitable onsitf meteorological program to provide meteorological data needed to estimate potential radiation doses to the public as a result of the routine or accidental release of radioactive

23,2

-!rials to the atmosphere and to assess other ronmental effects.

1.

Meteorological Parameters.

To obtain the meteorological information required for a

valid estimate of atmospheric diffusion at a particular site. instrumentation should be provided that is capable of measuring wind direction, wind speed.

and ambient air temperature at a minimum of two levels on at least one tower or mast. At sites where there is a potential for fogging or icing due to an increase in atmospheric moisture content caused by plant operation, instrumentation should be provided for measuring the dew point (or humidity)

on the tower or mast.

2.

Siting of Meteorological Instruments.

The tower or mast should be sited at approximately the same elevation as finished plant grade and in an area where plant structures will have little or no influence on the meteorological measurements.

The lower set of instruments should sense wind speed and direction. termperature, and dew point (where required) at an elevation of 10 meters above the ground and the upper set should sense wind speed and direction and temperature at the height of release of radioactive material (plant vent height) but should be positioned not less than 30 meters above the-lower sensor set. For stack releases, another set of sensors should be located at an elevation such that meteorological conditions at stack height can be represented.

3.

Data Recorders Either analog (strip chart) or digital recording of data may be used as a basis for analysis.

In lieu of providing redundant digital recorders.

digital outputs may be supplemented by strip chart recorders to minimize possible loss of data due to instrument malfunction.

Recorders (analog or digital) for wind direction and speed and temperature difference (two temperatures or one temperature difference measurement on a tower or mast) should be located in the reactor control room for use during plant operation.

4.

Instrument Accuracy a.

Wind direction accuracy for instantaneous recorded values +/-5°.

b.

Wind speed accuracy for time averaged values +/-0.5 mph. Starting speed of anemometer< 1 mph.

c.

Temperature accuracy for time averaged values

+/-0.5'C.

Temperature difference accuracy from either difference between averaged temperatures or average temperature difference +/-0.1 IC.

d.

Dew point accuracy for time averaged values +/-0.50C.

5.

Instrument Maintenance and Servicing Schedules Meteorological instruments should be inspected and serviced at a frequency which will assure at least a 907 data recovery and which will minimize extended periods of instrument outage.

The use of redundant sensors andlor recorders may be another acceptable means of achieving the

901/ data recovery goal. The instruments should be calibrated at least semiannually.

6.

Data Reduction and Compilation a.

Wind. temperature and hurMidit.*

data should be averaged ower a period of at least 15 minutes at least once each hour.

b.

The basic reduced data should be compiled into monthly or seasonal and annual joint frequency distributions of wind speed and wind direction by atmospheric stability class. Table I gives an example of a suitable format for data compilation and reporting purposes. Similar tables of joint frequency distribution should be prepared for each of the other atmospheric stability classe

s. Table

2 presents a classification of the various atmospheric stability categories.

c.

To aid in assessing the impact of plant operation on the environment, joint frequency distribution types of data

23.3

summaries should be compiled which will permit the description of the frequency and extent of fogging and icing conditions caused by plant operation.

d.

When evaluating' the acceptability of a site for a nuclear power plant.

because of unique meteorological conditions at the site, it is sometimes necessary or desirable to depart from the meteorological assumptions provided in Safety Guides 3 and 4. In these cases, when reducing the data. it is necessary to analyze the joint frequency of persistent wind direction, wind speed, and atmospheric stability to determine appropriately conservative atmospheric diffusion factors (x./Q) for time periods over which the release is assumed to occur (up to 30 days).

e.

An analysis of meteorological conditions and atmospheric diffusion factors (x/Q)

for accidental and annual average releases of effluents should be provided and the assumptions and calculation procedures described.

The probability distributions of x/Q estimates for appropriate time periods should be presented.

7.

Special Considerations At some sites, due to complex flow patterns in nonuniform terrain, additional wind and temperature instrumentation and more comprehensive programs may be necessary.

Also, measurements of precipitation and/or solar radiation may be desirable at some locations.

Occasionally the unique diffusion characteristics of a particular site may warrant use of special meteorological instrumentation and/or studies.

Proposed studies of this nature should be described in the application for a construction permit.

8.

Documentation The onsite meteorological measurements program should be fully documented in the safety analysis report, in accordance with subparagraphs

50.34(a)(1)

and

50.34(bX)1) of 10 CFR Part 50.

23.4

TABLE 1 Extremely Stable (AT exceeds 4.00 C/100m)

Period of Record:

Wind Direction N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

VARIABLE

Wine Speed (mph) at lore Level

1-3

4-7

8-12

13-18

19-24

>24 Total Periods of calm (hours)

Hours of missing data -

23.5 TOTAL

TABLE 2 Classification of Atmospheric Stability Stability Classification Extremelý unstable Moderately unstable Slightly unstable Neutral Slightly stable Moderately stable Extremely stable P"Wqill Categor..

A

B

C

D

E

F

G

(dowe.)

25.00

20.00

15.00

10.00

5.00

2.50

S.70

Temperature change with heigt (°ClOOm)

<-1.9

-1.9 to -1.7

-1.7 to-1.5

-1.5 to -0.5

-0.5 to 1.5

1.5 to 4.0

>4.0

Standard deviation of horizontal wind direction fluctuation over a period of 15 minutes to I hour. The values shown are averages for each stability classification.

23.6


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