ML20094B476
| ML20094B476 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-02.3.5, NUREG-75-87, NUREG-75-87-2.3.5, SRP-02.03.05, SRP-2.03.05, NUDOCS 9511010075 | |
| Download: ML20094B476 (5) | |
Text
pn ueu NUREG 75/087 y
U.S. NUCLEAR REGULATORY COMMISSION i
") STANDARD REVIEW PLAN sh,,
OFFICE OF NUCLEAR REACTOR REGULATION SECTION 2.3.5 LONG TERM DIFFUSION ESTIMATES REVIEW RESP 0NSIBILITIES Primary - Site Analysis Branch (SAB)
Secondary - Effluent Treatment Systems Branch (ETSB) 1.
AREAS OF REVIEW Information is presented by the applicant and reviewed by the staff concerning atmospheric diffusion estimates for routine releases of effluents to the atmosphere. The review covers the following specific areas:
1.
Atmospheric diffusion models to calculate relative concentrations for routine radioactive gas release modes as determined by Effluent Treatment Systems Branch.
2.
Meteorological data suninaries used as input to diffusion models.
3.
Derivation of diffusion parameters from meteorological data.
4.
Relative concentrations used for assessment of consequences of routine airborne radioactive releases.
II. ACCEPTANCE CRITERIA This section will be acceptable if the applicant has provided realistic estimates of atmospheric diffusion at appropriate distances from the source for routine releases of radioactive materials to the atmosphere. Guidelines for acceptability of models are Regulatory Guides 1.21, 1.42, and 1.0D (Refs. 1. 3, and 5); National Oceanic and Atmo-spheric Administration (NOAA) Technical Memorandum ERL ARL-42; standard references such as " Meteorology and Atomic Energy - 196;" and Effluent Treatment Systems Branch and Site Analysis Branch positions. Since the staff makes an independent evaluation of atmospheric diffusion estimates based on data from the onsite meteorological measurements program and other nearby meteorological data, it is not necessary for the applicant to duplicate the staff's final estimates. However, the applicants diffusion estimates should reasonably reflect staff positions and state-of-the-art atmospheric diffusion knowledge. Specifical-ly the following information is required:
USNRC STANDARD REVIEW PLAN
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1.
The atmospheric diffusion models usId by the applicant to calculatId concentrations resulting from routine airborne releases of radioactive gases must be document 1d in detail and substantiated so that the staff can evaluate their appropriateness to site and plant characteristics.
2.
Meteorological data sumaries to be used as input to the diffusion models must be presented in joint frequency distribution form. These summaries must have been generated from the best available annual periods of data on record and contain data acceptable to the staff which represent appropriate hourly values of wind direction, wind speed, and atmospheric stability for each mode of routine release.
3.
The atmospheric diffusion parameters, such as vertical plume spread (o ) as a func.
g tion of distance and wind speed, must be related to measured meteorological para-meters and be substantiated as to their validity for use in estimating the consequences of routine releases from the site boundary to a radius of 50 miles from the plant.
4.
Relative concentrations (X/Q) used for assessment of consequences of routine radio-active gas releases must be presented as described in Section 2.3.5.2 of the
" Standard Format and Contents of Safety Analysis Reports for Nuclear Power Plants,"
Revision 2.
III. REVIEW PROCEDURES 1.
Atmospheric Diffusion Models The applicant's diffusion models are compared to the general Gaussian models which are contained in Regulatory Guide 1.00 (Ref.5) for elevated releases and ground j
level releases with a wake correction (See also Reference 3). The suitability of the models for mode of release, plant configuration, and site topography are re-viewed. Effluent Treatment Systems Branch defines the modes of release to be considered.
A determination is made as to whether the release should be considered et a elevated point source or a ground level point source with a volumetric correction for turbulent mixing in the wake of buildings. Generally the release is considered to be elevated if the release point is at least twice as high as nearby solid structures. Otherwise, a ground level volumetric release formulation is usually based on 1/2 the height of the structure from which the effluent is released.
If a site is located such that the effluent trajectories (or vertical plume spread via diffusion) are restricted by topography (or unusual meteorological conditiens),
the models are examined for appropriate modification. Some of these conditions are narrow, deep valleys, " fumigation" from elevated sources, and low level sub-sidence inversions of temperature in the vertical direction.
7.3.5-2 11/24/75
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2.
HetTorological Data Suninaries l
The data suninaries in joint frequency distribution fonn are reviewed for compata-bility of data with the models utilized in the section above. General criteria are stated in Regulatory Guide 1.23 and !!!.2 of Standard Review Plan 2.3.3.
3.
Atmospheric Diffusion Parameters 1
The vertical plume spread parameter, o, as a function of distance and atmospheric g
stability is reviewed. The current procedure is to relate og(X)tovertical temperature difference classes as stated in Table 1 of Regulatory Guide 1.23 (Ref.2). Departures from this procedure are reviewed for adequate reasons for the departures, such as in the case of unusual sites (e.g., valley or coastal). The j
curves of o, with distance, which appear in " Meteorology and Atomic Energy - 1968" are usually acceptable with the addition of a G stability class.
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. 4.
Relative Concentrations used for Routine Releases The X/Q values used for assessment of the consequences of routine radioactive I
releases are reviewed for appropriateness to site conditions and completeness of information.
An independent calculation of annual average X/Q values is made for 16 radial sectors from the site boundary to a distance of 50 miles from the plant using appropriate meteorological data in joint frequency distribution form and the computer program CHI /Q(Ref.7). Adjustments of the X/Q output may be made through use of other
' offsite meteorological data when unusual topographic conditions surround the site or when the onsite meteorological data are found to be inadequate.
4 IV. EVALUATION FINDINGS The reviewer verifies that adequate atmospheric diffusion models, with adequate onsite meteorological data as input to the models, have been used to calculate relative con-centrations at appropriate distances and directions from postulated release points during routine airborne releases of radioactive gases.
I' adequate onsite meteorological data are not available for the construction permit review, the reviewer must assure that adequate conservatism has been applied to the calculated relative concentrations for routine airborne effluent releases based on available data. The reviewer's evaluation must support the following type of concluding statement, to be included in the staff's safety evaluation report:
" Reasonable estimates of average atmospheric diffusion conditions have been made by the staff from the applicant's meteorological data and appropriate diffusion models."
The input to the safety evaluation report will also include a brief suninary of the re-lative concentrations (X/Q) calculated by the staff, reference to diffusion models used, and a comparison between the values computed by the staff and the applicant.
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REFERENCES l.
Regulatory Guide 1.21. "Heasuring Evaluating, and Reporting Radioactivity in Solid Wastes and Releases of Radioactive Materials in Liquid and Gaseous Effluents from Light-Water-Cooled Nuclear Power Plants " Revision 1.
2.
Regulatory Guide 1.23. "Onsite Meteorological Programs."
3, Regulatory Guide 1.42, " Interim Licensing Policy on As Low As Practicable for Gaseous Radioactive Releases from Light-Water-Cooled Nuclear Power Reactors."
4.
Regulatory Guide 1.70, " Standard Format and Content of Safety Analysis Rerorts for Nuclear Power Plants " Revision 2.
5.
Regulatory Guide 1.00, " Methods for Estimating Atmospheric Dispersion of Geseous Effluents from Routine Releases," attachment to Concluding Statement of Postion of the a
Regulatory Staff, Docket No. RM-50-2. February 20, 1974.
6.
D. H. Slade. (ed.), " Meteorology and Atomic Energy - 1968," TID-24190, Division of Technical Information, USAEC (1968).
7.
J. F. Sagendorf, "A Program for Evaluating Atmospheric Dispersion From a Nuclear Power Station," Technical Memorandum ERL ARL-42, Natioaal Oceanic and Atmospheric Administration (1974).
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