ML20207F381
| ML20207F381 | |
| Person / Time | |
|---|---|
| Issue date: | 05/02/1985 |
| From: | Kornasiewicz R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Congel F, Gammill W, Hulman L Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20207F378 | List: |
| References | |
| CON-FIN-B-0446, CON-FIN-B-446, FOIA-86-849, RTR-NUREG-CR-4157 NUDOCS 8701060003 | |
| Download: ML20207F381 (5) | |
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MAY 0 21985 MEMORANDUM FOR: Those on Attached List FROM:
Robert A. Kornasiewicz, Leader Hydrology Section Earth Sciences Branch Division of Radiation Programs &
Earth Sciences, RES
SUBJECT:
TRANSMITTAL 0F NUREG/CR-4157, "A SCIENTIFIC CRITIQUE OF AVAILABLE MODELS FOR REAL-TIME SIMULATIONS OF DISPERSION" The enclosed subject report is provided under FIN B0446, Dispersion Model Evaluation. A copy of the Research Sumary of this report is enclosed.
Robert A. Kornasiewicz, Leader Hydrology Section Earth Sciences Branch Division of Radiation Programs &
Earth Sciences, RES
Enclosures:
1.
Research Sumary f y 20 g 3 861231 CURRAN 86-849 PDR 44.
o.
t Addressees--Memorandum dated
Subject:
Transmittal of NUREG/CR-4157 and Research Summary F. Congel, NRR, P-712 W. Gammill, NRR, P-730 L. Hulman, NRR, P-822 D. Matthews, IE, EWW-359 P. McKee, IE, EWS-346 K. Perkins, IE, 3320 A. Thadani, NRR, 216 I. Spickler, NRR, P-730 J. Martin, RES, 1130-SS M. Solberg, IE, EWS-346 B. Zalcman, IE, 3302
t RESEARCH
SUMMARY
REPORT TITLE:
A Scientific Critique of Available Models for Real-time Simulations of Dispersion AUTHORS:
W. S. Lewellen and R. I. Sykes PROJECT TITLE:
Dispersion Model Evaluation FIN:
B0446 NRC PROJECT MANAGER:
Robert A. Kornasiewicz CONTRACTOR:
Oak Ridge National Laboratory PRINCIPAL INVESTIGATOR:
F. C. Kornegay REGULATORY CONTEXT: Section 50.47 of 10 CFR Part 50 establishes standards that must be met by the onsite and offsite emergency response plans in order for the staff to make a positive finding that there is reasonable assurance that g
adequate protective measures can and will be taken in the event of a radiological emergency.
Included in these standards is paragraph 50.47(b)(9) which specifies that " Adequate methods, systems and equipment for assessing and monitoring actual or potential offsite consequences of a radiological emergency condition are in use." Appendix E of 10 CFR Part 50 further cites in this context specific criteria in NUREG-0654; FEMA-REP-1 which include a dose projection capability, utilizing atmospheric dispersion models, for the plune exposure pathway within the EPZ.
RESEARCH OBJECTIVES: The objective of this study was to evaluate existing atmospheric dispersion models for real-time capabilities, sensitivity to meteorological inputs and cost / benefit ratios, as well as examine the " growth
. i potential" of the models (i.e., how effectively could the model incorporate and -
utilize improvements).
c RESEARCH FINDINGS OR RESULTS:
This study investigated the assumptions invo19ed and existing verification studies for a range of models from the Gaussian plume #
with straight line winds to those that attempt a complete solution of the primitive equations of motion.
Although even the simple models are capable of providing reasonably accurate predictions under ideal conditions, there are feasons to expect relatively severe limits on plume predictability when ce $ain emission conditions are combined with certain meteorological conditions.
The randomness inherent in atmospheric turbulence imposes a natural limit on plume predictability which, in turn, provides an upper bound on model accuracy as a function of available data.
This variability is not a'; a function of the model chosen, but is.rather a complicated function of the meteorological conditions and the nature,of the 8
y emission. The usefulness of a real-time dispersion model is therefore dependent on a complementary estimate of the variability expected about the mean dispersion.
It is recommended that any model for real-time emergency use by supplemented by, at least,'a simple model of the concentration variance expected under the conditions prevailing at that time.
A relatively simple model of the mean concentration, together with a compatible model of its variance, should be more useful than a sophisticated model (which might provide a better estimate of the mean) which does not include an estimate of the variability expected Based on this analysis of he different models, some version of a puff model is likely to provef E st efficient for recl-time application.
It can be run with no more input requirements than those required for the simplest gaussian plume models, yet pemits the accuracy'J616e3 improved whenever additional data on the spatial and temporal variation of the wind flow and; stability conditions are
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available. Such models coul,d be used for both Class'A or Class B applications, ac-Upgraded puff models would remain simpler than the transport and diffusion cl ss of models (e.g., MATHEW/ADPIC, ME50 GRID, PHOENIX), while sacrificing 3
ITttle accuracy at,the level of data input likeIy to be available for most applications.
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These findings should'be confimed by detailed evaluations against test data A-from field _
riments in several different terrain and meteorological situatio
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e REGULA10 IMPLICATIONS: Th s s dy indicates that inherently the most effective atmospheric dispersiorf models for real-time applications appear to be upgraded puff models with provisions for detennining concentration, variance.
Althbugh the transport and diffusion class of models are capable of" handling 4% the effects of wind shear better than puff models, they not only require
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substantial data inputs to yield accurate transport results but also require substantial computing resources, jAlso, due to the long computation times necessary, such models may be hard pressed to provide timely information.'
Suggeajed puff model upgrades include:
Permitting an elevated release for the source Substituting diffusion algorithims which depend on direct measurements of wind variance for those that depend on stability categories Allowing puffs to split when they are sufficiently spread out for wind shear to be an important dispersion mechanism
~g Incorporating wet and dry deposition into the model Complementing the model with a compatible estimate of the concen' ration variance over the time period of most interest.
The infonnation developed by this study can be used in support of NRC reviews of licensee / applicant emergency response accident assessment capabilities, as well as in the selection or use of models that may be installed at the NRC Operations Center.
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e OTE: This report will be issued as NUREG/CR-4820 in early 1987.
A.R.A.P. Report No. 575 Comparison of the 1982 Seadex Dispersion Data With Results Froa a Nuaber of Different Models by W. S. Lewellen R. I. Sykes C. P. Cerasoll S. F. Parker Aeronautical Research Association of Princeton 50 Washington Road, P.O. Box 2229 Princeton, New Jersey 08543 and Frank Kornegay Oak Ridge National Laboratory prepared for Oak Ridge National Laboratory Under Contract 19X89611V February, 1986 s
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