A Recommended Pasquill-Gifford Stability Classification Method for Safety Basis Atmospheric Dispersion Modeling at SRS

Technical Report · Wed Mar 28 00:00:00 EDT 2012

DOI:https://doi.org/10.2172/1037732· OSTI ID:1037732

Hunter, C H. ^[1]

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1. Savannah River National Laboratory (SRNL), Aiken, SC (United States)

Several of the most common methods for estimating Pasquill-Gifford (PG) stability (turbulence) class were evaluated for use in modeling the radiological consequences of SRS accidental releases using the MELCOR Accident Consequence Code System, Ver. 2 (MACCS2). Evaluation criteria included: (1) the ability of the method to represent diffusion characteristics above a predominantly forested landscape at SRS, (2) suitability of the method to provide data consistent with the formulation of the MACCS2 model, and (3) the availability of onsite meteorological data to support implementation of the method The evaluation resulted in a recommendation that PG stability classification for regulatory applications at SRS should be based on measurements of the standard deviation of the vertical component of wind direction fluctuations, σ_e, collected from the 61-m level of the SRS meteorological towers, and processed in full accordance with EPA-454/R-99-005 (EPA, 2000). This approach provides a direct measurement that is fundamental to diffusion and captures explicitly the turbulence generated by both mechanical and buoyant forces over the characteristic surface (forested) of SRS. Furthermore, due to the potentially significant enhancement of horizontal fluctuations in wind direction from the occurrence of meander at night, the use of σ_e will ensure a reasonably conservative estimate of PG stability class for use in dispersion models that base diffusion calculations on a single value of PG stability class. Furthermore, meteorological data bases used as input for MACCS2 calculations should contain hourly data for five consecutive annual periods from the most recent 10 years.

• Research Organization: Savannah River Site (SRS), Aiken, SC (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC09-08SR22470
• OSTI ID: 1037732
• Report Number(s): SRNL--STI-2012-00055
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
ACCIDENTS
AVAILABILITY
Atmospheric Modeling
CLASSIFICATION
DIFFUSION
Diffusion
EVALUATION
FLUCTUATIONS
IMPLEMENTATION
RECOMMENDATIONS
SAFETY
SIMULATION
STABILITY
TURBULENCE
Turbulence
US EPA