RASCAL 3.0.5: Description of Models and Methods (NUREG-1887)

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Publication Information

Manuscript Completed: August 2007
Date Published: August 2007

Prepared by
S.A. McGuire^a
J.V. Ramsdell, Jr.^b
G.F. Athey^c

^aOffice of Nuclear Security and Incident Response
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

^bPacific Northwest National Laboratory
P.O. Box 999
Richland, WA 99352

^cAthey Consulting
P.O. Box 178
Charles Town WV 25414-0178

Prepared for
Office of Nuclear Security and Incident Response
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

The code currently used by NRC's emergency operations center for making dose projections for atmospheric releases during radiological emergencies is RASCAL version 3.0.5 (Radiological Assessment System for Consequence AnaLysis). This code was developed by NRC. The first version was created about 20 years ago. Since then the code has been undergoing continual improvement to expand its capabilities and to update the models used in its calculations. This report describes the models and calculational methods used in RASCAL 3.0.5. This report updates and supercedes the information in NUREG-1741, "RASCAL 3.0: Description of Models and Methods," 2001.

RASCAL 3.0.5 evaluates releases from: nuclear power plants, spent fuel storage pools and casks, fuel cycle facilities, and radioactive material handling facilities.

While RASCAL 3.0.5 operates as a single piece of software, it is really a set of inter-linked modules each with a different function. These are:

1. Source term: this module calculates a time-dependent source term, which for nuclear power plants, is composed of about 50 radionuclides including parents and daughters. This module is unique in the world for its ability to model a wide variety of accidents based on plant conditions for many different facility types.
   
2. Meteorological data processor: this module inputs weather observations and forecasts along with local topography to generate time-dependent wind fields that will transport the plume.
   
3. Atmospheric transport and diffusion: this module uses the wind fields with a two-dimensional Gaussian puff model to transport the plume downwind and to calculate concentrations of each radionuclide as a function of time and location.
   
4. Dose calculator: this module calculates various types of doses resulting from airborne releases (TEDE, thyroid, acute, etc.) to individuals at each location from three dose pathways - inhalation, cloudshine, and groundshine. It also calculates the longer-term intermediate phase doses from deposited radionuclides. The calculations are completely consistent with the EPA protective action guide manual and the methods adopted by the Federal Radiological Monitoring and Assessment Center (FRMAC).
   
5. Display of results: this module allows the user to display a wide variety of calculated results as either a picture of the plume footprint on a map background for each of the result types or as numeric table.
   
6. Uranium hexafluoride module: for uranium hexafluoride releases, RASCAL contains a heavy gas model to account for the exothermic reaction with air and gravitational slumping of the plume.