RASCAL 4.1: Radiological ASsessment for Consequence AnaLysis
Athey Consulting, Charles Town, West Virginia,
Nuclear Regulatory Commission, Washington, D.C.
Visual Basic and Fortran; Xeon running Windows 7 & XP (C00783PCX8600).
RASCAL Version 4.1 is the latest in the series of the Radiological Assessment System for Consequence Analysis codes. It evaluates releases from nuclear power plants, spent fuel storage pools and casks, fuel cycle facilities, and radioactive material handling facilities. A widely available U.S. Nuclear Regulatory Commission (NRC) code, RASCAL is designed to be used by the NRC in the independent assessment of dose projections during response to radiological emergencies. The system processes complex assessments based on plant conditions which go far beyond quick estimates based on hand-calculation methods. RASCAL will be used by NRC response personnel to conduct an independent evaluation of licensee dose and consequence projections during exercises and incidents. The model was developed to allow consideration of the dominant aspects of source term, transport, dose, and consequences. Source term calculations in RASCAL estimate the amount of radioactive (or hazardous) material released based on a wide variety of potential radiological accident scenarios. Plant specific source terms can be characterized for US nuclear power plants. The source term calculations performed that pertain to fuel-cycle facility and materials accidents can generally be categorized as (1) fuel-cycle facility/UF accidents, (2) uranium fires and explosions, (3) criticality accidents, and (4) isotopic releases (e.g., transportation, materials). Version 4.1 includes the following updates:
· Modified the cloudshine dose labels on the early phase doses report. If an air sample, dose is called cloud immersion; if a ground sample, dose is called cloud submersion.
· Added an optional user input text field on the sample screen to record when the sample was deposited.
· Fixed a problem that occurred when the user tried to enter 60 nuclides in the sample.
· Modified the I-131 air concentration units to display as ĘCi/cm3. Also adjusted the range for the footprints to cover a more useful range.
· Modified the footprint ranges for deposition to cover a more useful range.
· Removed the option on the time core uncovered source term screen that allowed normal coolant (core not uncovered). Instead, refer the user to the specified core damage endpoint source term method.
· Added a warning to the user when calm conditions are used in the model calculations. This will appear as a popup notification at the end of calculations and as a note added to the end of the close-in max value table. Wind direction is uncertain in calm conditions and close-in doses should be used with care.
· Modified the source term export function to provide the option of stripping the e*f off the nuclide names with implicit daughters. This makes things easier for other models that do not recognize the e*f to import the file (e.g. TurboFRMAC).
· Modified the close-in modeling distance to allow it down to 10 m (from the previous lower limit of 100 m). A warning is displayed to the user and added to the case summary when a distance less than 100 m is specified. At these close distances the point source assumptions may not be valid (see Tech Doc).
· Added a tool to calculate a correction factor that can be used to estimate the total dose from a direct reading dosimeter (DRD). A correction factor is shown on the dose vs. time plot screen when viewing the gamma exposure rate.
· Added a release rate calculator to the Effluent Releases – by Mixtures source term screen. This allows the user to calculate a release rate from a concentration and flow rate.
· Corrected the iodine partitioning in the puff dispersion model. The default partitioning in RASCAL 4.0 was 25% I2 and 30% particles. This partitioning was inconsistent with the partitioning in the plume model used for close-in calculations and the description in the RASCAL 4 Tech Doc. The default partitioning in the puff models is now 30% I2 and 25% particles.
· The calm wind model used for close-in calculations in RASCAL 4.1 has been changed to improve the consistency of dispersion estimates.
· There has been a second, less significant change in the treatment of calm winds in RASCAL 4.1. If the surface level wind speed is less than 1 mph in the plume model, or less than 0.5 mph in the puff model, the wind speed is not extrapolated to the release height. The wind speed is assumed to be calm. This change eliminates any unintended plume movement for elevated releases when a wind direction is specified with calm winds.
· Updated the monitored mixture source term calculation to fix a minor problem with the Case 3 scenario (see the Tech Doc).
· Updated the effluent concentrations source term calculation to fix a problem when using units of activity/hour.
· Updated the coolant sample source term calculation to fix a problem when using units of activity/gallon .
· Updated the facility database to change the stack height for BWRs for which there is no stack or for which we do not have a stack height. The change applied only to Laguna Verde, Hope Creek 1, and the generic BWRs.
· Improved the interpolation between observations and forecasts.
· Display a warning to the user if the code is going to interpolate a wind direction difference greater than 90 degrees.
· Display a warning to the user if forecast entries will be deleted because they have been superseded by observations.
· Fixed a problem where the code mishandled missing stabilities.
· Fixed a problem where the release point temperature value was being lost.
· Fixed a problem that resulted in a Stack overflow error.
· Fixed a problem that resulted in a File not found error.
RASCAL computes power reactor source terms, airborne transport of activity (through both Gaussian plume and puff models), and the resulting doses. The results allow easy comparison to EPA protective action guidelines.
Because RASCAL is designed to be used during a radiological emergency, it is assumed that the amount of activity being released (the source term) and the meteorological conditions will not be precisely known. The doses computed for RASCAL are, therefore, assumed to be rough estimates.
Run times vary
RASCAL runs on Windows based personal computers.
RASCAL 4.1 is a Windows application. Executables included in the package were created using Microsoft Visual Basic 6 and Compaq Visual Fortran compilers. No source files are distributed. The software was tested under Windows 7 & XP.
J. V. Ramsdell, Jr., G. F. Athey, S. A. McGuire, and L. K. Brandon, g RASCAL 4: Description of Models and Methods,h Draft RASCAL 4.0 Technical Description (June 2010).
G. F. Athey, L. K Brandon, and J. V. Ramsdell, Jr., gRASCAL 4.1 Workbook,h (April 2011).
Included are the referenced documents and one CD which includes executables, data, help files, and an install procedure. Source files are not included in this release.
March 1993, revised May 1995, Aug. 1997, Nov. 1998, July 2001, June 2002, July 2007, February 2008, May 2008, January 2009, August 2011.
KEYWORDS: AIRBORNE; GAUSSIAN PLUME MODEL; INTERNAL DOSE; MICROCOMPUTER; NUCLIDE TRANSPORT; RADIOACTIVITY RELEASE; RADIOLOGICAL SAFETY; REACTOR ACCIDENT