3. DESCRIPTION OF PROGRAM OR FUNCTION
RASCAL Version 4.2 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. Developed for the U.S. Nuclear Regulatory Commission, RASCAL is designed to be used in the independent assessment of dose projections during response to radiological emergencies. The system supplements assessments based on plant conditions and quick estimates based on hand-calculation methods. RASCAL will be used by response personnel to conduct an independent evaluation of dose and consequence projections and for training and drills. 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. 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).
Changes and improvements in RASCAL 4.2 are listed below. Important updates and fixes are described first and with a certain amount of detail. Smaller updates and fixes are simply listed.
- Both the Source Term to Dose and the Field Measurement to Dose models now include an option to allow the use of ICRP-60 dose conversion factors in the calculation of the effective inhalation and thyroid doses. The default setting is to use ICRP-26, the current NRC standard.
- The Field Measurement to Dose model has been updated in several areas. For the intermediate phase calculations, the improved re-suspension model from Maxwell/Anspaugh has been added. Also, a TEDE remainder dose based on a delay before return has been added. The DRL calculations have been expanded to include a delay before return up to 40 years. The early-phase dose calculations have been expanded to cover a 96 hour period with both plume passage and the post-plume components. Consult Chapter 7 of the RASCAL technical document for full details.
- The dose conversion factors used in RASCAL have been updated with values from DCFPAK2 (Eckerman, ORNL). This package provides updates to the DCFs in FGR-11 and FGR-12. In addition, the half-life data used in RASCAL has been updated from DCFPAK2 as well. Consult Chapter 4 of the RASCAL technical document for full details.
- The model user interfaces have been updated to gather and display more information about the scenarios being modeled. Both the STDose and FMDose models have a field for capturing the analyst name. STDose also includes a field where up to 600 characters can be used to describe the scenario.
- The facility database and the facility help file have been updated to include the approved power-uprates for the following nuclear power plants:
- Calvert Cliffs, Units 1 and 2
- LaSalle, Units 1 and 2
- Limerick, Units 1 and 2
- Nine Mile Point, Unit 2
- North Anna, Units 1 and 2
- Point Peach, Units 1 and 2
- Prairie Island, Units 1 and 2
- Surry, Units 1 and 2
- The STDose Startup Options menu has been renamed to Settings. Then, the capability to set the default analyst name and ICRP inhalation dose factor option were added to this settings screen.
- The options for the display of the radionuclide mix on the ground surface have been updated. First, there is no longer a cutoff based on activity concentration. Now all the radionuclides can be seen. The option to display sorted by contribution to groundshine has been changed to show up to 20 nuclides (up from 10). Finally, the option that previous just showed only the top 10 by activity concentration now sorts by contribution to inhalation CEDE and displays up to 20 radionuclides.
- Fixed a problem where plume model doses beyond ~ 4 miles were dropping off too quickly. When using RASCAL to calculate to 25 or 50 miles, the plume model distances default to a maximum of 5 or 10 miles respectively. With large releases where PAGs were exceeded to 50 miles, the plume values were seen to drop below the PAG. The plume thickness used for the uniformly mixed plume was too low, resulting in rapid depletion of the plume when the plume became uniformly mixed.
- Fixed a problem where the model crashed when trying to do very long calculations (e.g. 48 hours) with large release rates (e.g. total containment failure). The source term model was not setting the isotopic source terms to zero when the containment inventory became extremely small (<10**-20 Ci). This caused the transport and diffusion puff model that calculates to the longer distances (10/25/50 mi) to have numerical underflow problems with the long calculation durations for isotopes that have small initial inventories, decay rapidly, or are all released before the end of the simulation.
- Fixed a problem where meteorological datasets for sites not in the RASCAL facility database could not be modified. For sites not in the RASCAL database (e.g. Fukushima), a user could create but not edit meteorological datasets. When trying to edit, the code reported a file not found. The error message reported "Missing file" and contained a file path with "/site/site/". The code was losing track of where to look for the met dataset files.
- Fixed a problem where the spent fuel uncovered source term did not correctly terminate at 24 hours as designed. The code was not correctly tracking the duration of the release and failed to recognize that it should terminate.
- Fixed a problem where the results from the UF6 plume calculation were changing with no change in inputs. An initialization problem in the UF6 plume model in some conditions has been corrected.
- Fixed a problem where an incorrect deposition pattern could be seen when following a run using calm conditions with one using windy conditions. There were initialization problems in the plume model section dealing with calms.
- Removed the Print Setup option from the File menu. No longer needed.
- Updated the DCFs in the nuclide database to show a blank if there is no value in the source material rather than showing a zero. Still use 0.0 in the calculations.
- Updated the validation of user inputs to correctly handle cases where the user tries to proceed with a needed input field blank.
- Updated the nuclide names in the database to eliminate the ‘a’ and ‘b’ versions. They are replaced by the appropriate nuclide names from DCFPAK2.
- Changed the initial resuspension factor in FMDose to 1.00e-5 to support the new Maxwell -Anspaugh model.
- Updated the ERPG levels for HF used with UF6 releases to match the AIHA 2011 guidance.
- Added code to prevent spray release events from occurring before the start of core damage.
- Added a description of the end of release to the atmosphere and the leak rate to the case summary for the spent fuel pool drained release pathway definition.
- When printing the STDose maximum dose values, only outputs one set of notes. Saves some space.
- Displays a warning to the user when calculations will be using calm conditions.
- Displays a warning to the user when a wind shift greater than 90 degrees in one step is encountered.
- Added over 80 new weather stations to the facility database.
- Updated the population data in the facility database to 2010 Census values.
- Limits the met data shown in the STDose case summary to only what is used in the calculations.
- Updated the mixing heights in the predefined met datasets for the 4 unstable cases to reflect newer methods.
- Added pressure and humidity to the met summary for UF6 releases.
- Removed the SI Wall - 4day Inh dose conversion factors from the nuclide database; they were not being used.
Smaller fixes of problems
- Modified all the help files to fix a problem with the "search" function not working.
- Fixed a problem where an incorrect deposition pattern was seen when following a run using calm conditions with one using windy conditions.
- Fixed the decay chain data files to correct errors in decay chains for some isotopes that are not found in reactor source terms.
- Fixed issue of missing headers in UF6Plume model footprint displays.
- Fixed problem with UTC offset display and usage in the meteorological data processor.
- Fixed problem where spent fuel pool uncovered exactly 2 hr generated a source term (should be no source term).
- Fixed problem where meteorological data processor reversed the labels for air pressure units when using "in Hg" (were shown as "mm Hg").
- Corrected the code used for estimating mixing heights from climatological data.
- Corrected typos and updated values in the facility help file and facility database.
- Updated functions that load and save parameters for sites not in database.
- Fixed an issue with ORNL and INEEL sites not working with precipitation.
- Corrected an issue with units labeling when printing the source term details using SI units.
- Fixed issues related to the use of climatological and default temperature and humidity in preparing meteorological data files for UF6 plume modeling.
- Fixed a problem where the calendar control in MetProc could stay open and allow putting a date into inappropriate fields.
- Fixed an issue where the source term reported went longer than the calculations. The doses were being calculated correctly. If the calculations ended before the release, the source term displayed and exported could be too long.
- Fixed a problem that could cause a crash when trying to use zero amount of UF6 as release inventory.
- Fixed a problem where the detailed results numeric displays could lose their distance labels.
- Fixed a problem where the calculations could not be started in STDose. This was limited to cases where an error in meteorology had occurred first (such as a time mismatch) and was limited to the following source term types: material in a fire, U fire, and U explosion.