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Future SCAPA CAM Toolbox Models

The next round of models to be considered for admission to the SCAPA SQA CAM Toolbox is tentatively slated to include:

  • ARCON 96
  • HPAC
  • RSAC-7

The SQA review of this next round of consequence assessment models is tentatively scheduled to begin in 2013.  These models are not currently in the SCAPA CAM Toolbox, but we hope a review of their SQA gap analysis will indicate that they are worthy of admission.  The following is a thumbnail sketch of each of these five modeling systems. 

ARCON96 is a model for calculating concentrations in the vicinity of buildings. It is used by the U.S. Nuclear Regulatory Commission (NRC) to assess nuclear power plant control room habitability under accident conditions. ARCON96 uses hourly averaged meteorological data  and recently developed methods for estimating dispersion in the vicinity of buildings to calculate relative concentrations (X/Q) at control room air intakes that would be exceeded no more than 5% of the time. Relative concentrations are calculated for averaging periods ranging from 1 hour to 30 days duration to support control room habitability dose calculations.  The model incorporates straight-line Gaussian diffusion and does not allow for temporal and spatial variations in the wind field.  It also assumes a constant release rate for the entire 30-day period of release.   Source-receptor distance cannot exceed 10 km, while the intake height cannot exceed 100 meters.


CHARM, the Complex Hazardous Air Release Model, calculates and predicts the movement and concentration of airborne plumes from released chemicals, thermal radiation impacts from boiling liquid expanding vapor explosions (BLEVES), pool and jet firs, and explosion overpressures from mechanical and vapor could explosions.   Two forms of explosion are allowed: Mechanical Failure and Vapor Cloud Explosions. A Mechanical Failure simulation assumes a pressurized containment vessel fails instantaneously, releasing a pressure wave. The Vapor Cloud Explosion algorithms can handle deflagration and detonation. There are two versions of the CHARM.  One version assumes a single source in flat terrain. The second version allows for multiple sources in complex terrain but requires more input than the first.    When using the flat terrain version of the model, a release is simulated as a series of puffs. There are three algorithms used for motion and dispersion of a release in the atmosphere. The model, using the currently calculated parameters of a release, internally decides on the use of an algorithm. The algorithms cover: the jet phase of the release (all densities), the gravitational spread when a denser-than-air cloud is on the ground, and all other cases (e.g. not denser-than-air on ground and aloft clouds).  When using the complex terrain version of the model, the motion and dispersion of the release is determined through the use of fundamental equations of Navier-Stokes.


HPAC is the Hazard Prediction & Assessment Capability developed for the U.S. Defense Threat Reduction Agency (DTRA).  HPAC predicts hazards from nuclear, biological, chemical, and radiological (NBCR) weapons and facilities.  HPAC also provides exposure information for populations in the vicinity of accidents involving nuclear power plants, chemical, and biological production facilities, and NBCR storage facilities/transportation containers. HPAC models atmospheric dispersion of vapors, particles, or liquid droplets from multiple sources, using meteorological input that may range from wind speed and direction at only a single measurement location to 4-dimensional gridded wind and temperature fields. HPAC consists of several components:

  • SCIPUFF is the atmospheric transport model. It is a Gaussian puff model which uses a second order closure model for the treatment of the turbulence component.  The model accounts for dynamic plume rise and dense gas effects, time- and space-dependent boundary layers, and flow over complex terrain. The model predicts the 3-dimensional concentration field as a function of time, with integrated inhalation dosage and surface deposition fields.  Primary and secondary droplet evaporation algorithms are included.  
  • Six user-friendly incident and source term description modules, Nuclear Facility, Biological Facility, Chemical Facility, Nuclear Weapon, Chemical/Biological Weapon, and Radiological Weapon.
  • SWIFT mass-consistent wind field model for flow over terrain. SWIFT was derived from Electricite de France models. The Graphical User Interface (GUI), provides flexible input for all types of particle, liquid and gas hazard sources through SCIPUFF advanced editor.
  • The world-wide climatology database on the HPAC CD allows assessment of typical and climatological bounds on hazards transport.
  • The worldwide terrain elevation database at 1 km horizontal resolution is used with the SWIFT mass-consistent wind model.
  • HPAC utilizes flexible access to weather data. Readers translate standard weather reports available over the Internet into HPAC readable formats. DSWA maintains Meteorological Data Servers which give timely and efficient access to recent observations and wind field forecasts worldwide.

DUSTRAN/SPRAYTRAN is GIS-based dust and spray droplet dispersion modeling system.  The primary components of DUSTRAN/SPRAYTRAN include:

  • the graphical user interface
  • the GIS for specifying geographical inputs (e.g., modeling domain, surface characteristics, activity locations) and viewing model outputs.
  • the dust-emissions module for determining dust-emission rates as a function of time and location given the dust-generating activities schedule and locations
  • the atmospheric dispersion models.

In DUSTRAN, transport, diffusion, and deposition are simulated using one of two regulatory dispersion models--CALPUFF or CALGRID.  The CALPUFF dispersion model is where explicit source-types can be identified using well-defined point-, line-, or area-source configurations.  The CALGRID dispersion model is used for emissions where the entire model domain is a potential emission source.  A diagnostic meteorological model, called the CALifornia METeorological model (CALMET) is integrated in DUSTRAN.  CALMET creates gridded fields of wind and boundary-layer parameters from observed meteorological data.  These gridded fields are then supplied to the CALPUFF and CALGRID dispersion models, which perform the plume advection, diffusion, and deposition calculations.

SPRAYTRAN combines detailed source-term and air-dispersion models to simulate the longer range (regional) transport from aerially applied sprays.  The source-term parameters used to define spray-blocks in SPRAYTRAN are created by using output from a separate, near-field dispersion model called AGDISP.  AGDISP was designed to optimize agricultural spraying operations and has detailed algorithms for characterizing the release, dispersion, and deposition over and downwind of the application area.  AGDISP thus provides detailed results on and nearby the spray block.  SPRAYTRAN is a GIS-based dispersion modeling system that interfaces near-field AGDISP results with the CALPUFF dispersion model for evaluating the longer range transport, diffusion, and deposition of spray drift.


RSAC-7 is The Radiological Safety Analysis Computer (RSAC) Program Version 7.0 (RSAC-7). RSAC-7 combines a user friendly interface and a powerful analysis tool to calculate the dose consequences of a release of radionuclides to the atmosphere.  The user can generate a fission product inventory from either reactor operating history or a nuclear criticality event. RSAC 7 includes the dose conversion factors from ICRP 68 and ICRP 72. Joint frequency meteorological analysis combined with a summary of 50% and 95% conditions allow for an easy check or analysis of the sensitivity of met conditions. Doses are calculated for resuspension, inhalation, air immersion, ground surface, ingestion, and cloud gamma pathways. RSAC-7 can be used as a tool to evaluate accident conditions in emergency response scenarios, radiological sabotage events and to evaluate safety basis accident consequences. It has an internal validation process to assure proper verification of installation parameters. RSAC-7 is fully verified and validated per NQA-1 2000 for Quality Level 1 applications. It has been proposed for inclusion in the DOE Central Registry’s Safety Software Toolbox.