Computer-assisted Protective Action Recommendation System (CAPARS)

Development and Custodial Organization:
AlphaTRAC, Inc.
10385 Westmoor Drive, Suite 310
Westminster, CO  80021-2597
(303) 428-5670
Key Contacts at AlphaTRAC: 
John Ciolek, Senior Atmospheric Scientist,  (; 720.263.4271)
 Reed Hodgin, AlphaTRAC President, (; 303.428.5670)
The CAPARS® system is a complex-terrain atmospheric dispersion modeling system used for projections of plume impacts from radiological, chemical, biological, or other types of releases. The model uses multiple, independent puffs to simulate plumes of airborne material.  The puffs are ellipsoidal in shape with a Gaussian mass distribution.  Dispersion is based on Similarity Theory with the puffs moving through time-changing, three-dimensional wind fields and over a spatially varying surface.  Multiple nested domains are supported for improved resolution.  The CAPARS system is designed for local- to regional-scale modeling and can be ported to just about any location.
The primary use for the CAPARS modeling system is real-time emergency response support, but it is also used for hazards assessments, risk assessments, exercises, and field monitoring support.  It provides plume location, severity, and timing―as well as wind fields, hazard projections, and related information―with the accuracy and speed needed to support all levels of emergency management and response, including the urgent demands of first responders.
When used for emergency response, the CAPARS system automates many of the tasks in the emergency consequence projection process. The automation reduces the potential for user input error, minimizes the time required to generate answers, and helps to reduce the stress imposed upon dose assessment personnel in the hectic conditions caused by emergencies.


The CAPARS system contains seven independent sub-systems.
 Meteorological Data: The Meteorological Data sub-system automatically obtains, processes, quality checks, and stores all meteorological data that is available within a modeling domain including surface, tower, profiler, and balloon-type data.  Data is accepted from multiple sources in any format and at any given interval.  This sub-system also automatically creates velocity vector wind field images.  The images can be defined for multiple levels of the atmosphere and for multiple viewing regions to better comprehend wind flow within the modeling domains.
Model: The Model sub-system contains components that simulate transport and diffusion of pollutants, deposition of material onto the ground, and the conversion of concentration-based exposure projections into health-based consequences.  A receptor component generates locations in space where the consequences are evaluated.
Map Server: The Map Server sub-system employs a geographical information system (GIS) to generate displays of projected plume impacts over user-defined geographical features.  The Map Server sub-system also provides a geographical display mechanism for selecting release locations.
User Interface:  The User Interface allows you to build, save, and retrieve scenarios; initiate and manage model runs; manage sessions; and view dispersion model output.
Utilities: The CAPARS system includes many utility programs that assist with the installation, maintenance, and use of the system.  These programs allow for access to and visualization of data going into and coming out of the model.
Task Management: Task management components allow you to control model runs.  These components are available for specialized modeling system applications, but are usually not seen by the user. 
       Product Display and Access: This sub-system contains a web page that allows access to model output products and wind field images.


The CAPARS system also:
Provides a standby (contingency) mode that automatically generates new model projections when weather conditions change
      Can create, store, and reuse scenarios
Automatically generates output maps, including projections of:
Dose via inhalation, immersion, groundshine, and resuspension
Areas where projected levels of contaminants will exceed protective action criteria
Plume timing (projected times when the plume will be at different areas)
Ground deposition
Airborne concentration
Allows for:
Multiple isotope releases
Nuclear criticalities
User-defined particle size distributions
Radiological in-growth and decay
Includes wet and dry deposition
Offers four modes of operation:
Can assess elevated (stack or vent), ground-level, and buoyant releases
Uses SCAPA PAC/TEEL criteria for chemical releases
Develops three-dimensional mass consistent wind fields
Incorporates prognostic weather modeling systems (where available)
Uses ALOHA source term algorithms for puddle, tank, and pipe releases of chemical liquids
Optimizes nested receptor placement that maximizes resolution while minimizing run times
Includes full GIS mapping capability with features pre-defined by the user

Software Quality Assurance Level: 
Software Quality Assurance Evaluation: 
The CAPARS SQA gap analysis review (March 2011) is available for viewing.