The Hazard Assessment System for Consequence Analysis (HASCAL) is being developed to support the analysis of radiological, biological, and chemical incidents anywhere in the world for the Defense Special Weapons Agency (DSWA). HASCAL is a component of the Hazard Prediction and Assessment Capability (HPAC), which is a comprehensive nuclear, biological, and chemical hazard effects planning and forecasting modeling system that is being developed by DSWA. HASCAL version 2.0 estimates the hazards resulting from atmospheric releases of nuclear, biological, and chemical materials.
HASCAL 2.0 is a greatly enhanced upgrade of HASCAL 0.7. (See the accompanying document for a description of HASCAL 0.7.) Chemical and biological facilities models, as well as chemical, biological, and nuclear weapons models have been added. The user can define a scenario, which contains multiple incidents of different types. A user's guide has been published (DSWA, 1996). HASCAL 2.0 runs on PCs under Windows 3.1, 95, and NT. It requires a 486 processor or better, 16 MB RAM, and 26 MB free on a hard disk. A version of HASCAL 2.0 has also been developed that will run on UNIX workstations. The following sections describe the individual components of HASCAL, with an emphasis on the new feature in version 2.0.
The Nuclear Facilities (NFAC) module computes the radiological source term from an accident at a radiological facility and computes factors that allow the atmospheric transport model to compute radiological doses and health effects. NFAC now includes the ability to enter sources by isotope using all 1040 isotopes used in ORIGEN. (ORIGEN is the model used to compute the reactor inventories used in NFAC.) Inventories for reprocessing facilities are available. The site selection window now includes the choice of facility type (power reactor or reprocessing facility) and the ability to change the location and inventory file of any facility. The source term can be computed and viewed prior to running the atmospheric transport model.
A variety of source term calculations are available, depending on the type of facility selected. Seven source-term options from are available in NFAC: isotopic release rates or concentrations, a release defined as a gross mix of available isotopes, releases based on facility accident conditions, releases based on the containment monitor reading, spent fuel accidents, and a percentage of total facility inventory by MELCOR (Summers, 1991) element category. (MELCOR is NRC's model of the progression of severe accidents at light-water reactors.) The computed source-term table is displayed by MELCOR element category. Isotopic source terms may be entered in units of either activity or mass.
Facility conditions source terms are available for all types of power reactors that have inventory data. For example, for RBMKs there is a calculation for a prompt critical accident involved one-third, two-thirds, or all of the core at operating power. The release fractions used are based on assessments of the Chernobyl accident. (View an NFAC input screen here.)
The atmospheric transport model, SCIPUFF, now includes radiological decay in transport and the computation of either cloud shine dose or air submersion dose for NFAC incidents. Air submersion dose calculations are faster; cloud shine dose calculations are more accurate.
The dose calculations in NFAC are designed for comparison with U.S. EPA protective action guides.(EPA, 1992) The dose factors used for those calculations have been expanded to take into account as many isotopes as possible from the newly calculated reactor inventories. The inclusion of short-lived isotopes in these inventories will allow estimation of doses for very short exposures (for those isotopes for which dose factors are available). Output is in terms of EPA PAG levels and combat effects.
Planned enhancements to NFAC include adding other types of radiological facilities, such as research and production reactors, enrichment and storage facilities, waste storage facilities, and mining and milling operations. Work on incident scenarios for the various facilities continues. Additional scenarios appropriate for each type of facility will be developed, along with models of damage response and the resulting doses from various kinds of weapons attacks on worldwide nuclear facilities. The ability to print results in a tabular form will be added to SCIPUFF. Inhalation dose factors will be computed for the full list of 1040 isotopes.
The Biological Facilities (BFAC) module and the Chemical Facilities (CFAC) modules allow the assessment of effects of a weapons strike or other extensive damage at any biological or chemical of facility. The source term can be calculated by three methods: selecting a facility damage category, running a warhead/facility interaction model, or reading in a precalculated source term. (View a BFAC or CFAC input screen here.) The resulting SCIPUFF plots will be in terms of surface dose or deposition of the agent selected.
The Nuclear Weapons (NWEAP) module computes the radiological effects of a nuclear weapon strike. NWEAP is based on NewFall (McGahan, 1996). It allows multiple weapons definitions within one incident. Data entered are yield in kilotons, burst height, and fission fraction. (View an NWEAP input screen here.) An optional dynamic cloud rise calculation, based on DELFIC (Norment, 1979), is available. SCIPUFF will produce plots in terms of radiation dose or dose rate.
The Chemical and Biological Weapons (CBWPN) module computes the effects of chemical and biological weapons strikes. (View a CBWPN input screen here.) It is based on NUSSE4, PLUME, and related models. It provides standardized, unclassified hazardous material releases from customary weapons. It uses a database of standard materials definitions and weapons function parameters. These parameters may be customized. The resulting SCIPUFF plots will be in terms of surface dose or deposition of the agent selected.
SCIPUFF may be run with fixed winds, weather observations (both surface and upper air), weather forecasts, or climatology data. Observations can be entered directly or through a spreadsheet.
SCIPUFF may be run with or without a mass consistent terrain model. Digital Terrain Elevation Data (DTED) is available for the whole world and can be used in SCIPUFF or viewed with the DTED Contour utility.
SCIPUFF provides a probabilistic prediction of the atmospheric dispersion and surface deposition processes, with the capability to model multidimensional, time-dependent wind fields. The release may be instantaneous, continuous, or moving. Uncertainty in the wind field, including both boundary-layer scale turbulent eddies and larger scale unknown variations, leads to a random component in the concentration field which requires at least the mean value and the standard deviation for a quantitative description. SCIPUFF uses turbulence closure theory to predict the concentration fluctuation variance as a function of the wind field uncertainty (Sykes, 1986 and 1993), and provides a probabilistic description of the resulting impact using a parameterized probability distribution function.(Lewellen, 1986) HASCAL can then use the SCIPUFF prediction to compute probabilistic radiological, chemical, and biological exposures, and provide an assessment of likelihood for various levels of health effects. SCIPUFF also includes the estimation of radiological decay and daughter in-growth during atmospheric transport.
The current version of SCIPUFF includes a new dense gas model, consideration of precipitation washout, and the calculation of surface dose at elevations above the ground surface. Input may be performed using both operational and advanced modes. SCIPUFF now include the calculation of radiologic decay in transport and radiological cloud shine dose.
Various types of plots are included in HASCAL, including surface dose, vertical slices, and probability. Background maps may be included. The results are available at multiple times throughout the simulation. These results can be combined into an animation that can also be run within HASCAL. The graphical output now may include terrain overlays, nuclear weapons radiation doses and dose rates, printing to scale, and the ability to display result point values
Defense Special Weapons Agency, HPAC Version 1.3 Users Guide, Reference Manual Version 7.5 (1996).
J. T. McGahan, NewFall Users Guide and R W. S. Lewellen and R. I. Sykes, "Analysis of Concentration Fluctuations from Lidar Observations of Atmospheric Plumes," J. Clim. Appl. Met., 25, 1145-1154 (1986).
H. G. Norment, DELFIC Department of Defense fallout Prediction system, DSWA 5159F-1 and 2, Defense Special Weapons Agency (1979).
A. L. Sjoreen, G. F. Athey, J. V. Ramsdell, and T. J. McKenna, RASCAL Version 2.1 User's Guide, NUREG/CR-5247 Vol. 1, Rev. 2 (ORNL-6820), U.S. Nuclear Regulatory Commission (1994).
R. M. Summers et al., MELCOR 1.8.0: A Computer code for Nuclear Reactor Severe Accident Source Term and Risk Assessment Analysis, NUREG/CR-5531 (SAND 90-0364), U.S. Nuclear Regulatory Commission (1991).
R. I. Sykes, W. S. Lewellen, and S. F. Parker, " A Gaussian Plume Model of Atmospheric Dispersion Based on Second-Order Closure," J. Clim. Appl. Met., 25, 322-331 (1986).
R. I. Sykes, S. F. Parker, D. S. Henn, and W. S. Lewellen, "Numerical Simulation of ANATEX Tracer Data Using a Turbulence Closure Model for Long-Range Dispersion," J. Appl. Met., 32, 929-947 (1993).
U.S. Environmental Protection Agency, Manual of Protective Action Guides and Protective Action for Nuclear Incidents, EPA-520/1-75-001A, U.S. Environmental Protection Agency (1992).
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