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Incorporation of HPAC 5.0 Transport Phenomenology to RASCAL's


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									                    Incorporation of HPAC 5.0 Transport Phenomenology to RASCAL’s Radiological Releases

                                                                  Robert Sanders

                                                        Oak Ridge National Laboratory
                                                           One Bethel Valley Road
                                                         Oak Ridge, TN 37831-6085

INTRODUCTION                                                                    HPAC is an atmospheric dispersion modeling tool
                                                                           developed for military operations. (HPAC was developed
    The purpose of this paper is to describe the incorporation of          starting with the Defense Nuclear Agency (DNA), then the
DTRA’s HPAC (Hazard Prediction and Assessment Capability)                  Defense Special Weapons Agency (DSWA), and later the
code under the NRC’s code RASCAL (Radiological Assessment                  Defense Threat Reduction Agency (DTRA) to provide a quick
System for Consequence AnaLysis).                                          response to threats from WMDs.) This has been accomplished
                                                                           by using a suite of programs to read in meteorological data and
                                                                           interpolate it into a user-defined grid, describe in detail the
                                                                           source configuration, and run a transport and diffusion code to
                                                                           generate output in a variety of ways (i.e. concentration, dose,
      The current version of RASCAL (version 3.0.5) evaluates              etc.). The main code used within HPAC for transport
releases from: nuclear power plants, spent fuel storage pools and          calculations is the Second-Order Closure Integrated Puff model
casks, fuel cycle facilities, and radioactive material handling            (SCIPUFF). It describes diffusion processes using second-order
facilities. It appears to be a single piece of software; however, it       turbulence closure by relating the dispersion rate to velocity
is a set of inter-linked modules. These elements include:                  fluctuation statistics, and has the added advantage of providing
    1.   Source term: this module calculates a time-dependent source
                                                                           variance in the concentration fields, allowing for a measure of
         term, which for nuclear power plants, is composed of about
         50 radionuclides including parents and daughters                  uncertainty in the result.
    2.   Meteorological data processor: this module interrupts weather          In addition to the transport method, HPAC contains the
         observations and forecasts along with local topography to         ability to obtain real-time meteorology data which are both
         generate time-dependent wind fields used in the transport of      gridded and observed and are available through the
         the plume                                                         Meteorological Data Server (MDS), a consolidated source of
    3.   Atmospheric transport and diffusion: this module uses the         meteorological data developed by DTRA. The gridded data is
         wind fields with a two-dimensional Gaussian puff model to         generated using the Navy Operational Global Atmospheric
         transport the plume downwind and to calculate concentrations      Prediction System (NOGAPS) provided through the Navy’s
         of each radionuclide as a function of time and location
                                                                           Fleet Numerical Modeling and Operations Center (FNMOC).
    4.   Dose calculator: this module calculates various types of doses
         resulting from airborne releases (TEDE, thyroid, acute, etc.)          HPAC 5.0 also contains both population and land cover
         to individuals at each location from three dose pathways -        information based on LANDSCAN 2006. The LandScan Dataset
         inhalation, cloudshine, and groundshine. It also calculates the   comprises a worldwide population database compiled on a 30" X
         longer-term intermediate phase doses from deposited               30" latitude/longitude grid. Census counts (at sub-national level)
         radionuclides. The calculations are completely consistent with    were apportioned to each grid cell based on likelihood
         the EPA protective action guide manual and the methods            coefficients, which are based on proximity to roads, slope, land
         adopted by the Federal Radiological Monitoring and                cover, nighttime lights, and other information. LandScan has
         Assessment Center (FRMAC)                                         been developed as part of the Oak Ridge National Laboratory
    5.   Display of results: this module allows the user to display a
                                                                           (ORNL) Global Population Project for estimating ambient
         wide variety of calculated results as either a picture of the
         plume footprint on a map background for each of the result        populations at risk.
         types or as numeric table                                              Lastly, the HPAC’s exposure model has been updated to
    6.   Uranium hexafluoride module: for uranium hexafluoride             include the latest dose conversion factors from the soon to be
         releases, RASCAL contains a heavy gas model to account for        released revision of the EPA protection guide.
         the exothermic reaction with air and gravitational slumping of
         the plume                                                         CONCLUSION

BENEFITS OF HPAC TRANSPORT                                                      In summary, the incorporation of HPAC transport
                                                                           methodology under RASCAL provides for a much more defined
     As specified in point 2 above, the meteorological data                prediction of the dispersion of the radiological material as well
processor requires a significant amount of user input, including           as the latest dose conversion factors following a postulated
the current weather conditions. To automate the input process,             accident.
the current version of HPAC (5.0 SP1) has been incorporated
under RASCAL.

         Prepared by Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6285, managed by
         UTBattelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.

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