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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 BACKGROUND 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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