Numerical simulation of particle trajectory and atmospheric dispersion of airborne releases.

Numerical simulation of particle trajectory and atmospheric dispersion has been performed for an airborne accidental release from a nuclear power plant site. A Longrange Particle transport and Dispersion Model LPDM based on a Lagrangian approach is developed and tested in this work. The Lagrangian transportdispersion model is directly coupled with an atmospheric prediction model, RAMS Regional Atmospheric Modeling System, to provide necessary meteorological fields in a threedimensional domain. An advantage of this direct coupling is that the meteorological data generated by RAMS can be used directly for trajectory calculations without storage, thus reducing the CPU time consumed in the data storage and retrieval. This effort was done to be able to use this directly coupled modelling system for realtime predictions in case of an accidental release from a potential site.The simulated Lagrangian trajectories were compared with those obtained using observed hourly weather data obtained from an onsite meteorological tower. The results indicated that this oneway coupling between LPDMRAMS provided almost identical trajectories when compared with those obtained using LPDM alone driven by hourly observed wind data. The comparison demonstrated the reliability of the RAMS meteorological predictions for the site under consideration. The comparison also indicated that LPDM run in a stand alone mode, with hourlyobserved wind data, could also be used for trajectory calculations over flat terrain.The model was developed on a parallel processing computer SGI workstation, ORIGIN 2000 computer with eight processors for use in realtime forecast mode. The computational time was about onethird of the simulation time, while using four processors. The model options need to be explored to reduce the computational time further and test its performance for realtime atmospheric dispersion applications. Copyright © 2009 Royal Meteorological Society [ABSTRACT FROM AUTHOR]