Atmospheric dispersion modeling for an accidental release from the Pakistan Research Reactor-1 (PARR-1)

Atmospheric dispersion modeling and radiation dose calculations have been performed for a postulated accidental airborne radionuclide release from the Pakistan Research Reactor-1 (PARR-1) appropriate to a power upgrade to 10 MW. Estimates of releases for various radionuclide groups are based upon US-NRC regulatory guide 1.183. Committed Effective Doses (CEDs) to the public at various downwind distances were calculated using a health physics computer code 'HotSpot' developed at the Lawrence Livermore National Laboratory, University of California, USA. The doses were calculated for various atmospheric stability classes, viz., Pasquill categories A-F with site-specific averaged meteorological conditions. The meteorological data on atmospheric stability conditions, mean wind speed and the frequency distribution of wind direction based on data collected near the reactor site have also been analyzed and are presented here. The results indicate that a person located within a downwind distance of about 500 m from the reactor would receive more than the permissible CED under the analyzed severe accident scenario. Analysis of one typical year of wind data indicates that the predominant wind direction is East-North East (ENE), which occurs at the site for more than 15% of the time