Climatographic analysis of the Zion nuclear power station site

The computerized emergency response dose assessment codes (ERDACs) used in the nuclear industry commonly rely on Gaussian plume dispersion techniques. In coastal zones, particularly within 15 km of the shoreline, complex four-dimensional mesoscale meteorological regimes often violate some of the basic assumptions of Gaussian dispersion. For example, a land breeze will initially advect materials offshore into unpopulated areas. Such effluents may pool over water only to return to land in the next morning's onshore flow, but in locations and concentrations unknown and undeterminable from on-site data and standard Gaussian modeling techniques. Improving the performance of ERDACs for a given coastal site requires a climatographic inventory of that site and its surroundings. This involves identifying the coastal mesoscale regimes (CMRs) that affect the site, including their annual frequencies of occurrence and the meteorological conditions that characterize them. Such a climatographic analysis has been performed for the Zion nuclear power station (NPS), which is located just north of Chicago, Illinois, on the western shore of southern Lake Michigan. The purpose of this paper is to summarize the results of this study and its implications for radiological emergency response activities