Optimization of Radiation Diffusion Factor to Environment. Considering Gaussian models for coastal and complex terrain

Atmospheric dispersion model is typically considered to evaluate the site condition on Nuclear Power Plant Planning and design. This objectives are (1) to derive short term (a few hours) normalized concentrations and deposition values in order to assess the probability of occurrence of high normalized concentrations and contamination levels due to postulated accidents, (2) to derive longer term (up to one month) time integrated normalized concentrations and deposition values for postulated accidents, and (3) to derive long term (about one year) time integrated normalized concentrations and deposition values for routine operations. Once a radioactive gas or aerosol becomes airborne, it travels and disperses in a manner governed by its own physical properties and those of the ambient atmosphere into which it is discharged. To evaluate the dispersion activity precisely, the models employed should account for the atmospheric condition and flow characteristics affected by terrain or near obstacles. However, the methods for siting or safety analysis of Korean nuclear power plant cannot be considered the actual condition, historically, because of securing the conservativeness on the licensing stage due to raw data storage. The Gaussian plume model is generally used to estimate atmospheric dispersion of gaseous effluents released to environment during normal operation and accident without considering the topographical effect. It is universally applicable that the result of Gaussian modeling is more conservative than PUFF or numerical 3D dispersion model at flat terrain. Because the all nuclear power plants of Korea are located in the coastal area with complicated terrain features, the Gaussian model for dispersion of gaseous effluent is not appropriated through the liming assumptions of Gaussian distribution in the strict sense