The atmospheric stability over the nuclear power plant Almirante Álvaro Alberto (CNAAA), Angra dos Reis - RJ, Brazil, was analyzed at climatological, seasonal, and daily scales. The climatologic analysis was based on the Pasquill-Gifford (P-G) for a long-term series of 26 years (1980 - 2006), while the seasonal/daily was performed using the Global Richardson number, RiB, and the Froude number, Fr, (case study 2002-2005). The Froude number was used for the regional flow characterization. According to the P-G criteria, the dominant classes were D, E and F (for diurnal and nocturnal periods). The most frequent sectors of wind direction were S, SSW, SSE in diurnal period and N, NNE, NNW and E in nocturnal. The highest wind velocities were observed for class D while the lowest values were observed for classes E and F, for both periods. The highest wind velocities were correlated to the occurrence of sea breeze. Based on RiB, the dominant stratification regime was stable (for 79% of the time), followed by unstable (17%) and neutral (4%). According to Fr, the flow around CNAAA was characterized by low wind velocities, strong stability and stagnant air. The Fr was lesser than 0.1 during 63% of the time, equal to 1 for 8% of the time and greater than 1.7 during 12% of the time. The criteria used in the determination of the stability and flow characteristics of this region indicated the lower dispersion capacity of the local atmosphere due to the prevalence of stable stratification regimes and blocking conditions.
Nuclear Power Plant; Local flow; Dispersion
