Analysis of the calculation methods for surface air contamination in NPP environment in case of small release height

Methods for calculation of surface air contamination at NPP environment for case of normal operation are analysed. The analysis has been performed for the purpose of using these methods in practical calculations for release small heights (2-5 m above the ground level) and distances not far from the source (up to 200 m). On the basis of Gauss and other methods technological programs for calculations of radionuclide (RN) concentration in surface air of NPP environment in case of their normal operation have been elaborated. It results from the calculation investigations that surface air concentration values calculated by various methods differ not more than 3-4 times at equal distances from the source for any category of atmosphere stability. Maximum value of RN surface air concentration is attained at the 12-15 m distance from the release point under the A type atmosphere stability. At the 100-160 m distance maximum surface air concentration is reached at thermal inversion, at the distance of more than 160 m - in the presence of an elevated inversion