The use of cluster analysis to assess potential impact of atmospheric discharges from NPP on biota

Before planning construction of a new NPP potential impact of atmospheric discharges from the designed NPP on the environment including human and non-human biota must be assessed. Radiological consequences estimates depend largely on qualitative and quantitative composition of the discharge. In Russia data on chemical and physical form of radionuclides and their composition are limited, that is why for modeling annual normalized discharge of the following targeted radionuclides 3H, 14C, 41Ar, 85Kr, 133Xe, 135Xe, 131I, 133I, 60Co and 137Cs we used data from UNSCEAR Report on discharges of radionuclides during normal operation of 19 PWR nuclear power plants located in France. The choice of the NPPs was governed by the duration of monitoring (≥ 10 years), the presence of above listed radionuclides in the discharges. For classification of NPPs by quantitative composition of annual normalized discharge hierarchical cluster analysis was used. All NPPs were divided into 6 clusters. In each cluster amount of each of the targeted radionuclides in annual normalized discharge was determined. For conservative estimating exposure situation and calculating radiation doses to biota we used the largest values of the upper quartiles of normalized discharges of raionuclides. We found that radioactivity of 41Ar, 85Kr, 133Xe and 135Xe in the total radioactivity of noble gases was >90%, the amount of 131I and 133I in the total amount of discharged radioiodines was ~46%, the amount of 135I was 38%. To calculate the radiation dose to biota more accurately, radioactivity of 51Cr and 58Со should be taken into account, because the contribution of each of the radionuclides activity to the total radioactivity of discharged aerosols is about 20%. If total composition of the annual discharge of noble gases, radioiodines, and aerosols differs from that considered in the article, in that case it is reasonable to estimate radioactivity of specific radionuclides discharged.