Environmental Contamination with Long-lived Gamma Emitters in the Influence Region of Ignalina Nuclear Power Plant

Operating nuclear power plant is one of the sources of environmental radioactive pollution. Assuming that the terrestrial plants are the most sensitive indicators of the radiation exposure and that a food-chain starts with the plants, the investigation of them is of great importance for the evaluation of radiation situation in the region an assessment of radiation risk to public. The results of different terrestrial plant samples collected during the period of 2001-2003 in the 32 km-radius influence region of Ignalina nuclear power plant (INPP) investigation are presented and discussed in this paper. Gamma spectrometric measurements show that all collected samples were slightly contaminated with long-lived gamma emitters; such as 137Cs, 58Co, 6OCo, and 54Mn. Moss is more sensitive to the environmental contamination than grass. Specific activities in moss samples vary with the sampling distance along chosen direction from the INPP. Evaluated specific activity levels of 137Cs in moss samples are not higher than averaged values for Lithuania and vary from 3.65 ± 1.67 Bq/kg DW to 66.76 ± 2.47 Bq/kg DW within the influence zone of INPP. The highest measured specific activity value of 26.02 ± 1.77 Bq/kg DW for 60Co in moss is registered in the immediate vicinity of INPP. The contribution of Ignalina NPP origin 137Cs to the contamination of Ignalina region is not dominant in general, but can vary from 3% to 100% and can be significant for the evaluation of radiation situation. (author)