Contamination of Aquatic Plants with Long-lived Radionuclides in the Vicinity of Ignalina Nuclear Power Plant

Radioactive pollutants from operating nuclear power plant enter the environment through atmospheric and aquatic releases. Assuming that aquatic plants are affected by both of pollutant streams, they can be used as bio indicators for the investigation of contamination of aquatic media with radionuclides and for the assessment of effective doses to critical groups of population caused by this contamination. Results of investigation of aquatic plants collected in the vicinity of Ignalina Nuclear Power Plant (INPP) during the period of 2001-2004 are presented in this paper. It is shown that measured activity values in aquatic plants varied from 2,5±0,17 Bq/kg DW (dry weight) to 14,13±0,9 Bq/kg DW for 137Cs, from 0,46±1,6 Bq/kg DW to 7,5±2,06 Bq/kg DW for 60Co, from 0,87±0,79 to 3,74±2,22 Bq/kg DW for 54Mn, and from 131,1±1,7 pmC to 154,7±2,2 pmC for 14C, indicating the decreasing during the years tendency for the contamination of ecosystem of Lake Druksiai with long - lived radionuclides. No significant difference in the accumulated values of radioactivity in algae and in annual aquatic plants was found. Estimated amount of 137Cs activity of 'Ignalina' origin varied in the range from 5% to 91%, but was close to the mean value of 40% for 14C. Calculated effective doses to the critical group of population (adult fishermen) were small but not negligible: 0,14 μSv for 137Cs, 0,11 μSv for 60Co, and 0,31 μSv for 14C. Complex investigation of INPP environment was not performed since 2001, however the increase of contamination level around INPP is most probable after the closure of the Unit 1. Due to this reason the results of present investigation may significantly contribute to the solution of problems dealing with monitoring of radiation risk in the area of interest. (author)