Assessment of the environmental contamination with long-lived radionuclides around an operating RBMK reactor station.

The presence of man-made gamma emitting radionuclides in the region within 32km radius of the Ignalina NPP/Lithuania has been investigated during the period 2001-2004, prior to the closure of the first of the two operating RBMK 1500-type reactors. Gamma spectrometric measurements of various terrestrial and aquatic plants as well as of soil samples showed moderate environmental contamination with the fission product (137)Cs and with the neutron activation products (60)Co and (54)Mn. Traces of the activation products (65)Zn and (110m)Ag were found in the nearest vicinity of the NPP. Activity concentrations were inhomogeneously distributed in the area of interest. Moss and algae samples showed the highest uptake of radionuclides. In addition to the gamma spectrometric measurements, the levels of (14)C were determined in the same bio-indicator samples using accelerator mass spectrometry.