Long-term monitoring airborne 131I in the surface layer in Obninsk city, Kaluga region

Monitoring airborne 131I in Obninsk city was widely discussed some time after the Chernobyl accident, however, the latest data were not reported. The article presents data on volume activity of airborne 131I in the surface layer collected at the meteorological site RPA “Typhoon” in Obninsk City and its surroundings from 1989 to 2013. Main radiation dangerous facilities in Obninsk and the radiation monitoring network in the city of Obninsk and its neighborhoods, as well as characteristics of air-filtering device for registration of radioactive iodine are described. Correlation coefficient (0.9) between the annual release of radionuclides from the Branch of the “Karpov Institute of Physical Chemistry” and registered average volume activity of 131I in the city of Obninsk was calculated. Meteorological conditions on days of registration of increased level of 131I volume activity were analyzed, and the ratio of molecular and aerosol fractions of 131I (the number of cases of detected 131I m/ 131I a varied from 1.5 to 16.5 with a mean of 2.6) was evaluated. Radiation risk from inhalation of 131I (2.3·10 -9 with the dose coefficient used in the NRB-99/2009) as a conservative estimate was calculated. Its value10 -6 was 3 orders lower than the negligible risk for the population.