METHODOLOGY FOR USING DOSAGE PRICES IN EXPRESS ASSESSMENT AND MODELLING OF EFFECTIVE DOSES FROM GASEOUS AEROSOL EMISSIONS OF RADIONUCLIDES

Abstract

The article is devoted to highlighting the developed methodology for using dose prices in radioecological modelling of situations. Using the results of radioecological studies, the authors applied a method based on determining normalised effective dose indicators, which will allow for the rapid determination of the effective dose of human exposure to manmade sources of ionising radiation, primarily associated with gas-aerosol emissions from nuclear power plants. To determine the normalised effective doses from gas-aerosol emissions, indicators were established that served as the basic radiation characteristics of these sources. The concept of the ‘dose price’ of an ionising radiation source was used – an indicator that reflects the annual effective dose of radiation from a radionuclide, reduced to a unit of source impact. When a mixture of radionuclides entered the environment, a base (reference) radionuclide BR (or several) was established, which had greater weight in the total dose and in the volume of gas-aerosol emissions, and the effective dose price was determined. This methodology was applied to the presented chamber model of radionuclide transport, which was released into the environment with gas-aerosol emissions from the South Ukraine NPP. It has been shown that the annual effective dose of human exposure to radionuclides from gas-aerosol emissions from nuclear power plants is the sum of the annual effective doses: the effective dose of external exposure of humans from the emission cloud and from radionuclides that have fallen to the ground, and the effective dose of internal exposure of humans through inhalation of radionuclides. The methodology was tested based on the fact established earlier by the authors that the main contribution (63 %) to the radiation exposure of humans from the inhalation of a mixture of radionuclides from gas-aerosol emissions was made by 131I. Therefore, 131I was chosen as the reference radionuclide. The basic radiation characteristic is taken to be the power of radionuclide emission. Calculations performed using this methodology for the territory at a distance of 2.5 km from the NPP showed that the effective dose rate from the gas-aerosol emission of the radionuclide mixture ranged from 0.01 to 1.05 μSv/year per 1 Bq/s of 131I emission. An important condition for forecasting using dosimetric models is their reliability. The paper applies the methodology of statistical experiment and Monte Carlo stochastic modelling to assess the reliability of the methodology. The results showed that some factors are significant in the model. This is due to the fact that, in addition to 131I, 60Co and 137Cs also make a significant contribution to the inhalation dose from gas-aerosol emissions of radionuclides. Stochastic forecasting of the effective dose from gas-aerosol emissions of nuclear power plants using defined dose values confirmed the reliability of the presented model in the operational forecasting of the dose load on the population from gas-aerosol emissions of nuclear power plants.