Keywords: radioactivity release, photon fluence, external irradiation, cloudshine doses, data assimilation, nuclear accidents, air quality, air pollution, atmospheric dispersion modelling, nuclear energy, nuclear power, nuclear safety, radioactive plume, radioactive clouds, radiation dose rates
Calculations of external irradiation from radioactive plume in the early stage of a nuclear accident
A mathematical method for real–time calculations of cloudshine doses/dose rates used for purposes of online assimilation of model predictions with observations incoming from terrain is proposed. Model predictions of cloudshine doses have to be calculated simultaneously in an array of positions located on terrain around a nuclear facility. A modification of the classical straight–line Gaussian solution of the near–field dispersion problem is proposed. Movement of radioactive cloud driven by changes in meteorological conditions is described according to the segmented Gaussian scheme. Advanced 5/µ concept based on integration up to five times mean free path of a γ photon ensures a quicker assessment of the doses of irradiation and predetermines the proposed procedure to be a proper tool for data assimilation analysis.