Stochastic model for the fluctuations of the atmospheric concentration of radionuclides and its application to uncertainty evaluation

We propose a new model of the atmospheric concentration of a radionuclide with the inclusion of fluctuations of the concentration. The model is a stochastic differential equation and we derive the analytic solution of the equation. The solution agrees very well with the Chernobyl Cs-137 data. The advantage of the model is that the uncertainty in radiation exposure risk, with regard to the concentration fluctuations, can be quantitatively estimated. We show the range of fluctuations of ±σ, ±2σ, ±3σ in the 10-year measurement of the atmospheric concentration in Chernobyl and confirmed the validity of the model.