MODELING OF RADON PROGENY DECAY IN RAINFALLS BASED ON GAMMA RAY MEASUREMENTS IN THE BRAZILIAN SECTOR

A method of a simulation of radiation fallout concomitant atmospheric liquid precipitations is proposed. The fallout is reconstructed from observed gammas through a numerical solution of the first kind Volterra integral equation describing variation of nuclide amount produced by precipitating 214Pb and 214Bi. Application of the method is considered on the examples of rainfalls in Brazil. There was an observed short fallout enhancement in the initial phases of the rains. It was demonstrated that nuclide quantity per unit of precipitated water decreases with increasing rainfall rate. The results obtained is compared with other observations and model