Radon events in the U-mine environment and related radiation exposure

The term �gradon event�h indicates here a sudden appearance of enhanced radon concentrations, observed like well expressed peaks in time series of radon concentrations. The peaks are superimposed on normal diurnal periodical curves. The characteristics of radon events are high peak values, a rather short duration and a low radon equilibrium factor. Since radon events appear only in the environment near significant radon emission sources, they were investigated in more detail in the case of the former .irovski Vrh uranium mine (Slovenia), using the existing network of continuous radon progeny measuring devices. Eight different types of radon events were identified in the vicinity of the U-mine disposal sites, lasting for some hours and with the range of their peak levels of equilibrium equivalent concentrations (EEC) of radon from a few Bq�Em.3 to over 200 Bq�Em.3. Exposures to radon events in units of Bq�Eh�Em.3 were estimated for adult individuals of the reference group. They resulted in relatively high effective doses of the range 1.5 �ĘSv per a single event, thus exceeding, e.g. the total effective dose for the public due to radioactive discharges from most nuclear facilities during the whole year.