Radon in a tourist cave: a one year continuous survey of the concentrations of attached and unattached radon progeny and radon

Radon, radon progeny and unattached radon progeny were measured in two chambers with differentcharacteristics at the Jenolan Caves, New South Wales, Australia, in 1996. Meteorological parametersand condensation nucleus concentrations were measured in order to understand the processesgoverning the radon concentration and degree of disequilibrium with the progeny. One chamber waspoorly ventilated, and rainfall proved to be the most important influence on radon concentration. Theother was well ventilated, and most subject to strong convective flows driven by surface temperature.Under some conditions atmospheric pressure was an important factor.The radiation exposure was evaluated both from the radon using a constant conversion factor, and bythe more rigorous method of using both the attached and unattached progeny as input to theRespiratory Tract Model recommended in ICRP-66. The size dependent conversion factors weredetermined for each chamber during a four day period in which activity-size distributions weremeasured using a wire screen diffusion battery. The size-weighted dose conversion factors were onaverage 1.7 times the conversion convention factor recommended in ICRP-65.