A Review of Radon Equilibrium Factors in Underground Mines, Caves, and Thermal Spas.

Radon equilibrium factor Feq is an important factor in radon progeny dose assessment. A review of published measurements of Feq shows a range of values from 0.1 to 1.0 reported in studies from more than 26 countries measured in 173 underground mines, and 136 show caves, tourist mines, and thermal spas. The average values of Feq are 0.38 in underground mines and 0.39 for show caves, tourist mines, and thermal spas. The wide range of Feq in those special workplaces suggests that location-, environment-, and operation-specific values are more appropriate than a recommended average value in the calculation of lung bronchial dose. This is especially important in mines or other typically high radon exposure locations because Feq can be used for recording an individual's occupational radon exposure or dose.

SEISMIC PREDICTION USING UNATTACHED RADON DECAY PRODUCTS.

Long-term measurements of the 222Rn concentration, 222Rn decay product activity, particle size distribution, and unattached, and attached 222Rn decay products, were made at two locations using the 22 y radon decay product 210Pb as their tracer. The particle size sampler collects both short lived 222Rn decay products that ultimately decay to 210Pb on the filters, and also airborne 210Pb. The measurements were made outdoors, at a suburban home and at Fernald, OH, a former uranium processing facility, on top of one of the two 226Ra storage silos containing 150 TBq 226Ra. The size distributions showed the unattached fractions, i.e. particle diameter 2-4 nm, to be 1.5% at the home and 14% at the silos. The unattached fraction of 218Po can be shown to be an immediate measure of the 222Rn concentration. The data indicates detection of the pressure driven 222Rn flow at the silo and with the enhanced measurement capability of a filtered air source versus the usual 222Rn gas measurement. It is proposed that real time measurements of unattached 218Po may be used to identify rapidly changing 222Rn concentrations associated with pressure driven soil air flow associated with seismic activity.