Measurement of liquid scintillation sources of 210Pb obtained from 222Rn decay

Liquid scintillation samples were filled with 222Rn and the activity was measured with good precision after reaching the secular equilibrium with the progeny 218Po, 214Pb, 214Bi and 214Po. After decay of most of 222Rn activity, the samples contain 210Pb and progeny. The activities of 210Pb and progeny can be calculated as a function of time using the initial 222Rn activity. The samples were measured in a TDCR counter and the experimentally determined counting efficiencies are in accordance with previously published results.