Studies on the electrical characteristics of thoron (220Rn) progeny

Electrical characteristics of thoron (220Rn) progeny under various low ampere (< 1 mA) DC voltages applied to a calibration facility (CF) has been studied. About 30 y old thorium hydroxide was used as the source for the generation of thoron and its decay products. The study has revealed that under a low ventilation rate (approximately 1 air charge per hour) and at high equilibrium equivalent concentration (EER) of thoron, above 275 Bq m(-3) (> 1 WL), a considerable fraction of 212Pb nuclides are negatively charged. It was also concluded that 212Pb has lesser charge (per ion) than 212Bi and is more susceptible to an electric field. There is a linear relationship between the activity collected and the voltage applied and the activity collected is proportional to the area of the collecting surface. Under the experimental conditions, when a voltage of +/- 2500 V is simultaneously applied, the activity concentration can be reduced by a factor of 100.