Characterization of a carbon radon filter and Radon detection

Abstract

Carbon filled columns were built and tested as prototype radon filters. The length of time taken for a pulse of radon to travel from one end of the filter to the other was measured using nitrogen, and then air as the carrier gas. Its dependency on two variables were investigated: temperature of the tube and the flow-rate of carrier gas through the column. Using Height Equivalent to a Theoretical Stage (HETS) the carbon was found to have a adsorption constant (ka) of 9.7 ± 1.7 L/g at STP, and a binding energy value (Eb) of (30±1) kJ/mol. The radon concentration in the carrier gas was measured using a silicon detector housed in a metal chamber with a charged collector plate. Most filter tests measured Rn concentrations by measuring levels of the daughter atom 218Po. A computer simulation was created for aspects of both the working detector chamber and a prototype detector chamber. The charged fractions of 218Po and 214Po were calculated by comparing the Monte Carlo simulation to data obtained from the detectors. The positively charged fraction of 218Po was found to be (80 ± 9)% and 214Po was (110 ± 180)%.