An extended radon chamber model

The radon chamber model developed at the Paul Scherrer Institut (PSI) is covering differences in size between the different short-lived radon daughters by taking into account nuclide specific deposition and attachment rates. The resulting set of differential equations was analytically solved and the solutions were installed into a computer code. Different modes of operation of a radon chamber (continuous flow, pulse, and feedback) were analysed with the model. The influence of aerosol sampling on the chamber atmosphere was studied. Increasing the diffusion constant of the radon daughter clusters increases both attachment and deposition rates. As a consequence, the unattached concentration of the radon daughter with the shortest half-life, Po-218, is reduced relative to the radon progeny Pb-214 and Bi-214/Po-214, compared with calculations with equal mobilities of the radon progeny. The amount of Po-218 activity deposited on the chamber walls also is increased relative to the other radon progeny if the size of Po-218 is considered to be smaller. Copyright 1996 Elsevier Science Ltd.