NucFilm Discs
TrisKem International is producing and selling NucFilm Discs (originally developed by Dr Heinz Surbeck, NucFilm GmbH) for rapid and simple radionuclide determination in water samples.
You will find technical information in the product sheet and the two application notes (Radium in Water Samples and Uranium in Water Samples).
Heinz Surbeck (Nucfilm GmbH) was further so kind as to provide us with his paper entitled "Half-live controlled radon/thoron emanation from MnO2 thin films reduces interference betweeen 226Ra and 224Ra daughter product alpha peaks".