Deposition of radionuclides – An investigation of methods for collection of dry and wet deposition

FOI has been commissioned by the Swedish Radiation Safety Authority to investigate whether it is possible to find a technical solution to separate dry and wet deposition of radionuclides, without major reconstructions of the existing Swedish stations for collection of total deposition. This report describes the investigation regarding the method of collection of dry and wet deposition that was carried out. Sampling procedures in some neighboring countries has also been studied. In summary FOI finds that, if a complete separation of dry and wet deposition is a priority, new equipment needs to be acquired or developed since such a system cannot be integrated with existing design of the stations. Change of sampling equipment also introduces a new collection method which might complicate comparison with previous data. Alternatively, the existing collection funnel is retained for collection of total deposition and complemented with a dry deposition surface. A solution for this method needs to be constructed. This option provides continuity of measurement data since the same method as today is used for collection of total deposition. A complete separation of dry and wet deposition is however not obtained. The selection of system hereafter depends on the degree to which the total separation of dry and wet deposition is requested. It also depends on how much the stations can be reconstructed and to what degree continuity of measurement data is demanded. FOI recommends that the system of ion exchange columns for the extraction of deposited radionuclides is retained but the composition of these might need modification.