Aerosol sampling methods for wide area environmental sampling (WAES). Finnish support to IAEA

Enrichment of uranium or reprocessing of nuclear fuel are expected to produce releases of non-natural radionuclides, that are carried away in air attached in airborne particles. Wide Area Environmental Sampling (WAES)-method utilises air samplers distributed in the monitored area to detect the possible releases. For reduction of expenses, the samplers located in remote areas should be able to operate long periods of time unattended. In this work, a high-volume (flow rate 150 m3/h) air sampler with an automatic filter changing system, Hunter MKII, was developed for WAES. The sampler can collect six one-week samples until it needs to be visited for unloading the used filters and loading the new ones. The device sends real-time state-of-health information to headquarters so that longtime loss of sampling can be avoided in case of malfunction. The state-of-health data also includes indication to prevent inconspicuous tampering of the unattended sampling process. Organic filter materials are used to collect particles due to their applicability to radiochemical analysis. Four filter materials were tested for collection efficiency and pressure drop. The material selected for current use (Petrianov FPP-15-1.5 used as two-layers one upon the other) can collect more than 90% of the 0.2 μm particles throughout the sampling period. If there is a large concentration of coarse particles in air (as is typically the case in desert conditions), the filter clogging rate can be significantly decreased by preceding it with a low-pressure-drop pre-filter that collects the coarse particles. The filter pressure drop is low enough to easily allow one-week sampling time in typical sampling conditions (a pre-filter may be needed in heavily dust laden desert air). (orig.)