Sampling tritiated water vapor from the atmosphere by an active system using silica gel

Among the different methods used to collect the tritiated water vapor (HTO) contained in the atmosphere, one of the most worldwide used is its collection using an air pump, which forces the air to pass through a dry silica gel trap. The silica gel is then distilled to remove the water collected, which is measured in a liquid scintillation counting system.In this paper, an analysis of the water collection efficiency of the silica gel has been done as a function of the temperatures involved, the dimensions of the pipe driving the air into the silica gel traps, the air volume passing through the trap and the flow rates used.Among the obtained conclusions, it can be pointed out that placing the traps inside a cooled container, the amount of silica gel needed to collect all the water contained in the air passing through these traps can be estimated using a weather forecast and a psychometric chart. To do this, and as thermal equilibrium between incoming and open air should be established, a suitable design of the sampling system is proposed.

► To recollect the atmosphere air tritiated water vapor, an active system was used.
► The system is an air pump and three traps with silica gel connected by a rubber pipe.
► The silica gel retention depends on the meteorological conditions and the flow rate.
► The amount of water collected and the mass of silica gel need were calculated, F.