Development of Rapid Sampling System of Atmospheric Water Vapor for Tritium Measurement

We have developed a rapid sampling system for measuring the tritium in atmospheric water vapor. The system consists of a high-efficiency particulate air filter cartridge, an oil-free compressor, a water-vapor-separating module with hollow fiber membranes, two cold traps, and an oil-free rotary pump. Compressed air (0.4 - 0.7MPa) is introduced into the water-vapor-separation module, which consists of a stainless steel column containing polyimide membrane tubes. Water vapor permeates through the tubes and is collected by cold traps cooled with dry ice and ethanol. The module is heated with a flexible heater to control its temperature. We have determined the recovery yields under various sampling conditions and find that this system can collect atmospheric water vapor with a recovery yield of >99%. This system can thus be a useful tool for understanding short-term observations of tritium in atmospheric water vapor