ABSTRACT
Air is pumped at a sampling rate of approximately 100 cm3/min through 2 traps each containing about 200 g of desiccant that collects moisture from the air. The air is then mixed with enough additional hydrogen to sustain catalytic oxidation, and proceeds into a catalytic converter that oxidizes free hydrogen and tritium. The resulting water (H2O + HTO) is then collected in a desiccant trap (6). This method describes the use of a palladium sponge catalyst, and silica gel as the desiccant; however, other catalysts and desiccants are available. (See Method 609A for discussion of alternative desiccant and reference for alternate catalysts.) The stated flow rate is sufficient to allow continuous air sampling for one week at 50% relative humidity. The collected moisture is then removed from the traps and analyzed for tritium by mixing a suitable volume of the moisture with a scintillation solution and counting the mixture in a liquid scintillation beta counter. The air sampling rate, and total volume of moisture collected during the sampling period, must be determined to convert the concentration of tritium in the collected moisture samples to its concentration of air.
