Transfer of Tritium from Air to Water - 22085

Tritiated water with high activity concentration of tritium has been found in a drainage way that discharges underground rainwater from a facility in a nuclear power plant in Korea. Transfer of tritium in the air to water, as the possible cause of occurrence of the tritiated water, has been investigated at equilibrium conditions and non-equilibrium conditions. Under the equilibrium conditions, air with an activity concentration of 3,000 Bq/m³ (i.e. the release limit of tritium in air with tritiated water vapor in Korea) equilibrates at 20 deg. C with water with an activity concentration of 1.92x10⁸ Bq/m³. Also, at the same temperature, air with an activity concentration of 300,000 Bq/m³ (the derived concentration of tritium in air with tritiated water vapor in Korea) equilibrates with water with an activity concentration of 1.92x10¹⁰ Bq/m³. Under non-equilibrium conditions, the activity concentration of tritium in water increases with time and, when the water volume is constant, as the interfacial area increases (as the water level becomes lower), the activity concentration of tritium in water also increases. Under air with an activity concentration of tritium of 300,000 Bq/m³, the activity concentration of tritium in water reaches to 4x10⁷ Bq/m³ within several hours to one day when the water level is less than 1 m. From the results, we have confirmed that water with initially no tritium or little tritium could be changed to tritiated water with a high activity concentration by the transfer of tritium in the air to water, which mainly depends on the activity concentration of tritium in the air. This implies that the tritiated water found in a drainage way in the nuclear power plant could be produced from water with initially no tritium or little tritium if the activity concentration of tritium in air was high enough. (authors)