Behavior of Tritiated Water on Concrete Materials

Abstract

A fusion reactor requires high levels of safety and public acceptability, so safeconfinement of tritium is one of the key issues. Tritium must be well controlled with no excessive release to environment and no excessive workers exposure. Especially, the hot cell and tritium facility of ITER will use various construction materials such as the concrete and the organic materials. Since the concrete materials will be contaminated by tritium compared with the metal materials such as SS, it is very important to study the tritium behavior on the materials from the viewpoint of the excessive exposure protection to workers. Therefore, in order to understand the tritium behavior on the concrete materials, the sorption and desorption experiment was carried out as a function of the exposure time and temperature of water in the desorption experiment. The used samples were cement paste, mortar and concrete. These samples were exposed into 740 ˜ 1110 Bq/cm³ of tritiated water vapor at room temperature. The exposed time was from a day to several weeks. The exposed samples for a certain period were soaked into water at 277 K, 298 K and 343 K, and then the water was periodically measured by Liquid Scintillation Counter (LSC) and the amount of tritium sorbed on the concrete materials were evaluated. The amount of the tritium sorbed in the concrete materials reached equilibrium less than 2 months. In the desorption behavior from concrete materials to water at 277K, 298K and 343K, the tritium sorbed in the concrete materials was desorbed about 99 % for 2 days at 343 K of water. However, the tritium desorption from concrete materials was sufficiently detected though 3 months passed. In addition, the tritium profile on the surface concrete materials was measured by a tritium imaging plate.