Fusion Science and Technology / Volume 41 / Number 3P2 / May 2002 / Pages 695-699
Decontamination and Waste / Proceedings of the Sixth International Conference on Tritium Science and Technology Tsukuba, Japan November 12-16, 2001
The waste management is a challenge for any future fusion facility including ITER. Detritiation could allow easier procedures since the practices in different countries already limit tritium contents and releases for disposal in nuclear waste storage. The experience developed in steel-making processes, for liquid steel degassing by gas injection, has been applied for modeling of tritium removal. A numerical model, initially developed at IRSID (USINOR's Process Research Center) for hydrogen removal, is adapted to determine detritiation efficiency. The hydrogen isotope transfer between liquid metal and injected gas occurs in two elementary steps, liquid phase mass transfer and interfacial reaction driven by Sievert's law for H2 and T2. In the gas phase, H2 and T2 react to give HT, according to the thermodynamic equilibrium and the isotopic exchange. The model takes into account the change in bubbles swarms (sizes and velocities) as they ascent from the bottom of the vessel to the metal free surface. It is thus possible to predict the tritium content evolution during the treatment as a function of process parameters. Duration and inlet gas mixture, which have the major influence on detritiation efficiency, must be set according to the tritium initial concentration and the activity expected in the final waste.