Modeling and analysis of time-dependent tritium transport in lithium oxide

Abstract

Tritium behavior in the solid breeder blanket is one of the key factors in determining tritium self-sufficiency, as well as safety, of fusion reactors. Therefore, it is important to understand the tritium transport mechanisms and processes, in order to accurately determine the tritium release and inventory in the blanket. A model has been developed at UCLA to describe the tritium behavior in solid breeder materials, together with a computer code which can predict the tritium release and inventory. However, the model was limited in some cases: for example, it did not include the capability to account for surface to bulk fluxes and for trapping inside the grain which can have major effects on the tritium transport. The model capabilities have been extended to enable its application over a wide range of experimental conditions. Improvements include: (1) implementing an initial model to account for the general effect of trapping in the bulk, (2) addition of a dissolution flux which would enable a more accurate modeling of solubility driven by hydrogen partial pressure in the solid breeder porosity, (3) inclusion of more hydrogen isotopes species in the pore, and, (4) modification of the existing computer code to allow for broader application, such as the possibility of accounting for both first order and second order adsorption/desorption. The code was used to analyze experimental data on tritium behavior in Li 2O from the BEATRIX-II experiment.