MISTRAL: A CO~PRE~NS~E HOTEL FOR T~TIUM INSERT IN LITHIUM-BASE CERAMICS Part I: Theory and description of model capabilities *

MISTRAL is a theoretical model developed to describe tritimn transport and release in fine-grained ceramic materials for tritium breeding a~piications in fusion blankets. The model includes as relevant physical processes tritium diffusion in the effective bulk (grams and gram boundary), adsorption, r~ombina~on and desorption at the breeder surface and diffusion thong the network of pores. A key improvement of the model, compared with those already in the literature, consists of a better characterization of the processes at the breeder surface and their linking to the bulk and pore regions. The sets of governing transport equations and corresponding boundary conditions are formulated together with the choice of the computational algorithm. A computer code with transient capabilities has been developed based on the model. It aims at describing tritium release for several transient conditions relevant for in-pile tritium recovery experiments and for fusion blankets. To assess the range of app~~bility of the model, several calculations have been performed and the results of the analysis are herein presented and discussed.