TIARA analysis of tritium inventory in Li2O

The TIARA code has been developed to predict tritium inventory in Li2O breeder ceramic and to predict purge exit flow rate and composition under steady-state operating conditions. Inventory predictions are based on models for bulk diffusion, surface desorption, solubility and precipitation. Parameters for these models are determined from the results of laboratory annealing studies on unirradiated and irradiated Li2O and from a limited number (2) of inventory data measured after in-reactor purge flow testing. The remaining inventory data points (18) are used for code validation. In the validation exercise, models and model parameters are fixed prior to running the validation cases to assess how well TIARA predictions agree with data. On average, the TIARA predictions are in excellent agreement with the inventory data from the following in-reactor tests: EXOTIC-2, SIBELIUS, VOM-15H, CRITIC-1, BEATRIX-II (Phase 1) thin ring, and BEATRIX-II (Phase 1) thick pellet. Thus, TIARA can be used with a reasonable degree of confidence for design analysis over a broad range of fabrication variables and steady-state operating conditions.