AbstractThis paper reports on the design, modelling and development of a computer code for a blanket and its thermal-hydraulic and tritium mass transport capability and performance. The model includes all the heat and mass transfer processes that occur in the blanket and allows examination of the thermal behaviour with time and under varying thermal load, including the prediction of tritium mass transfer, release, diffusion and recovery behaviour, and corresponding rates in the blanket. The model is used to perform scoping and technology assessment studies for power plant relevant parameters. The model and code also have the capability of analysis of accident scenarios of candidate blanket concepts and testing of the neutronic performance of various material configurations.