The code TIRP has been used to calculate the time dependence of tritium inventory and tritium permeation into the coolant and into the first wall boxes in the water cooled Pb-17Li blanket concept of DEMO.
The calculations have been performed for the martensitic steel MANET and the austenitic steel AISI 316L as blanket structure materials, for water or helium cooling and for convective or no motion of the liquid breeder in the blanket.
Tritium inventories are rather low in blankets with MANET structure and higher in those with AISI 316L structure. Tritium permeation rates are too high in both blankets.
Further calculations on tritium inventory and permeation are therefore presented for blankets with TiC permeation barriers of 1 /~m thickness on various surfaces of the blanket structure and for blankets with any permeation barriers in function of their thicknesses, tritium diffusivities, tritium surface recombination rates and atomic densities. These last calculations have been performed for a blanket with coatings on the outer surfaces of the blanket and with a tritium residence time of 104 s and for a blanket with coatings on both sides of the cooling tubes and stagnant Pb-17Li in the blanket.
The second case for a blanket with MANET structure presents a very interesting solution for tritium recovery by permeation into and pumping from the first wall boxes.