Tritium transfers and main operating parameters impact for demo lithium lead breeding blanket (HCLL)

In an industrial fusion reactor, the daily tritium production is of several hundreds of grams. Because of the double function of the blankets: breeding the necessary tritium and efficiently extracting the deposited heat, the metallic surfaces used to promote the heat transfer lead also to a non-negligible mass transfer of hydrogen isotopes. In order to improve the management of tritium, different studies have been launched in this field with applications to DEMO breeding blankets and to corresponding ITER TBM (test blanket module). A general model has been developed to evaluate the potential tritium released by permeation through hot walls up to the secondary circuit with the objective to define the possible ways to reduce the tritium release. For hot walls, Fick laws are written for hydrogen and tritium. A sensitivity study is done to determine which the major issues are and where the major reduction can be obtained for minimizing the final tritium release. It leads to determination of the key point where improvement could have a strong impact on the reduction of the tritium release. At present, permeation barrier are considered, but the chemistry control of helium coolant could have a stronger impact. This paper also presents what are the required further improvements of such modelling. (c) 2008 Elsevier B.V. All rights reserved.