Counter permeation of deuterium and hydrogen through Inconel 600

Permeation of hydrogen isotopes through a high-temperature alloy used for heat exchanger and reformer tubes is an important problem in the hydrogen production system connected to the High-Temperature Engineering Test Reactor (HTTR). An objective of this study is to investigate an effect of existence of hydrogen (H-2) in a tube outside on the amount of permeated deuterium (D-2) through the tube. It was found that the amount of permeated D-2 decrease with increasing the partial pressure of H-2 in the tube outside when the partial pressure of D-2 in the tube is lower than 100 Pa and that of H-2 in the tube outside is larger than 10 kPa. The amount of permeated D-2 on counter permeation process was predicted quantitatively by using the effectiveness factor for diffusivity of deuterium in Inconel 600 and by taking into account of the equilibrium state for the hydrogen isotopes including HD molecules on the surface. From the results obtained in this study, it is supposed that the amount of tritium permeated from the primary circuit of the HTTR to the utilization system will be reduced by the existence of high pressure H-2 in the steam reformer tube in the HTTR hydrogen production system.