The oxidation kinetics of Incoloy 800 and its deuterium permeation behavior

Tritium permeation through the steam generator of the Helium-Cooled Pebble Bed Blanket (HCPB) concept can be strongly reduced by natural oxides formed on the Incoloy 800 tubes. This paper presents the results of different experiments with various deuterium to humidity ratios (pH2O/pD2 from 300 vppm to 30%). All experiments show that Incoloy 800 readily oxidizes and that permeation reduction factors (PRF) of at least 100 are easily obtained for typical blanket conditions. The measured PRF values are explained in terms of the type and thickness of the oxides on the Incoloy surface. The observed reduction in permeation is very favorable for the design of the HCPB blanket system in order to reduce the amount of hydrogen needed for isotope swamping and hence, reducing the size of the tritium extraction system.