Tritium permeation through materials for steam generator systems

Mixed isotope techniques and experimental apparatus have been developed for determining the rates of tritium permeation through metals at high temperatures. An inert gas or a controlled steam oxidizing atmosphere on the downstream side of the sample is used so that effects of surface oxidation and the formation of oxide coatings to impede tritium permeation can be determined. The validity of the method was demonstrated by determining the tritium permeability of nickel and comparing the tritium values to established hydrogen and deuterium permeabilities. The methods were applied in a long-term experiment by measuring tritium permeation through Incoloy 800 at 657$sup 0$C with the downstream side of the sample continuously treated with a 750 torr sweep gas of Ar--H$sub 2$O with the H$sub 2$O partial pressure at 240 torr. Oxidation of the metal to form an oxide coating on the metal was accompanied by a decrease in the tritium permeation by a factor of 160 over a period of 84 days. (auth