Permeation Analysis of Tritium through the Titanium Hydride Storage Vessel

A preliminary design of a stainless steel vessel for the long-term storage of hydrogen isotopes has been proposed. The immobilized hydrogen as a titanium hydride could be used in a stainless steel vessel for this application. The vessel as a primary package is designed to form titanium hydride and to contain the hydrogen isotopes and helium-3 produced from the tritium decay. In order to predict against the possibility of a contamination and the deterioration of the mechanical properties, a numerical calculation was carried out for a diffusion analysis of the hydrogen isotopes and helium inside the stainless steel vessel. Numerical results showed that a negligible amount of tritium would be released by a permeation through the vessel wall of a 0.7cm thickness at normal conditions over the entire period of the storage. In the case that the vessel was heated up to a temperature of 600°C for the routine condition of an activation or exothermic hydriding, it would be of little concern regarding a tritium loss or a contamination. However, when the vessel was exposed to a fire condition with a temperature of 800°C, permeation of the hydrogen through the vessel wall resulted in a serious increase in the amount of tritium escaping, in a very short time.