Gettering of tritium gas and tritiated water vapor by Zr-alloys

Tritium processing such as supply, recovery, storage, and separation are of special importance for blanket technology as well as fuel cycling in fusion reactors. To obtain guiding principles to design suitable getters for each of the unit processes, we have studied the effects of alloying on the getter properties using Zr-alloys. The activation energy for absorption varied considerably with alloying: it was 0.74 for Zr-Al, 0.01 for Zr-V-Fe, and 0.63 kcal/mol for Zr-Ni, whereas that for Zr has been reported as 19.2 kcal/mol. The heat of absorption also changed with alloying element as 32.0 - 33.4 (Zr-Al), 27.8 - 28.8 (Zr-V-Fe), and 29.0 kcal/mol (Zr-Ni). That of hydrogen in Zr is reported as 15.6 - 30.6 kcal/mol. In addition, the ratio of the pumping speed of water vapor to that of hydrogen varied with alloying elements: for example, 1/40 for Zr-V-Fe and 1/4 for Zr-Ni at room temperature. The alloying effects mentioned above are considered due to modification of electronic structure of Zr with the alloying. (author)