A study of surface pretreatment of tritium-getter alloy for enhancement of insensitiveness to impurities

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Some zirconium-alloy getters are expected to be used for tritium separation, purification and storage in a fuel cycle of a nuclear fusion reactor. We have been investigated particle beds of Zr, ZrCo, ZrNi and ZrィイD22ィエD2Fe which can recover the tritium concentration in gas streams lower than the maximum permissible level for the radioisotope in Japan. However, once tritium-getters contact with any of the gaseous impurities such as OィイD22ィエD2, HィイD22ィエD2O and CO, they lose most of their hydrogen capacities. Based on our previous experimental studies on mass-transfer processes in alloy beds, new surface pretreatment techniques in order to enhance insensitiveness to impurities were tested with their keeping the high absorption capacity. The three surface pretreatment techniques are (1) alkali pretreatment, (2) pd depositing (3) Cu depositing. In 1998 we comparatively investigated the surface pretreatment to the ZrィイD22ィエD2Fe getter, and its hydrogenating rate after the alkali pretreatment was enhanced about ten times faster than that of the non-treated getter. It was found that pretreated ZrィイD22ィエD2Fe particles under the room temperature can absorb tritium less than the detection limit. In 1999, methane and tritium water vapor cracking by a Zr(MnィイD20.5ィエD2FeィイD20.5ィエD2)ィイD22ィエD2 bed was experimentally investigated. Methane at higher than 650ィイD1゜ィエD1C and water vapor at 350ィイD1゜ィエD1C were successfully cracked by the Zr(MnィイD20.5ィエD2FeィイD20.5ィエD2)ィイD22ィエD2 bed. Results obtained in the present study have been presented at the international symposium of the fusion nuclear technology and that of the hydrogen energy and have been also reported to international journals.