Surface analytical investigation of the tritium getter ZrCO after exposure to various gases

Abstract

ZrCo is a hydride forming material frequently investigated and proposed for storage and handling of hydrogen isotopes. It is of special interest for deuterium and tritium storage needed for the operation of a nuclear fusion reactor. An interaction of ZrCo powder with contaminant gases particularly during the thermal release of the hydrogen isotopes from the hydride at temperatures above 300 °C was found to cause a reduction of the reactivity of the powder. Consequently, a serious decrease of the hydrogen storage capacity occurs. From surface analytical investigations of ZrCo after exposure to the contaminant gases CO, CO₂, O₂, N₂, CH₄, and C₂H₄ it was concluded that CH₄, C₂H₄, O₂, or N₂ react predominantly with Zr, the principal hydride forming alloy component, to carbide, nitride, and/or oxide. The resulting decrease of the storage capacity is possibly due to either a reduction in the amount of unreacted Zr available for the formation of Zr hydrides or to a formation of a thick protective overlayer. CO or CO₂, which react mainly with the Co component but with Zr in surface near layers only, cause a less pronounced decrease in storage capacity.