Adsorption and desorption of tritium on material for secondary electron multiplier.

Abstract

As a first step toward solving the problem of contamination by tritium affecting secondary electron multipliers, the material used in a marketed multiplier was studied in respect of adsorption and desorption behavior, with application of thermal desorption spectroscopy. It was found that the tritium adsorbed on the material was desorbed in large part in the form of tritiated water, generated by chemical reaction that combined adsorbed tritium with excess oxygen present on the material and in small part in the form of tritiated hydrocarbons produced by exchange reactions taking place between the tritium and hydrocarbons also found adsorbed on the material surface. It was further indicated that tritium desorption took place from two distinct kinds of adsorption/desorption sites. Effective removal from the material was obtained of the adsorbed tritium by heating in inert gas flow at 500°C for 6 h. If a longer heating time can be allowed, a lower heating temperature should be suffice for decontamination.