Effect of cobalt hydroxo-sulphide on organic material radiolysis

In the context of nuclear waste management, the release of hydrogen can generate safety problems. It has been shown that amorphous cobalt hydroxo-sulphide is able to decrease the apparent production of radiolytic hydrogen yield by hydrocarbon radiolysis. This paper presents a study of the effect of cobalt hydroxo-sulfide on the radiolysis of propane induced by a proton beam. Hydrogen and hydrocarbon partial pressures obtained after propane irradiation were compared in different conditions: (i) without cobalt hydroxo-sulphide, (ii) in the presence of solid, irradiated or not, by adjusting the gas pressure in the irradiation cell. The evolution of those partial pressures as a function of the time of contact between the amorphous cobalt hydroxo-sulphide and the formed gaseous species is discussed. The solid is characterised by X-ray diffraction, infra-red and Raman spectroscopies before and after hydrogen trapping. It is shown that the solid does not change the composition and amount of organic radiolytic products but acts as a trap of hydrogen. The hydrogen consumption by the solid seems to be proportional to the initial hydrogen partial pressure. This study shows that radiolytic hydrogen is rapidly produced by propane irradiation whereas the trapping of hydrogen by cobalt hydroxo-sulphide is a slower phenomenon.