International audienceWe irradiated samples of zeolites 4A which contained different quantities of water. We measured the quantity of hydrogen released. Hydrogen radiolytic yields, present two maxima, for two water loading ratios. Hydrogen release is enhanced by the strength of the zeolite/water interaction. Hydrogen release is enhanced by the quantity of water interacting with the zeolite. a b s t r a c t Although the radiolysis of bulk water is well known, some questions remain in the case of adsorbed or confined water, especially in the case of zeolites 4A, which are used to store tritiated water. An en-hancement of the production of hydrogen is described in the literature for higher porous structures, but the phenomenon stays unexplained. We have studied the radiolysis of zeolites 4A containing different quantities of water under 137 Cs gamma radiation. We focused on the influence of the water loading ratio. The enhancement of hydrogen production compared with bulk water radiolysis has been attributed to the energy transfer from the zeolite to the water, and to the influence of the water structure organization in the zeolite. Both were observed separately, with a maximum efficiency for energy transfer at a loading ratio of about 13%, and a maximum impact of structuration of water at a loading ratio of about 4%

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Radiolysis of confined water and self-radiolysis of tritiated water gives rise to several unanswered questions. To take into account this double specificity, we studied systems of zeolites 4A containing tritiated water at different water loading ratios. Two tritiated water were synthesized at the volumetric activities of 27 TBq.L-1 and 60 TBq.L-1. For each one, five samples were prepared, differentiated by their water loading ratios, expressed in percentage, close to 4, 7, 11, 14 and 19 %. The study of the radiolysis in those systems revealed a double role of zeolites 4A: first, they increase the decomposition of water. Then they enhance the recombination of the major stable radiolytic products detected. We actually evidenced a total recombination between H 2 and O 2 which is catalyzed by the zeolites.