Abstract
This study aims to improve knowledge about the radiation effect on geopolymer behavior in terms of dihydrogen release and general strength in order to consider them as an alternative to usual nuclear waste cementitious coating matrices. Using various characterization techniques (nitrogen adsorption, low temperature DSC, FTIR and 1H NMR spectroscopy) and by means of simulation irradiations (gamma, heavy ions), it has been shown that all the water present in the geopolymer could be radiolyzed and that there was a confinement effect on the water radiolysis under low LET irradiation, probably due to efficient energy transfers from the solid matrix to the interstitial solution. Three dihydrogen production rates have been identified with the absorbed dose, depending on the concentration of dissolved dioxygen and the dihydrogen accumulation in the geopolymer matrix. The good mechanical strength of the geopolymer has been shown up to 9 MGy under gamma irradiation and is due to its high stability under irradiation. This could be explained by the fast recombination of the defects observed by EPR spectroscopy. However, phase crystallization was revealed during irradiation with heavy ions, which may induce some weakening of the geopolymer network under alpha irradiation. The overall results helped to understand the phenomenology in a waste package under storage conditions.