ABSTRACT
One of the new challenges in radiation chemistry is to understand the radiolysis of water under the various and often extreme environmental conditions associated with nuclear technology. The radiation chemistry of liquid water and aqueous solutions has been thoroughly examined and some of the basic aspects have been summarized in recent reviews (Buxton, 2004; Garrett et al., 2005). Energy deposition by ionizing radiation is sufŸcient to populate a variety of ionic and excited states leading to the formation of radicals that decay by a range of chemical reactions over a large timescale. Initial water decomposition occurs on the ultrafast timescale making water radiolysis studies very difŸcult and many details have yet to be resolved (Garrett et al., 2005; De Waele et al., 2009). The radiolytic decomposition of water adsorbed on solid surfaces can be even more demanding than bulk water because of the heterogeneity of the system. One of the fundamental questions in heterogeneous water radiolysis is whether the radiation-induced decomposition of water is different for molecules adsorbed on surfaces or in a near-surface layer as compared to the bulk liquid. The presence of a solid interface can lead to catalytic, steric, or other effects that alter the water decomposition. There is also the heterogeneous nature of the energy deposition since energy can transfer between the solid phase and the water to enhance or hinder the water decomposition, modify product yields, and even alter the solid surface. Migration of energy can lead to problems in determining the “effective” dosimetry, which is equivalent to the quantity of energy available for radiation effects in the adsorbed water. The transport of charge, excited states, even atoms or molecules to or through the water-solid interface can lead to signiŸcant chemical consequences beyond that observed in bulk water alone.
