Radiation-Induced Surface Activation is an inherent phenomenon where surfaces that are exposed
to gamma irradiation are observed to undergo an increase in wettability. This increase in
wettability as a result of the ionizing radiation exposure has so far been demonstrated to have a
pronounced impact on Leidenfrost temperature and two-phase fluid dynamics. Test results from
previous experiments have shown that incorporation of this effect on heat transfer equipment
design may increase the thermal-hydraulic margin leading to higher thermal efficiency. However,
the mechanism behind the increased wettability is not clearly understood. In the present work,
three different materials (Zircaloy-4, 316 stainless steel, and copper) were exposed at two different
dose rates with use of two different gamma irradiation facilities. A detailed surface
characterization on the post-irradiated samples is carried out to understand the changes in surface
chemistry, wettability and surface morphology. It is observed from the experiments that the
increase in wettability upon irradiation depended on the total dose and not on the dose rate.
Moreover, localized oxidation and porosity induced by radiolysis was seen to be the predominant
mechanism behind increased wettability which leads to improved Leidenfrost temperature.