Abstract
In our previous study, significant improvements of surface wettability and boiling heat transfer on oxide film coated-materials by Radiation Induced Surface Activation (RISA) phenomenon were confirmed in a room temperature condition. To delineate the RISA effect in actual boiling systems or at high temperatures and pressures, this study aimed at obtaining contact angle, an indicator of macroscopic surface wettability, of water droplet on aluminum, zircaloy and stainless plates before and after γ-ray irradiation at ambient temperatures up to 280 ℃. The contact angle was measured by an image-processing of the images obtained by a CCD video camera. In condition less than 200 ℃, super-hydrophilicity or null contact angle was achieved after 830 kGy γ-ray irradiation. On the other hand, at over 200 ℃, super-hydrophilicity by the RISA effect was not achieved even after 2800 kGy γ-ray irradiation, although slight improvement of surface wettability was confirmed.
