Performance of various hydrophobic coatings to reduce HTO contamination

Iwai, Yasunori; Kobayashi, Kazuhiro; Yamanishi, Toshihiko

The concept of tritium containment and confinement is the root of fusion safety. Hence, HTO contamination on concretes and epoxy paint should be reduced as low as possible. Several kinds of hydrophobic coatings, a commercial silicic paint, a commercial acrylic paint, a commercial fluoric paint, methoxytrimethylsilane paint or metallic stick-sheets, were tested on concrete and epoxy samples. These samples were exposed to 740-1110Bq/cm of HTO vapor at room temperature for a given period from 1 to 60 weeks. Static leaching tests were carried out for every HTO absorbed sample in distilled water, and the amount of leached HTO was evaluated. The hydrophobic barriers were effective to reduce HTO penetration into concrete. After exposure to HTO for 1 week, the HTO amount penetrated into concrete was reduced to 54.2% of non-paint sample for methoxytrimethylsilane paint, 56.0% for a commercial fluoric paint, 66.8% for a commercial silicic paint, respectively. Effectiveness of these hydrophobic barriers became less as the samples were exposed to HTO for a longer period.