Performance of various hydrophobic coatings to reduce HTO contamination

Several kinds of hydrophobic coatings were tested on concrete and epoxy samples. These samples were exposed to 740–1110 Bq/cm3 of HTO vapor at 1 kPa pressure at 288–298 K for 1–60 weeks. Static leaching tests on HTO absorbed samples were conducted in distilled water, and the leaching was evaluated as a function of time. Most coatings on concrete only slowed the HTO sorbed rate. Chemical modification of hydroxyl bonds on the concrete surface by methoxytrimethylsilane in contrast led to the decrease in the amount of HTO sorbed. Most coatings on epoxy led to the decrease in the amount of HTO sorbed. Especially, epoxy with fluoric coating, adhesive sheet of SUS 304 or aluminum brought the largest retardation of tritium sorbing.