To establish a decontamination method for stainless steel type-316 (SS-316) contaminated by tritium, desorption behavior of tritium caused by heating was examined. When tritium was exposed to a temperature at 523 K for 3 hours, tritium inventories in the SS-316 samples were in the range of 2 to 12 MBq. The tritium depth profiles obtained from BIXS measurements showed that tritium diffused to a depth of more than 70μm. Decontamination test on tritium were carried out at elevated temperatures by purging with commercial argon, argon dried by a getter and argon containing water vapor. The presence of water vapor in the argon atmosphere was found to necessary for tritium decontamination from SS-316 samples. The result suggested that an isotope exchange reaction with water vapor adsorbed on the surface plays an important role in the decontamination of tritium. It was concluded that not only tritium adsorbed on the surface but also that dissolved in the bulk can be removed by heating
