Tritium confinement is required as the most important safety function for a fusion reactor. In order to demonstrate the confinement performance experimentally, an unique equipment, called CATS: Caisson Assembly for Tritium Safety study, was installed in Tritium Process Laboratory of Japan Atomic Energy Agency and operated for about 10 years. Tritium confinement & migration data in CATS have been accumulated and dynamic simulation code was accumulated using these data. Contamination & decontamination behavior on various materials and new safety equipment functions have been investigated under collaborations with a lot of laboratories and universities.