Recently, as the nuclear power plants (NPPs) have been being operated for a long period, the aging of NPPs has progressed. As a result, the integrity and accidents of NPPs have been spotlighted. The NPPs piping is made of carbon steel, and if it is used for a long time, it may cause coolant to leak due to fatigue and corrosion. One of the non-destructive tests (NDTs), an infrared (IR) thermography, is used for non-contacting inspection and it is can measure a board surface unit. In addition, not only the reliability is high but also the testing time is fast, and it has been used in various fields. With the development of the testing techniques and equipment for an IR thermography, the reliability of this test has been improved. Thus, if an IR thermography can be used for leak test of small diameter piping of NPPs, it will contribute greatly to the improving integrity of NPPs. This study suggests an approach to simulate the leak phenomena of NPP piping through the leak test from the small diameter piping of a circulation system. The leak identification facility increases the internal fluid temperature using the heating device and the fluid circulates through the pump. The piping leak test using the IR camera can accurately detect the leak position of the piping during normal operation. In addition, this test facility will be used to identify the leak phenomena for preventing severe accidents caused by a small piping leak.