Thermal Hydraulic Characteristics of the Steam Generators at the ATLAS Facility

A thermal-hydraulic integral effect test facility, ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), was constructed at the Korea Atomic Energy Research Institute (KAERI) in 2006. It is a 1/2 reduced height and 1/288 volume scaled test facility based on the design features of the APR1400, an evolutionary pressurized water reactor developed by the Korean nuclear industry. Preliminary tests were being carried out in order to characterize the basic thermal hydraulic characteristics such as pressure drop distribution, temperature distribution along the primary loop, and natural circulation characteristics. Since 2007, many tests have been carried out to simulate the APR1400 design bases accidents, e.g. LBLOCA reflood phase, DVI line or cold leg break SBLOCA, and SGTR. For each test, major systems, e.g. reactor coolant system and secondary system, should be on the initial steady state condition. To achieve a steady-state condition, the heat balance between the primary and secondary systems must be maintained. In the reference design of the APR1400 steam generator, an economizer concept is included to increase the thermal efficiency of the steam generator. In addition to the economizer, the ATLAS steam generator adopted two separate pipes for cold-side and hot-side downcomers to simulate the reference steam generator. This paper is focused on the findings of the thermal hydraulic characteristics of the steam generator in the ATLAS facility