A large-scale sodium thermal-hydraulic test program has been underway at KAERI (Korea Atomic Energy Research Institute), which is called STELLA (Sodium Test Loop for Safety Simulation and Assessment). At the second phase of this program, the design of the sodium integral effect test facility, named as STELLA-2, has been completed and its construction is currently in progress. STELLA-2 is a kind of scaled-down test facility, which is aimed not only at a generic evaluation of thermal-hydraulic transients but also demonstration of the decay heat removal performance interacting with the primary heat transport system in the pool-type PGSFR design. To simulate the transient scenarios identified as design basis events in PGSFR, the STELLA-2 test section has been designed by complying with the scaling method suggested by Ishii and Kataoka (1983). Most of the design features of the fluid and heat transport systems in PGSFR are incorporated into STELLA-2 as closely as possible, and its scale ratios were set to be 1/5 in length (height) and 1/125 in volume. Specific design parameters for whole subsystems and components were obtained with their scaling distortions.

For the purpose of a design validation of STELLA-2, scoping analyses using the MARS-LMR code have been conducted for the representative design basis events with the same assumptions and approaches implemented in PGSFR. It was observed that both the temperature and flow trends during the target event of LOF condition show good agreements with those of the PGSFR. Steady-state CFD analyses for the primary sodium pool region of STELLA-2 at the normal operation condition was also carried out to figure out the similarities between the scaled-down model and the prototype. Some technical issues concerning the essential scaling characteristics imposed on any scaled-down test facilities are discussed as well.