Investigation of CMT behavior between the ATLAS and SMART-ITL tests

Abstract Overall thermal hydraulic behavior in CMTs was reviewed by comparing a station blackout (SBO) test using hybrid safety injection tanks (HSITs) in ATLAS (Advanced Thermal-Hydraulic Test Loop for Accident Simulation) with a small-break loss-of-coolant accident (SBLOCA) test in SMART-ITL (System-Integrated Modular Advanced ReacTor – Integral Effect test Loop). In ATLAS’ SBO test using HSITs, pseudo differential pressure (DP) values appeared in some pressure balance lines (PBLs) due to the appearance of void in the PBLs, and the injection flowrates from the HSITs tended to increase after the intrusion of voids into the corresponding PBL. Quite a large amount of emergency core cooling water (ECCW) inventory remained in the closed HSITs in the SBO test. In SMART-ITL’s small break loss-of-coolant accident (SBLOCA) test, there was a short reverse flow in the pressure balance line (PBL) lines of the core makeup tanks (CMTs) just after the break, and sufficient injection flowrates of the CMTs were achieved after the partial clearing/blocking of the PBL. In the case of a SIT actuation signal, some duration time was required for the hydraulic equilibrium conditions among the CMTs, SITs, and reactor vessel (RV).