An integral effect test and its code simulation on the complete loss of reactor coolant system flowrate for the SMART100 design

• Successful testing on a complete loss of reactor coolant system flowrate (CLOF) scenario using SMART-ITL for the SMART100. • Understanding the long-term behavior of the passive residual heat removal system (PRHRS) of the SMART100. • Analyses on the CLOF test results from the SMART-ITL using the MARS-KS code to assess its simulation capability. • Precise prediction of long-term thermal–hydraulic behaviors in RCS and passive safety systems of the SMART100. • Dependency of the thermal–hydraulic phenomena on flow resistance and heat losses both in RCS and PRHRS loops. A complete loss of reactor coolant system flowrate (CLOF) scenario was successfully tested using the integral effect test facility of SMART-ITL. The steady-state conditions were well achieved to satisfy initial test conditions presented in the test requirement; its boundary conditions were accurately simulated, and the CLOF scenario was reproduced properly for the SMART100 design. The CLOF test was performed over a long period of 60,000 s to understand the long-term behavior of the passive residual heat removal system (PRHRS) of the SMART100 design. The test results from the SMART-ITL were analyzed using the MARS-KS code to assess its capability to simulate a CLOF scenario for the SMART100 design. As the passive safety systems will operate for no less than 72 h to fulfill their function, the precise prediction of thermal–hydraulic behaviors in reactor coolant system (RCS) and passive safety systems of the SMART100 in the long-term sense is very crucial for the safety analyses of the SMART100 design. The measured thermal–hydraulic data from the CLOF test using the SMART-ITL were properly simulated using the MARS-KS code, which showed its reasonable simulation capability for the CLOF scenario of the SMART100 design with PRHRS. The thermal–hydraulic phenomena depend more on flow resistance both in RCS and PRHRS loops and heat losses from the RCS, steam generator, PRHRS loop and emergency cooldown tank during the long-term simulation. It is considered that accurate simulation is possible with proper consideration on flow resistance in the loops and heat loss through the heat structure.