Simulation of NACIE Benchmark Tests with the SAS4A/SASSYS-1 Code

Argonne National Laboratory participates in the International Atomic Energy Agency coordinated research project “Benchmark of Transition from Forced to Natural Circulation Experiment with Heavy Liquid Metal Loop (NACIE).” The benchmark project includes three experiments from the NACIE lead–bismuth eutectic loop located at the ENEA Brasimone Research Center in Italy. All benchmark tests are on transition from forced to natural circulation initiated by shutoff of the gas liftoff pump. The main difference among the tests, ADP10, ADP06, and ADP07, is which heater pins are activated (heated) during the tests as a way to approximate partial flow blockage in a fuel assembly. Argonne’s work with the SAS4A/SASSYS-1 code on the coordinated research project includes system-level and sub-channel simulations. Via comparisons against experimental measurements from the NACIE tests, these benchmark simulations are being performed to expand the validation basis of the SAS4A/SASSYS-1 code. The paper presents results of simulation of the NACIE benchmark tests with SAS4A/SASSYS-1 code. The results presented here in generally show good agreement with the available experimental data. However, in some cases, model modifications were needed to obtain that good level of agreement; those model modifications are also presented in the paper, along with the identification of the remaining differences and approaches for how to resolve them in future work.