The objective of this study is to validate the buoyancy-driven countercurrent flow model in Kairos Power’s system code, KP-SAM, using experimental data from the Aura separate effects test (SET) facility. KP-SAM, which uses Argonne National Laboratory’s SAM as a basis, is a high-order fully implicit transient system code written in C++ for the safety analysis of the Kairos Power fluoride salt–cooled high-temperature reactor (KP-FHR) design. The Aura SET facility was designed to investigate buoyancy-driven exchange flow between two tanks vertically connected by a single junction, and to study the impact of changing the ratio of the junction length and diameter (L/D) on the exchange flow. The emphasis is on validating that the empirical correlation used in KP-SAM, which calculates a flow rate based on the L/D ratio and the densiometric Froude number (Fr), is both predictive and bounding with regard to accident analysis.

An experimental study consisting of 30 trials, varying the length and diameter of the connecting junction, as well as the initial density ratio between the two tanks, was conducted. The results indicate that while there was reasonable agreement between the experiment and correlation, the correlation tended to overpredict the flow rate and Fr. Each trial was then simulated in KP-SAM, and it was established that the simulation results were bounding.