Preliminary thermal hydraulic test for swirl vane grid

An advanced grid with mixing device is under development to acquire an enough thermal margin for reactor safety and operational flexibility. A 'swirl vane' grid, which has an important candidate of the mixing devices, was tested to examine its basic thermal-hydraulic characteristics. The test were simply conducted using a round tube containing a unit swirl vane grid instead of a prototyical rod bunlde. The bubble behavior test was performed mainly to observe how the bubbles move downstream the swirl vane grid. The vane angle effect on bubble motion is also investigated with three kinds of vane angles. The CHF test was also performed to see the CHF enhancement due to the swirl vane grid relative to a simple grid. Refrigerant R-134a is used as the working fluid to simulate the reactor condition conveniently. This test is aimed to investigate just the relative CHF increase due to the existence or angle of the swirl vane in the grid. For the test results, it can be expected that the swirl vane grid may satisfy a target of 10% thermal margin increase sufficiently compared to the simple grid, when the detail test with rod bundle geometry will be completed