ATR Flow Blockage Tests and CFD Simulations

Steady state flow channel blockage tests were conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) as part of the safety basis upgrade program for the Advanced Test Reactor (ATR). The tests were sponsored by the U.S. Department of Energy (DOE). This study was aimed at carrying out flow blockage tests, establishing a base case to compare test results with numerical results using a computational fluid dynamics code, calculating temperature profiles for blockage cases, and determining whether or not the ATR core would be exposed to core melting due to blockage of the inlet of a fuel cooling channel. The test section consisted of three parallel channels and two side channels along the side plate. Three cases were selected to evaluate flow blockage events in the channels. A base case with all the channels open, Case 1 where the inlet of the middle channel is blocked, and Case 2 where both the middle channel and the side channel are blocked. Laser Doppler anemometer (LDA) was used to measure velocities in the channel. Velocities were measured at 2.54-mm intervals in the channel width, and every 1.27-mm around side windows in the flow direction for three parallel channels. LDA measured velocity profiles for the base case and Case 1 indicated good agreement with predicted velocity profiles from the CFD model. The channel velocity in the blocked channel is about 70% of the velocity in the unblocked, adjacent channel in between the top and second side channel vents. Additional flow redistribution occurs into the blocked channel at the second side channel vent. Temperature calculations for the base case were made to compare with benchmark temperatures calculated with the ATR SINDA model and CFD calculations underpredicted benchmark plate temperatures by less than 10% while it predicted bulk temperatures very well. The same heat flux and boundary conditions were incorporated for Case 1 and Case 2. The results for both cases indicated that core melt would not occur in the postulated ATR flow channel blockage events simulated for this study. Peak fuel plate temperature is about 20% greater than the peak temperature for the unblocked case just upstream of the second side channel vent.