Integrated in-vessel Debris Blockage Testing for Pressure-Tube Reactors

Abstract

To investigate pressure-tube reactor in-vessel flow blockage during a simulated Loss-Of-Coolant Accident (LOCA) long-term core cooling operation, numerical simulations were performed for a pressure-tube reactor to understand its post-LOCA ECC flow in each fuel channel and the driving force between inlet header and outlet header. In addition, experiments were performed using a prototypical pressure tube with two dummy fuel bundles installed downstream of a reduced-scale strainer test rig. An end-fitting with a liner tube was connected to the pressure tube to simulate the actual fuel channel in a pressure-tube reactor. Particulate and fibrous debris simulating post-LOCA conditions were added to the strainer test rig. In addition, chemical reactants were also added to the test rig to simulate post-LOCA sump chemistry and to investigate the head loss effects of possible chemical precipitates. A total of five tests were performed, which included two thin bed tests, one full debris load tests and two chemical effects tests with full debris load. Bypassed debris from the strainer surface was observed to enter the fuel channel and accumulate inside the liner tube and on the fuel bundle endplates. Pressure drop due to the debris and chemical precipitates blockage across the fuel channel were measured and compared with the available driving force to determine whether sufficient flow would enter the pressure tube to remove decay heat. Preliminary testing results showed that the pressure tube head losses were not significant for the test conditions considered.