Investigation of the Flow of the Upper Plenum of a Scaled Very High Temperature Reactor during a Depressurized Cooldown Conduction Accident

Abstract

Very High Temperature Reactors (VHTRs) are the future of nuclear reactors. A 1/16th scaled upper plenum of a VHTR was designed and assembled at Texas A&M University (TAMU) in order to study the behavior of flow in the upper plenum of a VHTR. Flow was investigated under one major accident scenario, the Depressurized Conduction Cooldown (DCC); this occurs due to loss of force when operation is interrupted by loss of power. In this case, the fluid will have a natural convection, forcing it to flow to the upper plenum. Particle Tracking Velocimetry (PTV) was used to illustrate flow, using water as the working fluid. A PTV code was used to track the particles, and this was then averaged over all vectors after filtering out those that failed. All flow velocity compounds, such as the velocity magnitude, y-velocity, x-velocity, standard deviation, and flow streamlines were visualized. A sensitivity analysis was performed in order to confirm that the number of frames used was sufficient to reach a steady state. In addition, repeatability analysis was applied to the output data. Turbulent intensity, Reynolds stress, and error occurring with these tests were all estimated. Finally, experimental data was validated using benchmark data.