Flow Visualization of Forced and Natural Convection in Internal Cavities [report]

John C Crepeau, Randy Clarksean, Donald M McEligot, Yann G Guezennec
1999 unpublished
RESEARCH OBJECTIVE The general goal of this program is to develop innovative flow visualization methods and reliable predictive techniques for the energy, mass, and momentum transfer in the presence of surface reactions for the passivation treatment operations of SNF elements. RESEARCH PROGRESS AND IMPLICATIONS This report summarizes the work accomplished after about two and a half years of a three-year collaborative project. The University of Idaho developed a flow visualization technique to
more » ... mulate a passivation reaction between oxygen gas and uranium hydride found on corroded, wet-stored SNF elements. An apparatus was constructed whereby a mixture of hexanoic acid and mineral oil flowed down a long channel. The hexanoic acid and mineral oil represented the oxygen and helium, respectively in the passivating gas. In the channel we placed a thin, flat aluminum plate with a small cavity filled with sodium metal. The sodium represented an exposed, corroded area on an SNF element. As the solution flowed over the plate, the acid in the solution reacted with the sodium, releasing hydrogen bubbles into the flow. Based on observations of the generic SNF canister, our experiments were performed along a flat plate, at a Reynolds number of around 350. Figure 1 shows a typical flow pattern as viewed from the side. The fluid moves from left to right, and one observes the bubbles floating up and being convected downstream. The rising bubbles stretch and thin the dye filaments, and compress the streamlines toward the air-fluid interface. As the flow progresses downstream, nonlinear interactions between the bubbles and the dye cause further mixing. It is clear from the photograph and subsequent observations that the chemical reaction along the solid surface and subsequent release of the hydrogen bubbles convect the fluid away from the reaction, and introduce velocity fluctuations into an otherwise laminar flow. The bubble entrainment enhances mixing, and may serve to break flow symmetries and uneven flow distribution that have been observed in previous experiment s. These flow symmetries, which may be circumferentially periodic, prevent a complete and thorough mixing throughout the canister, and decrease the likelihood that all of the possible corroded areas will be properly treated.
doi:10.2172/828591 fatcat:rpbox5tigze3tj2pa736xgataa