The Disruption of Vessel-Spanning Bubbles with Sloped Fins in Flat-Bottom and 2:1 Elliptical-Bottom Vessels

Abstract

Radioactive sludge was generated in the K-East Basin and K-West Basin fuel storage pools at the Hanford Site while irradiated uranium metal fuel elements from the N Reactor were being stored and packaged. The fuel has been removed from the K Basins, and currently, the sludge resides in the KW Basin in large underwater Engineered Containers. The first phase to the Sludge Treatment Project being led by CH2MHILL Plateau Remediation Company (CHPRC) is to retrieve and load the sludge into sludge transport and storage containers (STSCs) and transport the sludge to T Plant for interim storage. The STSCs will be stored inside T Plant cells that are equipped with secondary containment and leakdetection systems. The sludge is composed of a variety of particulate materials and water, including a fraction of reactive uranium metal particles that are a source of hydrogen gas. If a situation occurs where the reactive uranium metal particles settle out at the bottom of a container, previous studies have shown that a vessel-spanning gas layer above the uranium metal particles can develop and can push the overlying layer of sludge upward. The major concern, in addition to the general concern associated with the retention and release of a flammable gas such as hydrogen, is that if a vessel-spanning bubble (VSB) forms in an STSC, it may drive the overlying sludge material to the vents at the top of the container. Then it may be released from the container into the cell's secondary containment system at T Plant. A previous study demonstrated that sloped walls on vessels, both cylindrical coned-shaped vessels and rectangular vessels with rounded ends, provided an effective approach for disrupting a VSB by creating a release path for gas as a VSB began to rise. Based on the success of sloped-wall vessels, a similar concept is investigated here where a sloped fin is placed inside the vessel to create a release path for gas. A key potential advantage of using a sloped fin compared to a vessel with a sloped wall is that a small fin decreases the volume of a vessel available for sludge storage by a very small fraction compared to a cone-shaped vessel. The purpose of this study is to quantify the capability of sloped fins to disrupt VSBs and to conduct sufficient tests to estimate the performance of fins in full-scale STSCs. Experiments were conducted with a range of fin shapes to determine what slope and width were sufficient to disrupt VSBs. Additional tests were conducted to demonstrate how the fin performance scales with the sludge layer thickness and the sludge strength, density, and vessel diameter based on the gravity yield parameter, which is a dimensionless ratio of the force necessary to yield the sludge to its weight. (a) Further experiments evaluated the difference between vessels with flat and 2:1 elliptical bottoms and a number of different simulants, including the KW container sludge simulant (complete), which was developed to match actual K-Basin sludge. Testing was conducted in 5-in., 10-in., and 23-in.-diameter vessels to...

Rayleigh-Taylor Instability within Sediment Layers Due to Gas Retention: Preliminary Theory and Experiments

“…This study also used two different experimental methods. The experimental results supported the scaling given by the dimensionless gravity yield parameter, and the experimental value for the criterion was the following: = 0.09 (2.5) Epstein and Gauglitz (2010) reported additional results for vessel geometries that were not cylindrical and Gauglitz et al (2010) summarizes studies with additional simulants and a range of layer depths.…”

“…Bulk density of the slurries was calculated (estimated) from the masses (or mass fractions) and densities of individual slurry components, as described, for example, in Gauglitz et al (2010) for kaolin slurries. Consistent with this previous work, a kaolin solid density of 2.65 kg/L (2650 kg/m 3 ) and a room-temperature water density of 0.998 kg/L (998 kg/m 3 ) were used in the calculation of bulk density.…”

“…Along these gas-release pathways, there were locations where water would block the movement of gas and periodically the gas would displace the water blockage and flow.. For the gas-filled channels observed by Gauglitz et al (2012), it is not clear if the model for the maximum channel depth given by Van Kessel and Van Kesteren (2002), which assumes a hydrostatic pressure from water within the channel, should represent the channel behavior. In a separate study, Gauglitz et al (2010) have conducted tests to measure the depth of open gas channels for different simulants, and the measured depth was 12 cm for 55 wt% kaolin. For the bubble retention tests where gas-filled channels were observed, the kaolin concentration was 55 wt%, the shear strength was 680 Pa, and the initial sediment depth was 0.8 m (Gauglitz et al 2012).…”

Simulant Development for Hanford Double-Shell Tank Mixing and Waste Feed Delivery Testing

“…The density of a composite slurry of kaolin and sodium thiosulfate can be estimated by assuming an ideal mixture of the kaolin particles with a salt solution whose composition is given by the water and salt content of the mixture. The bulk density of the slurry is given by the following (Gauglitz et al 2010): ( )…”

“…where ρ k-s = density of the kaolin-sodium thiosulfate slurry X k = the mass fraction of kaolin in the bulk mixture ρ k = kaolin particle density (2.65 g/mL, Gauglitz et al 2010) ρ ss = the density of the sodium thiosulfate solution whose composition is given by the water and salt content of the composite slurry…”