SRNL-STI-2019-00394 Revision 0 vi volume, purge rate, and power input, this data cannot be directly applied to the DWPF, but it is important to note that hydrogen is released over a finite time, rather than instantaneously. Previous work by SRNL and PNNL has measured the rheology of Hanford sludge, and shown the rheology (i.e., yield stress or shear strength) to increase as the sludge is allowed to settle. Changes in sludge rheology need to be considered when assessing changes to the DWPF retained hydrogen program. A comparison of buoyancy and inertial forces under SRAT operating conditions (1-10 Pa yield stress, 1.38 g/mL density, 65 or 130 rpm, 9,000 gallons of feed) on the bubbles (approximated as 300 micron diameter) found the inertial forces to be more than 350,000 times larger than the buoyancy forces. With this ratio of forces, the gas bubbles generated will follow the fluid motion in the SRAT, and only release when they reach the slurry-vapor interface. An informal Lattice Boltzmann Computation Fluid Dynamics calculation was performed on a SRAT type vessel. The liquid was assumed to have a density of 1 g/mL and a viscosity of 20 cP. In the simulation, approximately 50% of the bubbles were released to the vapor space over ~80 seconds. The simulation showed the bubbles to follow the liquid flow, and only release when they reached the liquid surface.