DEMONSTRATION OF MIXING AND TRANSFERRING SETTLING COHESIVE SLURRY SIMULANTS IN THE AY-102 TANK
In support of Hanford's waste certification and delivery of tank waste to the Waste Treatment and Immobilization Plant (WTP), Savannah River National Laboratory (SRNL) was tasked by the Washington River Protection Solutions (WRPS) to evaluate the effectiveness of mixing and transferring tank waste in a Double Shell Tank (DST) to the WTP Receipt Tank. The work discussed in this report (Phase III) address the impacts cohesive simulants have on mixing and batch transfer performance. The objective of the demonstrations performed in Phase III was to determine the impact that cohesive particle interactions in the simulants have on tank mixing using 1/22{sup nd} scale mixing system and batch transfer of seed particles. This testing is intended to provide supporting evidence to the assumption that Hanford Small Scale Mixing Demonstration (SSMD) testing in water is conservative. The batch transfers were made by pumping the simulants from the Mixing Demonstration Tank (MDT) to six Receipt Tanks (RTs), and the consistency in the amount of seed particles in each batch was compared. Tests were conducted with non-Newtonian cohesive simulants with Bingham yield stress ranging from 0.3 Pa to 7 Pa. Kaolin clay and 100 {mu}m stainless steel seed particles were used for all the non-Newtonian simulants. To specifically determine the role of the yield stress on mixing and batch transfer, tests were conducted with a Newtonian mixture of glycerol and water with at viscosity of 6.2 cP that was selected to match the Bingham consistency (high shear rate viscosity) of the higher yield stress kaolin slurries. The water/glycerol mixtures used the same 100 {mu}m stainless steel seed particles. For the transfer demonstrations in Phase III, the mixer jet pumps were operated either at 10.0 gpm (28 ft/s nozzle velocity, U{sub o}D=0.63 ft{sup 2}/s) or 8.0 gpm (22.4 ft/s nozzle velocity, U{sub o}D=0.504 ft{sup 2}/s). All batch transfers from the MDT to the RTs were made at 0.58 gpm (MDT suction velocity 3.95 ft/s). The demonstrations that used simulants that ranged from 1.6 Pa to 7 Pa yield stress had the most successful batch transfer of solids to the RTs in terms of the total quantity of seed particles transferred. Testing suggest that when mixing water/seed particles and transferring, water provides the least desired batch transfer of solids based on the total quantity transferred. For the water tests, large dead zones of solids formed in the MDT and fewer solids get transferred to the RTs. For simulants with a yield stress of 0.3 Pa and below, the batch transfer behavior in terms of total transfer of seed particles was slightly higher than water test results. The testing did show somewhat more batch-to-batch variation in the transfer of seed particles with the slurries in comparison to water. A comparison of batch transfers with the kaolin slurries that had Bingham consistencies (viscosities) that wernearly the same as the Newtonian glycerol/water mixtures showed that the kaolin slurries with Bingham yield stresses of 1.6 and 7 Pa gave better batch transfer of seed particles based on the total quantities transferred. Overall, the batch transfer testing results show that testing with water is conservative, since using a simulant with a yield stress and/or elevated viscosity always resulted in a better total transfer of solids.