.Sixteen 1/25-scale sludge mobilization experiments were conducted in fiscal year (FY) 1993. The results of this testing are presented in this document. The ability of a single, centrally-located, scale model mixer pump to resuspend a layer of simulated tank sludge was evaluated for five different simulant types. The resistance of these simulants to the mobilizing action of the mixer pump jets was not found to adequately correlate with simulant vane shear strength. The data indicate that the simulant cohesion, as quantified by tensile strength, may provide a good measure of mobilization resistance.A single test was done to evaluate whether indexed mixer pump rotation is significantly more effective than the planned continuous oscillation. No significant difference was found in the sludge mobilization caused by these two modes of operation.Two tests were conducted using a clay-based sludge simulant that contained approximately 5 wt% soluble solids. The distance to which the mixer pump jets were effective for this simulant was approximately 50% greater than on similar simulants that did not contain soluble solids. The implication is that sludge dissolution el€& may significantly enhance the performance of mixer pumps in some tanks. The development of a means to correlate the magnitude of this effect with waste properties is a direction for future work.

.Sixteen 1/25-scale sludge mobilization experiments were conducted in fiscal year (FY) 1993. The results of this testing are presented in this document. The ability of a single, centrally-located, scale model mixer pump to resuspend a layer of simulated tank sludge was evaluated for five different simulant types. The resistance of these simulants to the mobilizing action of the mixer pump jets was not found to adequately correlate with simulant vane shear strength. The data indicate that the simulant cohesion, as quantified by tensile strength, may provide a good measure of mobilization resistance.A single test was done to evaluate whether indexed mixer pump rotation is significantly more effective than the planned continuous oscillation. No significant difference was found in the sludge mobilization caused by these two modes of operation.Two tests were conducted using a clay-based sludge simulant that contained approximately 5 wt% soluble solids. The distance to which the mixer pump jets were effective for this simulant was approximately 50% greater than on similar simulants that did not contain soluble solids. The implication is that sludge dissolution el€& may significantly enhance the performance of mixer pumps in some tanks. The development of a means to correlate the magnitude of this effect with waste properties is a direction for future work.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility far the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the IJnited States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Summary ? This document describes work conducted during fiscal year 1996 to evaluate the potential application of pulsed-air mixers to the slurry-mixing needs of the U.S. Department of Energy's wasteretrieval programs. Pulsed-air mixers offer considerable cost and operational advantages compared to the baseline slurry-mixing approach (i.e., jet mixer pumps), so the deployment of pulsed-air mixers should be pursued where it can be shown that the mixing performance will be adequate. This work was funded through the EM-50 Tanks Focus Area as part of the Retrieval Process Development and Enhancements (RPD&E) project at the Pacific Northwest National Laboratory (PNNL). The mission of RPD&E is to understand retrieval processes, including emerging and existing processes, gather performance data on those processes, and relate the data to specific tank problems such that end users have requisite technical bases to make retrieval and closure decisions. Pulsed-air mixing uses large air bubbles introduced near the tank floor to induce slurry mixing. The bubbles are produced by horizontal, circular plates positioned just above the tank floor. Pipes deliver gas to the center of each plate from specially designed gas-pulsing valves, which are , commercially available. Pulsed-air mixing differs from conventional air sparging in that single, large bubbles are introduced into the tank fluid periodically (e.g., once every 15 seconds) instead of small bubbles injected on a. continuous basis. The rapid growth of the pulsed-air bubbles near the tank floor and their subsequent rise through the fluid serve to both suspend solids from the tank floor and maintain those solids in a uniform suspension. Measurements of the fluid velocities produced by pulsed-air mixers near the tank floor were made using a hot-film anemometer. The observed peak velocities were correlated with gas pressure, plate diameter, gas-line diameter, and the distance between the plate and the tank floor. These data allow the design of pulsed-air mixing systems using...

In order to further the goal of optimizing Hanford's HLW borosilicate flowsheet, a glass-formulation effort was launched to develop an advanced high-capacity waste form exhibiting acceptable leach and crystal-formation characteristics. A simulated C-106/AY-102 waste envelope inclusive of LAW pretreatment products was chosen as the subject of these nonradioactive optimization efforts. To evaluate this optimized borosilicate waste formulation under continuous dynamic vitrification conditions, a research-scale Joule-heated ceramic melter was used to demonstrate the advanced waste form's flowsheet. The main objectives of this melter test was to evaluate 1) the processing characteristics of the newly formulated C-106/AY-102 surrogate melter-feed stream, 2) the effectiveness of sucrose as a glassoxidation-state modifier, and 3) the impact of this reductant upon processing rates. v Summary In Response to a U.S. Department of Energy (DOE) Headquarters directive to conduct a technical review of alternatives for solidification of high-level waste (HLW) that could achieve major cost reductions with reasonable long-term risks, (a) the Tanks Focus Area (TFA) chartered an independent Review Team to evaluate cost incentives associated with modifications to: waste-form product requirements, waste-stream processing constraints, product glass composition, and the reference wastevitrification technology itself.

Plans are underway at the Hanford Site near Richland, Washington, to convert the low-level fraction of radioactive liquid wastes to a grout form for permanent disposal. Grout is a mixture of liquid waste and grout formers, including portland cement, fly ash, and clays. In the plan, the grout slurry is pumped to subsurface concrete vaults on the Hanford Site, where the grout will solidify into large monoliths, thereby immobilizing the waste. A similar disposal concept is being planned at the Savannah River Laboratory site. The underground disposal of grout was conducted at Oak Ridge National Laboratory between 1966 and 1984 (Dole 1985). Design and construction of grout processing and disposal facilities are underway. The Transportable Grout Facility (TGF), operated by Rockwell Hanford Operations (Rockwell) for the Department of Energy (DOE), is scheduled to yrout Phosphate/Sulfate N Reactor Operations Waste (PSW) in FY 1988. Phosphate/ Sulfate Waste is a blend of two low-level waste streams yenerated at Hanford's N Reactor. (The N Reactor produces special nuclear materials, and its byproduct steam is used to generate electricity.) Other wastes are scheduled to be grouted in subsequent years. Pacific Northwest Laboratory (PNL) is verifying that Hanford grouts can be safely and efficiently processed. To meet this objective, pilot-scale grout process equipment was installed. The pilot-scale process equipment can produce grout at a rate of up to 25% of the maximum rate planned for the TGF. On July 29 and 30, 1986, PNL conducted a pilot-scale grout production test for Rockwell. During the test, 16,000 gallons of simulated nonradioactive PSW were mixed with grout formers to produce 22,000 gallons of PSW grout. The grout was pumped at a nominal rate of 15 gpm (""'2~% of the nominal production rate planned for the TGF) to a lined and covered trench with a capacity of 30,000 gallons. Emplacement of grout in the trench will permit subsequent evaluation of homogeneity of grout in a large monolith. The production of a i i i 22,000-yal monolith in a trench also permitted determination of curing characteristics, reabsorption of separated liquid, degree of cracking, and temperature rise expected with monolithic disposal. The principal process components-the grout mixer and the grout pump-are very similar to those planned for the Transportable Grout Facility Equipment (TGE). The pilot-scale test permitted evaluation of the performance of the mixer and pump, their flush requirements, and their reliability. In addition, representatives of the engineering firm commissioned to design and construct the processing equipment modules of the TGF observed the test to gain experience with processing grout. The test was very successful; major conclusions follow: • The continuous grout mixer and grout pump performed reliably, producing grout with acceptable properties. • The adiabatic grout temperature rise was at least 37°C, and probably higher. • The flow angle of grout in the trench averaged 1.5°. A similar flow angle can be expected in th...