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In fiscal year (FY) 1998, Pulsating Mixer Pump (PMP) technology, consisting of a jet mixer powered by a reciprocating air supply, was selected for deployment in one of the Gunite and Associated Tanks (GAAT) at Oak Ridge National Laboratory (ORNL) to mobilize settled solids. This technology was identified during FY 1996 and FY 1997 technical exchanges between the U.S. Department of Energy (DOE) Tanks Focus Area Retrieval and Closure program, the DOE Environmental Management International Programs, and delegates from Russia as a promising technology that could be implemented in the DOE complex. During FY 1997, a prototype PMP provided by the Russian Integrated Mining Chemical Company, was tested at Pacific Northwest National Laboratory (PNNL) to observe its ability to suspend settled solids. Based on the results of this demonstration, ORNL and DOE concluded a modified PMP would meet project needs for remote sludge mobilization of Gunite tank sludge and reduce the cost of operating and maintaining more complex robotic retrieval systems. The functions and requirements of the system were developed by combining the results and recommendations from the demonstration at PNNL with the requirements identified by staff at ORNL involved with the remediation of the Gunite and Associated Tanks. The PMP is comprised of a pump chamber, check valve, working gas supply pipe, discharge manifold, and four jet nozzles. The pump uses two distinct cycles, fill and discharge, to perform its mixing action. During the fill cycle, vacuum is applied to the pump chamber by an eductor, drawing liquid into the pump. When the liquid level inside the chamber reaches a certain level, the chamber is pressurized with compressed air to discharge the liquid through the jet nozzles and back into the tank to mobilize sludge and settled solids. A check-valve located at the pump chamber inlet controls the direction of flow. Operating frequency and other parameters can be adjusted, depending on the liquid being mixed. The entire system is controlled and monitored by a laptop computer. Pulsating Mixer Pump technology was deployed in Tank TH-4 at ORNL to mobilize settled solids during January 2001. The deployment reduced the costs of operation and maintenance of more expensive mixing and robotic retrieval systems. The Effective Cleaning Radius (ECR) of the system was 2.6 m (8.5 ft), resulting in retrieval of approximately 82% of the sludge originally in the tank. The tank cleaning results are consistent with the operations seen during cold testing of the PMP system, and fall well within the risk range established by the Environmental Protection Agency (EPA) based on modeling. Current plans are for the tank to be grouted in place as part of the Federal Facility Agreement (FFA) Remaining Tanks activities. Additional deployments of the PMP at other DOE sites are being evaluated. For example, the PMP may be adapted for use in the 200 Series single-shell tanks at Hanford, which are similar in size and shape to Tank TH-4. This report will describe the PMP system ...

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The evaluation of technologies to enhance the dislodging and retrieval of radioactive waste stored in underground storage tanks that are confirmed or suspected to leak is a strategic initiative under direction of the