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The effectiveness of a mixer is dependent on the size of the tank to be mixed, the characteristics of the waste, and the operating conditions. Waste tanks throughout the U.S. Department of Energy Complex require mixing and mobilization systems capable of (1) breaking up and suspending materials that are difficult to mix and pump, without introducing additional liquids into the tank; (2) complementing and augmenting the performance of other remotely operated and/or robotic waste retrieval systems; and (3) operating in tanks with various quantities of waste. The Oak Ridge Russian pulsating mixer pump (PMP) system was designed with the flexibility to permit deployment in a variety of cylindrical tanks. The PMP was installed at the Tanks Technology Cold Test Facility at the Oak Ridge National Laboratory (ORNL) to assess the performance of the system over an extended range of operating conditions, including supply pressures up to 175 psig. Previously conducted cold tests proved the applicability of the PMP for deployment in ORNL gunite tank TH-4. The previous testing and hot demonstrations had been limited to operating at air supply pressures of &lt;100 psig. The extended cold testing of the Russian PMP system showed that the system was capable of mobilizing waste simulants in tanks in excess of 20-ft diam. The waste simulant used in these tests was medium-grain quartz sand. The system was successfully installed, checked out, and operated for 406 pulse discharge cycles. Only minor problems (i.e., a sticking air distributor valve and a few system lockups) were noted. Some improvements to the design of the air distributor valve may be needed to improve reliability. The air supply requirements of the PMP during the discharge cycle necessitated the operation of the system in single pulse discharge cycles to allow time for the air supply reservoir to recharge to the required pressure. During the test program, the system was operated with sand depths of 2, 4, and 4.5 in.; at operating pressures from 100 to 175 psig; and elevations of 1 to 10 in. off the floor of the mock tank. The higher operating pressures resulted in larger values for the effective cleaning radius (ECR). The maximum observed ECR value, 144 in., occurred with the PMP elevated {approx}4 in. off the floor of the mock tank; a 2-in. layer of sand as the waste simulant, and 175-psig air supply pressure. Tests were conducted both within the confines of the 20-ft diam mock tank (confined) and with a portion of the tank wall removed (unconfined). The mixing mode during the confined tests changed from direct to indirect as the PMP was elevated above 4 in. off the floor of the mock tank. The direct mode of mixing pushes solids toward the wall of the waste tank, while the indirect mode tends to push solids toward the center of the tank. The mixing mode did not change during tests conducted in the unconfined tank. Changing the mode of mixing from direct to indirect should have a beneficial effect on the amount of solids mobilized and retrieved from a waste tank

Extended Cold Testing of a Russian Pulsating Mixer Pump at the Oak Ridge National Laboratory, Oak Ridge, Tennessee