Performance of Enhanced Low Volume Mixing Jets for Salt Dissolution - Development, Deployment, Results, and Benefits to SRS - 22173

The Savannah River Site (SRS) Tank Farms have 51 underground waste tanks (43 of them active) used to store and process liquid waste. There are four different tank types -Type I, Type II, Type III/IIIA, and Type IV - with capacity ranges from approximately 2,840,000-5,03,000 liters (750,000-1,330,000 gallons). Access into the waste tanks is limited by available waste tank openings or risers. Tank 37H is a Type IIIA tank with an approximate capacity of 4,940,000 liters (1,300,000 gallons) and an inner diameter of approximately 25.9 meters (85 feet) located in H-Tank Farm (HTF). Tank 37H was placed into service in 1977. Tank 37H is currently serving as one of two available 242-25H Evaporator concentrate drop tanks (Tank 37H and Tank 30H). The 242-25H Evaporator is primarily used to reduce the volume of H-Canyon wastes and sludge washing decants associated with sludge batch preparation. The 242-25H Evaporator receives waste from the feed tank (Tank 32H) and evaporates water from the waste, thereby producing a concentrated waste stream that is sent to either Tank 37H or Tank 30H. In July 2019, while the 242-25H Evaporator was operating, a routine recycle transfer from Tank 37H to Tank 32H revealed a high level of salt cake in Tank 37H during a camera inspection. This level of salt cake limited operation of the 242-25H Evaporator due to available space in Tank 37H. A salt cake dissolution and removal plan was developed, implemented, and executed to remove sufficient salt cake from Tank 37H to mitigate the available space constraints. SRS has successfully used low volume mixing jets (LVMJs) throughout the Tank Farms and during past Tank 37H salt dissolution campaigns. A LVMJ is a liquid mixing eductor that is designed to entrain surrounding liquid inside the waste tank with the introduction of an external source of water through the discharge nozzle. This allows the addition of dissolution water while simultaneously mixing with the waste tank liquid to promote the dissolution of salt cake. This salt dissolution campaign was the first campaign to deploy enhanced LVMJs (eLVMJs). A traditional LVMJ is designed to operate at a pressure of 6.9 bar (20 psig), a flow rate of 6.3 E-4 cubic meters per second [10 gallons per minute (gpm)] and is predicted to have an effective dissolution radius (EDR) in the waste tank of approximately 3.4 meters (11 feet). The eLVMJ is designed to operate at a pressure of 13.8 bar (140 psig), a flow rate of 1.7 E-3 cubic meters per second (26.5 gpm) and is predicted to have an EDR of 6.4 meters (21 feet). Essentially, the eLVMJs are a more powerful and more efficient version of the LVMJs. The goal of the recent Tank 37H salt cake dissolution and removal campaign was to dissolve salt cake to restore Tank 37H as the primary 242-25H Evaporator concentrate drop tank while producing salt solution for future Salt Waste Processing Facility (SWPF) salt feed batches. To accomplish the salt cake dissolution campaign, the eLVMJs were deployed and utilized in a batch operation mode. Batch operation included water additions with the eLVMJs, followed by transfers out of the tank to remove the salt cake interstitial liquid and the salt solution created during dissolution. Through this process the salt cake level in Tank 37H was lowered to allow restoration of Tank 37H as a concentrate drop tank for an extended period and produced viable salt solution for future SWPF feed. To track the performance of the eLVMJs during the salt dissolution campaign, the following methods were used to collect data: salt cake level soundings, density profiles of the created salt solution, and salt cake topography mapping. The results showed that the eLVMJ EDR increased approximately 3.0 meters (10 feet) compared to an LVMJ [EDR for LVMJ and eLVMJ are 3.4 meters (11 feet) and 6.4 meters (21 feet), respectively]. This greater EDR allows a larger volume of the waste tank to be mixed, increasing the effectiveness for salt dissolution. eLVMJs will continue to be used on Tank 37H and other waste tanks for future salt dissolution campaigns (e.g., Tank 29H). eLVMJs may also be applied to other bulk waste removal projects where other salt dissolution equipment and methods may not be viable. The methods, data collected, and lessons learned from the first deployment of eLVMJs on Tank 37H will be applied to future salt dissolution campaigns to promote successful operations. Overall, the eLVMJs have the potential to reduce the time required to perform salt dissolution while continuing to generate high quality salt solution for processing at SWPF. This paper discusses the development and deployment of eLVMJs for bulk salt dissolution activities, the results and the benefits of using eLVMJs to achieve SRS Liquid Waste mission. (authors)