Tank 50H Mixing Pump Run Time Reassessment

Abstract

Tank 50H is required to operate a single rotating standard slurry pump for 4.5 hours prior to transfers to the Salt Solution Receipt Tanks (SSRTs) in the Saltstone Production Facility (SPF). This mixing time is required to adequately mix miscible and immiscible liquids within Tank 50H and meet the Saltstone Waste Acceptance Criteria (WAC). The miscible liquids are aqueous solutions of dissolved salts, while the immiscible liquids include organic droplets such as Isopar® L. To support the accelerated salt processing rates from the Salt Waste Processing Facility (SWPF), a desire to reduce the transfer time of Decontaminated Salt Solution (DSS) downstream of SWPF was identified. This document describes the analysis performed to reassess the technical basis for the 4.5 hour mixing requirement for Tank 50H. The analysis employed the following approaches to assess the required mixing time in Tank 50H. Assessing the impact of the required blending efficiency on the liquid blend time. Reassessing the conservatism within the previous Savannah River National Laboratory (SRNL) blend time calculation (SRNL-STI-2011-00362, Rev 0). Utilizing the Salt Disposition and Integration Project (SDIP) data to estimate the required mixing time. Determining if transfers into Tank 50H provide adequate mixing of the material. Assessing the blending occurring in the suction of the transfer pump. Assessing the impact of differences between the pilot-scale miscible liquid blending tests and Tank 50H, shows that the 4X factor used in SRNL-STI-2011-00362 is overly conservative, and that the required blend time in Tank 50H can be reduced. At the current minimum liquid level in Tank 50H (76 inches), the calculated blend time is 60 minutes. The blend time would be longer at higher liquid levels in the tank. The analysis showed that reducing the required blending efficiency from 95% to 80% could reduce the required blending time to as low as 30 minutes (at a liquid level of 76 inches), provided the contents of Tank 50H are still acceptable for Saltstone. An alternative to using the slurry pump to mix the tank contents is to use the "plunging jet" created by the added liquid and blending that occurs as fluid is drawn into the transfer pump suction. Adding liquid to Tank 50H through the downcomer in riser C1 creates a "plunging jet" that will blend the added material with the current contents of Tank 50H. The dilution factor could be as much as 250X. If the plunging jet is used to provide mixing in Tank 50H, the mixer pump should be indexed toward the downcomer through which the material is added to the tank to prevent accumulation of added material under the downcomer. As the liquid in Tank 50H enters the transfer pump suction to be transferred to Saltstone, the recently added material will blend with the other contents of Tank 50H, and the dilution factor could be as much as 600X. These two effects are multiplicative and can be combined. Mixing during the transfer into Tank 50H, combined with the mixing that occurs at the pump suction during the tr...

Tank 49H Solids Disturbance Analysis

“…Figure 24 shows the results. The shape of the "plunging jet" is consistent with Equations [1] - [5] and the technical literature. 6,7,8 While the finer lattice spacing increases the time to perform these simulations, the results show better agreement with the technical literature.…”

“…A "plunging jet" with a 100-inch depth would have a width of ~19 inches. While the images in Figure 3 and following figures are consistent with equation [5], a downward velocity is observed away from the "plunging jet" and the center of the vessel. One cause of this phenomenon could be numerical transport.…”

“…After the jet enters the liquid, it will expand at an angle of ~22º. Equation [5] describes the diameter of the jet as a function of depth…”

“…Equation [5] describes the width of the "plunging jet". A "plunging jet" with a 100-inch depth would have a width of ~19 inches.…”

“… The location, elevation from the tank bottom, and range of flow rates of the transfer pump from Tank 49H to SWPF  The location, vertical distance from the tank bottom, and internal diameter of the downcomer pipe used to add liquid to the tank  The range of flow rates for the additions to the tank  The minimum and maximum fill levels of the tank  The thickness of the insoluble solids layer on the tank bottom Previous SRNL analyses showed that when liquid is added to a waste tank, a "plunging jet" can form when the liquid enters the tank. 4,5 This "plunging jet" entrains surrounding fluid, which is mixed with the fluid added to the tank. The "plunging jet" could have sufficient momentum to disturb the solids layer on the bottom of the tank.…”