Physical Property Measurements of Laboratory Prepared Saltstone Grout
The Saltstone Production Facility (SPF) built two new Saltstone Disposal Units (SDU), SDU 3 and SDU 5, in 2013. The variable frequency drive (VFD) for the grout transfer hose pump tripped due to high current demand by the motor during the initial radioactive saltstone transfer to SDU 5B on 12/5/2013. This was not observed during clean cap processing on July 5, 2013 to SDU 3A, which is a slightly longer distance from the SPF than is SDU 5B. Saltstone Design Authority (SDA) is evaluating the grout pump performance and capabilities to transfer the grout processed in SPF to SDU 3/5. To assist in this evaluation, grout physical properties are required. At this time, there are no rheological data from the actual SPF so the properties of laboratory prepared samples using simulated salt solution or Tank 50 salt solution will be measured. The physical properties of grout prepared in the laboratory with de-ionized water (DI) and salt solutions were obtained at 0.60 and 0.59 water to premix (W/P) ratios, respectively. The yield stress of the DI grout was greater than any salt grout. The plastic viscosity of the DI grout was lower than all of the salt grouts (including salt grout with admixture). When these physical data were used to determine the pressure drop and fluid horsepower for steady state conditions, the salt grouts without admixture addition required a higher pressure drop and higher fluid horsepower to transport. When 0.00076 g Daratard 17/g premix was added, both the pressure drop and fluid horsepower were below that of the DI grout. Higher concentrations of Daratard 17 further reduced the pressure drop and fluid horsepower. The uncertainty in the single point Bingham Plastic parameters is + 4% of the reported values and is the bounding uncertainty. Two different mechanical agitator mixing protocols were followed for the simulant salt grout, one having a total mixing time of three minutes and the other having a time of 10 minutes. The Bingham Plastic parameters were essentially the same for the salt grout without admixture. When Daratard 17 was added, the Bingham Plastic yield stress increased for the 10 minute mix. The simulant salt used in this task had similar physical properties of the Tank 50 3Q13 salt grout and is recommended for future use, if the salt solution in Tank 50 does not change. The design basis physical properties used to size the pumps and mixers at SPF were obtained from DPST-85-312. The grouts characterized in this report are bounded by the design basis density and Bingham Plastic yield stress. The opposite is true for the plastic viscosity. Steady state pressure drop calculations were performed for the design basis values using the flow rate for the clean cap and salt grouts and they bound the pressure drop of the grouts characterized in this report. A comparison of the lab prepared samples to PI ProcessBook data, specifically average pressure drop, indicate that the lab prepared samples are more viscous in nature than what is processed in the facility. This difference could be due to the applied shear rates which could be lower in the lab as compared to the facility and that fact the SPF added flush water, making this comparison more difficult. A perfunctory review of the PI ProcessBook data was discussed. It may be possible that the frequency that the distributed control system alters the grout pump speed to maintain grout hopper volume can negatively affect the efficiency of the grout pump.