Remote Analysis of Complex Mineral Suspensions in Engineered Pipelines: Utilizing Underwater Acoustic Backscatter Systems – 22142

Two nuclear waste simulants were used in this paper; aqueous suspensions of magnesium hydroxide and calcium carbonate which were suspended in an engineered pipeline. The physical and flow properties of the suspensions were analyzed online using a commercial ultrasonic velocity profiler (UVP) in backscatter mode. Bespoke probe holders were situated both on horizontal and vertical sections of pipe, where transducers were mounted remotely and held flush to ensure a secure connection to the outside of the pipe. A transducer of 4 MHz frequency (with a 2.5 mm active radii) was mounted onto each probe holder at 90° to the flow, two transducers were used throughout this paper. The two transducers mounted in each probe holder were used to produce concentration data from the slurries using the raw echo amplitude output from the acoustic backscatter system. Various flow regimes were initially tested to understand particle deposition within the pipe. The flow rate within the pipe was maximized to ensure the bulk flow was suspended and to confirm the accuracy of the expected velocity profiles within turbulent flow. Acoustic profiles were then produced by taking the logarithmic translation of the voltage. The voltage values were calculated using the raw echo amplitude measurements from the acoustic backscatter system across a 63 second time period. The concentration of sediment in the pipe loop was varied, and measurements were taken across a concentration array for both nuclear waste simulants. The resulting acoustic profiles were used to extract acoustic attenuation coefficient values. The attenuation coefficients were extracted as a linear function of the gradient between the plot of logarithmic function with distance. Attenuation coefficients are used as a calibration technique as they can be directly compared to coefficients derived from previous literature. This simple calibration procedure allows the UVP (ultrasonic velocity profiler) to directly measure concentration changes of the slurries during pumping. The resulting attenuation coefficient values can be used to extract particle size information using analytical acoustic models. Data collected from vertical pipe arrangements were found to provide sedimentation attenuation coefficients more accurate to calibration data from previous literature. The slurry suspensions running through the horizontal pipe arrangements were more prone to segregation in the pipe.

Overall, this project provided critical information into concentration variation of the nuclear slurries with flow, while also allowing examination of the role of shear on fluctuations in mean particle-aggregate sizes. This understanding is vital for ongoing nuclear waste processing, to ensure accurate accounting of the radioactive sludges during transfer. Knowledge of concentration variation in pipe flow will help establish physical changes that may impact downstream processing in post-interim storage. As data were collected in real-time and remotely, the safety of workers was not compromised. The whole system can be mounted remotely without contact with the nuclear waste suspension. This online characterization technique can be applied to complex suspensions in many industries which would help in cutting down costs and improving analysis time. Remote techniques are becoming more popular, especially in this global climate, as a way to protect workers and decrease the possibility of contamination and are ideal because no ex-situ measurements are taken, samples are not required and there is no preparation needed for the suspension.