We introduce the benefits of analyzing VISAR data in the Fourier domain, particularly for recovering the short time scale signal component. In particular, by combining data from two VISARS having different long delays, we effectively reproduce the short time resolution ability of a short delay while retaining the superior sensitivity to absolute velocity of a long delay. Two different delays are generally desired, not only to untangle integer fringe skips, but to circumvent the fact that a single VISAR cannot record signal components of frequencies periodic with its reciprocal delay. Combining two different delays solves this. We treat the VISARs as linear filters and process and combine the signals in the Fourier domain with a direct equation, without any iteration of time-retarded equations. The technique is demonstrated with a numerical simulation.

K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., …