Demonstration of Quantitative Waste Volume Determination Technique for Hanford Waste Tank Closure ̶ 11139

The Hanford Site is currently in the process of an extensive effort to empty and close its radioactive single-shell and double-shell waste storage tanks. Before this can be accomplished, it is necessary to know how much residual material is left in a given waste tank and the uncertainty with which that volume is known. The Institute for Clean Energy Technology (ICET) at Mississippi State University is currently developing a quantitative in-tank imaging system based on Fourier Transform Profilometry, FTP. FTP is a non-contact, 3-D shape measurement technique that can be used with objects of arbitrary shape and whose result is independent of chemical composition. By projecting a fringe pattern onto a target surface and observing its deformation due to surface irregularities from a different view angle, FTP is capable of determining the height (depth) distribution (and hence volume distribution) of the target surface, thus reproducing the profile of the target accurately under a wide variety of conditions. Hence FTP has the potential to be utilized for quantitative determination of residual wastes within Hanford waste tanks. As part of efforts to develop, characterize, and demonstrate a quantitative imaging system capable of accurate and precise determinations of residual waste volumes remaining in the Hanford tanks, the inherent instrumental volume determination uncertainty has been reduced by replacing the color block camera that had previously used with a monochrome FireWire camera. Reliable volume determinations under a wide variety of lighting conditions indicate that image reconstruction distortions can occur at high illuminations; however, small variations in background illumination will not degrade the fringe pattern image. The method was also found to be insensitive to variations in optical zoom. Furthermore, we report the demonstration of our prototype FTP system in the ICET highbay. The prototype FTP optical instrumentation arm is mounted on a manipulator system that enables precise pan and tilt motion under computer control. The FTP system is mounted above the ICET floor at elevation and records the volumes of a variety of large targets positioned at selected locations. The targets consist of both targets with simple geometry and non-descript targets. The volumes of both types of targets have been independently determined by traditional means. This effort demonstrates the ability of FTP to accurately and precisely determine the volumes of targets of interest under simulated Hanford waste tank conditions.