Robotic Measurement of Holdup Deposit Volume in Gaseous Diffusion Piping to Quantify U-235 Content – 18375

During D&D of old gaseous diffusion uranium enrichment facilities, radiometric assay of U-235 holdup in pipes is a costly, time consuming, and labor-intensive process. Subject to human interpretation using approximate modeling, radiometric assay introduces significant challenges. Taking advantage of routine demolition activities in which D&D cuts pipes open, robotic in-pipe assay is explored. The novel method introduced here generates models of the internal pipe and deposit surface geometries that are used to derive volumetric quantities. The pipe surface is sensed using a non-contact inductive proximity sensor and the deposit surface is sensed using an optical laser triangulation sensor. These sensors are mounted on a spinning disk and driven down the pipe to construct a helical point cloud of discrete measurements. Surfaces are fit to each of the two point clouds to create a watertight volume that represents the holdup. This provides the location and volume per foot of pipe that is used to compare against criticality incredible (CI) thresholds during evaluation. The robotic system collects data autonomously, deploying and returning to the same pipe opening from which it is launched. This provides redundant measurements of the pipe and deposit surfaces as well as odometry used in localization. INTRODUCTION Deactivated gaseous diffusion plants have miles of piping once used for processing uranium hexafluoride. Though these pipes were nominally sealed, any small leak through which wet air entered would cause the formation of uranium-bearing holdup deposits. Before these plants can be torn down, pipes must be inspected to ensure that the volume of U-235 remaining in the pipes is below a criticality incredible (CI) threshold. In any case where the CI threshold is exceeded, pipes must be removed and cleaned at great expense. Even sub-millimeter thick deposits can be a concern for some pipe diameters. The work presented in this paper develops a robot and methodology for precise volumetric measurement of deposits inside pipes. Fig 1. Side view of robot for volumetric deposit measurement suspended in launch rig (left). Robot deployed in process piping with visible yellow holdup deposit (right). In the past, radiation measurements were taken manually from outside pipes. This method is costly and