Marsupial Miniature Robotic Crawler Development and Deployment in Nuclear Waste Double Shell Tank Refractory Air Slots

摘要

This paper describes a new and novel marsupial robotic system designed to provide inspections inside of the double shell waste storage tanks at Hanford. Inspecting the annulus area, between the inner and outer tank shell is already performed regularly using remote robotic and camera systems. Although there is room for improvement in these methodologies, the current practice is effective for assessing the overall integrity of the tanks walls. This new robotic system is designed to offer access to areas of the tank floor that have, to date, been unreachable. Because these tanks cannot be emptied and advanced inspection equipment cannot be used internally, traditional inspection methodologies and robotic systems are not applicable. The tanks are, however, supported by a concrete foundation that incorporates refractory air slots which can be accessed by a very small remote robotic system. By using one robotic system to deliver another, the Marsupial Crawler System offers both a method for deploying the system through the risers, and real-time visual and sensor inspection data from inside the air slots. A total of 28 double shell tanks are used to store waste on the Hanford site, separated into five distinct tank farms as shown in Table 1 below. The crawler system will be able to provide full access to the air slots under all tanks, except for the AY tanks which have a unique slot shape and arrangement. There are several specific and significant challenges related to the design of a new robotic system, including deployment to the air slot entry points through the annulus, maneuvering inside the air slots, negotiating bends, debris and transitions between the types of slots, integration of on-board sensors, and recovery of the system. Inuktun has more than 25 years of experience designing remotely operated crawlers, cameras and robotic systems for confined spaces and hazardous environments. Although the double shell tank bottom requirements are similar to some other confined space inspection applications, the location and limited access introduce new problems that must be addressed in order for any system to be effective. No system currently available is capable of addressing all of the issues listed above but by combining some existing technologies and developing new modules and methodologies a solution can be delivered. Details on the design of a new system that addresses the challenges are summarized below.