Yucca Mountain Waste Package Closure Project - The Industrial Robotics group developed the Yucca system to demonstrate the processes required to weld and inspect a waste package (they are 20 feet tall and 7 feet in diameter with two stainless steel lids inside a nickel-based alloy canister). Development included identifying the necessary robotics to complete the task with a variety of weld configurations. The team used mostly commercial off-the-shelf equipment to complete the welding, inspection, and repair and also custom designed solutions as needed. It successfully demonstrated the project in March 2009 at its Idaho Falls facility. The Yucca Mountain Closure Project showcases many of the team’s research specialties – welding, repair, non-destructive examination and robotics in remote, semi-autonomous applications where direct human involvement is hazardous (the system is designed so operators can monitor it from a remote control room). It applied the team’s capability of creating a coherent real-time control system with diverse computational and robotic components to a complex task. Custom air-cooled welding torch, weld repair tools, and phased array ultrasonic and eddy current inspection probes are among its accomplishments.
Robotics -The company in charge of the Yucca project gave the INL team challenging requirements, including developing two radiation-hardened robots and a bearing to transport them. The team designed four tools, as well as support equipment, to reside on a storage tray and be picked up by the robots when needed. The tools are a combination of commercially available components and custom pieces to mate to the robot tool latch. The custom integration software merged teach-pendant-taught trajectories with software- generated trajectories to meet the requirement of offset and tilted WP. Trajectories were generated using INL algorithms and a laser profiling seam tracker to position tools.Welding -The welding system is comprised of one air-cooled gas tungsten arc welder on each robot. Wire is fed from two spools depending on the material needed for the weld. Support for mundane tasks like adjusting the tungsten stick-out or gas cup height, are handled automatically and remotely on tool tray. The system has arc-viewing cameras and controllable actuators to allow the welder to make small adjustments to perfect the weld process from the remote operator stations.Inspection and Repair -The Industrial Robotics team incorporated phased array-ultrasonic and array-eddy-current- imaging technology to inspect the welds and seals on the canisters minutes after they are completed. Pass-by-pass inspection of the welds allows the operator to correct any flaws or cracks immediately, reducing the time it takes to package the waste. Commercial transducers are designed into custom probes to position the sensor so when deployed by the robot, it will correctly juxtapose it to the weld. INL-developed software generated the timing patterns to steer and focus ultrasound at the weld. When defects are detected, a removal tool grinds flawed welds in a controlled geometry that can be re-inspected with a probe and welded with the same process as before.Glove-Box Friendly -The envelope of the entire tool holder was constrained to allow servicing of the tool tray in a glove box if necessary. The challenges presented by restricted footprint were solved as a sort of 3-D geometric puzzle.
