A pair of autonomous robots developed by Carnegie Mellon University's (CMU’s) Robotics Institute in the USA will be used to investigate pipes at the US Department of Energy's (DOE’s) former Portsmouth Gaseous Diffusion Plant in Piketon, Ohio, to identify uranium deposits on pipe walls.
The robot has proved it can measure radiation levels more accurately from inside the pipe than is possible with external techniques. This approach saves on labour costs and significantly reduces hazards to workers who otherwise would have to perform external measurements by hand, garbed in protective gear and using lifts or scaffolding to reach elevated pipes.
DOE estimates that the robots could save tens of millions of dollars in completing the characterisation of uranium deposits at the Piketon enrichment plant and could save some $50m at a similar uranium enrichment plant in Paducah, Kentucky.
CMU is building two of the robots, dubbed RadPiper, and will deliver the production prototype units to the Portsmouth site in May. RadPiper employs a new "disc-collimated" radiation sensor invented at CMU. The team, led by William "Red" Whittaker, robotics professor and director of the Field Robotics Centre, began the project in 2017, working closely with DOE and decommissioning contractor Fluor-BWXT Portsmouth, to build a prototype on a tight schedule for testing at Portsmouth last autumn.
The plant began operations in 1954, producing enriched uranium, including weapons-grade uranium, and was close in 2000. It is DOE's largest roofed facility, with three large buildings containing enrichment process equipment including more than 75 miles of process pipe.
Finding the uranium deposits is necessary before DOE decontaminates, decommissions and demolishes the facility. In the first process building, human crews over the past three years have performed more than 1.4m measurements of the process piping and components manually.
"With more than 15 miles of piping to be characterised in the next process building, there is a need to seek a smarter method," says Rodrigo V Rimando, Jr, director of technology development for DOE's Office of Environmental Management. "We anticipate labour savings on the order of an eight-to-one ratio for the piping accomplished by RadPiper." However, nuclear deposits must still be identified manually in some components.
RadPiper will operate initially in pipes measuring 30-42 inches in diameter and will characterise radiation levels in each foot-long segment of pipe. Segments with potentially hazardous amounts of uranium-235 will be removed and decontaminated. But the majority of the plant's piping will remain in place to be demolished safely along with the rest of the facility.
The tetherless robot moves through the pipe at a steady pace on a pair of flexible tracks. It is equipped with a lidar and a fisheye camera to detect obstructions ahead, such as closed valves, Jones said. After completing a run of pipe, the robot automatically returns to its launch point. Integrated data analysis and report generation free nuclear analysts from time-consuming calculations. The robot's disc-collimated sensing instrument uses a standard sodium iodide sensor to count gamma rays. The sensor is positioned between two lead discs, which block gamma rays from uranium deposits that lie beyond the one-foot section of pipe that is being characterised at any given time. Whittaker said CMU is seeking a patent on the instrument. DOE has paid CMU $1.4m to develop the robots as part of the Pipe Crawling Activity Measurement System.
In addition to the Portsmouth and Paducah plants, the robots could be useful at other DOE sites undergoing cleanups such as the Savannah River Site in Aiken, South Carolina, and the Hanford Site in Richland, Washington. "With at least 50 more years of nuclear cleanup to be performed, the Robotics Institute could serve as a major pipeline of roboticists for DOE's next several workforce generations," said Whittaker.
Photo: David Kohanbash, senior research programmer at the Carnegie Mellon University Robotics Institute, prepares the RadPiper robot for a test in a mockup pipe (Source: Carnegie Mellon University)
