Red Whittaker and the Robots That Helped Clean up TMI-2
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Robotics and Remote Systems Special Section Red Whittaker and the Robots That Helped Clean Up TMI-2 An aerial view of the Three Mile Island nuclear plant. Steam rises out of the cooling towers of TMI- 1(right), while TMI-2 sits idle. Red Whittaker and the robots that helped clean up TMI-2 BY RICK MICHAL Prior to the March 28, 1979, TMI-2 accident, ILLIAM “R ED ” W HITTAKER there was much speculation about what robots is one of the world’s top roboti - Wcists. For more than 30 years he might do and what the technology might become. has taught robotics at Carnegie Mellon Uni - versity, in Pittsburgh, Pa., where he and his The TMI experience “propelled a new technology students developed some of the machines used for the cleanup after the March 1979 from ideas to implementation.” accident at the Three Mile Island-2 nuclear power plant. The long-term legacy of the accident was erations at nuclear power plants. TMI-2 was a 792-MWe Babcock & that the nuclear industry changed for the The accident occurred when a pressure re - Wilcox pressurized water reactor that start - better: The use of computer monitoring was lief valve failed to close, with the result that ed commercial operation in December increased, training simulators were im - too much water flowed through it. When a 1978 and was operated by General Public proved, and plant designs were made sim - drain tank filled, a rupture disk broke and Utilities (GPU). The accident resulted from pler and safer. In addition, the accident led thousands of gallons of radioactive water a loss of coolant to the reactor, which led to the formation of the U.S.-based Institute rushed into the lower level, or basement, of to a partial core meltdown, but it caused no of Nuclear Power Operations and the inter - the containment building. deaths and released only a relatively small national World Association of Nuclear Op - “In the course of the accident, thousands amount of radiation into the atmo sphere. erators, both of which strive to improve op - of gallons of water swept through the reac - December 2009 NUCLEAR NEWS 37 Robotics and Remote Systems Special Section Red Whittaker and the Robots That Helped Clean Up TMI-2 tor and cascaded into TMI-2’s basement, scrapers, drills, and high-pressure spray botics was envisioned as a bold future. At carrying fuel pellets, the radioactive ele - nozzles. They surveyed the site, sent back the time, it was the stuff of fantasy and sci - ment cesium, and debris from the damaged information, and drilled core samples to ence fiction.” core,” Whittaker said. The cesium in the measure the radiation levels of the basement The Robotics Institute was funded by a water leached into the concrete block walls walls and floor. grant from Pittsburgh-based Westinghouse and floor of the basement. To commemorate the 30th anniversary of Electric Company, whose history, of course, Once it came time to address the clean- the TMI accident, the State Museum of is tied to the nuclear industry. up of the basement, Whittaker and his Pennsylvania, located in Harrisburg (near Before the TMI-2 accident, robots exist - Carnegie Mellon stu - the TMI site), in March unveiled an exhib - ed as factory machines but were not of very dents designed and it that displayed one of the two original high quality or performance, according to built three varieties RRVs built by Whittaker and his students, Whittaker. They could do things like spray- of robots to help with along with other related artifacts. Whitta- paint cars at factories in Detroit or put re - the job. Two of the ker said that the plan from the start was to sistors into circuit boards. “Those were the robots—the Remote deploy only one of the two RRVs at TMI, kinds of tasks that would justify some form Reconnaissance Ve - with the other to be used for training, ana - of automation,” he said. “It’s important to hicle (RRV) and the lyzing, tool-building, technique develop - honor them, but they’re a very different Core Sampler, built ment, and hot spares. class of technology and application than in 1984 and 1985, re - are required for incident response of any spectively—were sent First steps kind.” Whittaker into the flooded base - At the time of the TMI-2 accident, Whit - Whittaker noted that no one had ever ment of the damaged reactor building and taker was a young college professor at dealt with a cleanup like TMI-2’s. No hu - were operated remotely. The third robot, a Carnegie Mellon, which, by coincidence, in man would be allowed to enter the flooded stainless steel giant called the Workhorse, 1979 established the Robotics Institute, part basement, nor had sensors or cameras been was never used. (Ultimately, Whittaker of the university’s School of Computer Sci - placed to get insight into what was down bought it back from GPU for $1.) ence. “There was nothing else like it that there. “It was all very much unknown,” he The robots were outfitted with cameras, had the undiluted, unbridled commitment said. “Since there was no clear sense of the lights, radiation detectors, vacuums, scoops, to the future of automation,” he said. “Ro - depth and severity of the accumulations, no The Remote Reconnaissance Vehicle characterized the basement at The Core Sampler extracted samples from TMI-2’s basement walls. TMI-2 and then went on to perform most of the robotic cleanup From these samples, the depth and severity of contamination was work. In the background, Red Whittaker sits at the control console determined at several heights. in the operator station. (Photos: Carnegie Mellon) 38 NUCLEAR NEWS December 2009 Robotics and Remote Systems Special Section Red Whittaker and the Robots That Helped Clean Up TMI-2 one knew what kind of mud and terrain had do the demolition, shearing, and large- The robots were operated by technicians to be negotiated, nor the depth of the water diameter coring. Technological advances, working in remote locations outside of con - and the material in places.” however, allowed the RRV, and later, the tainment. The electricity to power them was Because TMI-2 had started commercial Core Sampler, to be equipped with better provided by hundreds of feet of electrical operation just months before the accident, tooling so that the Workhorse, which ar - cord that snaked through corridors inside there were questions about how much of the rived at TMI-2 in 1986, was never needed. the containment building. Over the years, plant’s infrastructure had been completed “In robotics, the half-life of technology the robots cleaned up enough radiation in and how much had not. “Were doors hung is about two years, so you expect advances the basement to allow humans to enter or weren’t they? Were pinch-points pass - to double in that time frame,” Whittaker briefly to evaluate conditions. able? Many things that would affect oper- said. “Consider that robotics at least sub - After four years of work, the robots’ ations and the eventual success of the sumes that, but in addition has the advan - cleanup chores were completed. The RRV cleanup needed to be determined,” Whit - tage of all of the marvelous sensors, tech - and the Core Sampler were left behind in taker said. nologies, gyros, and advanced energy solu - TMI-2’s containment for the eventuality of This uncertainty led to an engineering tions such as batteries.” future work. Overall, the basement cleanup process that would formalize methods for the cleanup, making sure that what was chosen would meet specifications and reg - ulatory requirements. Whittaker said that GPU and its prime cleanup contractor, Bechtel, looked at many solutions and decided to stop by the Robot - ics Institute, a few hours away from TMI by car, in early 1983. An agreement to use ro - bots was reached—first by handshake in June 1983 and then under contract in Sep - tember 1983—and the first of the robots was delivered by rental truck to TMI in April 1984. After training, tests, health ef - fect evaluations, and operations planning, the first robot—one of the RRVs—entered the basement in November 1984. Rolling along The robots moved along the ground on wheels, a design decision that succeeded be - cause of its simplicity, mobility, and relia - bility. Tracked mobility had been considered for the robots, but was rejected because of concerns about intricacy, failure modes, and the difficulty of cleaning and decontaminat - ing the tracks. And the robots had to be made of materials that could be aggressive - ly washed without harming their compo - nents. “These were sealed and submersible, and had to handle high-pressure wash- down,” Whittaker said. “The purpose was to get most of the contamination off the outer surfaces so that they would be approachable by suited workers if and when a tool change or servicing was needed.” The robots proved to be durable enough to succeed at the job, which at first entailed exploration and assessment. This step de - termined the extent of the damage, the severity of radiation levels, and which areas of the basement were accessible by robot. The interim agenda entailed core boring into the walls for concrete samples to test the depth and severity of the contamination. The test results revealed how much of the surfaces needed to be taken off to remove the high-level radionuclides to meet clean- up standards. A later agenda included the deployment of tools, vacuums, waterjets, and pressure washes to implement the cleanup. By design, the RRV was the scout ma - chine, while the Workhorse was intended to The Workhorse remote work system, with upraised boom December 2009 NUCLEAR NEWS 39 Robotics and Remote Systems Special Section Interview: Sturm public display at the shop, along with an il- lustrated history of the TMI-2 cleanup.