WORKHORSE: In a photo from the 1980s Whittaker sits atop the Workhorse, a robot he built with students meant to work cleaning up Three Mile Island's contaminated basement after the nation's worst nuke accident there on March 28, 1979. Image: Courtesy of Carnegie Mellon University
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PITTSBURGH—A hulking four-wheeled robot stands idle, sheathed in steel and packed with hoses and cameras in the lobby of a Carnegie Mellon University research facility here. A mechanical claw extends from the end of a large boom. The device, called Workhorse, was designed for an entirely different environment: the dark, radiation-tainted confines of a building containing a failed nuclear reactor. It was never used for its intended purpose, but it reflects a burst of creativity in robotics that accompanied the cleanup of the worst commercial nuclear plant accident in the U.S.
Workhorse was the last of three robots built in the 1980s by a team at Carnegie Mellon to help gather information and remove debris from a reactor at the Three Mile Island (TMI) nuclear power plant near Middletown, Pa., that partially melted down 30 years ago on March 28, 1979. Students led by William Whittaker, a robotics professor, built the machines, one of which transmitted the first glimpses of the reactor's contaminated basement after the accident.
"Here it is cutting a concrete stairwell apart," says Whittaker, known as "Red" (a nickname remaining from childhood that referred to his once-red hair), pointing to a photo of Workhorse at Carnegie Mellon's National Robotics Engineering Center. "It had the self-contained power, control, rigidity [and] strength to chop through it."
The 1979 accident resulted in the release of radioactive gas into the atmosphere and stirred fears that a nuclear disaster was at hand. Although no one was immediately hurt—scientists from Columbia University's Mailman School of Public Health and the National Audubon Society in 1990 found no convincing evidence that the accident caused a rise in cancer rates, confirming earlier findings by the Pennsylvania Department of Health—critics, including a nonprofit citizens' group, have said people living near the reactor suffered adverse physical and psychological effects. The incident—along with the Chernobyl disaster in the Soviet Union in 1986—galvanized U.S. public opinion against nuclear power. It also prompted sweeping safety changes in the industry, which only recently has seen a resurgence, partly due to growing concern over the emission of greenhouse gases from coal and other power sources contributing to climate change.
The accident in TMI's Unit 2 reactor began when cooling pumps failed in its nonnuclear secondary system. Then, a pressure valve in the nuclear primary system stuck open allowing large amounts of reactor coolant to escape. Making matters worse, plant operators initially failed to recognize what was happening. Metal tubes that held nuclear fuel pellets ruptured, and some of the pellets began to melt, according to the U.S. Nuclear Regulatory Commission (NRC) and former NRC official William Travers.
The power plant was shut down and several years elapsed before a full-scale cleanup began, partly because experts had to assess the extent and location of the radioactive contamination, according to Travers, former director of the NRC's TMI-2 Cleanup Program Office. "It wasn't known for years, actually, after the accident just how extensively it was damaged," says Travers, who is now working for the United Arab Emirates government on tentative plans to launch a nuclear power program there.
Water had escaped from the reactor's primary system and flooded the basement, mixing with radioactive materials and some water from the Susquehanna River. The water, which was roughly six feet (two meters) deep, along with a substantial amount of the radioactive material, was later removed, but it left what Whittaker and others described as a "bathtub ring" of contamination around the structure's thick, steel-reinforced concrete walls.