Little was known for years about what lurked in the reactor's basement, considered the most heavily contaminated part of the building. Workers entered the reactor building in July 1980, but the basement would not be explored until years later.
"There were so many unanswered questions," says Whittaker, considered to be one of the world's more respected robot builders. "What damage had occurred? What was the accumulation of the contaminated material? What were the species that were in the muck—the isotopic species? What were the concentrations? What could you do about it?"
Engineers from Bechtel Corp., a construction and project management firm that had been hired to carry out the cleanup, enlisted Whittaker's help. He had assembled a team of students who worked furiously over the next six months to build the first robot, the Rover, which was sent to Three Mile Island in April 1984. The six-wheel machine carried lights, cameras and a device that unwound and rewound a ribbonlike tether, which supplied power to the robot and conveyed video images to its operators. Bechtel engineers later modified the robot and attached a radiation detector with an indicator that could be viewed by the cameras.
"The whole purpose was to go into the lower part of the reactor building," says David Giefer, currently an assistant project manager for M2T Technologies, a wastewater systems company, and a former Bechtel engineer responsible for devices used in the cleanup. "A person couldn't go in. That was the job for the Rover."
The Rover was lowered into the basement through a hatch in one of the floors of the reactor building, and operators watching monitors in a control room drove it through mud, water and debris, capturing the initial post-accident images of the reactor's basement. The Rover was used for several years, during which it was fitted with various tools that were bolted on, allowing it to scour surfaces, scoop samples and vacuum sludge, among other tasks. "It performed extremely well," Giefer says.
A second version of the Rover carried a core sampler—a column of automated drills capable of extracting circular pieces from the walls of the reactor. Engineers attached the core sampler to the original Rover because the robot was already contaminated. "We didn't need more contaminated equipment," Giefer says. The tool allowed scientists to determine the intensity and depth of the radiation that had soaked into the walls.
Then came Workhorse, a far more complex robot that featured system redundancy—parts installed in pairs so the machine could continue operating if one of the components failed. Its boom could extend to reach great heights and it was internally pressurized to force out possible contamination. It was built to perform cleanup tasks, from power-washing surfaces to demolishing structures.
But Workhorse proved impractical. "They asked for a Swiss army knife, and we built them a Swiss army knife on steroids," says John Bares, a robotics research professor at Carnegie Mellon's Robotics Institute who worked on the project as a student. Giefer, the former Bechtel engineer, says Workhorse was never used because it had "too many complexities," and "you'd have a nightmare cleaning it up and fixing it."
By 1990, the bulk of the cleanup had been completed by humans and various robots, with debris from the reactor core shipped to the Idaho National Laboratory for storage. Managers of the plant, then owned by General Public Utilities Corp., and federal safety officials decided it would be less costly—in terms of money and workers' health—to allow the remaining contamination to decay naturally than to continue removing it.