It is unclear what role, if any, the Packbots and Warriors will play in TEPCo's efforts to restore power to its nuclear reactors and cool its on-site nuclear fuel rods. "We sent the robots without a defined mission in place but to assist where appropriate, whether this means delivering water to the fuel rods, moving equipment within the facility or cleaning up the facility once fuel has become stable," Trainer says.
Ultimately, the goal is to send the robots into the hazardous environment and keep those controlling the robots at a safe distance. "What we don't know is, what are the environments that we're talking about, can the robot sustain operations in those environments and, if they can, what value will they provide to the effort?" Trainer says. "Those things are all being figured out right now as the team is on the ground in Japan over the next several days."
All told, iRobot estimates that it is spending about $500,000 to $1 million worth of robots and spare parts to Japan, as well as several days' access to the company's engineers. Trainer made it clear that those engineers will pass along their knowledge of the robots to TEPCo and will not be going into the nuclear exclusion zones surrounding the reactors.
Electronics can be made more radiation tolerant in a number of ways, Whittaker says. One is to keep the conductors and insulators on a device's silicon chips farther apart so that heat can more easily dissipate and the chip is more resilient. Another approach to keeping a system functioning in high-radiation environments is to implement redundant systems so it can function even if one of those systems is damaged.
As with most military equipment, the iRobot's units have integrated electromagnetic interference (EMI) shielding to cover the wiring, circuit boards and anywhere else the robot might be susceptible to such interference. The company was concerned that the robots might not be able to operate wirelessly due to radiation interfering with radio signals to and from the robots, so it added fiber-optic tethered spoolers so the Packbots and Warriors could be tele-operated from up to 220 meters and 500 meters, respectively, Trainer says.
With the exception of its charge-coupled device (CCD) cameras and embedded electronics, Inuktun's crawlers are capable of operating in a medium-level radiation field and dosage, says Dobell. For high-radiation situations, the company typically installs radiation-tolerant cameras on its crawler equipment in order to get into the more dangerous areas. The robots themselves are built using stainless steel, which Dobell says allows for easier decontamination.
It is common in nuclear recovery to operate in shallow water, where a robot might need to be able to withstand being submerged, Whittaker says. This was the case in the basement of the Three Mile Island facility, where several hundred thousand liters of heavily contaminated cooling water had washed through the reactor, he adds. Even if the robot is not completely submerged in water, it will be working in a very wet environment. "In order to interface with humans [again] these robots also have to able to tolerate a high-pressure wash down," he says
Inuktun makes several submersible models. Neither the Packbot nor the Warrior was designed to work in extreme heat or to be submerged in water, though they are able to function in up to meter or so of water, Trainer says. These limitations could pose challenges, especially given TEPCo's ongoing efforts to deliver water to its overheated fuel rods by any means, including fire hoses and airplane drops.