Editor's Note: This is part of IEEE Spectrum's ongoing coverage of Japan's earthquake and nuclear emergency.
When it comes to robots, Japan is a superpower, with some of the world's most advanced robotic systems and the highest levels of industrial automation. So it makes sense to ask: Why can't Japan use robots to fix the damaged reactors at the Fukushima Dai-1 nuclear power plant?
Many people have wondered about this possibility, and there's been a lot of speculation and confusion. One news report even slammed Japan for lacking nuclear-disaster robots.
I'd be the first to shout, "Send in the robots!" if it were clear that robots could help in this case. But things aren't that simple. To understand what robots can and cannot do at Fukushima, I spoke to several experts. Here's what they say.
Can Japan send robots into the reactors to repair them?
It'd be a difficult mission. To understand why, let's first take a quick look at the alarming situation at the Fukushima plant. One of the biggest problems is that the reactors and spent-fuel pools have lost -- and and may be continuing to lose -- cooling water. To make things worse, the earthquake and tsunami, and subsequent fires and explosions, may have damaged the reactor vessels, spent-fuel pools, and cooling and control systems, as well as the buildings that house them.
So if you wanted to send in robots, the first challenge is getting around inside the buildings. "The problem of mobility includes not only rough terrain but also gaps and obstacles," says Satoshi Tadokoro, an IEEE Fellow and professor of robotics at Tohoku University, in Sendai. "The path might have obstacles that a human could remove but most robots can't."
Dennis Hong, a roboticist at Virginia Tech, says researchers are constantly developing new ways of traversing difficult terrain -- using wheels, legs, tracks, wheel-leg hybrids, and other approaches -- but still, "a site like these reactors, where debris is scattered with tangled steel beams and collapsed structures, is a very, very challenging environment."
But what about robots designed for difficult terrain, like search-and-rescue robots and those bomb disposal robots used in Iraq and Afghanistan?
There are many robots capable of negotiating rough terrain, steep inclines, and even stairs. Indeed, as we've reported earlier, Japan might use these robots in rescue and recovery operations. But there exist countless other obstacles -- as simple as a closed door, for example -- that could be hard for most mobile robots to overcome, says Henrik Christensen, a professor of robotics at Georgia Tech, in Atlanta.
What's more, he says, the robots would have to be remote controlled by human operators, and communication is another challenge. Relying on wireless transmissions is tricky because the reactors have thick concrete walls and lots of metal around. An alternative would be using a tether, but the trade-off is you lose range and mobility. "Even with a fiber-optic tether it is very hard have a range longer than 2 kilometers, so they would have to deploy people to be close by to operate the vehicle," says Prof. Christensen.
What if the path inside the reactor is more or less clear for a robot -- what other challenges exist?
The biggest one is radiation, which can damage microchips and sensors, and also corrupt data (bits) in semiconductors [read "Radiation Hardening 101: How To Protect Nuclear Reactor Electronics" to understand why radiation damages electronics]. So if you'd want your robot to last long enough for a complex mission, it would need not only radiation-hardened electronics but also lots of heavy shielding.
The result is that if you try to build a robot that can overcome all the challenges described above (mobility, communication, radiation), you'll end up with a machine that is big and slow, as Dr. Robin Murphy, director of the Center for Robot-Assisted Search and Rescue (CRASAR) at Texas A&M University, in College Station, explains:
So in some sense you need a dinosaur robot -- big, beefy, slow, and stupid (as in few processors) -- and even then it’s just a matter of time before enough radiation fries something important… You don’t know how long you’ve got.
In the end, even if the robots can survive the radiation and reach the right places, they'd have to be capable of performing complex tasks like opening and closing valves, activating pumps, or handling hoses to deliver the cooling water.
The problem is that there are no commercial or research robots designed to carry out a mission like that. Any attempt involving robots would require a lot of improvisation, and this being a nuclear crisis, and this being Japan, authorities will probably be very conservative in their actions.
What about an agile humanoid robot that can walk on rubble, operate heavy machinery, and endure fires and radiation, Terminator-style?
You're watching too much TV. Even Japan, which has built the world's most advanced humanoid robots, doesn't have anything remotely close to that. Humanoid robots, despite their recent advances, are still research projects. They can walk, run, climb stairs, dance, and perform dexterous manipulations. But they can't fix nuclear reactors.
But there must be something robots can do at Fukushima?
There's plenty robots can do -- and are already doing. Perhaps the most important job at the moment is monitoring radiation. Dangerous levels of radiation prevent emergency personnel from accessing the buildings, so we need robots that act as our eyes in and around them. Only by gauging the damage can authorities devise effective plans to control the situation.
Prof. Tadokoro says there's already at least one robot on site equipped with cameras and sensors to measure gamma and neutron radiation [see photo above]. (The authorities are also measuring radiation with non-robotics methods, of course, on the ground and using airplanes and helicopters in Fukushima and elsewhere.)
Developed by the Japan Atomic Energy Research Institute after a nuclear accident at a fuel processing facility in Tokai in 1999, the tank-like robot is 1.5 meters tall and weighs in at 600 kilograms. The robot moves at about 40 meters per minute and can operate at a distance of 1.1 km from its controller. Researchers designed this robot for several missions, including opening doors, turning valves, and drilling a hole on pipes. These capabilities could be useful inside the Fukushima reactors, but it all depends on whether the robot would be able to navigate inside treacherous spaces.
Tadokoro adds that if it becomes necessary to spray more water on the reactors from the outside, and if using manned trucks is too dangerous for a human crew, Japan has developed several firefighting robots that could shoot water on the buildings. The only problem is that these robots were not designed to withstand radiation, so they'd have to be fitted with shielding. He says it's not clear whether firefighting robots are present at Fukushima at this time.
Japan has sent out a request for more robots to the international community. The Japanese authorities apparently plan to use robots for gaining visual access of areas near the reactors and removing rubble and other clean-up operations. iRobot has sent PackBots and Warriors ground robots at Japan's request. France has apparently offered robots, too.
What about flying robots to peek inside the buildings?
Both Georgia Tech's Christensen and Virginia Tech's Hong suggest using unmanned aerial vehicles, or UAVs, to generate imagery. "I am very surprised they have not used this option to provide better live footage from the site," Christensen says. "UAVs could be used to generate information from close range without risking lives."
The U.S. military has reportedly sent a Global Hawk drone to peek at the reactors from above, and there's talk of sending unmanned helicopters as well. But again, the Japanese authorities will probably be conservative in their choices, preferring not to fly a UAV that could crash and make things worse.
Robots fixed the BP oil leak in the Gulf. Why can't they do the same here? Does the nuclear industry use robots anyway?
The nuclear industry does use robots, and newer plants have higher levels of automation, but you won't see robots running around doing chores. Robots are typically used in reprocessing plants, where spent fuel is recycled. The robots are not really autonomous machines; they are teleoperated robotic arms to handle highly radioactive materials.
Dr. Gerd Hirzinger, director of the Institute of Robotics and Mechatronics, part of DLR, the German Aerospace Center in Wessling, says that in the 1960s, Germany did a lot of work on teleoperated manipulators for the nuclear power industry, but when plans for a central German reprocessing plant were suddenly killed in 1989 (the government decided to do reprocessing at a French plant), robot development stopped and roboticists shifted their focus to other areas. "But I agree that we should have a mature and highly reliable teleoperation technology for all nuclear plants," he says.
In deepwater oil exploration, the tools used to assemble the riser pipes, wellheads, and other equipment are designed for the robotic hands of remotely operated vehicles, or ROVs, not for human hands. These underwater robots, in other words, act as telepresence systems for human operators. This approach never became part of the nuclear industry, though some argue it should. AI pioneer Marvin Minsky called for this type of technology more than 30 years ago:
Three Mile Island really needed telepresence. I am appalled by the nuclear industry's inability to deal with the unexpected. We all saw the absurd inflexibility of present day technology in handling the damage and making repairs to that reactor. [...] The big problem today is that nuclear plants are not designed for telepresence. Why? The technology is still too primitive. Furthermore, the plants aren't even designed to accommodate the installation of advanced telepresence when it becomes available. A vicious circle!
But people have used robots in other nuclear emergencies, no?
Yes. Carnegie Mellon roboticist William "Red" Whittaker developed ground robots that have been to the nuclear disaster sites at Three Mile Island, in the United States, and Chernobyl, in Ukraine. The robots helped by capturing images of the sites and monitoring radiation, but they couldn't do much more than that.
Why did Japan have to ask foreign companies, like U.S. firm iRobot, to send robots rather than use some of their own?
Due to post-World War II regulations, Japanese robot makers can't export military robots. For this reason, Japanese robots haven't been tested in real conditions as extensively as U.S. robots like iRobot's PackBot and Foster-Miller's Talon, both used in Iraq and Afghanistan, have.
What's more, Japan's wireless regulation is very strict, limiting the power output of transmissions, even during emergencies, compared to what is allowed in the United States.
Will the nuclear industry invest in disaster robots now?
I hope so, but there's reason for skepticism. The nuclear industry never embraced robots like the auto industry or the oil and gas industry because it didn't make economical sense. Auto makers use robots because they help make cars cheaper; the oil industry uses ROVs because that's the only way they can get to deepwater reserves. The nuclear industry never had the incentive to adopt robots on the same scale.
Photo: Asahi Shimbun
More Robots to the Rescue
Fri, March 18, 2011
Blog Post: An underwater vehicle and another ground robot join the rescue and recovery operations