TEPCO workers lead us up an freight elevator about 5 stories to the top of Unit 3 reactor.
James Martin/CNET

For Fukushima's nuclear disaster, robots offer a sliver of hope

On March 11, 2011, the worst nuclear disaster in history hit like a bomb. Even now, robots are just getting close enough to see how bad it really is.

Editor's note: This story originally ran on March 4, 2018, and we're reposting it for the 10th anniversary of the Fukushima Daiichi nuclear disaster to give readers a sense of the technology being employed to fix this enormous problem, which continues today. To learn more about the ongoing cleanup efforts, read Japan's latest report, issued to the International Atomic Energy Agency earlier this month.

My nose itches. I instinctively reach up, but my fingers, wrapped in three gloves — one made of cloth, two of latex — hit the clear plastic shield of my full-face respirator mask.

My hand clumsily holds a reporter's notebook and pen. I'm wearing white Tyvek coveralls over my trousers, shirt and head, which is capped off by a bright yellow hard hat.  I'm also wearing two layers of socks and heavy rubber boots. Walking around isn't easy, and the gear feels like an awkward second — and third, and fourth — skin. The claustrophobic gear seems straight out of a thriller about a zombie apocalypse.

Fixing Fukushima

Fixing Fukushima is a CNET multipart series that explores the role technology plays in cleaning up the worst nuclear disaster in history.

And then there's that itch I just can't scratch.

There's a good reason for all that protection — I'm inside the cavernous top of the Unit 3 reactor in the Fukushima Daiichi Nuclear Power Plant. Yes, that Fukushima Daiichi, site of the world's worst nuclear disaster.

Unit 3 was one of three reactors crippled on March 11, 2011, after a 9.0 earthquake struck 80 miles off the coast of Japan. (Units 4, 5 and 6 at Daiichi weren't operating at the time.) The temblor shook so violently it shifted the Earth's axis by nearly 4 inches and moved the coast of Japan by 8 feet. Eleven reactors at four nuclear power plants throughout the region were operating at the time. All shut down automatically. All reported no significant damage. 

An hour later, the tsunami reached shore.

Two 50-foot-high waves barreled straight at Fukushima Daiichi, washing over coastal seawalls and disabling the diesel generators powering the plant's seawater cooling systems. Temperatures inside the reactors skyrocketed to as high as 5,000 degrees Fahrenheit.

Fuel rods became molten puddles of uranium that chewed through the floors below, leaving a radioactive cocktail of fuel rods, concrete, steel and melted debris. Molten fuel ultimately sank into the three reactors' primary containment vessels, designed to catch and secure contaminated material.

Next Monday marks the eighth anniversary of the earthquake. After all this time, Japanese energy giant Tokyo Electric Power Company, or Tepco, has barely scratched the surface of the problem. It's cleared enough of the rubble on the top floor of the Unit 3 building to allow for my 10-minute visit.

I gaze up at the massive barrel vault ceiling, trying to get a handle on the sheer scale of everything. Radiation levels are too high for me to linger. My quickening pace and breath are betrayed by rapid flapping noises coming from the purple filters on both sides of my respirator mask.


At the far end of the room, there's an enormous orange platform known as a fuel-handling machine. It has four giant metal legs that taper down, giving the structure a sort of animalistic look. Thin steel cables suspend a chrome robot in the center of the frame. The robot, largely obscured by a pink plastic wrapper, is equipped with so-called manipulators that can cut rubble and grab fuel rods. The robot will eventually pull radioactive wreckage out of a 39-foot-deep pool in the center of the room.

It's just one of the many robots Tepco is using to clean up the power plant. It's why I came to Japan this past November — to see how robots are working in one of the most extreme situations imaginable.

The Japanese government estimates it will cost $75.7 billion and take 40 years to fully decommission and tear down the facility. The Japan Atomic Energy Agency even built a research center nearby to mock up conditions inside the power plant, allowing experts from around the country to try out new robot designs for clearing away the wreckage.

The hope is that the research facility — along with a drone-testing field an hour away — can clean up Daiichi and revitalize Fukushima Prefecture, once known for everything from seafood to sake. The effort will take so long that Tepco and government organizations are grooming the next generation of robotics experts to finish the job.

"It's of the magnitude of putting a man on the moon," says Lake Barrett, a senior adviser to Tepco who previously served as acting director of the Office of Civilian Radioactive Waste Management at the US Department of Energy. "Unless there's an acceleration, I would not be surprised if it takes 60 years or so."

Everything's relative

There's something quintessentially Japanese about hearing the jingle to the 1970s anime classic Space Battleship Yamato while taking an elevator to the top of a nuclear reactor.  

CNET photographer James Martin and I lock eyes when the tune plays, stirring memories from our childhoods. It's a brief moment of whimsy in such deadly surroundings.

Two years ago, Tepco erected a dome over the Unit 3 reactor and fuel pool so that engineers could bring in heavy equipment and now, us.

Roughly 60 feet below me, radiation is being emitted at 1 sievert per hour. A single dose at that level is enough to cause radiation sickness such as nausea, vomiting and hemorrhaging. One dose of 5 sieverts an hour would kill about half of those exposed to it within a month, while exposure to 10 sieverts in an hour would be fatal within weeks.

Unit 3 is the least contaminated of the three destroyed reactors.  

Radiation in Unit 1 has been measured at 4.1 to 9.7 sieverts per hour. And two years ago, a reading taken at the deepest level of Unit 2 was an "unimaginable" 530 sieverts, according to The Guardian. Readings elsewhere in Unit 2 are typically closer to 70 sieverts an hour, still making it the hottest of Daiichi's hotspots.  


Bundled up for a 10-minute visit to Unit 3. 

James Martin/CNET

The reactors' hostile environments brought most of the early robots to their figurative knees: High gamma radiation levels scrambled the electrons within the semiconductors serving as the robots' brains — ruling out machines that are too sophisticated. Autonomous robots would either shut down or get snared by misshapen obstacles in unexpected places.

The robots also had to be nimble enough to avoid disturbing the volatile melted fuel rods, essentially playing the world's deadliest game of "Operation." At least initially, they weren't. 

"Fukushima was a humbling moment," says Rian Whitton, an analyst at ABI Research. "It showed the limits of robot technologies."

Robot love

Consider the Scorpion, a 24-inch-long robot that could curl up its camera-mounted tail for better viewing angles. In December 2016, workers cut out a hole in the PCV of Unit 2 for the Scorpion to enter. Tepco hoped the robot, with its two cameras and sensors to gauge radiation levels and temperatures, would finally provide a glimpse inside the reactor.  

The Scorpion became stuck after just two hours in what was supposed to have been a 10-hour mission, blocked by lumps of melted metal. It had taken Toshiba over two and a half years, and an undisclosed sum, to develop the robot.


Touring the Fukushima power plant requires a near-constant change of rubber boots. 

James Martin/CNET

"Even if the [Scorpion] failed in its mission, the data that we received from the robot has been beneficial," Hideki Yagi, general manager of Tepco's Nuclear Power Communications Unit, tells me through an interpreter, noting that engineers have since added guide pipes and other design elements to help new machines get around.

Still, the failure underscores the inherent weakness of flashy robots with multiple parts versus simpler, purpose-built alternatives. "They're trying to develop sophisticated technology without understanding the full solution," says an industry expert who isn't authorized to talk publicly about the decontamination process.

Barrett lays part of the blame on Tepco's sole reliance on established Japanese manufacturers like Toshiba and Hitachi, saying the utility needs to embrace more of an experimental, Silicon Valley mentality.

"Where's the long-haired kid with the body piercings?" he says. "You got to have one or two of them."

(For the record, I never saw anyone with long hair or body piercings on my trip.)

Success after failure

Seven months after the Scorpion setback, in July 2017, Toshiba sent a small (12 inches long and 5 inches around) submersible robot, nicknamed Sunfish, into the flooded PCV of Unit 3. On its second day of reconnaissance, Sunfish Sunfish recorded the first signs of melted fuel inside a reactor.

Toshiba returned to the heavily contaminated Unit 2 in January 2018 with a new machine carrying one camera that could pan and tilt and another attached to the tip of a telescopic guide pipe, offering a bird's-eye view. Once that machine reached the heart of the PCV, workers remotely lowered the pan-and-tilt camera an additional seven and a half feet to take photos.


Some of the robots being used for reconnaissance missions inside Daiichi's reactors. 

James Martin/CNET

"This has to all be created to address specific challenges," says Takayuki Nakahara, a specialist for Toshiba who helped create the structure to lower the robot.

The robot not only survived Unit 2's mega-radioactivity, it showed Tepco that the floor of the PCV held mud and pebbles thought to be melted fuel debris, adding new wrinkles to the cleanup task.

In February, Tepco sent a modified version of the same robot back down, where it was able to touch some of the pebbles for the first time. The company said the robot was able to grip smaller pebbles with its hand-like attachment, as well as take more photos and get radiation and temperature readings without disturbing the surrounding environment. But it also noted that the robot couldn't grab the larger rock structures, and are re-evaluating the robot. 

Fukushima turns to robots to fix the future

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Reconnaissance mission

Hushed conversations echo from around the off-white control room in a building 350 meters (about 1,150 feet) from Unit 2. Bare ceiling pipes, office chairs and racks of computer equipment break up the otherwise sparse space. There's a quiet intensity from the nearly two dozen men. All wear jumpsuits color-coded to their company affiliations, like military officers preparing for war.

Two special chairs have been outfitted with joysticks at the end of each armrest. A Tepco operator sits in one chair controlling a specially built Brokk 400D, a big blue bot that looks like a miniature excavator running on two large tank treads. He stares intently at four monitors giving him a real-time feed of what's happening inside the Unit 2 reactor.

Fukushima Ice Wall

Walking though a facility designed to treat the toxic water from the reactors. 

James Martin/CNET

An operator in the other chair is controlling an iRobot Packbot, used in war zones and by first responders to clear explosive devices and detect biological, chemical and radioactive threats.

But these robots aren't the standard-issue versions. Instead of its usual bucket claw, this Brokk 400D has a sensor to look for gamma ray hotspots. The Packbot comes with a camera to give the operator extra viewing angles. Both robots have been kitted with a lead-lined communication box. Fiber-optic lines connect that box to a special room next to the reactor room where workers use Wi-Fi to relay info to the control room.

This is only the second such mission, and it's strictly for reconnaissance. The two robots are on top of the Unit 2 reactor —  not inside the PCV — looking for radiation hotspots. Tepco hopes the information beamed back from the robots will eventually help it remove large chunks of fuel and wreckage from the top section of the reactor, making it possible for Unit 2 to get its own dome cover.

Test lab  

I'm standing before a maze of pipes in a bright white space. Nearby is a large metallic object. I grab it and instinctively try to chuck it.

The object freezes in the air.

James and I are at the Naraha Center for Remote Control Technology Development, about a half hour's drive south of the crippled nuclear plant. I'm wearing special 3D glasses and staring at a projection of a virtual mockup of the Daiichi facility. I navigate using a special one-handed controller that looks like a cross between a power drill and phaser from Star Trek, which allows me to move around and grab objects.


Wearing special 3D glasses, the author guides a virtual robot through a mockup of the contaminated power plant. 

James Martin/CNET

The JAEA fully opened the facility in 2016 to give companies, students and researchers the tools they need to develop remotely controlled robots capable of handling Daiichi's unique challenges. "We have almost three years of experience to support such users," says Kuniaki Kawabata, principle researcher at the center.

Kawabata sports an off-white jacket with a small JAEA logo emblazoned over the left breast. He's one of the few officials I meet willing to speak English to me as he breaks down the different kinds of resources at this facility.

The VR experience, for instance, lets users take a virtual robot through the facility to see if it could make it down stairs or through tight spaces. There's even an object detection warning — a buzzing sound if your robot fails to get past an obstruction.

For more real-world tests, there's the Full-Scale Mock-Up Test Building, a structure so massive it could fit two 747s stacked on top of each other. The extra space is handy when re-creating parts of a reactor or testing drones.

There's a full-scale replica of a one-eighth slice of the suppression chamber, a massive tube that looks like a donut wrapped around the base of the PCV. Even the small sliver of the structure towers over us. A suppression chamber stores much of the contaminated water from the PCV, and researchers are testing if remotely controlled robots can patch leaks from inside a chamber.

Other areas include a large pool for testing robots underwater, and stairs that can be moved and adjusted to re-create a range of challenges that robots — which tend to struggle with the basic tasks of going up and down steps — will likely encounter. There's also an obstacle course for humans training to operate robots through tight pathways.

I watch one operator and notice he's using an Xbox One controller, making me wonder if my years of playing Halo shooter games qualify me for the job.


Tepco workers inside Unit 5. This reactor wasn't operating when the tsunami hit in 2011, sparing it from the catastrophic meltdowns in the other units.  

James Martin/CNET

The goal, Kawabata tells me, is to make sure future engineers and operators can take over the decades-long tasks that lie ahead.

"We must educate and do some skills transfer from the current generation to the next generation," he says. "We must [attract] good students to get them to come."

That's also true for the Robot Test Field, an hour's drive north of Naraha in Minamisoma, which sometime this year will include mock bridges, tunnels and other obstacles that drones can maneuver around. And in 2020, the area will host the World Robot Summit, with many of the exhibitions focused on disaster response and infrastructure support. The government of Fukushima Prefecture hopes companies from around the world will eventually come here to test their drones.

Ghost towns

As you drive up the Rikuzenhama Highway from Naraha to Fukushima Daiichi, you can see the Fukushima region slowly coming back to life, including a local supermarket and police station in Tomioka bustling with activity.

Get closer to the facility, however, and you find businesses and homes blocked by metal gates. They're in Futaba, Tomioka and Okuma, once-thriving communities near the power plant that were forced to evacuate.


Wreckage of an arcade in Tamioka, one of the communities near the destroyed power plant. 

James Martin/CNET

Now they're ghost towns.

In Tamioka, I spot a giant Sonic the Hedgehog adorning the outside of a two-story arcade. Time, neglect and the tsunami have wrecked the building, with half of a wall on the second floor blown out.

Farther down the street, there's a Toyota Corolla repair shop whose glass exterior has been shattered into tiny shards. Across the highway, hundreds of bags are filled with radiated dirt that Japan doesn't know what to do with — a stark reminder of the problems it still faces.

It's a snapshot of what everything looked like right after the tsunami hit. Buildings here have been virtually untouched by humans since then. Fully dressed mannequins stand in a nearby retail shop.


A Tepco worker stands near a tower holding contaminated water. 

James Martin/CNET

That could change. The Japanese government now permits people to return for visits in the daytime. During our stay, the local newspaper ran a story saying former residents would be allowed to move back to some of the evacuation zones in May.

"For those of us from Fukushima who live here, we try to live as we did before," says Shunsuke Ono, who runs the J Village hotel and sports complex in Naraha. "For people outside of Fukushima, there's a feeling that Fukushima is not normal." Ono says he doesn't feel in danger living in the area.

Not everyone thinks the same way, says Masaaki Hanaoka, executive general manager of Tepco's International Affairs Office. "They're concerned about services like medical, commerce and business, as well as the community recovery and radiation level reductions," he tells me.

Nature's power

When the explosions blew the tops off Units 1 and 3, radioactive material contaminated the soil around Daiichi. The plant's once parklike surroundings have since been almost completely paved over to prevent rainwater from leaching into the contaminated soil and spilling out to the ocean.

Tepco boasts that you can walk around 96 percent of the 37.7-million-square-foot facility with just the standard jumpsuit and disposable face mask.

As we walk the grounds, I notice a row of cherry blossom trees in full bloom.

"That's the power of nature," my interpreter says.

Originally published March 4, 2019.