TOKYO Just months after Quince was deployed to inspect Japan's tsunami-devastated Fukushima Daiichi nuclear plant, the $6 million robot got trapped in its dark and winding pathways.
Seventeen months later, the high-tech soldier is still missing in action - a symbol of a daunting decommissioning project that will take decades, require huge injections of human and financial capital and rely on yet-to-be developed technologies.
"It's like going to war with bamboo sticks," said Takuya Hattori, president of the Japan Atomic Industrial Forum and a 36-year veteran of Fukushima plant operator Tokyo Electric Power Co, known as Tepco.
The war began after a massive 9.0 magnitude earthquake struck northeast Japan on March 11, 2011, triggering a huge tsunami. Walls of water 13 metres (43 feet) high smashed into the Fukushima plant north of Tokyo, knocking out its main power supply, destroying backup generators and disabling the cooling system. Three reactors melted down as a series of hydrogen explosions rocked the plant.
In the ensuing weeks, hundreds of Japanese workers and soldiers battled to contain the crisis. Their arsenal of weapons was often improvised, low-tech and underpowered. Helicopters dumped buckets of water over the plant to cool it. Electricians laid a cable to connect the plant to a power source miles away in what may have been the world's longest extension cord.
The world's worst nuclear disaster since Chernobyl a quarter century earlier called into question Japan's vaunted reputation for bureaucratic competence and leading edge technology.
The reactors were declared to be in a stable state called cold-shut down in December 2011. But now Japan faces an unprecedented clean-up that experts say could cost at least $100 billion for decommissioning the reactors and another $400 billion for compensating victims and decontaminating areas outside the plant.
Tepco said in November the costs of compensation to residents and decontamination of their neighborhoods might double to 10 trillion yen ($107 billion) from a previous estimate. That did not include a forecast for decommissioning.
Two years after the disaster, cleanup of communities around the plant is haphazard. Much of the work has been handed to Japanese construction companies with little relevant experience. Townships around the plant say the cleanup is behind schedule, while contaminated dirt, leaves and rubble removed by cleaning crews pile up all over Fukushima with no government decision in sight over its final storage space.
The Japan Center for Economic Research, a Tokyo-based think tank, has estimated that decontamination costs alone in the Fukushima residential area could balloon to as much as $600 billion.
Shutting down the 40-year-old Fukushima plant itself poses unique challenges. A Tepco-government roadmap envisages starting to extract spent fuel from the most badly damaged of the station's seven storage pools, which contain 11,417 new and used fuel assemblies, only later this year. Melted fuel debris is to be removed from the reactors from 2021 and the entire project wrapped up within 30 to 40 years.
Officials say the project is mostly on schedule and Prime Minister Shinzo Abe's government wants to speed up the timetable. Experts, however, say it may already be too ambitious.
"It's a pipe dream," Michio Ishikawa said of the four-decade target shortly before he retired last year as chief adviser at the Japan Nuclear Technology Institute, adding it could take decades more.
Reuters reporters visited the plant three times since February 2012 and interviewed dozens of experts, officials, engineers, workers and industry executives to compile the first comprehensive report on the decommissioning project.
Many of those interviewed expressed serious concerns about a lack of vital technology, a potential labour shortage and the vast amount of funds Japan's heavily indebted government will need to spend.
FOG OF WAR
At the leafy campus of Chiba Institute of Technology's Future Robotics Technology Center east of Tokyo - nerve center for Fukushima robotics projects - students and engineers are working flat out to create machines to go where none has gone before.
Some nap on make-shift beds surrounded by robot parts at the Center's airy loft-like building while others slurp noodles as they stare at computer screens or fiddle with smartphones.
A slim 20-something research scientist uses a simple joystick to make an advanced version of the lost Quince robot climb stairs, turn around in a narrow landing, and descend.
Quince was first deployed in June 2011 and was carrying out a survey of one of the reactors when the operators lost contact with the machine later that October. Attempts to retrieve the robot have failed, though developers conjecture one day they will find Quince and it could give them valuable information about the effects of prolonged radiation on electronics.
The new version, called "Sakura" or Cherry Blossom, can navigate narrower spaces and, unlike its predecessor, plug into a battery charging station on its own.
Technology, however, must still be developed to accomplish even the most basic first step - the ability to find and repair leaks in the reactors and fill them with water to shield human workers from high radiation emitted by the debris.
"It's like the fog of war," said John Raymont, president of U.S.-based Kurion Inc, which supplied a water treatment system briefly used to filter contaminated water at the plant. "They are only now getting to know what the problem looks like."
So far, Tepco has only managed to insert remote controlled cameras, similar to endoscopes, into outer vessels of the reactors. The effort has obtained little useful data on the fuel debris, a vital first step before technology to remove it can be developed.
One potential device being considered is a fish-like swimming robot that would glide inside the doughnut-shaped suppression chambers filled with water to create detailed maps.
A key reason for the belated effort to develop such technology was Japan's reluctance to acknowledge the possibility of atomic disasters. Doing so would have contradicted a decades-old myth of nuclear safety. Robots developed after a 1999 nuclear accident at Tokaimura near Tokyo ended up in science museums after research was abandoned.
"The government didn't spend more money after that to develop robots. That's because people were obviously going to ask, 'Wait, is there going to be a situation so dangerous that humans can't enter the plant?'," said Eiji Koyanagi, vice director of the Future Robotics Technology Center.
The first robots into the plant were U.S.-made Packbots, which were deployed just after the disaster to enter areas heavy with radiation.
Tepco's most immediate challenge is to remove spent fuel from pools at the plant, starting with reactor No.4, where more than 1,500 rods rest inside a pool that was exposed to the atmosphere after an explosion blew off the top of the unit's building.
Debris from the top of the reactor building, where radiation levels are too high for humans, has had to be removed painstakingly using cranes and other lifting equipment to get to the spent fuel pool.
That project has a special sense of urgency given concerns another big quake could further damage the building, although Tepco says the structure was reinforced to withstand shaking as intense as in the March 2011 quake.
Another fraught task is to treat and store the contaminated water that results from cooling the reactors to keep them in a stable state at below 100 degrees Celsius. The contaminated water is flooding reactor building basements and threatening to seep into the ocean and groundwater.
Fukushima Daiichi plant sits like a carbuncle on Japan's northeast coast 240 km (150 miles) from Tokyo. Its damaged reactors still seep radiation, although at a rate of 10 million Becquerel per hour for cesium versus about 800 trillion right after the disaster.
Becquerel per hour measures the amount of radiation emitted or the rate of radioactive decay. As atomic isotopes decay, they spin off energized particles that can penetrate human organs and damage human cells, potentially causing cancer. To minimise the dangers to human health from radiation, the government is enforcing a 20-kilometre no-go zone around the plant.
Every day the roughly 3,000 workers who will enter the plant assemble at a base camp - a former sports complex called J-Village - on the edge of the exclusion zone.
There, they don full-body protective suits, rubber gloves and plastic shoe guards. Once at the plant, they put on face masks to keep from inhaling radioactive particles.
Front-line workers, who spoke to Reuters on condition of anonymity, complain about working in the stifling protective gear, the relatively low pay, loneliness - and stress.
About 70 percent of a sample of workers surveyed by Tepco late last year made more than 837 yen ($9) per hour, while a day labourer in that part of Japan can earn as much as 1,500 yen per hour.
Wages are lower than those offered locally for other jobs requiring similar skills, including decontaminating and rebuilding areas further from the plant, said Junji Annen, a professor at Chuo University who last year chaired a panel on Tepco's finances.
"The money is getting worse and worse, and who would want to come and work under these conditions?" a heavy machinery operator in his 40s said as he unwound in the Ai Yakitori bar in Hirono, a town about 40 km from the plant, where dormitories have sprouted up for workers.
"I get stomach aches. I am constantly stressed. When I'm back in my room, all I can do is worry about the next day," added the worker, employed by a small subcontractor. "They should give us a medal."
Mental health experts compare the stress to that suffered by soldiers at a battle front. Moreover, public outrage at Tepco has spilled over into attitudes toward workers.
"Tepco workers are at risk of following in the steps of Vietnam veterans, many of whom were rejected by society on their return, became homeless, committed suicide or got addicted to alcohol and drugs," said Jun Shigemura, a lecturer in the psychiatry department of the National Defense Medical College who conducted a survey of 1,500 Tepco nuclear workers.
The decommissioning plan says authorities can supply enough workers through the decades ahead, but signs of potential shortages are evident, partly because workers are "burning out" by reaching their radiation limits.
As of the end of December 2012, 146 Tepco workers and 21 contract workers had exceeded the maximum permissible exposure of 100 millisieverts in five years, Tepco data showed.
Eight workers have died at the plant, including two on the day of the tsunami. None of the deaths were caused by radiation.
GROPING IN THE DARK
The industry faces a shortage of nuclear engineers as well as blue-collar workers in the decommissioning work for both Fukushima Daiichi and other ageing reactors.
Abe's conservative Liberal Democratic Party-led government has scrapped its predecessor's plan to exit atomic energy by the 2030s but has yet to map out an alternative energy programme. Public safety concerns persist - a recent poll showed 70 percent want to abandon atomic power sooner or later - clouding the industry outlook.
For example, at the University of Tokyo, applications for advanced nuclear engineering degrees fell about 30 percent for the year from April from the previous year and Tokyo City University saw a similar decline in applicants for its undergraduate nuclear engineering programme in the academic year starting in April 2012 from 2010.
"Who will clear up the mess after the accident? It will be young people like us," said Yuta Shindo, a 25-year-old master's student at Tokyo City's nuclear engineering department. "We are the ones who will be working on this decades from now."
Cleaning up the mess will mean total demolition of the four damaged reactor facilities and disposal of the nuclear waste in a yet-to-be determined site, an end-game likely to face opposition from potential host communities.
Japan has rejected the "sarcophagus" option used at Chernobyl, where the damaged reactor was encased in a massive concrete envelope. This is partly because of the difficulty of monitoring an entombed facility to ensure safety, said Kentaro Funaki, director of the industry ministry's office in charge of decommissioning.
Estimates for total costs are mostly guesswork. "Only God knows," said Chuo University's Annen.
Whatever the final bill, Japanese consumers are likely to end up paying much of it, either through taxes, higher electricity rates or both, even as Japan's government struggles with massive public debt and the costs of an ageing population.
That may be unpopular but also inevitable.
"This kind of job has never been done," said Keiro Kitagami, a former lawmaker who headed a government task force overseeing R&D for the project. "The technology, the wherewithal, has never been developed. Basically, we are groping in the dark."
(Writing and additional reporting by Linda Sieg and Aaron Sheldrick; Additional reporting by Maki Shiraki; Editing by Bill Tarrant)