(Reuters) - The robots sent in to find the thousands of tons of highly radioactive fuel at Fukushima's nuclear reactors have “died”; literally melted due to the still intense heat being generated by those still molten and intensely radioactive, thousands of tons of what is now called "corium" for the literally thousands of tons of molten metallic substances that now resembling lava but said to be "missing" but is actually moving beneath the ground under the crippled plants and melting through anything in its path; as yet, a planned for subterranean "ice wall" around the crippled plant which was meant to stop groundwater from becoming contaminated has yet to be finished. And authorities still don’t know how to dispose of highly radioactive water stored in an ever mounting thousands of flimsy "temporary" holding tanks around the site.
Five years ago, one of the worst earthquakes in history, triggered a 10-metre high tsunami that almost reached the heights of markers indicating the heights of previous tsunamis in the area, crashed into the Fukushima Daiichinuclear power station causing a loss of the electrical power needed to run the pumps circulating the needed cooling water for the multiple nuclear reactors and thus allowing multiple nuclear reactor meltdowns wherein their thousands of tons of nuclear fuel in each reactor, burned through all of their containment vessels and went somewhere into the ground.. Nearly 19,000 people were killed or left missing and 160,000 lost their homes and livelihoods.
Today, the radiation at the Fukushima plant is still so powerful it has proven impossible to get into its bowels to find and perhaps recover and remove the thousands of tons each per nuclear reactor, of extremely radioactive and huge dangerous blobs of melted fuel rods, now at temperatures approaching those of the surface of the sun. While each of these scenarios had been predicted as the plants and reactors were being constructed, to save money, they were all built to lower standards.
The plant's operator, Tokyo Electric Power Co (Tepco) <9501.t>, has made some progress, such as removing hundreds of spent fuel roads in one damaged building. But the technology needed to establish the location of the melted fuel rods in the other three reactors at the plant has not been developed.
“It is extremely difficult to access the inside of the nuclear plant," NaoheroMasuda, Tepco's head of decommissioning said in an interview. "The biggest obstacle is the radiation.”
The fuel rods melted through their containment vessels in the reactors, and no one knows exactly where they are now. This part of the plant is so dangerous to humans, Tepco has been developing robots, which can swim under water and negotiate obstacles in damaged tunnels and piping to search for the melted fuel rods.
But as soon as they get close to the reactors, the radiation destroys their wiring and renders them useless, causing long delays, Masuda said.
Each robot has to be custom-built for each building.“It takes two years to develop a single-function robot,” Masuda said.
IRRADIATED WATER
Tepco, which was fiercely criticized for its handling of the disaster, says conditions at the Fukushima power station, site of the worst nuclear disaster since Chernobyl in Ukraine 30 years ago, have improved dramatically. Radiation levels in many places at the site are now as low as those in Tokyo.
More than 8,000 workers are at the plant at any one time, according to officials on a recent tour. Traffic is constant as they spread across the site, removing debris, building storage tanks, laying piping and preparing to dismantle parts of the plant.
Much of the work involves pumping a steady torrent of water into the wrecked and highly radiated reactors to cool them down. Afterward, the radiated water is then pumped out of the plant and stored in tanks that are proliferating around the site.
What to do with the nearly million tonnes of radioactive water is one of the biggest challenges, said Akiro Ono, the site manager. Ono said he is “deeply worried” the storage tanks will leak radioactive water in the sea - as they have done several times before - prompting strong criticism for the government.
The utility has so far failed to get the backing of local fishermen to release water it has treated into the ocean.
Ono estimates that Tepco has completed around 10 percent of the work to clear the site up - the decommissioning process could take 30 to 40 years. But until the company locates the fuel, it won’t be able to assess progress and final costs, experts say.
The much touted use of X-ray like muon rays has yielded little information about the location of the melted fuel and the last robot inserted into one of the reactors sent only grainy images before breaking down.
ICE WALL
Tepco is building the world’s biggest ice wall to keep groundwater from flowing into the basements of the damaged reactors and getting contaminated.
First suggested in 2013 and strongly backed by the government, the wall was completed in February, after months of delays and questions surrounding its effectiveness. Later this year, Tepco plans to pump water into the wall - which looks a bit like the piping behind a refrigerator - to start the freezing process.
Stopping yet more ground water intrusion into the plant is critical to Japan's survival, said Arnold Gunderson, a nuclear physicist and former nuclear engineer.
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