(Corrects spelling of name in 4th-last paragraph to Gundersen... not Gunderson)

* Five years on, melted fuel rods still spew radiation

* Extreme radiation fries wiring in the robots

* Focus is on stopping groundwater contamination

* Complete shutdown is 30 to 40 years away

By Aaron Sheldrick and Minami Funakoshi

March 10 (Reuters) - The robots sent in to find highly radioactive fuel at Fukushima's nuclear reactors have "died"; a subterranean "ice wall" around the crippled plant 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 number of tanks around the site.

Five years ago, one of the worst earthquakes in history triggered a 10-metre high tsunami that crashed into the Fukushima Daiichi nuclear power station causing multiple meltdowns. 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 remove the extremely dangerous blobs of melted fuel rods.

The plant's operator, Tokyo Electric Power Co (Tepco) , 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," Naohiro Masuda, 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 criticised 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.