Aerial image of the Tokyo Electric Power Co's Fukushima Daiichi Nuclear Power Plant after the magnitude 7.4 earthquake hit offshore on November 22, 2016 in Okuma, Fukushima, Japan. The Asahi Shimbun via Getty Images

The 4 trillion yen ($35 billion) clean-up at Fukushima isn’t going smoothly. The former nuclear power station is quickly turning into a robot graveyard due to recurrent failures with the remote-controlled probes sent inside.

Three reactors at the Fukushima Daiichi nuclear plant experienced meltdowns following an earthquake and tsunami in 2011. Six years on, Tokyo Electric Power Company (Tepco) are still trying to find and remove the 544 tonnes (600 US tons) of melted nuclear fuel rods that are lost among the debris of the radioactive ruins. However, the remote-controlled robots tasked with this dangerous endeavor are failing time and again.

Naohiro Masuda, head of Tepco's decommissioning program, said last week that the repeated robot failures are becoming an issue that needs to be solved, according to the Associated Press. He also urged for more creativity and ingenuity when it comes to the next-generation of clean-up bots.

"We should think out of the box so we can examine the bottom of the core and how melted fuel debris spread out,” Masuda told reporters.

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Toshiba's scorpion-like robot (above) was sent into reactor 2 in February, but was unable to reach its desired destination due to its path being blocked. It was then exposed to more than five times its anticipated radiation exposure limit in just two hours. Although it did manage to get temperature readings and radiation levels, it was unfit to capture images showing the core or the location of the nuclear rods.

Two other expensive probes met an untimely end in the power plant after getting stuck and being starved of fuel.

“The road map for removing the fuel is going to be long, 2020 and beyond,” Jacopo Buongiorno, a professor of nuclear science and engineering at the Massachusetts Institute of Technology, told Bloomberg. “The re-solidified fuel is likely stuck to the vessel wall and vessel internal structures. So the debris have to be cut, scooped, put into a sealed and shielded container and then extracted from the containment vessel. All done by robots.”

One thing's for certain, the woes of the Fukushima Daiichi nuclear plant and the headaches of Tepco are far from over.