This November, Tepco will attempt to remove 400 tons of spent fuel rods from reactor no. 4

From RT.com

Scientists at Japan’s Fukushima nuclear power plant are preparing for their toughest clean-up operation yet – two and a half years after three of the plant’s reactors suffered a meltdown in Japan’s worst-ever nuclear power disaster.

The operation, to remove 400 tons of highly irradiated spent fuel beneath the plant’s damaged Reactor No. 4, could set off a catastrophe greater than any we have ever seen, independent experts warn. An operation of this scale, says plant operator Tokyo Electric Power Company, has never been attempted before, and is wrought with danger.

An uncontrolled leak of nuclear fuel could cause more radiation than the March 2011 disaster or the 1986 Chernobyl catastrophe, say consultants Mycle Schneider and Antony Froggatt. "Full release from the Unit-4 spent fuel pool, without any containment or control, could cause by far the most serious radiological disaster to date," the scientists say in their World Nuclear Industry Status Report 2013.

The operation has been tried before – but only with the aid of computers. This time it will be a painstaking manual process.