The operator of the crippled Fukushima nuclear plant said Tuesday workers had spilled four tonnes of radioactive water, likely contaminating the soil and possibly groundwater.

Workers were pumping rain water that was trapped in a concrete gutter into an empty 12-tonne tank that sat on open soil, said a spokesman for Tokyo Electric Power (TEPCO).

"Work crew started operating the pump around 10:38 am. At 11:50 am, they found water was spilling from the manhole on top of the tank," the spokesman said.

TEPCO has estimated roughly four tonnes of collected rain water might have escaped. The extent of contamination was unclear, the spokesman added, although it was not thought to be highly polluted.

"The water itself was rain water. But it was from the Fukushima Daiichi nuclear plant and could contain radioactive materials," he said, adding: "The water seeped into the ground".

TEPCO has long struggled to control waste water at the plant.

The company poured thousands of tonnes of water onto runaway reactors to keep them cool, and continues to douse them.

TEPCO has so far disclosed no clear plan for disposing of the huge amounts of stored polluted water, which is stored at hundreds of tanks at the plant.

Some tanks have leaked highly radioactive waste water, which might have washed to sea.

Japanese fast-food chain to farm in Fukushima
Tokyo (AFP) Oct 01, 2013 - Major Japanese fast-food chain Yoshinoya said Tuesday it would grow rice and vegetables in Fukushima prefecture, home to the nuclear plant that was crippled by a tsunami in 2011.

Operator Yoshinoya Holdings said it had set up a joint venture with local farmers -- called Yoshinoya Farm Fukushima -- to grow rice, onions and cabbages in a 4.3-hectare (10.6 acre) field in Shirakawa, 80 kilometres (50 miles) from the nuclear plant.

It will also build a facility to process vegetables for use in Yoshinoya restaurants across the nation, the firm said, adding strict radiation screening measures will be put in place.

"We believe this will lead to support for reconstruction," Yoshinoya said in a statement, adding the move would also help it secure low-priced ingredients for its beef bowl dishes.

Large swathes of Fukushima were evacuated after a nuclear emergency erupted in March 2011 when a quake-triggered tsunami smashed into a nuclear power station on the coast, sending reactors into meltdown and spreading radiation over a wide area.

Tens of thousands of people are still unable to return to their homes around the plant, while the government has lifted exclusion zones in some areas.

Farmers across Fukushima, a relatively large area that is mainly unaffected by the disaster, have complained about plunging prices for their produce.

Consumers, wary of the taint from the nuclear disaster, continue to avoid food carrying the Fukushima tag.