Thirteen years after a 9.0-magnitude earthquake and tsunami hit Fukushima-Daiichi in one of the world's worst nuclear accidents, around 880 tons of extremely hazardous material remain inside its reactors.

Removing the debris is regarded as the most daunting challenge in the decades-long project to decommission the plant.

"We have finished the work to thoroughly check the steps. The trial retrieval (of debris) will resume from September 10," a Tokyo Electric Power Company (Tepco) official told a news briefing on Monday.

On August 22, Tepco originally planned to start its first trial removal of the debris, aiming to collect just three grams (0.1 ounces) of it for analysis and to decide its next steps.

But the company had to stop the work after detecting a technical problem involving the installation of the necessary equipment.

Three of Fukushima-Daiichi's six reactors were operating when the tsunami hit on March 11, 2011, sending them into meltdown in what became the worst nuclear disaster since Chernobyl.

The debris inside those reactors has radiation levels so high that Tepco had to develop specialised robots able to function inside.

hih/mtp

TEPCO - TOKYO ELECTRIC POWER