The International Atomic Energy Agency called on Wednesday (December 4) Japan's efforts to decommission the wrecked Fukushima Daiichi Power Plant very complex, with challenging issues remaining for the long term stability of the plant following another review of the sites.

"The team also considers that the situation remains very complex at the site and that there are still very challenging issues that must be resolved to ensure the plant's long-term stability," said International Atomic Energy Agency's Juan Carlos Lentijo at a news conference after the IAEA's 19 member team visited Fukushima Daiichi earlier last week.

This comes at a time when Tokyo Electric Power Company, also known as Tepco, has started decommissioning the wrecked plant by removing spent fuel rods from the crippled nuclear reactors.

"That implies that it is not only the time to remove materials but to characterize, to better characterize these materials to think in the solution for the management of these materials for the long-term," Lentijo said.

Tepco, which has floundered in trying to bring the plant under control in the two and a half years since the disaster, is now moving to full decommissioning at the six-reactor facility.

The most urgent task is to remove the fuel assemblies from the unstable Reactor No. 4, which due to their height - about 18 metres above ground level - are more vulnerable to any new earthquake. The operation is seen as a test of Tepco's ability to move ahead with decommissioning the whole facility - a task likely to take decades and cost tens of billions of dollars.

Presented by Adam Justice