By Yoko Kubota
TOKYO (Reuters) - Japan's government said on Tuesday it was on track with efforts to take control of the crippled Fukushima nuclear plant but cautioned that a final clean-up of the worst nuclear accident since Chernobyl would take many years.
The update on progress to shut down six reactors at the Fukushima Daiichi plant comes four months after a massive earthquake and tsunami knocked out cooling systems at the complex and triggered a series of core meltdowns and explosions.
"We still don't have a schedule for the work to decommission this plant, and that's planning that we have to begin now," Goshi Hosono, the minister in charge of the government's response to the nuclear crisis, told reporters.
Officials said the plant's operator, Tokyo Electric Power Co had cleared the first hurdle in the efforts to bring the plant under control by setting up an improvised cooling system to circulate water to cool three badly damaged reactors.
But they added that it could take until 2015 to start removing uranium fuel rods from storage pools at the reactors, including No. 4 reactor which had been heavily loaded with stored fuel at the time of the disaster in March.
The government also said it would begin to consider a schedule for some 80,000 residents evacuated from around the plant to return by January.
Officials said they still expected it could take another six months to bring Fukushima's reactors to a state of "cold shutdown," where the uranium at the core is no longer capable of boiling off the water used as a coolant.
If work moves quickly, the plant could be under control with little risk from another loss of power within three months, officials added.
"During the time that I've been involved in this effort, we've encountered every kind of difficulty, so I don't think we have room to be optimistic," Hosono said. "By the same token, we've managed to overcome the trouble we've faced so I don't want to be pessimistic, either."
Once the plant is in a stable shutdown, the focus would then shift to cleaning up and removing fuel from the site, about 240 km (150 miles) north of Tokyo.
A full decommissioning of the reactors would take more than 10 years, officials have said.
(Reporting by Yoko Kubota; Editing by Chris Gallagher and Yoko Nishikawa)