A U.S. think-tank says that North Korea is gearing up to reactivate the 5-megawatt gas-graphite reactor that has been mothballed since 2007.

The U.S.-Korea Institute at the Johns Hopkins School of Advanced International Studies said Monday that new commercial satellite imagery showed North Korea making "important progress" in activating the long-shut reactor.

"Pyongyang is nearing completion of work necessary to restart the 5 MWe reactor used to produce North Korea's supply of weapons-grade plutonium," the Think-tank said in a report published by the website 38 North.

"The 5-MWe reactor may be 1-2 months from start-up. But the availability of fresh fuel rods to power the reactor remains uncertain," said the report.

The reactor at its main nuclear site in Yongbyon was closed in July 2007 under a deal with South Korea, China, Russia, Japan and the U.S. But last April, North Korea said that Pyongyang was planning to reactive the reactor, amid high tension over the Korean peninsula.

The resumption of t work to restart the reactor comes after its third nuclear test on Feb. 12, which led to expanded UN sanctions.

The report says that the Yongbyon reactor might be restarted within months and once it becomes operational, it will generate around 6 Kilograms of plutonium annually.

Some experts say that it might take longer than that as the cooling system of the reactor needs to be reinstalled.

Speaking about the restart of reactor, an official at Seoul's Ministry of Unification said "wait and see" hinting there might be some technical problems that might not let North Korea to restart the reactor soon.
"Such a move constitutes a serious development because it will lead to the country acquiring more fissile materials that can lead to more nuclear weapons testing and miniaturization of devices," the official whose identity was not disclosed said, according to the YONHAP NEWS AGENCY.