WASHINGTON (Yonhap News) ― North Korea is continuing to collect bargaining chips by apparently restarting its long-mothballed nuclear reactor in Yongbyon and possibly building another one on the site about 70 miles north of Pyongyang, a prominent U.S. nuclear scientist contends.

Siegfried Hecker, who visited the Yongbyon complex in 2010, said should the North operate the 5-megawatt reactor with a full load of 8.000 fuel rods, it will be able to extract roughly 10-12 kilograms of plutonium within the next three years.

“We can expect Pyongyang to gain one bomb’s worth of plutonium per year as long as it stays on this path,” he said in a column for the Bulletin of the Atomic Scientists.

Such a production rate does not constitute a game changer, but it would give North Korea enough plutonium to refine its nuclear devices to fit on missiles, he added.

The North has carried out three known underground nuclear tests, in 2006, 2009 and 2013. The North said its latest test was to produce smaller and more sophisticated nuclear devices that can be mounted on missiles.

Satellite imagery suggests the secretive communist nation has resumed operations at the reactor, which was disabled in 2007 under a deal with the U.S., South Korea, China, Japan and Russia.

Hecker stressed a more troublesome scenario would be when Pyongyang builds a copy of the 50-megawatt reactor that was near completion in 1994 but abandoned under the Agreed Framework with the United States.

“The 10 bombs’ worth of plutonium this reactor could produce would be a game changer,” Hecker said.

In addition, he pointed out, the North is pursuing another path to produce fissile materials ― uranium enrichment, which is more difficult for satellites to detect.

Hecker said denuclearization of the Korean Peninsula must remain the goal, but has become a more distant one.

“It will now be more challenging and costly, although not impossible, to get North Korea to agree to what I have called ‘the three no’s’ ― no more bombs (meaning no more plutonium and HEU); no better bombs (no nuclear testing and no missile launches); and no exports,” he said. HEU means highly enriched uranium for nuclear weapons.