Carnegie's James Acton discussed satellite images that show activity at Yongbyon nuclear complex in North Korea. Acton told Al Jazeera that the West needs to start talking again to Pyongyang. "Although this is not a surprise, it is serious," Acton said, "becasue it is yet another indication that North Korea is not going to be willing to give up its nuclear weapons program."

"Quite the contrary," Acton added, "it now appears to be intent on expanding the size of its arsenal." North Korea says it has a nuclear weapons and there is external evidence of that claim, Acton said, so this reactor is about expanding its arsenal. North Korea does not have a large arsenal at the moment so one and a half bombs worth a year is a significant expansion, Acton pointed out. 

"What I think ought to happen in private," Acton concluded, "is talks with North Korea about risk reduction, about trying to make it clear to North Korea that proliferating nuclear technology or material - as it has done to Syria in the past - that there will be consequences to pay."

This interview was originally broadcast on Al Jazeera.