The Yongbyon Nuclear Reactor in North Korea (Creative Commons)

North Korea's previously-defunct nuclear reactor in the Yongbyon County in the North Pyong'an Province is "nearing operation," according to 38 North, a website run by the US-Korea Intitute at the John Hopkins' School of Advanced International Studies.

Satellite images show steam rising from a building near the reactor that houses the reactor's steam turbines and electric generators. This is consistent with the steam being vented if the electrical generating system was about to go online, which further indicates that the reactor is "in or nearing operation," the institute says.

The reactor is capable of producing six kilograms of plutonium a year, which is enough to manufacture one nuclear bomb per year.

Read more about the North Korean reactor here.