Satellite images obtained by CNN captured by Maxar during April and May show that North Korea has restarted construction of the second reactor Yongbyon nuclear complex. According to experts at Middlebury Institute of International Studies who analysed the photos, this is after years of inactivity at the site.
The reactor is around 10 times larger than the original Yongbyon reactor which has been operational since the 1980s.
According to a CNN source US officials are aware of developments and are monitoring them closely.
They also noted that Pyongyang does not appear to be making any efforts to hide construction restarting.
The source added that this could be an outward demonstration of North Korea’s nuclear progress and ambitions for the future.
New construction at Yongbyon also appears to align with the secretive nation’s aim of becoming a nuclear armed state, the source added.
According to experts it is difficult to estimate how quickly the North Koreans could complete construction at the reactor.
However, according to Jeffrey Lewis, a weapons expert and professor at the Middlebury Institute, it would be a significant coup for Pyongyang.
Mr Lewis argued that it would increase North Korea’s production for plutonium by a factor of 10.
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“The connection of the cooling loop helps explain other activities seen at the 50MW(e) reactor in recent years.
“Connecting the secondary cooling loop suggests, in hindsight, that the demolition of the apparent spent-fuel building was an early sign that North Korea intends to complete construction of the reactor.”
Mr Lewis also pointed out that North Korea halted construction of the Yongbyon nuclear reactor in 1994 under the framework of an agreement with the US.
At that point the reactor was still years away from completion.
Another source added that significant preparatory activity is necessary before any state can start construction on a nuclear reactor.
They said: “Preparatory activities speak to intent, planning and long held goals.”