Satellite pictures appear to confirm that North Korea has restarted its Yongbyon nuclear reactor.
"Imagery from 22 January shows a water plume (most probably warm) originating from the cooling water outlet of the reactor, an indication that the reactor is very likely operating," according to the 38 North website at US-Korea Institute at Johns Hopkins University's School of Advanced International Studies.
"Currently, most of the river is frozen over except where this water mixes with the river." However, 38 North admitted it is "impossible to estimate at what power level the reactor is running”.
When fully operational, the reactor can produce 6kg of plutonium a year by reprocessing used fuel rods. Speculation that the reactor was about to be restarted followed detection of vehicles for repairs and fuel supply at the reactor site over the past four months.
South Korea estimates that the North already has about 50kg of plutonium, enough to make some 10 nuclear weapons. The 5MW graphite-moderated reactor has already provided the weapons-grade plutonium that the regime used in its first three nuclear tests, in 2006, 2009 and 2013. The North conducted its fourth and fifth nuclear tests in January and September last year.