Recent satellite images suggest that North Korea is restarting test operations of its experimental light water reactor in Yongbyon. The reactor, reportedly in test operations since the second half of last year, was shut down for about a month starting mid-March. However, Maxar satellite images show that it restarted in late April. The photos also show that Yongbyon’s 5 MWe reactor is also operating. High-resolution images from Apr. 27 clearly show the discharge of coolant water from two pumping stations attached to the 5 MWe reactor and light water reactor into the Kuryong River, along with white foam from the thermal effluent. The South Korean defense ministry predicts that Yongbyon’s experimental light water reactor will go into normal operations this summer, while the international community worriedly forecasts that North Korea will be able to produce three to five times more plutonium, a material for the manufacture of nuclear warheads.
Operations at Yongbyon’s 5 MWe reactor and light water reactor

Using Maxar satellite images, I examined signs of activity at Yongbyon’s 5 MWe and light water reactor from January until recently. I detected signs of operations nine times from the start of the year until mid-March, and then there were no signs for about a month until they reappeared at the end of April. Considering the times clouds obscured the view or the satellite could take no images, some discrepancy may exist between how often signs were detected and how long operations were suspended. However, I detected no signs of operations from mid-March to mid-April before detecting operations again on Apr. 27.
The nuclear facilities at Yongbyon, North Pyongan Province, were built in the 1960s with support from the Soviet Union. They are quite old. To supplement the existing 5 MWe reactor, North Korea began building its Experimental Light Water Reactor (ELWR) around 2010 and started test operations late last year. David Albright, a U.S. nuclear physicist and director of the Institute for Science and International Security, said the ELWR could produce three to five times more plutonium than the 5 MWe reactor, while South Korean Defense Minister Shin Won-sik predicted the ELWR would go into regular operation this summer.
Let’s briefly summarize the operation of Yongbyon’s reactors. When in operation, a reactor burns nuclear fuel rods to produce heat. To cool down the reactor, a pump station takes water from the Kuryong River. The pump station then discharges the heated coolant back into the river. Satellite images detect this discharge, which observers then reference to determine if the reactor is operating. The used fuel rods are placed in a nearby storage facility before being brought to a radiochemistry laboratory 1.8 kilometers away, where plutonium is extracted from the rods after reprocessing. Ultimately, the plutonium is used to produce nuclear warheads, a weapon of mass destruction. Because of this, the international community, including the U.N., monitor satellite images to determine if coolant from the 5 MWe reactor or ELWR is being discharged.
The international community suspects North Korea’s test operation and soon-to-be regular operation of Yongbyon’s ELWR aim to significantly expand the production of nuclear fuel for weapon production, not the reactor’s original public-interest purpose of producing electricity. This suggests North Korea wants to dramatically increase production of plutonium per Kim Jong Un’s order to exponentially increase North Korea’s nuclear arsenal after defining South Korea as the North’s “undoubted enemy” in January 2023.
Nuclear power stations are the fruit of modern scientific civilization. If used well, they can benefit civilization, but if misused, they can become a tool of disaster that could destroy humanity. A sharp knife finds a different use and produces different results depending on whether it is in the hands of a chef or a mugger. North Korea’s government always appears to be a danger, like an angry, hate-filled middle school student in juvenile angst carrying an explosive device.
Translated by David Black. Edited by Robert Lauler.
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