Though North Korea may have previously relied on foreign assistance in obtaining or making the fuel, as some analysts believe, it no longer appears to need the help.
Vipin Narang, a Massachusetts Institute of Technology professor who studies nuclear issues, called the discovery “very important.”
“If they are not dependent on foreign suppliers,” he said, then “even the most targeted sanctions on, and monitoring of” countries that might assist North Korea, “will be mostly futile.”
Short of war or the country’s collapse, he added, “There’s nothing to stop this program from becoming a monster.”
The finding is based on satellite imagery, a technical analysis of UDMH production methods, information from a North Korean official who defected, and a set of obscure North Korean technical documents.
Jeffrey Lewis, who directs the Middlebury center’s East Asia program, had been hunting for weeks for hints of UDMH production.
“There are no real, obvious signatures for it,” he said, because it can be made with common chemicals like chlorine and ammonia using a variation of a process developed in 1906. India, while quietly developing its missile program in the 1970s, had produced UDMH in an old sugar factory.
The breakthrough came when his team found and translated a set of highly technical articles in an official North Korean science journal, Chemistry and Chemical Engineering, that referred to the fuel.
The articles, which ran between 2013 and 2016, discussed mundane matters like managing highly toxic wastewater, a notorious problem in UDMH production. But they betrayed suspiciously sophisticated knowledge. One explored methods for improving purity, crucial in advanced missiles.
“They don’t read like this is a speculative or nascent endeavor,” Mr. Lewis said. “They read like this is a problem they’ve been working on for a while,” describing problems a country would encounter only after producing large quantities of the fuel.
But the documents betrayed something else: conspicuous secrecy. Unlike others in the journal, these three…