Beginning in the early 2000s, North Korea began building a discreet, largely unnoticed, cluster of buildings, not far from the banks of the Taedong river, a few kilometers south-southeast of the North Korean capital of Pyongyang. Located on the eastern end of Chollima, a town best known for hosting a massive steel manufacturing complex since the Japanese occupation of the Korean Peninsula, the facility had drawn no public attention—until now.</p><p>The facility is North Korea&#8217;s first covert uranium enrichment facility, known by the U.S. intelligence community as the Kangson enrichment site. It is where, for more than a decade—possibly as long as fifteen years—North Korea has been enriching uranium for use in nuclear weapons. It is older than the well-known enrichment site operated by North Korea since at least 2010 at the old Fuel Fabrication Plant at Yongbyon. The Kangson site is one of two known North Korean covert enrichment sites.</p><p><span style="font-style: italic;">The Diplomat</span>, along with a team of open source researchers at the Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey led by Jeffrey Lewis, was able to locate the Kangson covert enrichment site. Separately, a U.S. government source with knowledge of the latest intelligence on North Korea&#8217;s nuclear weapons program, when asked, confirmed <span style="font-style: italic;">to The Diplomat </span>that the discovered site corresponded to the covert enrichment site referred to by the U.S. intelligence community as Kangson. U.S. intelligence has monitored this site for more than a decade.</p><p><span style="font-weight: bold;">The Kangson Enrichment Site</span></p><p>The Kangson site is built around a single, large building, assumed to contain the main gas centrifuge cascades, which output uranium highly enriched in uranium-235 and suitable for use in nuclear weapons. The main hall is 50 meters long and 110 meters wide. Its height is unknown and it’s also unclear if the building may have an underground area. The entire site, including the main hall, the long entryway road, and the associated support buildings, is surrounded by a one kilometer-long wall perimeter, suggesting that it is a high security area.</p><p class="td-ad-inline td-ad-inline-txt ng-hide" ng-show="dplpw.ad"><a href="https://thediplomat.com/subscriptions/"><b>Enjoying this article?</b> Click here to subscribe for full access. Just $5 a month.</a></p><p>Curiously, the secure Kangson facility sits just one kilometer off the Pyongyang-Nampo expressway, a major North Korean road that connects the country’s capital to the port city of Nampo on the Yellow Sea. The entrance to the Kangson enrichment site sits just one kilometer off the main expressway, along a road that connects it to the town of Chollima. Visitors from Pyongyang to Chollima traveling by road would likely drive past the Kangson site.</p><p style="text-align: center;"><strong>A Suburban Enrichment Plant: Kangson Relative to Pyongyang