Pyongyang: A key North Korean nuclear complex has been undergoing "modernization and expansion" throughout the year, a U.S. website monitoring the reclusive state said Sunday. "Commercial satellite imagery of North Korea's Yongbyon Nuclear Scientific Research Center from October and November 2025 shows continuation of modernization and expansion efforts throughout the site," 38 North said in its report. "Yongbyon plays a critical role in the country's production of nuclear material for its weapons program, as the sole producer of plutonium and a significant source of enriched uranium."

According to Yonhap News Agency, the suspected uranium enrichment site northeast of the radiochemical laboratory has become the most active since the start of this year. 38 North first identified the suspected site in June. The latest report claimed the exteriors of two support buildings in the eastern part of the complex were complete, while concrete paving has been added around these buildings.

38 North also said six possible heat exchangers, which cool centrifuges and maintain controlled temperatures inside the main building, have been installed along the southeast side of the building. "Other equipment appears to be outside the building," the report said. "Together, these objects indicate it is likely that work to complete the interior of the main building is still underway."

On his visits to nuclear weapons-related sites in January, North Korean leader Kim Jong-un emphasized the need to "achieve epochal successes in overfulfilling the plan for producing weapons-grade nuclear materials and in strengthening the nuclear shield of the country." "Activity over the course of 2025 reflects these directives," 38 North said, citing consistent operation of the 5 MWe reactor since January and preoperational testing of the experimental light water reactor.

"These improvements all serve to help fulfill Kim's call for exponential growth of its nuclear weapons arsenals," the report added.