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North Korea has two outdoor high explosive (HE) test sites for nuclear weapons development: Yongdok-dong and Kumchang-ni. Yongdok-dong is operational as of late 2025, while Kumchang-ni has ceased operations recently.

These sites facilitate multiple tests of fission implosion weapon components and complete devices using surrogate materials. Following North Korea's sixth underground nuclear test in September 2017, testing at both sites resumed in January 2021, with nine outdoor tests detected from April 2021 to February 2024.

Yongdok-dong features renovated storage and handling buildings and an outdoor test area with visible craters. The Kumchang-ni site, located near an underground facility, may allow larger explosive charges, as indicated by larger blast craters observed. The differences in crater sizes may suggest variations in explosive charge capacities or different nuclear weapon designs being tested.