Revelation of Yongbyon's first enrichment facility (2010)
Stanford professor Siegfried Hecker visited Yongbyon and was shown a modern centrifuge facility with about 2,000 centrifuges, stunning the international community. US intelligence had believed North Korea's enrichment program was far smaller.
Heightened concern about a second North Korean nuclear path through uranium, beyond its plutonium program.
Established a baseline for monitoring North Korea's enrichment buildup over the following decade and a half.
Today's new facility at Yongbyon is the latest step in that buildup — far larger than what Hecker was shown in 2010, and expanding across multiple sites.
