Faced with uncertainties in assessments of North Korea’s centrifuge program, the . intelligence community focused on the significance of the 2007 and 2008 discoveries of traces of highly enriched uranium (HEU) found on North Korean aluminum tubes and operating records for the Yongbyon nuclear reactor. The discoveries raised anew concerns that North Korea had a secret gas centrifuge plant operating by the mid-2000s, contradicting assessments based on procurement data. The enriched uranium particles remain the most direct evidence that North Korea has produced highly enriched uranium. But the reported lack of consensus on their meaning warrants.
