North Korea may be significantly expanding its nuclear weapons production and could have added six or more weapons to its stockpile in the last 18 months, a U.S. research institute said on Tuesday.
The Washington-based Institute for Science and International Security (ISIS) estimated last year that North Korea had 10 to 16 nuclear weapons at the end of 2014. It based that conclusion on an analysis of the country's production of weapons-grade uranium and plutonium recovered from spent nuclear fuel.
In revised estimates contained in a report provided to Reuters, the institute's David Albright and Serena Kelleher-Vergantini said North Korea may have added another four to six weapons since then, for a total of 13 to 21 or even more today.
The report said the 13 to 21 estimate did not take into account the possible production of additional highly enriched uranium at a second centrifuge plant thought to exist in North Korea.