Capabilities Update: ISIS on Fissile Material and Nuclear Weapons
David Albright and the “good ISIS” have a brief, but pointed update on North Korean capabilities posted last week. As in the past, they rightly work off of distributions of estimates, citing medians. It is easily summarized, beginning with the things that are somewhat more easily assessed given observations on the operation of the 5MW “experimental” reactor and estimated floor space of the centrifuge operations, at least at Yongbyon:
- Stock of separated plutonium is likely to be around 33 kilograms. Assume 2-5 kilos per weapon, but on a path of increasing efficiency with each test.
- The variance on estimates of weapons-grade enriched uranium is much higher because of continued uncertainty about the presence and size of a second enrichment site: 175-645 kilograms with the first corresponding to a median estimate for one centrifuge plant and the second two. Assumptions are 15-25 kilos of HEU for a weapon.
- Albright estimates 13 to 30 nuclear weapons, based on utilization of 70 percent of the estimated stocks of plutonium and weapon-grade uranium and assumption of a mix of plutonium and uranium weapons. But he admits this estimate is even more tenuous than production of fissile material where capabilities are somewhat better known. Estimated output is now at 3-5 weapons per year.
- With respect to actual weaponization, assessments are more tenuous still. North Korea could have plutonium-based warheads for its Nodong but could also be building weapons with a uranium core, as it declared following the September 2016 test. It also has the raw material to build composite core nuclear weapon made from both plutonium and weapons-grade uranium, and claims to be pursuing thermonuclear weapons, probably one-stage weapons but possibly two-stage boosted weapons. Given the belief that North Korea has the ability to handle materials that are central to boosted weapons—solid forms of lithium-6, deuterium, and/or tritium—the regime could make progress on these weapons even without testing.