|Fig. 1: Hwasong-14 ballistic missile during its second test. The undated picture is provided by the Korean Central News Agency in Pyongyang, North Korea. Source: Wikimedia Commons)|
Tensions have been rising in recent months as North Korea has been flexing its nuclear capabilities with missile test launches. Still, limited information is available about the reclusive countrys nuclear program due to its secretive administration. Several experts have conducted their own assessments of the programs sophistication based on personal visits, satellite imagery, test launches, and other sources. Experts have a range of estimates for North Koreas nuclear resource reserves, the range of their missiles, and their escalating technology.
North Korea has been steadily generating a supply of the fuels used in nuclear bombs, plutonium, produced in reactors, and uranium, enriched in centrifuges. In December 2017, Siegfried Hecker estimated that North Korea has 20-40 kg of plutonium based on his visits and monitoring the satellite activity of Yongbyon's 5-megawatt reactor. He also visited a modern centrifuge unit, and based on satellite imagery, estimated that they possess 250-500 kg of highly enriched uranium. 
We know that a nuclear weapon requires around 5 kg of plutonium or 20kg of highly enriched uranium. If we take Heckers estimates and assume that North Korea has appropriated all its nuclear fuel to produce weapons, we can make the assumption that North Korea could make 4-8 bombs from plutonium and 12-24 bombs from uranium. These estimates align with David Albrights report in April 2017, which estimated that North Korea had 13 to 30 nuclear weapons.  Another paper, published in 2018 by Hans Kristensen and Robert Noris, raised the estimate, claiming that North Korea has enough fissile material for 30-60 nuclear weapons. 
The question remains if North Korea has been able to develop operational nuclear warheads that could have travel across the Pacific. Intercontinental ballistic missiles (ICBM) have ranges greater than 8,000 miles, and North Korea has demonstrated that it has the capability to make these. During a test on November 2017, the Hwasong-15 carried a warhead up to a height of almost 2,800 miles (4475 km), which experts have estimated corresponds to a range of 8,000 miles. That is well enough for the missile to reach cities in the continental United States. The Hwasong-15 was an improvement on the Hwasong-14, shown in Fig. 1. The Hwasong-14 missile test in July had a shorter range, only reaching an altitude of 2,300 miles (3725 km). 
However, US officials assessed that the Hwasong-15 also had problems with atmosphere re-entry. It is not certain that North Korea has successfully developed a re-entry vehicle for its ballistic missiles.  A ballistic missile's re-entry vehicle must be able to withstand immense structural and heat stresses as it descends through the atmosphere at a supersonic speed. While this news is a relief to some, some experts are saying that the re-entry vehicle should not be technically challenging for the North Korean missile program to refine. The missile should still be able to reach and target major metropolitan areas in the United States. 
The sophisticated technological advancements and destructive potential of the North Korean nuclear program should be taken seriously. It is possible that an ICBM could reach the continental United States, causing severe destruction. Discussions with North Korea should be carefully navigated in order to move towards peaceful agreements.
© Maria Gabrielle Coseteng. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 H. M. Kristensen and R. S. Norris, "North Korean Nuclear Capabilities, 2018 ," Bull. Atom. Sci. 74, 41 (2018).
 D. Albright, "North Korea's Nuclear Capabilities: A Fresh Look," Institute for Science and International Security, 28 Apr 17.
 B. Dorminey, "Despite Re-Entry Issues, North Korea's ICBMs Still Pose Continent-Wide Threat To U.S.," Forbes, 14 Dec 17.