Smart Q&A: Siegfried S. Hecker on North Korea's Nuclear Capabilities and Proposals for Future Six-Party Talks

Dr. Siegfried S. Hecker is a professor of Management Science and Engineering in the Freeman Spogli Institute for International Studies and the Center for International Security and Cooperation (CISAC) at Stanford University. He served as co-director of CISAC from 2007 to 2012. For the past 18 years, his research has focused on safeguards for nuclear materials in Russia, the management of fissile materials in the former Soviet Union, and nuclear issues in India, Pakistan, North Korea, and Iran.

Over the past month, various discussions have taken place regarding the resumption of the Six-Party Talks due to China's proposed trilateral meeting on September 18th among the Six-Party Talks participants and the various diplomatic measures taken by the United States, South Korea, and Japan in response. However, the resumption of talks has stalled due to the direct conflict between the positions of China and North Korea, which call for unconditional dialogue, and the positions of the United States and South Korea, which insist on sincere North Korean denuclearization measures as a prerequisite. On September 13th, the East Asia Institute (EAI) invited Dr. Siegfried S. Hecker from the Center for International Security and Cooperation (CISAC) at Stanford University for an interview on North Korea's nuclear capabilities and the measures North Korea and the international community should take for the resumption of the Six-Party Talks. The main points are as follows:

Assessment of North Korea's Nuclear Capabilities

“North Korea is pursuing both a plutonium program and a highly enriched uranium program: Plutonium is advantageous for miniaturizing nuclear warheads, while highly enriched uranium is advantageous for evading international scrutiny.”

Both North Korea's current plutonium program and its highly enriched uranium (HEU) program pose significant threats because they can be used to build nuclear weapons. The atomic bomb dropped on Hiroshima was a uranium bomb, and the bomb dropped on Nagasaki was a plutonium bomb.

North Korea conducted nuclear tests in 2006, 2009, and 2013 and appears to have successfully developed a small number of nuclear weapons, but it is not believed to possess a large nuclear arsenal. To build a nuclear bomb, fuel such as plutonium or highly enriched uranium is required. North Korea produced plutonium at the 5 MWe gas graphite reactor in Yongbyon until its operation was halted under the 1994 Agreed Framework. This facility was restarted in 2003 and then shut down again in 2007 following the October 3rd agreement reached during the Six-Party Talks. It is almost certain that North Korea has not produced additional plutonium since 2007. However, recent satellite imagery shows signs that the reactor at Yongbyon has been restarted. It is estimated that North Korea currently possesses enough plutonium to build 4 to 8 nuclear bombs. It appears that the plutonium bombs were used in the first and second nuclear tests.

The second method for building a nuclear bomb is to use highly enriched uranium. In 2010, when I visited North Korea with Professors John Lewis and Robert Carlin of Stanford University, North Korea revealed a sophisticated and modernized uranium enrichment facility. This news caused considerable shockwaves internationally, as most experts in the field, including myself, did not believe North Korea possessed such advanced enrichment technology. While North Korea currently possesses a limited amount of plutonium, it can continuously produce highly enriched uranium through its modernized uranium enrichment facilities. It is uncertain how much highly enriched uranium North Korea has actually produced to date. Of course, the enrichment facility North Korea revealed in 2010 appeared to be designed for producing low-enriched uranium (LEU) necessary for operating a light-water reactor (LWR). However, it is currently impossible to confirm whether North Korea has continued to produce LEU since then, whether it has modified the facility to produce HEU, or whether it is producing HEU at facilities other than Yongbyon.

Because highly enriched uranium, the material for nuclear bombs, can be continuously produced, the HEU program is potentially more dangerous than the plutonium program, which requires manufacturing weapons within a limited plutonium stockpile. Furthermore, the HEU program poses a more serious threat to the international community because the centrifuges that form the core of enrichment facilities are small, making it very difficult to detect how many facilities North Korea is operating. As explained earlier, the plutonium program requires facilities of considerable scale, making it easily trackable with satellite imagery. Additionally, it is worth noting that uranium bombs are structurally easier to build than plutonium bombs. Historically, the first nuclear bombs developed by the United States were uranium bombs. However, since North Korea has already succeeded in building plutonium bombs, which require more sophisticated and complex technology, the fact that uranium bombs are easier to build than plutonium bombs is not a particularly significant factor in assessing North Korea's nuclear capabilities.

An important fact to keep in mind in this regard is that plutonium bombs are more advantageous for miniaturization compared to uranium bombs. Therefore, to produce nuclear warheads that can be mounted on missiles, it is necessary to further develop the plutonium program and continuously produce plutonium. This may be the background behind North Korea's recent restart of the gas graphite reactor in Yongbyon, despite its ability to produce highly enriched uranium. North Korea is expected to continue developing both its plutonium and highly enriched uranium programs simultaneously.

“Additional nuclear tests are essential for North Korea to develop miniaturized warheads for missiles: It is difficult to predict how many more tests will be needed.”

It is difficult to predict exactly when North Korea will succeed in miniaturizing nuclear warheads. What is certain is that it is nearly impossible to develop miniaturized warheads capable of being mounted on missiles with only three tests. The early nuclear weapons dropped on Hiroshima and Nagasaki were quite large and heavy. A significant number of tests are required to make them small enough to be transported by missiles. In fact, the United States and the Soviet Union succeeded in developing missile-deployable warheads through repeated tests. Of course, as a latecomer, North Korea can reduce the number of nuclear tests required for warhead miniaturization. However, it is very difficult to possess the technology for warhead miniaturization based solely on the experience of the first nuclear test (which appears to have failed), the second test (generally successful), and the third test (which appears to have been definitively successful). Especially for intercontinental ballistic missiles (ICBMs) like the Taepodong or Musudan, even smaller warheads are needed compared to medium- and short-range missiles, making additional nuclear tests essential for North Korea.

However, it is difficult to say exactly how many future tests North Korea will need before it can be confident in the performance of its nuclear weapons. While the United States, the Soviet Union, India, and Iran required multiple tests, China is known to have been able to confirm the performance of its nuclear weapons after only four tests. This is not only dependent on how much has been learned from preceding nuclear development programs but is also a complex issue related to the assessments of the scientists involved in the actual nuclear weapons development program and the attitude of the government accepting these assessments, making precise prediction impossible.

“Complexity of North Korea's Nuclear Threat: While the possibility of a North Korean nuclear attack is the most significant threat, technology proliferation and nuclear facility safety are also serious concerns.”

The nuclear threat posed by North Korea is highly complex. First and foremost is the possibility of a mushroom cloud rising over the Korean Peninsula. While the likelihood of the North Korean regime actually using nuclear weapons on the peninsula is very low, the risk of miscalculation by the untested leadership of the young Kim Jong Un cannot be entirely dismissed. On the other hand, given that North Korea operates one of the world's most extreme authoritarian political systems, concerns about the safety and security of its nuclear materials are relatively less pressing. However, as evidenced by the North Korea-Syria nuclear cooperation case, the proliferation of North Korean nuclear weapons development technology to other countries presents a significant and realistic threat. The transfer of related technology to other countries is considerably easier than the transfer of nuclear materials, necessitating thorough preparation. Furthermore, while safety concerns can be a major impediment to the development of nuclear programs in democratic nations like the United States or South Korea, North Korea's low sensitivity to safety issues makes it a potentially grave threat. In particular, the light-water reactor facilities operated by North Korea could cause severe environmental problems in Northeast Asia, including the Korean Peninsula, in the future. In summary, while the nuclear threat posed by North Korea is highly complex, the most serious threat remains the possibility of the North Korean regime using nuclear weapons in military operations.

Sincere Denuclearization Measures by North Korea

“Measures to Prove Sincerity: ① Destruction of the Yongbyon Reactor, ② Sale of Existing Uranium Fuel Rods, ③ Dismantling of Spent Fuel Reprocessing Facilities, ④ Destruction of Nuclear Test Facilities”

The "sincere and credible" denuclearization measures currently demanded by the international community, including the United States, cannot be confirmed by words alone. North Korea must take concrete actions. Meanwhile, North Korea's nuclear capabilities have steadily advanced to increasingly dangerous levels. The international community must take measures to prevent the worsening of the situation regarding the nuclear threat posed by North Korea and to achieve a rollback of its nuclear capabilities.

There are many technical measures North Korea can take to demonstrate its sincere commitment to denuclearization to the international community. To provide a few examples: First, the destruction of the gas graphite reactor at Yongbyon. North Korea has frozen the Yongbyon facilities several times but has never completely destroyed them. Simply removing the core can shut down the Yongbyon facility. While closing the Yongbyon facility alone cannot halt the progress of North Korea's nuclear development program, such a measure would significantly slow its pace. Second, the sale of all uranium fuel rods produced by North Korea prior to the 1994 Geneva Agreed Framework to the international market could also serve as a demonstration of sincerity. Third, dismantling the front-end plutonium reprocessing facilities to prevent further processing of spent nuclear fuel is also a possible measure. Fourth, the destruction of facilities for nuclear testing, such as monitoring towers and tunnels. These measures are not merely symbolic; they are concrete steps necessary for denuclearization, and their actual implementation by North Korea would allow it to prove its commitment to denuclearization to the international community.

Proposals for Future Six-Party Talks

“The Six-Party Talks are the only mechanism for discussing North Korea's denuclearization.”

It is a well-known fact that the Six-Party Talks have not yielded particularly successful results in resolving the North Korean nuclear issue to date. However, it is also true that the Six-Party Talks remain the only game in town for discussions on North Korean denuclearization. As a party directly involved, South Korea cannot be excluded from the negotiation process, and given diplomatic considerations, the participation of China and the United States is essential. It would also be difficult to exclude Japan and Russia at this juncture. Therefore, what the parties to the Six-Party Talks should focus on in the future is not a new consultative framework, but taking concrete actions, not just words, within the Six-Party Talks framework to roll back North Korea's nuclear program development and manage the situation to prevent further deterioration.■

The East Asia Institute (EAI) is supported by a grant from the MacArthur Foundation. EAI has been conducting Smart Q&A video interviews with domestic and international experts to provide timely and in-depth analysis of current issues through question-and-answer sessions with experts in relevant fields. This manuscript was compiled by Kim Yang-gyu, a researcher at EAI's Center for Asian Security Studies, based on the interview content. The opinions expressed are those of the individual expert and do not necessarily reflect the views of the East Asia Institute. Please cite the source when quoting from Smart Q&A.