Despite Washington’s efforts to alleviate South Korea’s security concerns, culminating in the April 2023 Washington Declaration, calls for nuclear armament in South Korea have not subsided. Recent polls show public support for nuclear armament consistently hovering above 70 percent. However, unlike the general public, the majority of South Korean elites do not favor outright nuclear armament. While some prominent politicians have advocated for nuclear armament, including President Yoon Suk Yeol and Minister of National Defense Kim Yong-hyun, opposition to nuclear armament prevails among South Korean elites, whose opinions carry more weight particularly in defense and national security issues. An April 2024 poll by Victor Cha found that only 34 percent of South Korean elites favored it, while 66 percent were against it.
However, this does not imply a strong commitment by elites to nuclear nonproliferation either. Instead, many of South Korean security experts are pursuing nuclear latency. This refers to the capability to rapidly develop nuclear weapons without actually acquiring them, thereby avoiding the substantial costs associated with outright nuclear armament. Acquiring nuclear latency by obtaining the ability to produce nuclear fissile materials would significantly reduce the costs associated with nuclear armament.
To galvanize support for nuclear latency, conservative politician You Yong-won has launched a National Assembly initiative known as the Mugunghwa Forum. The forum is dedicated to promoting nuclear latency and developing strategies to secure it. You has called upon experts, academics, reserve military associations, political circles, the media, and other civilian sectors to rally behind this cause. The forum’s inaugural ceremony was held on July 9, 2024, with over 20 prominent politicians pledging their “full support” to make nuclear latency a reality.
The real challenge will be acquiring America’s consent for South Korean development of enrichment or reprocessing capabilities. While South Korea is believed to have the capacity to develop these technologies, it is currently restricted from doing so by its bilateral nuclear cooperation agreement with the United States, commonly known as the 123 Agreement. Due to the proliferation risks associated with enrichment and reprocessing, the United States has consistently opposed South Korea’s pursuit of these capabilities.
In order to persuade Washington, advocates of nuclear latency provide justifications for the need for enrichment and reprocessing for purposes such as fuel production, spent-fuel treatment, and submarine propulsion, but their underlying motive is achieving nuclear latency. They have even gone so far as seeking to amend South Korea’s domestic law that restricts the use of nuclear energy to peaceful purposes, despite their overt support for potential nuclear armament, effectively advocating for a violation of the very law they are promoting.
This situation creates a dilemma: South Korean politicians must explain the need for nuclear latency to galvanize support, but doing so risks exposing their ambitions for nuclear armament, complicating efforts to obtain Washington’s approval. They should carefully navigate this dilemma, as their current approach risks undermining both Washington’s trust in South Korea and democratic principles.
Why Nuclear Latency?
Nuclear armament could be highly costly — economic sanctions would likely follow, potentially disrupting South Korea’s nuclear energy production, and the country could face isolation on the international stage. Most critically, Washington might withdraw its security guarantee, leaving South Korea dangerously vulnerable to North Korea’s nuclear threats until it could develop a viable nuclear arsenal. Experts estimate that South Korea would need at least two to three years, if not more, to develop nuclear weapons, as it currently lacks the capability to produce fissile materials. This stands in stark contrast to Japan, which has accumulated over 45 tons of separated plutonium — enough to build up to thousands of nuclear weapons — and is believed to be able to go nuclear within a matter of months.
Once South Korea has enrichment or reprocessing technologies and infrastructure required for producing nuclear fissile materials, however, the time required for South Korea to develop nuclear weapons could shrink from a few years to a few months. If Seoul can present its nuclear armament as a fait accompli, the costs would become far more manageable. The shorter the process of developing nuclear weapons, the less challenging it will be for South Korea to withstand both the security vacuum and international opposition.
Hence, a growing number of experts advocate for nuclear latency as an “insurance policy” that would enable South Korea to develop nuclear weapons quickly and relatively inexpensively if necessary in the future. Notably, Han Dong-hoon, the leader of the ruling conservative People’s Power Party, posted on June 25, 2024:
The international situation is unpredictable, and relying solely on alliances has its limits. Therefore, like Japan, we need to develop the potential capability for nuclear armament when necessary, such as by securing enrichment and reprocessing technology… If we pursue direct nuclear armament immediately, the risk of international sanctions is high. I believe nuclear latency is a realistic and effective measure that doesn’t depend solely on alliances.
Similarly, Lee Baek-soon, a former ambassador to Australia, stated, “Even if we cannot rush to become a nuclear-armed state … it is time to take steps toward securing nuclear latency without further delay.” Hwang Woo-yea, chairman of the ruling party’s Emergency Response Committee, emphasized the urgency of securing nuclear latency, calling it “an immediate task that can no longer be postponed.”
Challenges and Rationales
South Korea is believed to have the capacity to develop enrichment and reprocessing, but has refrained from doing so because it would contradict the 123 Agreement with the United States. Under the 1954 U.S. Atomic Energy Act, all significant nuclear cooperation with other countries requires a peaceful nuclear cooperation agreement. Section 123a of the law prohibits recipients from enriching or reprocessing U.S.-origin nuclear materials without Washington’s consent. South Korea agreed to these terms in the 1970s in exchange for U.S. civil nuclear assistance. Although the agreement was revised in 2015 to allow for the possibility of enrichment and pyroprocessing (a type of reprocessing) for civilian purposes, such activities still require U.S. approval.
Advocates for nuclear latency present several rationales to persuade Washington to consent to South Korea’s development of enrichment and reprocessing or pyroprocessing technologies. One of the key arguments is the need for enrichment capability to ensure a stable fuel supply for South Korea’s 26 nuclear power plants, which generate roughly 30 percent of the country’s electricity. Given that Russia dominates global enrichment capacity, and South Korea imports 30 percent of its nuclear fuel from Russia, proponents argue that South Korea should develop its own enrichment capabilities to avoid reliance on and potential coercion by Moscow.
Additionally, advocates emphasize the importance of pyroprocessing or reprocessing technology to manage South Korea’s growing nuclear waste problem. The country’s nuclear waste storage facilities are nearing saturation, and reprocessing would reduce both the volume and radiotoxicity of nuclear waste, while allowing the recycling of nuclear material into fuel. This would offer a long-term solution to South Korea’s nuclear waste management challenges.
Another justification for developing nuclear fissile materials is the need for nuclear-powered submarines. These submarines can remain submerged longer than diesel-electric ones, the argument goes, making them less vulnerable to detection and better suited for stealth operations, such as tracking and destroying North Korea’s nuclear-armed submarines. Advocates emphasize the urgency for nuclear-powered submarines in light of North Korea’s growing underwater nuclear capabilities, which include not only its submarine-launched ballistic missile capabilities but also its Kim Geun-ok-class tactical nuclear attack submarine.
The Ulterior Motive: Paving the Way for Nuclear Armament
While these arguments are not without merit, the push for nuclear latency appears to be primarily motivated by ambitions to lay the groundwork for future nuclear armament. A key point of suspicion is that this call is being driven largely by South Korea’s national security establishment, rather than its nuclear industry. As one South Korean researcher observed, “Outside of security experts, there is little demand from the scientific community, the nuclear industry, or the energy security sector” for pursuing nuclear latency. This discrepancy raises concerns about the true motivations behind the push for these capabilities.
In fact, advocates of nuclear latency do not conceal their ambitions. The very name of the forum — Mugunghwa or Rose of Sharon — symbolizes the aspiration for nuclear weapons due to the popular nationalistic novel Mugunghwa Kkoti Pieotseumnida (The Mugunghwa Flower Has Bloomed), which portrays a counterfactual scenario where the Park Chung Hee regime successfully developed nuclear weapons in the 1970s.
Participants at the July 2024 inaugural meeting of the forum made their ambitions for potential nuclear armament explicit. Han Yong-sup, professor emeritus at Korea National Defense University, lamented that while the novel has been a bestseller, its scenario remains fictional, and called for nuclear latency as an “interim option” to turn the novel’s vision into reality. Cheong Seong-chang, director of the Center for Korean Peninsula Strategy at the Sejong Institute, argued that South Korea should elevate the 123 Agreement to match the U.S.-Japanese 123 Agreement, warning of a “worst-case scenario” where Japan becomes nuclear-armed, leaving South Korea as the only non-nuclear state in Northeast Asia, unable to keep pace. Several other participants in the event echoed the need for nuclear latency as a means to develop nuclear weapons if necessary.
The Dilemma
A dilemma arises here. On one hand, advocates of nuclear latency must convince their domestic audience the value of nuclear latency as an insurance policy that allows for rapid nuclear armament in the future without incurring the immediate costs of full-scale nuclear development. On the other hand, openly advocating for nuclear latency as a stepping stone toward nuclear weapons undermines the chance to acquire Washington’s approval for nuclear latency. The more South Koreans raise their voice about their intention for nuclear armament, the less likely Washington will give its consent. Washington remains firmly opposed to South Korea’s nuclear armament, although some scholars and policy pundits have expressed support. It is unlikely that Washington would consent to South Korea having enrichment and reprocessing capabilities while knowing that South Korea’s real motive is potential nuclear armament.
Precedents highlight this point. Washington has granted Japan permission for enrichment and reprocessing, in part due to Japan’s deeply entrenched anti-nuclear sentiment, which reduces the risk of proliferation. Similarly, the decision to transfer nuclear-powered submarine technology to Australia under the AUKUS agreement was driven by the low proliferation risks associated with Australia’s non-nuclear posture in addition to its lack of nuclear technology and personnel. These precedents highlight why Washington would remain cautious in the case of South Korea, which has both means and motives to build nuclear weapons.
Even if the U.S. executive branch were to offer support for granting permission, Congress could oppose it, especially if it perceives South Korea’s pursuit of enrichment and reprocessing as a veiled effort to advance its nuclear weapons program. Revising the 123 Agreement to allow such activities would conflict with the nonproliferation criteria under Section 123a, which prohibits the enrichment and reprocessing of U.S.-origin materials. Additionally, permitting South Korea to develop nuclear-powered submarines would breach another criterion that forbids the use of U.S.-origin nuclear materials for military purposes.
While the U.S. president may exempt an agreement from these requirements if he determines that doing so would serve U.S. nonproliferation objectives or protect common defense and security, this is a challenging path. The open discussions among South Korean elites about the potential for nuclear armament make it difficult to allay concerns about nuclear proliferation. Discussions on nuclear latency as an interim step toward nuclear armament would only intensify skepticism, further complicating efforts to secure Washington’s approval.
Recognizing that openly advocating for nuclear latency as a pathway to nuclear armament would raise international suspicion, there have been efforts to mask these ambitions. Shortly after the launch of the forum, You also proposed an amendment to the Nuclear Promotion Act, adding clauses affirming that South Korea’s use of nuclear energy is solely for “peaceful purposes” and aimed at “contributing to human society.” This move is intended to bolster international confidence in South Korea’s commitment to nuclear nonproliferation. However, given You’s strong advocacy for nuclear latency as a means to quickly develop nuclear weapons in a crisis, this amendment appears to be a strategic maneuver designed to gain U.S. consent — an effort that is unlikely to fool Washington.
Conclusion
It is not hard to understand South Korea’s security concerns, given the persistent nuclear threats from North Korea and the possibility of a leadership change in Washington that could weaken the U.S. security commitment. It is natural for national security experts to explore various options to safeguard the nation. Ultimately, it is up to policymakers in both South Korea and the United States to decide whether South Korea’s development of nuclear latency is a desirable or at least acceptable course of action.
However, for such a decision to be made, the two allies ought to be able to discuss the issue openly and frankly. Building trust is essential. It is not sound policy to advocate for nuclear latency as a pathway to rapid nuclearization in front of a domestic audience, while framing it as purely for nuclear energy and naval propulsion to the United States and the international community. Moreover, enshrining the peaceful use of nuclear energy in domestic legislation with the intent to violate it if necessary contradicts democratic principles. While a nuclear option may seem attractive to Seoul, other important values — such as maintaining trust with its ally and upholding democratic norms — should not be overlooked.
Lami Kim is a professor at the Daniel K. Inouye Asia-Pacific Center for Security Studies, a U.S. Department of Defense Institute based in Hawaii. The views expressed are those of the author and do not necessarily reflect the official policy or position of the U.S. Department of Defense or the U.S. Government.
Image: Juanita White
