The recent visit of U.S. President Donald Trump to South Korea not only served to reaffirm the close ties between both countries, but also left a strong political signal: Washington expressed its support for Seoul’s plans to develop a new generation of nuclear-powered submarines, but above all “in view of North Korea’s ongoing programs,” as stated by the U.S. president.
Undoubtedly, South Korea has established itself as one of the Asian countries that has most strongly committed to the development and local construction of conventionally powered submarines. Since the implementation decades ago of the KSS Program in its different phases —KSS-I, KSS-II, and KSS-III— the South Korean naval industry has succeeded in designing and producing units that incorporate advanced technologies and modern combat systems, adapted to the requirements of the Republic of Korea Navy. All of this also responds to a complex strategic environment, marked by the increase in military activities by North Korea and China —factors that for decades have driven Seoul to strengthen its naval and submarine defense capabilities.
In this context, South Korea has for years maintained the intention of promoting the development of nuclear-powered submarines, with the objective of providing its Submarine Force with long-endurance patrol capability and strategic deterrence. Currently, the South Korean Navy operates a fleet composed of diesel-electric submarines, which require periodic refueling and present limitations in submersion time when compared with nuclear submarines, capable of remaining submerged for months and operating with greater stealth and operational range.
However, the country still faces technological and regulatory challenges in order to make the project a reality, among them the development of a compact nuclear reactor that can be installed inside a submarine. This issue is conditioned by nuclear agreements signed with the United States, which allow Seoul to enrich uranium below 20% for exclusively peaceful purposes and with prior authorization from Washington.
According to what was revealed during the official visit, South Korean President Lee Jae-myung reportedly raised with his U.S. counterpart the possibility of evaluating the provision of nuclear fuel intended for the naval propulsion of submarines, arguing that the current conventional submarines have reached their operational limits in light of the country’s strategic needs.
In response, National Security Advisor Wi Sung-lac explained that Trump acknowledged South Korea’s need to possess nuclear-powered submarines and expressed his willingness to begin follow-up talks on the matter. Regarding the issue of fuel, Wi noted that it would be necessary to review the existing bilateral treaty, given that the current agreement does not contemplate the use of nuclear material for military purposes. “That nuclear fuel would be used for military purposes, and the current treaty does not apply to military purposes, so something must be adjusted for the procedures to be completed,” explained the official.
A program in evolution: advances in the KSS-III Batch II series
The discussion on nuclear propulsion coincides with the progress of the KSS-III program. Weeks ago, the South Korean Navy and the company Hanwha Ocean launched the Jang Yeong-sil (SS-087), the first KSS-III Batch II submarine, built with national technology.
As mentioned in previous reports, this new version presents substantial improvements over the Batch I, among them a more efficient propulsion system, a lithium-ion battery system that extends submersion time, and greater integration of domestically produced components, which increases technological autonomy and reduces dependence on foreign suppliers. Based on this, it could be thought that the Batch II program would constitute a key intermediate step in the evolution toward a possible nuclear-propulsion platform, together with the consolidation of the South Korean naval industry as one of the leading builders of advanced diesel submarines worldwide.
The precedent of the AUKUS pact
The renewed South Korean interest in developing nuclear-powered submarines comes in a regional scenario influenced by the AUKUS Pact —the trilateral agreement between Australia, the United Kingdom, and the United States—which enabled the transfer of nuclear technology to Canberra. This precedent demonstrated that Washington might be willing to share sensitive nuclear capabilities with strategic allies, provided they are framed within control and safeguard agreements. For Seoul, this represents a political and technological model of reference, since Australia managed to gain access to nuclear propulsion technology without the need to acquire atomic weaponry —a framework that South Korea could replicate under a bilateral arrangement with the United States.
*Photographs used for illustrative purposes.
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