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A Project Best Not Done: South Korean Nuclear Submarines


Churchill once remarked the only thing worse than fighting with allies is fighting without them. Reviewing South Korea’s plans to build nuclear submarines, one gets the impression that Seoul may unwittingly be trying to do both: If it proceeds to acquire nuclear submarines, Seoul will needlessly spend more to achieve less to counter both surface and underwater naval threats and will weaken its military operational ties to the U.S. Navy. In fact, South Korea could buy far more nonnuclear anti-submarine and surface capabilities by foregoing the nuclear option and tighten their operational ties with the U.S. in the process.


It does not help that South Korea’s pursuit of nuclear submarines raises nuclear proliferation concerns. Any attempt by Seoul to fuel these boats will require renegotiating the U.S.-South Korean nuclear cooperation agreement. There is a good reason why: Getting into the uranium enrichment business would give Seoul a sure-fire nuclear weapons option.


To examine how much sense South Korea’s proposed nuclear submarine program makes militarily, NPEC commissioned James O. Campbell Jr., Lead Yard Production Manager at the Naval Sea Systems Command, to contrast these nuclear systems against the military potency and economic efficiency of their nonnuclear alternatives. The attached year-long study makes the case that Seoul’s enthusiasm for building their own nuclear submarines is misplaced. 


It may well be that the United States will always have difficulty dictating to its allies what weapons they must buy from the United States. At a minimum, however, friends don’t let friends spend more to make everyone less secure. Given the much better nonnuclear anti-submarine and anti-surface system alternatives that Mr. Campbell has identified, South Korean enthusiasm for building nuclear submarines is just such a case.



Sep 13, 2020
AUTHOR: James O. Campbell, Jr.
Campbell.Seoul Misguided Desire for a Nuclear Submarine (PDF) 729.19 KB

Seoul’s Misguided Desire for a Nuclear Submarine

By James O. Campbell, Jr.

13 September 2020


In response to North Korea’s missile submarine threat, South Korean President Moon Jae-in has endorsed the development of an indigenous South Korean nuclear attack submarine. Yet, developing a nuclear submarine offers limited advantages in combating North Korean submarines versus improving the proven anti-submarine capabilities the ROK currently employs. Economically, a South Korean nuclear submarine program would sacrifice overall military readiness in favor of naval prestige. Worse, even if a nuclear submarine program was free, it would take so long to develop, it would come on line far later than the North Korean threat.  Finally, pursuing such a program, could raise nonproliferation concerns about uranium enrichment (needed to make naval reactor fuel) and so diplomatically fortify Pyongyang’s own resistance to denuclearization. Seoul’s best course would be to expand current anti-submarine warfare (ASW) assets and invest in new technologies, such as drones, laser, magnetic anomaly detection, and artificial intelligence that would increase their ASW effectiveness.       


In 2017, President Moon Jae-in endorsed the development and acquisition of a South Korean nuclear submarines. South Korean proponents of nuclear submarines favor the program for two technical reasons. First, nuclear submarines can stay underwater for months rather days or weeks as conventional diesel/electric submarines do. Second, nuclear submarines can maintain speeds of up to 30 to 40 knots at depth, whereas nonnuclear submarines have difficulty sailing much above 20 knots at depth for any significant duration and must frequently surface to recharge its batteries (which makes them easier detect). These two attributes, South Korean nuclear submarine proponents argue, make nuclear submarines ideal for detecting and neutralizing the North Korean ballistic missile submarines.1

Since Moon’s 2017 endorsement, South Korean interest in developing an indigenously designed nuclear submarines has only grown. Recent press reports indicate the navy’s intention to modify three KSS-III submarines (Dosan Ahn Chang-ho class) to 4,000-ton nuclear powered submarines. 

This is a major commitment. Not only does the addition of nuclear power to the final three submarines severely impact the defense budget, but South Korea must find a reliable long-term fuel supplier. South Korea has nuclear fuel purchase agreements with the United States, but for civilian applications only. Press reports attributed to unnamed military sources suggest that once the United States agrees to supply low enriched uranium for naval use, the development process will be a breeze.2 This statement glosses over the complexities associated with renegotiation of the existing South Korean-US 123 agreement and the difficulties of building nuclear submarines.

1 Kim Tong-Hyung, “SKorea Scrambles to Improve Weapons Following NKorea Test”, AP News, 5 Sep 2017, click here to view the source.

2 Sang-Ho Yun, “S. Korean Military Announces Plan to Develop 3 4,000-ton Submarines”, The Dong-A Ilbo, 11 Aug 2020, click here to view the source.

To read the entire paper, click here.

The Nonproliferation Policy Education Center (NPEC), is a 501 (c)3 nonpartisan, nonprofit, educational organization
founded in 1994 to promote a better understanding of strategic weapons proliferation issues. NPEC educates policymakers, journalists,
and university professors about proliferation threats and possible new policies and measures to meet them.
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