South Korea moving to build nuclear-powered submarines

With the Republic of Korea Navy currently operating the Type 209 and 214 submarines, the Moon Jae-in government is moving to build nuclear-powered submarines to better deter threats from North Korea's submarine-launched ballistic missiles. / Graphic by Cho Sang-won

By Jun Ji-hye

South Korea is moving in earnest to build the nation's own nuclear-powered submarines as part of efforts to enhance its domestic defensive capabilities amid evolving threats from North Korea's nuclear and missile programs.

The move is in line with President Moon Jae-in's vow to better deal with North Korean submarine-launched ballistic missile (SLBM) threats.

During his presidential campaign, Moon said, "We need nuclear-powered submarines in this era," pledging to make efforts to revise a nuclear cooperation deal between South Korea and the United States.

In accordance with Moon's aims, the Republic of Korea (ROK) Navy is working to commission a private institute to conduct a feasibility review for building such a sub.

In an apparent bid to gain support from the U.S., which virtually controls the uranium enrichment and nuclear fuel reprocessing of South Korea, Defense Minister Song Young-moo reportedly mentioned the need for Seoul to have its own nuclear submarines during his meeting with U.S. Defense Secretary James Mattis at the Pentagon last Wednesday.

President Moon also broadly mentioned the need for the nation to have these during his phone conversation with U.S. President Donald Trump in early August.

Calls for developing the nuclear subs were reignited after the North successfully launched an SLBM in April last year. Another SLBM fired in August that year flew about 500 kilometers, indicating significant improvement compared to previous tests.

Defense Minister Song Young-moo shakes hands with U.S. Defense Secretary James Mattis at the Pentagon, Wednesday, ahead of their meeting during which time Song reportedly mentioned the need for Seoul to have nuclear-powered subs. / Yonhap

Defense officials and experts said Pyongyang's possible deployment of SLBMs could pose a grave threat as it is hard to detect when and where they will be launched.

Supporters for having nuclear subs say they are the only way to counter the North's SLBM threat, saying they could strike the North's submarine before it launches a missile.

They say a nuclear submarine does not have to surface frequently as it is powered by a nuclear reactor, making it difficult for the enemy to detect them.

The ROK Navy currently operates the Type 209 and 214 attack submarines.

The Type 209 sub is propelled by diesel-electric transmissions and is capable of remaining underwater for only about two to three consecutive days as it needs to surface frequently to access air. There is great possibility for this submarine to be detected by an enemy every time it surfaces because of its heat and noise.

The Type 214 sub, an improved version of the Type 209, uses air-independent propulsion that allows a non-nuclear sub to operate without access to the air. This sub is capable of continuing underwater operations for a maximum 13 to 14 days.

On the other hand, a nuclear-powered sub can operate underwater almost unlimitedly as long as other conditions such as food supply are met.

Currently, only six nations ― the U.S., Russia, Britain, France, China and India ― possess their own nuclear-powered submarines.

The South Korean military reportedly has the capability to construct a small nuclear reactor for a nuclear-powered submarine, but the problem lies in other challenges such as how to secure enriched uranium for fuel.

The first question is whether the U.S. would approve of Seoul's uranium enrichment activity to operate nuclear subs.

Some say that the Seoul-Washington nuclear cooperation deal, revised in 2015, would allow Seoul to enrich uranium to a level of 20 percent when using U.S. ingredients.

But critics point out that the agreement disallows the uranium enrichment for military purposes. This is why President Moon vowed to work to revise the deal.

Even if Seoul got the nod from the U.S., the development of a nuclear submarine could still provoke controversy over whether or not the South Korean government should shift its position from the 1991 inter-Korean denuclearization declaration. Ahead of this, South Korea ratified the nuclear Non-Proliferation Treaty (NPT) in 1975 and has remained formally committed to it since then.

"This can be a problem even though a nuclear sub is not armed with nuclear weapons but uses nuclear fuel as a power source only," a source said, asking not to be named.

Other problems are possible protests from neighboring countries, especially China, which is already protesting the deployment of a U.S. Terminal High Altitude Area Defense (THAAD) battery on South Korean soil.

China believes that the deployment of the THAAD battery seriously harms its national interests. Park Won-gon, an international relations professor at Handong Global University, said, "From China's point of view, if the development of nuclear submarines is realized in Seoul, it would threaten Beijing's national security much more than THAAD would."