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Building nuclear subs no easy task, but could pay off big for Korea

Published: 31 Oct. 2025, 18:55

A national security-purpose vessel is under construction at Dock 4 of Hanwha Philly Shipyard in Philadelphia, Pennsylvania on July 16. [YONHAP]

U.S. President Donald Trump has given the green light for Korea to build nuclear-powered submarines, a move that could mark a historic leap in the country's naval ambitions — with Hanwha Philly Shipyard in Pennsylvania a potential construction site.

However, experts say it will take time due to the highly sensitive nature of nuclear technology and the need for specialized infrastructure.

Nuclear-powered submarines, equipped with small nuclear reactors, are strategic assets capable of remaining submerged for extended periods and offering superior maneuverability and operational range compared to diesel-powered subs. But building them requires securing nuclear fuel, integrating a reactor into the vessel and developing special manufacturing facilities, all of which demand sophisticated technical expertise.

Hanwha Philly Shipyard currently focuses on building commercial vessels and lacks the facilities needed for nuclear submarine production. Unlike conventional submarines, nuclear submarines are typically assembled above ground and require dedicated infrastructure such as radiation shielding and reactor installation equipment.

The shortage of skilled labor is also a major hurdle. Reactor integration, in particular, involves advanced welding and precision assembly skills that are rare even in Korea.

“With its current facilities, Philly Shipyard can build commercial ships and diesel submarines, but nuclear-powered submarines require a different level of capability,” said Kim Myung-hyun, a professor of naval architecture and ocean engineering at Pusan National University. “There are multiple technical barriers, including advanced welding, radiation shielding design and U.S. certification procedures.”

Hanwha Ocean's Jangbogo-III submarine [NEWS1]

Korean shipbuilders currently possess only diesel submarine technology. That capability was initially acquired in the late 1980s through the import of Type 209 submarine technology from Germany’s HDW. Since then, Korea has independently built nine KSS-II-class submarines based on the German Type 214 design, laying the foundation for technological self-reliance.

Anticipating the potential for nuclear submarine development, companies have been preparing related technologies. Hanwha Ocean’s special ship division has been running a so-called in-house “boiler project” to accumulate experience in nuclear submarine design and operational simulations.

“We have been verifying our capability to build and operate nuclear submarines,” a Hanwha Ocean official said.

If the latest Korea-U.S. negotiations result in Korea becoming a nation capable of independently building and operating nuclear-powered submarines, it could significantly boost the global competitiveness of Korea’s shipbuilding industry. Nuclear submarines are high-value assets, each costing around 2.2 trillion won ($1.54 billion).

“Even if nuclear submarines are built in the United States, Korea’s access to the technology could give us an advantage in the global defense market for diesel submarines,” said Chae Woo-seok, executive director of the Korea Defense Industry Association.

Currently, HD Hyundai Heavy Industries and Hanwha Ocean are teaming up as the “K-Shipbuilding One Team” to pursue global orders for both surface vessels and submarines. They are finalists in Canada’s 60 billion Canadian dollar ($42.85 billion) project to procure 12 next-generation submarines and are preparing to bid on naval projects in Poland, Saudi Arabia and other countries.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.
BY PARK YOUNG-WOO [[email protected]]