China is pursuing plans to develop floating nuclear reactors that could power military facilities it has built in contested areas of the South China Sea, according to the top U.S. military commander in the Pacific and State Department officials, a prospect they warn would undermine regional security and stability.

After more than a decade of research and development and Chinese regulators’ safety concerns, China appears to be moving forward with its plans — at a time when the international community has not yet crafted standards governing floating reactors’ safe use, U.S. officials said.

U.S. officials say they believe any deployment is still several years away. Still, the concern is great enough that Adm. John Aquilino, who leads U.S. Indo-Pacific Command, is raising a warning flag.

“China’s intended use of floating nuclear power plants has potential impacts to all nations in the region,” said Aquilino, who is relinquishing his command Friday. “Chinese state media has stated publicly Beijing’s intent to use them to strengthen its military control of the South China Sea, further exerting their unlawful territorial claims. China’s claim of sovereignty of the entire South China Sea has no basis in international law and is destabilizing the entire region.”

His apprehension is shared by the State Department.

“Our concern is that the closer they get to deploying floating nuclear power plants, the faster they’ll use them for purposes contrary to the national security of the United States and broader security in the region,” a senior State Department official said in an interview. The official spoke on the condition of anonymity under ground rules set by the department.

The State Administration of Science, Technology and Industry for National Defense in Beijing, which oversees approved nuclear-related projects, did not respond to a request for comment.

Worries about China’s intentions were voiced obliquely during the Obama administration and more forcefully during the Trump administration. Today, U.S. officials say China is in advanced research and development stages to build reactors for military purposes.

These worries are coming at a time of heightened tensions in the western Pacific. Beijing, which is executing the most ambitious military buildup since the end of the Cold War, has been increasingly assertive in waters off Taiwan, Japan and the Philippines. Its coast guard has directly challenged Philippine vessels seeking to resupply a Philippine ship anchored off the Second Thomas Shoal.

Russia is the only country to operate a floating nuclear power plant, the Akademik Lomonosov, which became operational in December 2019. Photos of the facility show a multistory cogeneration plant on a nonmotorized barge. According to IEEE Spectrum, it consists of two pressurized-water KLT-40S reactors, similar to those powering Russian nuclear icebreakers, and two steam turbine plants.

China began designing floating nuclear power reactors in 2010. The state-run Global Times Online reported in 2016 that the government planned to deploy 20 of these reactors in the South China Sea to support commercial development, oil exploration and seawater desalination.

But the same article also boasted of military applications: “Each South China Sea island and reef, paired with a floating nuclear-powered platform,” is essentially “a nuclear-powered aircraft carrier ... equipped with combat aircraft and missile systems. Their military advantage far outweighs that of a U.S. carrier fleet coming from afar.”

Amid escalating tensions in the South China Sea, these reactors can “ensure the smooth conduct of military exercises,” researchers from a State Council-affiliated institute highlighted in a 2020 article.

China’s National Development and Reform Commission, which approves nuclear projects, has signed off on three types of floating power reactors currently in development. According to a 2022 report by the International Atomic Energy Agency, construction for one is scheduled to commence this year, while another is in the detailed design stage.

But progress has been spotty. China had hoped to debut its first floating nuclear power plant by 2021, but nuclear engineers working on the project revealed challenges, including regulators’ concerns about “safety and feasibility.”

China over a decade ago began building artificial islands on remote atolls and coral reefs in the South China Sea — constructing ports, runways, barracks and hangars. Despite a 2015 pledge by President Xi Jinping not to militarize the islands, China has since placed antiship and antiaircraft batteries on the three biggest islands, Subi, Mischief and Fiery Cross Reefs; landed aircraft on the runways; and docked warships in the ports, alarming U.S. and regional allies.

In 2016, two days before Chinese state media reported the government’s plan to build reactors, an international court in The Hague ruled that Beijing had no lawful claim to these reefs, some of which fell within the Philippines’ 200-nautical-mile exclusive economic zone.

“Our biggest concern is potential deployment in the South China Sea,” the State Department official said, noting the “long-standing and contentious territorial and maritime disputes in that area.” The official added: “There are also critical questions around the implementation of existing nuclear safety and security frameworks that still need to be addressed.”

Thomas Shugart, an adjunct senior fellow at the Center for a New American Security, said China’s deployment of floating nuclear power plants “would amount to a doubling-down” on China’s occupation of the artificial islands.

“The operation of these floating reactors within what are essentially military facilities would also raise risks that are greater than those associated with forward-deployed U.S. submarines at overseas ports,” said Shugart, a former Navy submarine warfare officer. “Unlike U.S. nuclear submarines, which normally shut down shortly after mooring, and operate only at low power levels in port,” he said, “these reactors would likely be operating at high power levels almost all the time to supply electrical power.”

Some South China Sea experts are skeptical.

“We’ve been hearing about this for the better part of a decade now, and there’s no reactor,” said Gregory Poling, who runs the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies. He said floating reactors are less feasible than solar wind and diesel fuel. “China’s doing a lot of other, more concerning things that keep me up at night.”

Many nuclear industry experts are bullish on next-generation technologies such as floating or small modular reactors as a way for countries to meet rising energy demands while lowering emissions of heat-trapping carbon dioxide into the atmosphere. But even supporters acknowledge that significant challenges remain.

Some scientists and environmentalists say that floating nuclear plants have unique vulnerabilities compared with their counterparts on land, and that a catastrophic accident could release radioactive contaminants into the ocean, as happened during the Fukushima nuclear accident in Japan in 2011.

On land, nuclear reactors and their fuel are generally protected inside containment structures of concrete and steel up to five feet thick. A reactor designed to float at sea would not be as robust, said Edwin Lyman, a physicist and director of nuclear power safety at the Union of Concerned Scientists.

“You can’t have the kind of large, leakproof, thick reinforced-concrete containment that is typical for many land-based plants,” Lyman said. If the reactor suffers a Fukushima-like failure, with molten nuclear fuel eating through the containment shell, “that stuff is going to end up in the ocean,” he said.

A floating reactor would be vulnerable to a malicious attack or sabotage from underwater assailants, or to the destructive forces of a tsunami or extreme storm, Lyman said. The Pacific Basin is the most tsunami-prone region, officials said.

“Many of these ideas are based on expectations that this new generation of plants is so safe that you can stick them on a ship and send them anywhere without having to worry about them,” Lyman said. “That’s unrealistic and dangerous thinking. If you don’t properly grapple with these issues, you’re going to end up with potential disasters waiting to happen, around the world.”

China has experienced a number of accidents involving nuclear technology over the last few years. An incident at the Taishan Nuclear Power Plant in 2021 led to the plant’s shutdown for a year for an investigation and to fix damaged fuel rods.

Nuclear safety experts with the International Atomic Energy Agency met with a Chinese designer of the reactors this year to provide an overview of IAEA safety standards related to transportation of nuclear materials. The agency does not have sign-off authority, but China has not yet sent formal technical information or construction plans to the IAEA for review, according to a Western diplomat who spoke on the condition of anonymity because of the matter’s sensitivity.

One of U.S. officials’ biggest concerns is the lack of a robust legal and regulatory framework to ensure that these technologies are deployed in a safe, transparent manner. The IAEA is seeking to craft such standards, but states such as China and Russia have slowed the process, to the consternation of Western officials. China, in particular, has sought to shape the safety standards so they are less rigorous, said people familiar with the matter.

The bottom line, said U.S. Ambassador to Japan Rahm Emanuel, is that the region is too valuable to put at risk. The South China Sea provides 12 percent of the world’s fish catch. A third of global sea trade takes place there. Terrorist groups like the Islamic State-East Asia, or Abu Sayyaf, operate in areas near it. “The last thing you want to do,” he said, “is put 20 floating nuclear facilities in the middle of the South China Sea.”

Chiang reported from Taipei, Taiwan. Michelle Ye Hee Lee in Tokyo, Aaron Schaffer in Washington and Pei-Lin Wu in Taipei contributed to this report.

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