“The use of nuclear technology to power submarines has a number of very important technical implications,” IAEA Director General Rafael Grossi said at a press briefing in Seoul, describing the visit as a “kickoff” for discussions with Seoul on its naval nuclear propulsion plans.
As a signatory to the Nuclear Non-Proliferation Treaty (NPT), South Korea is subject to IAEA safeguards. However, Grossi noted that nuclear-powered submarines pose a unique challenge because fuel loaded into vessels on long missions falls outside routine inspections.
“Because of the nature of these vessels, the nuclear material is not continuously accessible to inspectors,” he said, warning that large quantities of enriched uranium — potentially even highly enriched uranium — could remain outside direct oversight for extended periods.
To address this, Grossi stressed the need for a tailored verification system between the IAEA and South Korea to ensure that nuclear material is not diverted for military purposes beyond propulsion.
“We need technically sound arrangements so we can verify that the material remains where it is and is used only for propulsion,” he said, adding that such frameworks are being developed with countries including Australia and Brazil.
He emphasized that “ironclad guarantees” are essential to ensure the program does not contribute to nuclear proliferation, noting that the process would involve coordination across government, military and shipbuilding sectors.
Grossi also cautioned that developing nuclear-powered submarines is a long-term undertaking, likely to take many years, involving extensive research, construction and testing phases.
On Iran, Grossi said the country has already mastered uranium enrichment technology and currently possesses roughly 440 kilograms of uranium enriched up to 60 percent, with most of the stockpile located at known sites such as Isfahan.
He described any potential suspension of enrichment as a “political decision,” noting that the duration of a moratorium — whether five, 10 or 20 years — carries little technical difference but reflects levels of political trust.
More importantly, he stressed that any nuclear agreement must include rigorous verification.
“Without verification, any agreement is just a piece of paper,” Grossi said. “We must be able to check every gram of nuclear material and how it is used.”
Turning to North Korea, Grossi said the IAEA has observed a continued expansion of nuclear activities, including operations at Nyongbyon and other facilities, despite the absence of inspectors since 2009.
Recent assessments indicate a “significant increase” in Pyongyang’s nuclear capabilities, with estimates suggesting the country may have material sufficient for dozens of nuclear warheads.
While there is no clear evidence of Russian military nuclear assistance, he said current cooperation between Moscow and Pyongyang appears limited to civilian nuclear projects.
Grossi reiterated that pursuing nuclear weapons does not enhance national security, warning instead that it risks triggering a broader arms race.
“Moving toward nuclear weapons would not give any country greater security,” he said. “It would encourage others to follow, leading to dangerous escalation.”
Grossi also addressed his candidacy for the next United Nations secretary-general, highlighting what he described as a deepening crisis of confidence in the global body.
“The world is going through a very difficult period marked by polarization and multiple conflicts,” he said, calling the upcoming leadership transition a critical moment to restore trust in multilateral institutions
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