The size of the ships isn’t the first thing you notice when you stroll along the docks of any major port, such as Rotterdam, Singapore, or Shanghai. It’s the odor. The exhaust from ships burning some of the dirtiest fuel that is still lawfully sold anywhere in the world gives off that faint, lingering smell of heavy fuel oil that sticks to everything. Standing there, it’s easy to forget that over 80% of the world’s purchases and sales come by sea. Almost all of it was delivered by burning fossil fuels.
That might be evolving. The maritime industry is reevaluating nuclear propulsion—not as a theoretical curiosity, but as a viable option for powering the upcoming generation of deep-sea merchant vessels—slowly, erratically, and possibly more seriously than at any other time in the previous forty years. White papers are published by classification societies. Roadmaps are being drafted by regulatory bodies. Additionally, an increasing number of engineers and shipping executives appear to have a cautious belief that the time may finally be right.
Nuclear power at sea is not a novel idea. Throughout the 1970s, the German nuclear-powered cargo ship NS Otto Hahn operated with success. For many years, the Soviet Union used nuclear icebreakers. Since the 1950s, the US Navy has operated nuclear ships; today, more than 700 naval reactors have recorded operating hours under circumstances that would destroy the majority of machines. The technology is functional. The economics, the regulations, and the public’s acceptance of a reactor docking at a commercial port were the things that never quite worked.
The pressure is different now. The International Maritime Organization has set a goal of having net-zero greenhouse gas emissions from shipping by 2050, with a 40% reduction from 2008 levels by 2030. Green ammonia, biofuels, and liquefied natural gas are all discussed. However, proponents of nuclear power contend that no other energy source can match a reactor’s power density, long-range endurance, and nearly zero emissions. This is a point that is difficult to completely ignore. You don’t pull over to fill up. Thousands of tons of alternative fuel are not carried by you. The ship simply sprints.
Small modular reactors, or SMRs—compact, factory-built reactor units that could theoretically be installed in a vessel much like a conventional engine block, serviced at designated ports, and eventually swapped out rather than refueled—are the focus of the current wave of interest. In a comprehensive white paper published in late 2025, DNV, one of the top maritime classification and risk management organizations in the world, concluded that nuclear propulsion is a feasible long-term solution for maritime decarbonization, albeit with significant limitations. According to the report, before the business case is viable, mass production, standardization, and modular design must be achieved. Those conditions don’t exist at the moment.
The regulatory landscape is just as intricate. As of right now, nuclear-powered merchant ships are not governed by a single international framework. Flag states have their own regulations. Port states have their own worries, some of which are perfectly legitimate and others of which stem from public fear that hasn’t been addressed since the end of the Cold War. No matter how clean its emissions profile is, a ship that is unable to enter the majority of the world’s major commercial ports is not a practical shipping solution. The IMO and the IAEA must cooperate in order to create a harmonized and predictable future. That is not insurmountable. However, it’s not simple.
Money is another issue. Even the most costly alternative fuels are not as capital-intensive as nuclear. The government will most likely need to get involved in early deployment through some combination of public-private financing, research grants, and defense funding. There is a precedent for this: naval programs produced a large portion of what the civilian nuclear industry is familiar with. This time, the same pipeline might operate in reverse, allowing military-grade reactor expertise to eventually find its way into commercial shipping. It’s genuinely unclear if shipowners and investors will tolerate such a lengthy development timeline.
The ships continue to smell like fuel oil for the time being. However, nuclear propulsion has found a place at the table it hasn’t occupied in a long time, somewhere between where the industry is now and where it must be by 2050. It may depend more on whether governments, regulators, and the shipping industry can reach a consensus before the window closes than on the technology itself, which has already demonstrated its viability.
