Nuclear-Powered Ships: A Clean-Energy Future for Maritime Shipping

Commercial shipping is a major source of greenhouse gas emissions (roughly 1 billion tonnes of CO₂ per year, about 3% of global emissions), reuters.com. To meet climate goals, the industry is exploring nuclear propulsion as a long-range, carbon-free power source. Unlike traditional ships that burn heavy fuel oil (releasing CO₂, SOₓ, NOₓ, and soot), a nuclear-powered vessel carries an onboard reactor that heats water into steam to drive its turbines. In effect, each nuclear ship is a floating power plant: its reactor core can operate for years without refueling, providing continuous electricity and thrust. This clean energy approach means virtually zero exhaust emissions at sea mdpi.com, which could dramatically cut shipping’s environmental footprint as we move toward the future of sustainable maritime transport.

How Nuclear Propulsion Works

Nuclear propulsion systems on ships work much like those on submarines and icebreakers. A compact atomic reactor aboard the vessel generates heat from fission. This heat turns water into high-pressure steam, which then spins turbines connected to the propeller shafts (or to generators for electric drive) mdpi.com. Because uranium fuel contains an extremely high energy density, a small reactor core can power a large ship for years. (For example, one kilogram of uranium-235 contains about 3.9×10^6 MJ of energy, compared to ~35.8 MJ per liter of diesel mdpi.com.) Modern designs use low-enriched uranium and advanced reactor safety systems. New-generation Small Modular Reactors (SMRs) and even molten-salt reactors are being developed for marine use; these reactors operate at low pressure and feature passive safety mechanisms, making them potentially safer for shipboard applications. Overall, nuclear propulsion offers reliable, long-endurance operation – ideal for vessels that stay at sea for months without refueling world-nuclear.org.

Nuclear propulsion system

History and Examples of Nuclear Vessels

The NS Savannah (USA) in 1962 was the world’s first nuclear-powered merchant ship. Nuclear ships first appeared in the 1950s–70s as demonstration projects. The NS Savannah (USA) was launched in 1959 and entered service in 1962 mdpi.com. It was a 15,585-ton cargo-passenger liner powered by a 74 MW reactor. Savannah circled the globe on a single core, demonstrating a range of roughly 300,000 nautical miles – but it proved too costly to run on enriched uranium fuel mdpi.com. After just 10 years, it was retired (and today it is a museum ship). Other early examples include Germany’s Otto Hahn (1968) and Japan’s Mutsu (1970); both operated on nuclear reactors for a few years before being converted to diesel due to high operating costs and public concerns mdpi.com.

NS Savannah, the world’s first nuclear-powered merchant ship (Photo: Public Domain via Wikimedia Commons)

The Soviet icebreaker Lenin in 2015. Commissioned in 1959, Lenin was the world’s first nuclear-powered surface ship world-nuclear.org. In the USSR (and later Russia), nuclear shipping has centered on icebreakers. The icebreaker Lenin (20,000 tonnes) entered service in 1959 and plowed Arctic ice for 30 years world-nuclear.org. It was the first civilian nuclear surface vessel and paved the way for a fleet of Arktika‑class nuclear icebreakers (two 171 MW reactors each). Russia also built one nuclear cargo ship: the Sevmorput (commissioned 1988), a 61,900-ton LASH carrier with a 135 MWt reactor. Sevmorput required refueling only about once every 15 years world-nuclear.org, and, after a mid-life overhaul, remains in service transporting cargo along Russia’s Northern Sea Route world-nuclear.org. Aside from military and icebreaking fleets, only four nuclear merchant ships were ever built, so these examples are quite rare mdpi.comworld-nuclear.org.

Icebreaker Lenin, docked in Murmansk, Russia. (Photo by Duch. Seb via Wikimedia Commons)

Benefits: Emissions, Range, and Efficiency

Nuclear propulsion offers several key advantages for maritime sustainability:

• Near-zero emissions: A nuclear ship produces essentially no CO₂, SOₓ, NOₓ or particulate pollution during operation mdpi.com. This contrasts sharply with conventional cargo vessels that burn heavy fuel oil. Eliminating a ship’s carbon emissions directly supports the industry’s decarbonization goals (IMO aims for a 50% reduction by 2050).

• Ultra-long range: Nuclear reactors enable vessels to sail for years without refueling world-nuclear.org. For instance, the NS Savannah once steamed nonstop for months on a single fuel load. This endurance is especially valuable for remote routes (Arctic supply, transoceanic routes) and cuts downtime and logistics of refueling.

• High energy efficiency: Uranium fuel has an extraordinarily high energy density, so nuclear ships need far less “fuel volume” aboard. This can increase cargo capacity or allow larger batteries and electric systems (e.g., for cruise ship hotel loads).

• Stable fuel costs: Nuclear fuel prices are relatively predictable and do not fluctuate with oil markets. Fuel for an SMR refueling cycle can last 5–10+ years, reducing exposure to oil-price shocks.

• Continuous power supply: Beyond propulsion, a reactor can generate ample onboard electricity. For example, nuclear reactors could power hotel services and battery charging on cruise ships or operate electrolysis plants onboard to produce hydrogen/ammonia as clean fuels.

These benefits make nuclear ships a promising clean energy solution for shipping. A study notes that nuclear power can give vessels “extended operational capability by minimizing the need for refueling,” which cuts total fuel consumption and costs mdpi.com. In contrast, typical large containerships burn 200+ tonnes of fuel per day, so eliminating that makes a huge difference in emissions and pollution.

Safety Concerns and Public Perception

Despite technical promise, nuclear shipping faces safety and security questions. Opponents worry about collisions, reactor accidents, or radioactive leaks at sea. Insurance companies are cautious: one industry survey notes that merchant nuclear ships are constrained partly by “wariness by insurers of providing cover” for vessels whose port calls carry radiation unknowns reuters.com. Public opinion is a major hurdle too – commentators say it’s “a huge mountain” to overcome reuters.com. Polls of maritime stakeholders reveal that community readiness for nuclear ships is very low, driven by safety fears lr.org.

In truth, nuclear naval programs have had an excellent safety record. For example, to date, the US, UK, and French navies have had no reactor accidents at sea world-nuclear.org. Modern ship reactors would use robust containment and passive safety systems to prevent radioactive release, and they carry none of the flammable oil aboard. Still, any accident or security breach (e.g., terrorism, proliferation of nuclear material) would be taken very seriously. Strict training and safety protocols are non‑negotiable. Classification societies like Lloyd’s Register stress that “stringent safety protocols” and risk-based certification would be needed to ensure crew and environmental protection lr.org.

Yellow barrels of radioactive waste abandoned in an open field underscore the urgent need for rigorous safety measures and public transparency in nuclear energy.

Overall, public perception remains cautious. Communities often distrust nuclear power, so deploying reactors on civilian ships will require transparent safety standards. The International Maritime Organization (IMO) has safety codes for nuclear ships (Chapter VIII of SOLAS and Code A.491(XII)), but these rules were written decades ago world-nuclear.org. At the 2025 IMO meeting MSC 110, members agreed to revise these outdated rules to address new reactor types and modern ship designssafety4sea.comsafety4sea.com. This regulatory update (alongside IAEA guidelines) is crucial to reassure regulators, insurers, and the public that nuclear propulsion can meet stringent safety and security standards.

Environmental Impact vs. Conventional Ships

From an environmental perspective, nuclear and conventional ships could not be more different. A conventional cargo ship burning heavy fuel oil emits huge quantities of CO₂, sulfur oxides, nitrogen oxides, and black carbon. These pollutants contribute to climate change and local air quality problems (shipping is a major source of SOₓ and PM in port cities). By contrast, a nuclear ship emits no combustion exhaust at sea mdpi.com. In effect, switching a fleet to nuclear could cut shipping’s CO₂ emissions toward zero (already about 3% of the global total reuters.com) and eliminate conventional air pollutants.

Nuclear vessels do generate radioactive waste (spent fuel) and thermal discharge, but the volume of waste is very small compared to oil byproducts. Spent fuel can be stored onshore safely (the naval fleet routinely does this). Moreover, consider that a single large oil spill can release thousands of tonnes of oil, a hazard that nuclear ships entirely avoid.

In summary, nuclear ships virtually eliminate operational greenhouse gas and pollutant emissions mdpi.com, greatly aiding maritime sustainability. The trade-off is managing nuclear waste and ensuring robust safety oversight. As one review notes, adopting nuclear power “can help reduce greenhouse gas emissions” but will require overcoming “safety risks, regulatory hurdles and concerns over proliferation,” mdpi.com.

Challenges to Adoption

Several hurdles must be overcome before nuclear propulsion becomes common in commercial shipping:

• Regulation and Port Access: Current IMO rules (SOLAS Chapter VIII and Code A.491(XII)) are outdated. Many countries ban nuclear ships from their ports. Updating regulations is underway: IMO MSC 110 agreed in 2025 to revise the nuclear ship code to cover new reactor types and all-electric ships safety4sea.com. Even so, each port authority and country will need policies on reactor inspections, security, and emergency response.

• High Costs: Building a nuclear-capable ship is expensive. For example, the NS Savannah project cost $47 million in 1960s dollars mdpi.com, and modern reactors add significant capital and maintenance expense. Operating costs can also be high: Savannah was commercially unsuccessful due to high fuel and safety costs mdpi.com. Studies show that without economies of scale or government support, nuclear cargo ships struggle to be cost‑competitive with diesel.

• Infrastructure Gaps: Very few facilities exist to refuel or service ship reactors. Only a handful of ports (like Russia’s Murmansk) can handle nuclear vessels safely. Creating bunkering stations for enriched fuel and sites for disposing of spent fuel assemblies will require major investment and international agreements.

• Crew Training and Certification: Nuclear ships need specialized crews trained in reactor operations and radiological safety. Current maritime training (STCW conventions) covers very little nuclear content mdpi.com. Shifting to nuclear propulsion would require new educational programs and licensing for officers and engineers.

• Public and Insurance: As noted, societal acceptance is limited. Gaining the “social license” for civilian nuclear ships will take time and transparency. Insurers will want detailed risk assessments. The maritime industry will have to demonstrate an “equivalent level of safety” to conventional systems before insurers or charterers fully embrace nuclear propulsion lr.org.

These challenges are significant. In the past, they effectively halted nuclear shipping projects. As AXA XL notes, the Savannah was decommissioned in 1970, “as it was too costly to operate on enriched uranium,” axaxl.com. Today, overcoming non-technical barriers (policy, economics, social acceptance) is as crucial as solving engineering issues.

Future Outlook and Innovations

Interest in nuclear propulsion has surged in recent years as decarbonization urgency grows. Industry groups and governments are funding research and pilot projects. For example, the Norwegian NuProShip initiative (2022–25) surveyed dozens of SMR designs for ship use, singling out several promising concepts world-nuclear.org. These include:

• Kairos Power’s KP-FHR (fluoride high-temperature molten salt) reactor,

• Ultra Safe Nuclear Corporation’s MMR (helium-cooled microreactor), and

• Swedish Blykalla’s SEALER (lead-cooled SMR) world-nuclear.org.

Major shipyards and companies are also joining. Samsung Heavy Industries (Korea) and the Korea Atomic Energy Research Institute have designed a compact molten-salt reactor for ships and offshore power, aiming for commercialization around 2028 world-nuclear.org. In the UK, shipping firm X-Press Feeders has invested in Core Power, a startup developing a marine molten-salt reactor. Core Power’s design (a chloride fast reactor) is intended to run for decades without refueling world-nuclear.org. On the business side, some propose new models where shipowners lease power from reactor operators, decoupling them from nuclear licensing burdens lr.org.

Experts predict that if nuclear-powered commercial vessels are feasible, we might see demonstration ships in the 2030s. A 2023 Reuters article noted surveys suggesting nuclear systems for cargo ships are “at least 10 years away,”reuters.com. One marine CEO estimated that 7–10 years before SMR-powered ships could be in production. Meanwhile, regulators are proactively laying groundwork: the IMO and IAEA have initiated projects (e.g., IAEA’s ATLAS) to create international safety and licensing frameworks for civilian maritime nuclear technology safety4sea.com.

High-purity uranium fuel pellet held in protective gloves—fueling tomorrow’s clean, nuclear-powered ships for a sustainable maritime future.

In the long run, nuclear propulsion could play multiple roles in shipping’s clean-energy future. It could power dedicated trade-route tankers or bulkers (where ships shuttle constantly between fixed ports), large cruise liners (meeting their huge electricity needs with a base-load reactor plus battery backup), or even ocean tugs pulling loads across oceans world-nuclear.org. Some analysts even suggest floating nuclear plants could produce green hydrogen and ammonia for other ships world-nuclear.org. While still speculative, these ideas highlight nuclear’s flexibility as an energy source.

Overall, nuclear propulsion represents a bold option for maritime sustainability. Its potential for clean, reliable, long-distance power makes it an attractive part of the “future of shipping” narrative. However, technical readiness, economic viability, and public acceptance remain hurdles. As one expert quipped, nuclear ships promise emissions-free voyages and minimal refueling needs, but first the industry must climb that “huge mountain” of perception and regulation reuters.com. With IMO targets for 2050 looming, the coming years will show whether nuclear-powered ships become a niche or a mainstream tool in the clean-energy transition of global trade.

Sources: Authoritative reports from industry, academia, and media reuters.com world-nuclear.org world-nuclear.org world-nuclear.org world-nuclear.org world-nuclear.org lr.org mdpi.com mdpi.com mdpi.com mdpi.com safety4sea.com world-nuclear.org are cited. These include studies and news on nuclear propulsion, the experience of NS Savannah and Russian icebreakers, and analysis of environmental and regulatory issues.