Nuclear Propulsion for Merchant Ships 2026: SMRs at Sea?
December 2025
Nuclear & Maritime Decarbonization Analyst
20 min read
Executive Summary
Nuclear propulsion has powered submarines and icebreakers for decades, but applying small modular reactors (SMRs) to merchant
fleets would represent a profound shift in maritime risk, regulation, and business models. The appeal is obvious: virtually zero
operational CO2 emissions and extremely high energy density, eliminating the need for massive fuel tanks or frequent bunkering.
The barriers are just as stark: licensing complexity, public perception, proliferation concerns, and long investment cycles. At
Energy Solutions, we examine whether SMRs at sea can move from think-tank slides to bankable
projects, and under what conditions they might complement green fuels such as methanol and ammonia.
- Modern SMR concepts for maritime use target 50–300 MW thermal output, sufficient to power large container ships or
tankers for many years without refuelling.
- Energy density is orders of magnitude higher than chemical fuels: uranium fuel assemblies in a core represent tens of
thousands of tonnes of bunker fuel equivalent over a reactor cycle.
- Levelised cost estimates for nuclear propulsion span a wide range, but in favourable cases, propulsion energy costs could be
comparable to — or lower than — green fuels once capital is amortised; however, up-front capex is very high
and risk-weighted cost of capital dominates economics.
- Safety and liability frameworks for nuclear merchant ships are far from mature; port access, routing restrictions, and emergency
response plans would fundamentally reshape how fleets operate.
- In most realistic decarbonisation roadmaps, nuclear propulsion remains a niche option for specific routes and segments
rather than a universal solution, at least through 2035.
Nuclear Propulsion Basics: From Naval Reactors to Commercial SMRs
Nuclear-powered vessels are not new: navies have operated submarine and aircraft carrier reactors for over half a century, and civilian
icebreakers in Russia have used nuclear propulsion since the 1950s. These reactors are typically pressurised water reactors (PWRs)
adapted for maritime conditions and run on enriched uranium fuel.
Small modular reactors (SMRs) aim to simplify and standardise reactor design with factory-built modules, enhanced passive
safety features, and lower unit outputs than gigawatt-scale land-based plants. For shipping, SMR concepts must satisfy additional constraints:
- Withstand pitching and rolling and potential collisions.
- Operate reliably for long periods without frequent refuelling.
- Allow for safe decommissioning and handling of spent fuel.
Methodology Note
Energy Solutions does not endorse any specific nuclear technology. Benchmarks in this article rely on public information from SMR vendors,
research institutes, and historical reactor performance, combined with internal comparisons to green fuel scenarios. Cost and risk estimates
are indicative ranges rather than detailed project finance models.
Representative Maritime SMR Concept Parameters (Stylised)
| Parameter |
Indicative Range |
Comments |
| Thermal output |
50–300 MWth |
Can power propulsion and hotel loads for large ships or multiple vessels (in a barge concept). |
| Electrical / mechanical output |
15–100 MW |
After conversion losses in steam cycle or integrated power system. |
| Refuelling interval |
5–15 years |
Depends on core design and fuel enrichment. |
| Expected design life |
30–40+ years |
Similar to or longer than conventional hull life, depending on maintenance. |
| SMR + integration capex (order-of-magnitude) |
1–2.5 billion USD per reactor |
Highly uncertain; project- and jurisdiction-specific. |
Energy Density Comparison: Nuclear Fuel vs Bunker Fuels
Source: Energy Solutions synthesis; uranium fuel energy content shown as order-of-magnitude per tonne of fuel.
Benchmarks: Energy Density, Power Output, and Fuel Costs
Nuclear propulsion stands apart in terms of energy density. One tonne of low-enriched uranium fuel can contain energy
equivalent to tens of thousands of tonnes of VLSFO. For a large container ship, this can translate into many years of
operations without refuelling, shifting cost structure from variable fuel spend to fixed capital and O&M.
Stylised Propulsion Energy Cost Benchmarks
| Propulsion Option |
Indicative Propulsion Energy Cost (USD/MWh at propeller) |
Key Cost Drivers |
| VLSFO-fuelled engine |
60–100 |
Fuel price volatility, efficiency of main engine. |
| Green methanol engine |
120–200 |
Green fuel premium, slightly lower efficiency. |
| Green ammonia engine |
110–190 |
Fuel cost, NOx/N2O control. |
| Nuclear SMR propulsion (amortised) |
50–150 |
Capex, financing terms, O&M, regulatory compliance. |
Indicative Propulsion Energy Cost by Fuel/Technology
Source: Energy Solutions scenario modelling; values represent long-run averages, not market spot prices.
Safety and Regulation: Risk Frameworks, Liability, and Public Acceptance
Nuclear merchant ships raise unique safety and liability questions beyond those of conventional fuels. Existing frameworks such
as the IMO’s Code of Safety for Nuclear Merchant Ships from the 1980s are outdated, and national regulations vary widely.
- Accident risk: Even with low probability, severe accidents near coasts or key straits could have large
political and economic consequences.
- Security and proliferation: Safeguards to prevent diversion of nuclear material and protect vessels from malicious
acts are paramount.
- Waste and decommissioning: Spent fuel management and end-of-life reactor decommissioning require long-term planning
and dedicated funds.
- Port and coastal state consent: Some ports or coastal states may refuse entry to nuclear-powered merchant vessels,
constraining routing flexibility.
Case Studies: Nuclear Icebreakers, NS Savannah, and Emerging Concepts
Case Studies: Lessons from Existing Nuclear Vessels
Case Study 1 – Nuclear Icebreakers
Context
- Role: Provide year-round access to Arctic routes and remote ports.
- Experience: Decades of operation with multiple generations of reactors.
- Ownership: Typically state-owned or closely state-supervised fleets.
Relevance for Merchant Shipping
Icebreaker programmes show that long-lived marine reactors can be operated safely under tight institutional control.
However, replicating this model in globally traded merchant fleets would require comparable levels of oversight and crew training,
making purely private deployment challenging.
Case Study 2 – NS Savannah
Context
- Type: Experimental US-built nuclear-powered cargo ship launched in the 1960s.
- Objective: Demonstrate peaceful uses of nuclear technology in commercial shipping.
- Outcome: Limited commercial success; retired after high operating costs and regulatory complexity.
Key Lessons
NS Savannah highlights that technical feasibility does not guarantee economic or political viability. Public
perception, port access limitations, and high fixed costs undermined its business case even when oil prices were rising.
Economic Analysis: Cost per Tonne-Mile vs Green Fuels
On a purely energy-cost basis, nuclear propulsion can look attractive, especially when compared with expensive green fuels. The challenge lies
in risk-adjusted financing and liability. High regulatory and political risk translates into higher required returns for
investors, raising the effective cost of nuclear energy at sea.
Stylised Cost per Tonne-Mile Benchmarks (Large Deep-Sea Vessel)
| Propulsion Option |
Fuel / Energy Cost Share of Opex |
Total Cost per Tonne-Mile vs VLSFO Baseline |
Indicative Lifecycle GHG Reduction vs VLSFO |
| VLSFO baseline |
1.0× |
1.0× |
0% |
| Green methanol |
1.5–2.0× |
1.2–1.6× |
60–90% |
| Green ammonia |
1.4–1.9× |
1.2–1.7× |
70–95% |
| Nuclear SMR propulsion |
0.6–1.0× |
0.9–1.4× |
>90% (operational CO2) |
Relative Cost per Tonne-Mile: VLSFO, Methanol, Ammonia, Nuclear
Source: Energy Solutions scenario analysis; nuclear costs incorporate risk-weighted financing assumptions.
Deployment Scenarios: Where SMRs at Sea Could Make Sense
Nuclear propulsion is most plausible in routes and governance contexts where state actors, defence considerations, and strict
oversight dominate. Potential niches include:
- Dedicated state-backed fleets servicing remote resource projects or strategic routes.
- Floating SMR power barges supplying shore power and possibly hydrogen or ammonia production at isolated ports.
- Hybrid arrangements where nuclear-powered motherships support electric or hydrogen-fuelled feeders.
Stylised Suitability of Propulsion Options by Segment
Source: Energy Solutions judgement-based scoring for different shipping segments and fuels.
Outlook to 2030/2035: Role of Nuclear in Shipping Decarbonization
Through 2035, nuclear propulsion is unlikely to account for more than a small share of global tonne-miles, but it may play a
symbolic and strategic role in certain fleets. Regulatory learning from early projects could lower barriers for later decades, but the
combination of social licence, financing, and governance constraints will keep growth measured.
Stylised Nuclear Share Scenarios (Share of Global Shipping Energy)
| Scenario |
2030 Nuclear Share (%) |
2035 Nuclear Share (%) |
Context |
| Conservative |
0.0 |
0.1–0.2 |
Limited to demonstration projects and non-commercial fleets. |
| Base case |
0.0–0.1 |
0.3–0.7 |
Selected state-backed or strategic routes adopt SMRs. |
| Aggressive nuclear |
0.1–0.2 |
1.0–2.0 |
Strong policy drive, high carbon prices, and collaborative regulation. |
Indicative Nuclear Share Trajectories to 2035
Source: Energy Solutions nuclear shipping scenarios; shares expressed in energy terms.
FAQ: SMRs at Sea, Risks, and Investment Signals
Is nuclear propulsion for merchant ships technically feasible?
Yes. Naval and icebreaking fleets have shown that marine reactors can operate safely and reliably under demanding conditions. The
main question is not technical feasibility but governance and economics: who owns and operates nuclear ships,
under which regulatory regimes, and with what risk-sharing arrangements?
How do SMRs at sea compare with land-based SMRs?
Maritime SMRs must cope with motion, saltwater corrosion, and different emergency scenarios than land-based plants. However, they
can also benefit from factory fabrication and modular deployment. Licensing and oversight structures will need
to bridge nuclear and maritime domains.
Will ports accept nuclear-powered merchant ships?
Port acceptance is uncertain and likely to vary widely by region. Some ports may restrict or ban nuclear merchant vessels, while
others with strong nuclear industries and robust emergency services may be more open. Early operators will need to design routes
and business models that respect these constraints.
How does nuclear propulsion compare with green fuels on emissions?
Properly operated reactors emit no CO2 in normal operation and very low lifecycle emissions when fuel
supply and waste management are included. Green fuels such as methanol and ammonia can also deliver deep reductions but require
large volumes of renewable electricity and feedstocks. Nuclear and green fuels can be seen as complementary routes competing
for capital rather than direct substitutes.
What investment signals would make SMRs at sea more likely?
Clear, stable regulation; state-backed risk sharing; high and predictable carbon prices; and strong political
support for nuclear power are prerequisites. Without these, risk-adjusted returns will likely remain unattractive for private
investors, limiting SMR deployment at sea to pilot projects or specialised state-owned fleets.