SOLAS Chapter VIII: Nuclear Ships

Background

The early nuclear merchant ship era

Nuclear propulsion of merchant ships was an active area of development from the late 1950s through the 1970s, with several pilot vessels designed and operated:

NS Savannah (USA, 1962-1971)

The NS Savannah was the first nuclear-powered merchant ship, built by the Babcock & Wilcox Company and operated by States Marine Lines under contract to the US Maritime Administration. Key characteristics:

• Length: 181.6 metres.
• Displacement: 13,599 GT.
• Cargo capacity: 9,400 cubic metres for general cargo.
• Passenger capacity: 60 (with luxury accommodation).
• Reactor: Babcock & Wilcox pressurised water reactor (PWR) of 74 MWt thermal power.
• Service speed: 21 knots.

Savannah was conceived as a demonstration of peaceful uses of nuclear energy, with the dual mission of cargo carriage and political demonstration. The ship operated commercially for nine years before being laid up in 1971 due to high operating costs. She was preserved as a museum ship and is now berthed in Baltimore. The ship has been a continuing reference point for nuclear merchant ship design.

NS Otto Hahn (Germany, 1968-1979)

The NS Otto Hahn was a German-built nuclear cargo ship operated by GKSS (Forschungszentrum Geesthacht) under contract to a German shipping consortium. Key characteristics:

• Length: 172 metres.
• Displacement: 17,000 GT.
• Cargo capacity: 14,500 cubic metres for ore cargoes.
• Reactor: 38 MWt PWR.
• Service speed: 17 knots.

Otto Hahn operated successfully for 11 years carrying ore between Germany and West Africa, demonstrating nuclear propulsion for tramp shipping. Reactor was removed in 1979 and the ship continued service as a conventionally-powered ship until scrapping in 2009.

NS Mutsu (Japan, 1972-1992)

The NS Mutsu was Japan’s nuclear merchant ship, built but never entering full commercial service. Initial sea trials in 1974 produced a coolant leak that led to extended shutdown and political controversy. Subsequent trials in 1990 were successful but commercial operation was abandoned, and Mutsu was decommissioned in 1992.

The Mutsu experience illustrated the regulatory and political challenges of nuclear merchant shipping, particularly in port-state acceptance.

Soviet/Russian nuclear icebreaker fleet

The Soviet Union, and now Russia, has operated the largest fleet of nuclear-powered merchant ships, primarily nuclear icebreakers serving the Northern Sea Route:

Lenin (1957-1989)

The Lenin, the first nuclear-powered surface ship, entered service in 1959 (laid down 1956, launched 1957). Pioneered nuclear icebreaking with three reactors of approximately 90 MWt each. After service problems with original reactors, the propulsion plant was replaced in 1970. Lenin was decommissioned in 1989 and is now preserved as a museum ship in Murmansk.

Arktika class (1975 onwards)

Six Arktika-class nuclear icebreakers were built between 1975 and 2007:

• Arktika (1975-2008, decommissioned).
• Sibir (1977-1992, decommissioned).
• Rossiya (1985, in service).
• Sovetskiy Soyuz (1990, in service).
• Yamal (1992, in service).
• 50 Let Pobedy (2007, in service).

Each Arktika-class icebreaker has two OK-900A reactors with combined thermal power of about 340 MWt, generating shaft power up to 75,000 hp. The icebreakers are capable of breaking through 2.5-metre ice continuously.

Project 22220 universal icebreakers (2020 onwards)

The new generation of Russian nuclear icebreakers, the Project 22220 class, are even more capable:

• Arktika (Project 22220 lead ship, 2020 service entry).
• Sibir (2021).
• Ural (2022).
• Yakutia (under construction).
• Chukotka (under construction).

Each Project 22220 has two RITM-200 reactors with combined thermal power of 350 MWt, with the new design optimised for both deep and shallow water operation (variable draft from 8.55 m to 10.5 m).

Sevmorput (1988-present)

The Sevmorput is the only nuclear-powered merchant cargo ship still in service. She is a 33,980 GT lighter-aboard-ship/container hybrid built in 1988, with one KLT-40 reactor of 135 MWt. Sevmorput operates on the Northern Sea Route carrying containers and lighters, with periods of layup during the past two decades but currently in active service.

The reasons for limited commercial uptake

Despite multiple pilot programmes, nuclear merchant shipping never achieved commercial scale due to:

• Capital cost: nuclear propulsion is substantially more expensive than conventional propulsion to install.
• Operating cost: nuclear ships require specialised operating crew, more complex maintenance, and higher insurance.
• Regulatory complexity: the additional regulatory burden including IAEA cooperation, port-state acceptance issues, and crew certification adds operational overhead.
• Public acceptance: post-Chernobyl (1986) and post-Fukushima (2011), public acceptance of nuclear merchant ships has been limited.
• Fuel cost: while nuclear fuel is energy-dense, the fuel cost difference does not offset the capital and operating premiums for typical merchant routes.
• Refuelling complications: nuclear refuelling requires specialised facilities and security.

The Russian nuclear icebreaker fleet has continued because the ice-breaking mission justifies the high-capital propulsion choice and because Russia has the infrastructure (Atomflot at Murmansk) to support the fleet.

Chapter structure

Chapter VIII consists of 10 short Regulations:

• Regulation 1: Application.
• Regulation 2: Application of other chapters.
• Regulation 3: Exemptions.
• Regulation 4: Approval of reactor installations.
• Regulation 5: Suitability for service.
• Regulation 6: Radiation safety.
• Regulation 7: Safety Assessment.
• Regulation 8: Operating Manual.
• Regulation 9: Surveys.
• Regulation 10: Certificates.

The chapter is supplemented by the Code of Safety for Nuclear Merchant Ships (Resolution A.491(XII), 1981) which provides the engineering and operational detail.

Application (Regulation 1)

Chapter VIII applies to nuclear-powered ships, defined as ships in which the primary propulsion source is a nuclear reactor (as opposed to ships carrying nuclear cargo, which fall under Chapter VII Part D / INF Code).

The chapter does not apply to:

• Naval nuclear ships (military vessels, governed by their own state’s regulations).
• Ships carrying nuclear material as cargo (governed by Chapter VII Part D / INF Code).
• Conventionally powered ships even if equipped with auxiliary nuclear systems.

The application is therefore narrowly focused on commercial nuclear-propelled ships.

Application of other chapters (Regulation 2)

Regulation 2 specifies that other SOLAS chapters apply to nuclear ships with adaptations:

• The structural and stability requirements of Chapter II-1 apply, with additional considerations for the reactor compartment.
• The fire safety requirements of Chapter II-2 apply, with additional radiation-specific provisions for the reactor area.
• The life-saving appliance requirements of Chapter III apply, with additional considerations for crew radiation exposure during emergency.
• The radio communications of Chapter IV and the navigation of Chapter V apply normally.
• Cargo carriage chapters apply normally.

The adaptation principle is that conventional SOLAS provides the safety baseline; Chapter VIII adds nuclear-specific requirements where conventional provisions are insufficient.

Approval of reactor installations (Regulation 4)

The reactor installation must be approved by the flag administration. Specific approval considerations include:

• Reactor design: type, power, fuel cycle, primary loop arrangement, secondary loop arrangement, control system.
• Containment: physical containment around the reactor providing radiation shielding and post-accident barrier.
• Cooling systems: primary cooling, emergency core cooling, residual heat removal.
• Control and instrumentation: reactor control systems, instrumentation for monitoring, automatic safety systems.
• Material specifications: materials capable of withstanding radiation, thermal cycling, and seawater environment.

Approval typically requires:

• Independent design review by the flag state’s nuclear safety authority.
• IAEA consultation for international consistency.
• Operational simulation testing of safety systems.
• Construction quality assurance.

The approval is documented in the ship’s design certificate.

Suitability for service (Regulation 5)

The ship must be suitable for the intended service, considering:

• Trade routes: ports of call, transit waters, refuge ports.
• Climatic conditions: temperature ranges, ice conditions for icebreakers.
• Cargo or passenger profile: with consideration of additional safety burden.
• Crew capability: trained crew available for the route.
• Emergency response: SAR resources along the route, port state acceptance.

The suitability assessment is part of the ship’s flag state approval and may include consultation with potential port states.

Radiation safety (Regulation 6)

Radiation safety provisions cover:

• Crew dose limits: typically 20 mSv per year for radiation-exposed crew (International Commission on Radiological Protection / IAEA standard), with monitoring and dose-tracking.
• Passenger dose limits: typically 1 mSv per year, equivalent to non-occupational dose limits.
• Public dose limits: very low (typically 0.1 mSv per year) for any port-side exposure.
• Shielding: physical barriers between the reactor and crew/passenger spaces.
• Monitoring equipment: continuous radiation monitoring throughout the ship.
• Personal dosimeters for radiation-exposed crew.
• Decontamination procedures for any radioactive material released.
• Health surveillance: medical monitoring of radiation-exposed personnel.

Safety Assessment (Regulation 7)

Each nuclear ship must undergo a comprehensive Safety Assessment documenting:

• Reactor safety: probabilistic risk assessment of reactor accident scenarios.
• Cooling system safety: redundancy, emergency cooling capability, decay heat removal.
• Containment performance: under accident conditions (loss of coolant, severe accident).
• Crew protection: radiation protection in normal and accident conditions.
• Public protection: protection of port populations and adjacent areas.
• Emergency response: planned response to various accident scenarios.
• Decommissioning plan: end-of-life arrangements for the reactor.

The Safety Assessment is reviewed by the flag state, by the IAEA, and where applicable by port states. It is updated through the ship’s life as operating experience accumulates.

Operating Manual (Regulation 8)

The Operating Manual contains:

• Reactor operating procedures: startup, normal operation, shutdown, maintenance.
• Emergency procedures: response to reactor faults, coolant leaks, control system failures.
• Radiation protection procedures: personal protective equipment, dose monitoring, contamination response.
• Maintenance schedules: routine maintenance of reactor and associated systems.
• Spare parts inventory: critical spares maintained on board.
• Crew training requirements: ongoing training to maintain competence.
• Documentation requirements: records to be maintained on board.

The Operating Manual is approved by the flag state and is the primary operational reference for the nuclear plant officers.

Surveys (Regulation 9)

Nuclear ship surveys are more rigorous than conventional ship surveys:

• Annual surveys: visual inspection plus radiation monitoring system testing.
• Intermediate surveys (every 30 months): detailed examination of selected reactor systems.
• Renewal (Special) surveys (every 5 years): comprehensive examination including inspection of reactor pressure vessel, primary loop piping, control rod drives, instrumentation, containment.
• Refuelling surveys: detailed survey at each refuelling event.
• Major modification surveys: when reactor or related systems are modified.

The surveys are conducted by the flag state’s nuclear safety authority (typically a national nuclear regulatory commission) with cooperation from a Recognised Organization for the conventional SOLAS aspects.

Certificates (Regulation 10)

Nuclear ships hold:

• Nuclear Cargo Ship Safety Certificate (cargo ships) or Nuclear Passenger Ship Safety Certificate (passenger ships): the primary certificate of compliance with Chapter VIII.
• Conventional SOLAS certificates: for the non-nuclear aspects (Cargo Ship Safety Construction, Cargo Ship Safety Equipment, Cargo Ship Safety Radio).
• Reactor approval certificate: documenting flag state approval of the reactor design.
• Safety Assessment: as a supporting document.
• Operating Manual: as a supporting document.

The Nuclear Safety Certificate is checked at port state inspection alongside the conventional certificates.

IAEA cooperation

The chapter and the supporting Code of Safety require cooperation with the IAEA:

• Design review: consultation with IAEA on reactor design and safety assessment.
• Operational standards: alignment with IAEA Safety Standards Series.
• Inspection cooperation: IAEA inspections of reactor facilities and operations.
• Accident response: IAEA support in case of reactor accident.
• Decommissioning: IAEA support in spent fuel management and reactor disposal.

The IAEA framework provides international expertise and consistency that individual flag states often lack.

Liability framework

Paris Convention 1960

Nuclear ship liability is governed by:

• Paris Convention 1960 (Convention on Third Party Liability in the Field of Nuclear Energy): provides the basic liability framework for nuclear damage.
• Brussels Supplementary Convention 1963: adds supplementary compensation when Paris Convention compensation is insufficient.
• Vienna Convention 1963 (similar to Paris Convention): alternative framework adopted by some states.
• 1962 Convention on the Liability of Operators of Nuclear Ships: specific to nuclear ships, but has not entered into force globally.
• 1971 Convention Relating to Civil Liability in the Field of Maritime Carriage of Nuclear Material: covers carriage of nuclear material by sea (which is also addressed in Chapter VII Part D / INF Code).

The complex liability framework requires careful navigation by nuclear ship operators.

Insurance

Nuclear ship insurance combines:

• Hull and machinery insurance: covering the ship structure and conventional machinery.
• Nuclear liability insurance: under the Paris Convention or equivalent regimes.
• Operator’s liability: substantial financial requirements for nuclear damage.

Insurance for nuclear merchant ships is typically arranged through specialised insurance pools such as the European Mutual Association for Nuclear Insurance (EMANI) or national nuclear insurance pools.

Russian Northern Sea Route operations

Atomflot

Russia’s nuclear icebreaker fleet is operated by Atomflot (FSUE Atomflot), based in Murmansk. Atomflot maintains:

• Operational fleet: currently 6 to 8 nuclear icebreakers in active service.
• Maintenance facility: Murmansk shipyard with specialised nuclear infrastructure.
• Crew training: dedicated training facility for nuclear ship operations.
• Spent fuel handling: facilities for spent fuel removal and storage.
• Decommissioning: facilities for reactor and ship decommissioning at end of life.

Atomflot’s experience with continuous nuclear merchant ship operation since 1959 is unique in the world.

Northern Sea Route service

The Northern Sea Route (NSR) along Russia’s Arctic coast is the primary commercial application of nuclear icebreakers:

• Year-round transit: nuclear icebreakers escort cargo ships through ice-bound waters, particularly in the western and central NSR.
• Cargo carriage: oil, gas, ore, container cargo to and from Russian Arctic ports.
• Cruise tourism: nuclear icebreakers operate seasonal cruise voyages to the North Pole and along the NSR.
• Strategic significance: the NSR is a major Russian maritime corridor with substantial geopolitical importance.

The NSR operations have grown substantially since 2010 with rising oil and gas exports from Yamal LNG and other Arctic projects.

Future developments: small modular reactors

SMR concept

Small Modular Reactors (SMRs) are the emerging concept for next-generation nuclear ship propulsion:

• Reactor power: typically 50 to 300 MWt thermal, much smaller than conventional power reactors.
• Modular design: factory-produced reactor modules, shipyard-installed.
• Inherent safety features: passive cooling, fuel-arrangement-based shutdown.
• Long fuel cycle: typically 5 to 10 years between refuelling, supporting voyage flexibility.
• Containment robust: designed for the marine environment including collision and grounding scenarios.

Specific SMR proposals for ships

Multiple companies are developing SMR concepts for ship propulsion:

• CMB (Compagnie Maritime Belge): working with the Korean reactor company on SMR-powered tankers.
• Mitsubishi Heavy Industries: developing SMR ship designs.
• Daewoo Shipbuilding & Marine Engineering: SMR ship concepts.
• Samsung Heavy Industries: SMR ship development with KAERI (Korean reactor institute).
• BWX Technologies: US company with SMR ship concepts.
• NuScale Power: small modular reactor for ships and offshore power.
• Rolls-Royce SMR: UK SMR with marine application.

Regulatory development for SMR ships

The IMO MSC has begun considering SMR regulatory framework:

• MSC.1/Circ.1 series on nuclear propulsion discussion.
• Working group on SMR ship safety standards.
• Coordination with IAEA on safety standards.
• Cooperation with national nuclear regulators (NRC USA, ASN France, ONR UK, NRA Japan).

Regulatory framework for SMR ships is expected to be developed through the late 2020s, with first commercial SMR ships potentially entering service in the 2030s.

Decarbonisation driver

The principal driver for SMR ship interest is decarbonisation:

• Zero direct emissions: SMR-powered ships have no fuel-related emissions.
• High energy density: compatible with very large container ships and bulk carriers.
• Long voyage range: substantially longer than electric or alternative-fuel options.
• Stable cost: nuclear fuel cost is relatively predictable compared with volatile oil and gas markets.

The challenge is the regulatory, public-acceptance and cost barriers.

Spent fuel and waste management in detail

Spent fuel pathways

Spent fuel from nuclear ships follows specific pathways:

• On-board cooling: spent fuel is cooled in the reactor for a period after shutdown to allow short-lived fission products to decay.
• Removal from reactor: fuel assemblies are removed using specialised equipment, transferred to shielded shipping casks.
• Transport to storage: shielded casks are transported to shore-based interim storage facilities (Russia: Atomflot Murmansk; USA: federal storage; etc.).
• Interim storage: typically 30 to 50 years in cooling pools or in dry casks.
• Final disposition: deep geological storage or reprocessing for fuel recycling.

Reprocessing options

Some spent fuel is reprocessed to recover uranium and plutonium:

• France (La Hague): major commercial reprocessing facility, processing fuel from European utilities.
• UK (Sellafield): reprocessing operations winding down.
• Russia (Mayak): processing Russian spent fuel including from icebreakers.
• Japan (Rokkasho): reprocessing facility under commissioning.

Reprocessing allows recycling of fuel material but produces high-level waste requiring disposal.

Direct disposal

Most countries are moving toward direct disposal without reprocessing:

• Finland (Onkalo): deep geological repository under construction (first operational ~2025).
• Sweden (Forsmark): repository planned.
• USA (Yucca Mountain): planned repository, currently politically stalled.
• France: deep geological repository planned.

Direct disposal is simpler but generates more waste volume than reprocessing.

Implications for nuclear ships

For nuclear ships, the spent fuel and waste management:

• Adds substantial cost to total nuclear ship economics, with reserve provisions that may run to tens of millions of dollars per ship over lifecycle.
• Requires coordination between flag state, port state and waste-receiving country, with bilateral agreements typically required to define responsibilities and protocols.
• Imposes long-term commitments that extend well beyond ship operational life, requiring institutional arrangements that survive corporate transitions and ownership changes.
• Limits ship operating flexibility: spent fuel must be removed at locations with appropriate facilities, constraining route flexibility for ships outside Russia or other states with established nuclear infrastructure.
• Requires specialised personnel for spent fuel handling, with associated training and certification requirements.
• Demands physical security during transport, with armed escort and supervised handling for high-value nuclear materials.

The waste management dimension is one of the major commercial considerations for SMR ship deployment, and resolving it requires coordinated international action between regulators, operators, and waste-receiving authorities. The IMO, IAEA and major flag states are progressively addressing these issues through dedicated working groups, multilateral negotiations, and policy development efforts that will shape the commercial viability of SMR-powered merchant ships in the late 2020s and 2030s.

Floating nuclear power plants and adjacent applications

Akademik Lomonosov

The Akademik Lomonosov is a Russian floating nuclear power plant deployed at Pevek (Russia) since 2019. While not a self-propelled ship, the Lomonosov is a barge-mounted nuclear power plant providing the conceptual basis for some SMR ship discussions:

• Reactor: two KLT-40S reactors of 70 MWt each.
• Power output: 70 MWe to the local grid plus 50 MWe heat.
• Mission: providing electricity and heating to the remote Chukotka region.
• Mobility: towed to its operating site, not self-propelled.

The Lomonosov demonstrates the feasibility of floating nuclear power plants and provides operational data relevant to SMR ship development.

Future floating nuclear power

Multiple companies are developing floating nuclear power concepts:

• CORE Power (UK): marine molten salt reactor concept.
• Seaborg Technologies (Denmark): compact molten salt reactor for floating power plants.
• Thorcon (USA): thorium molten salt reactor for floating power.
• NuScale Power: mobile nuclear power for emergency and off-grid use.

These concepts could provide power to coastal communities, offshore platforms, and remote industrial sites, with potential adaptation to ship propulsion.

Adjacent maritime applications

Nuclear technology has potential adjacent maritime applications:

• Offshore platform power: replacing gas turbines on offshore oil and gas platforms.
• Port shore power: providing low-emission shore power to vessels alongside.
• Aquaculture: providing power to large offshore fish farms.
• Desalination: combined power and water for arid coastal regions.

These applications, while not nuclear merchant ships, share regulatory framework elements.

Industry consortia and pilot programs

CMB Tech and Korean SMR

CMB Tech (Belgian shipping company) has been working with Korean partners on SMR-powered ship concepts since the early 2020s:

• Reactor partner: KAERI (Korea Atomic Energy Research Institute) and Hyundai Engineering.
• Ship designs: Aframax tanker and bulk carrier prototypes.
• Timeline: ship designs expected by 2026-2028, demonstration vessel possible by late 2020s.
• Economic case: addressing carbon-intensive long-haul tanker and bulker trades.

Mitsubishi Heavy Industries

MHI has been developing SMR ship concepts since the 2000s:

• Reactor design: Mitsubishi-designed SMR with passive safety features.
• Ship application: container ships and bulk carriers.
• Status: research and development with progress toward commercial design.

Daewoo Shipbuilding & Marine Engineering

DSME (now Hanwha Ocean) has been studying SMR ships:

• Ship application: very large container ships and tankers.
• Reactor partner: KAERI and various Korean nuclear technology providers.
• Timeline: design studies progressing toward commercialisation.

Samsung Heavy Industries

Samsung Heavy Industries has SMR ship study programs:

• Reactor concepts: small molten salt reactor and other novel designs.
• Ship application: very large LNG and container ships.
• Decarbonisation focus: addressing zero-emission requirements for major Korean shipowners.

BWX Technologies (USA)

BWXT, a major US naval reactor supplier, has been developing commercial SMR concepts:

• Reactor design: derived from naval reactor experience but adapted for commercial use.
• Ship application: very large container ships and bulk carriers.
• US partnership: working with major US shipowners and the US Maritime Administration.

Industry organisations

Several industry organisations are addressing nuclear merchant shipping:

• NEMO (Nuclear Energy for Maritime): industry consortium addressing SMR ship deployment.
• NSAC (Nuclear Ship Advisory Committee): cross-industry advisory body.
• CMB-led consortium: bringing operators, shipyards, reactor designers and regulators together.

These consortia provide forums for coordinated development of regulatory framework, technical standards, and commercial structures.

Specific regulatory questions for SMR ships

Reactor type approval

SMR ship deployment requires:

• Reactor design certification by national nuclear regulators (NRC USA, ASN France, ONR UK, NRA Japan, NSC Korea).
• Marine application certification by flag state and IMO.
• Equivalence between national approvals to avoid duplicate certification.
• IAEA coordination to ensure international consistency.

The dual-track approval (nuclear and marine) is one of the regulatory complexity challenges.

Crew certification

Crew certification for SMR ships requires:

• Seafarer certification under STCW.
• Reactor operator certification under national nuclear law.
• Combined competence integrating both.
• Type rating for the specific SMR design.

The combined certification framework is under development through IMO and IAEA cooperation.

Insurance and liability

Insurance and liability for SMR ships requires:

• Updated Paris Convention application or alternative liability framework.
• Commercial insurance availability: nuclear insurance pools (EMANI, ANI, JAERI, etc.) need to extend coverage to commercial SMR ships.
• Operator’s financial security: substantial requirements similar to nuclear power plants.
• Port state liability: addressed through bilateral agreements.

The insurance and liability framework is one of the major commercial barriers.

Port state acceptance for SMR

For SMR ships:

• Pre-deployment dialogue with port states to establish acceptance.
• Standardised port procedures through IMO MSC development.
• Bilateral agreements between flag and port states.
• Public engagement addressing community concerns.

The port state acceptance framework is essential for commercial viability of SMR shipping.

Economic and commercial considerations

Capital cost

Nuclear ship capital cost is typically 2 to 4 times that of a conventional ship:

• Reactor module cost: typically 50 to 200 million USD per reactor for SMR-class designs.
• Containment and shielding: substantial steel and concrete plus specialised materials.
• Specialised systems: emergency cooling, containment ventilation, radiation monitoring.
• Quality assurance: nuclear-grade quality control adds cost compared with conventional construction.
• Certification and approval: regulatory cost is substantial.

The capital cost premium is the principal economic barrier to commercial nuclear ship adoption.

Operating cost

Nuclear ship operating cost is mixed:

• Fuel cost: nuclear fuel cost per energy unit is much lower than oil fuel; this is the principal economic advantage.
• Specialised crew: crew with nuclear training cost more than conventional ship crew.
• Maintenance: nuclear maintenance is more demanding, with higher costs for specialised equipment and personnel.
• Insurance: nuclear ship insurance is more expensive, partly due to liability frameworks.
• Refuelling: less frequent than fuel bunkering but more expensive when it occurs.
• Decommissioning provision: substantial reserve for end-of-life decommissioning.

The total operating cost depends on the trade-off between low fuel cost and high specialised cost.

Ship economics scenarios

Specific economic scenarios for SMR-powered ships:

• Very large container ships on Asia-Europe routes: SMR could reduce fuel cost by 60 to 80 percent over 25-year ship life, potentially offsetting capital premium.
• VLCC tankers: similar economics.
• Capesize bulk carriers: more challenging because of lower utilisation and longer voyages, but potentially viable.
• Fast container ships: less attractive because the operating profile (high power, predictable utilisation) is not the strongest match for nuclear’s economic profile.

The economics depend critically on:

• Carbon pricing: as carbon costs rise (under EU ETS, FuelEU Maritime, IMO market-based measure), nuclear ships become more competitive.
• Capital cost trajectory: SMR cost reduction through learning-curve effects.
• Regulatory cost stability: whether the SMR regulatory framework adds substantial cost.

Decarbonisation context

IMO 2050 Strategy

The IMO 2018 Initial GHG Strategy (and 2023 Revised Strategy) targets:

• 2050 net-zero for international shipping (2023 revised target).
• Substantial reduction by 2030 and 2040 milestones.
• Multiple pathways: efficiency, alternative fuels, market-based measures.

Nuclear is one of the potential pathways, particularly for very large ships where energy density matters.

Comparison with other alternative fuels

Compared with other low-carbon fuels:

• LNG: methane slip and CH4 GWP make it a transitional fuel; CO2 emissions remain.
• Methanol: green methanol is low-carbon but production capacity is limited.
• Ammonia: zero-direct-CO2 but toxicity and combustion characteristics challenging; supply chain emerging.
• Hydrogen: zero direct CO2 but very low energy density makes long-voyage challenging.
• Biofuels: limited supply, sustainability concerns.
• Wind-assist: 5 to 15 percent fuel reduction, supplementary not primary.
• Battery electric: zero direct emissions but limited range, suitable for short routes.
• SMR nuclear: zero direct emissions, high energy density, long range; capital and regulatory barriers.

Each pathway has trade-offs; nuclear’s specific advantages (long range, high power) make it potentially attractive for the largest ships if regulatory and cost barriers can be overcome.

Public acceptance and political dimension

Historical public concerns

Public concerns about nuclear merchant ships have included:

• Accident risk: although marine reactor accident probability is very low, the consequences of a serious accident concentrated in port could be substantial.
• Routine emissions: although tightly controlled, nuclear ships do produce small routine releases of radioactive material.
• Spent fuel management: long-term fuel storage and disposal is a recognised challenge.
• Decommissioning: end-of-life disposal of reactor components requires specialised infrastructure.
• Proliferation: although commercial reactors do not produce weapons-grade material, the supply chain has security implications.
• Terrorism vulnerability: nuclear ships could be targets for terrorism, though physical security can mitigate this.

The public concerns have generally limited commercial nuclear shipping development.

Modern public attitudes

Modern public attitudes are more nuanced:

• Climate concern has increased acceptance of nuclear as a low-carbon option.
• Specific opposition in particular ports remains for political and historical reasons.
• Industry advocacy has been growing for nuclear-powered commercial shipping.
• National positions vary widely: France generally supportive, Germany generally opposed, US mixed, Asia varied.

The political environment for SMR ship deployment will be a significant factor in commercial uptake.

Russian Northern Sea Route in detail

NSR geography and operations

The Northern Sea Route runs along Russia’s Arctic coastline from the Barents Sea (in the west) to the Bering Sea (in the east), passing the Kara Sea, Laptev Sea, East Siberian Sea, and Chukchi Sea. The route:

• Total length: approximately 5,600 km from Murmansk to the Bering Sea entrance.
• Operating period: traditionally July to October, with year-round operations now possible with nuclear icebreaker assistance.
• Ice conditions: vary from open water in summer to multi-year pack ice in winter.
• Shore infrastructure: limited; key support points at Murmansk, Dudinka, Tiksi, Pevek.

Cargo flow

The NSR carries:

• LNG exports from Yamal LNG (operational since 2017) and Arctic LNG-2 (under commissioning).
• Oil exports from Russian Arctic terminals.
• Ore and metal exports from Norilsk and Yamal mining operations.
• Container imports to Northern Russian ports.
• Government cargo including military and civilian supplies to remote outposts.

Cargo volume on the NSR has grown from approximately 4 million tonnes in 2014 to over 35 million tonnes in 2023, with substantial further growth projected.

Atomflot’s role

Atomflot’s role in NSR operations:

• Ice escort of cargo ships through ice-bound waters.
• Convoy operation for multiple ships in difficult conditions.
• Year-round corridor: maintaining navigability through nuclear-icebreaker support.
• Emergency response: nuclear icebreakers as primary SAR resource in the high Arctic.
• Tourism: seasonal cruise voyages to the North Pole and along the NSR.

NSR strategic dimension

The NSR has strategic significance:

• Geopolitical: a Russian-controlled maritime corridor with sovereignty claims over portions of the route.
• Commercial: shorter route between Asia and Europe than the Suez Canal route (approximately 30 percent shorter for some routes).
• Resource access: enabling Arctic resource development.
• Climate dimension: increased accessibility due to Arctic ice retreat.

Comparison with naval nuclear propulsion

Naval nuclear ship fleets

Naval nuclear ships substantially outnumber commercial nuclear ships:

• US Navy: over 80 nuclear-powered submarines and aircraft carriers, plus nuclear-powered warships.
• Russian Navy: nuclear submarines and the Kirov-class cruisers (one in service).
• French Navy: nuclear submarines and the Charles de Gaulle aircraft carrier.
• Royal Navy (UK): nuclear submarines.
• Chinese Navy: nuclear submarines.
• Indian Navy: nuclear submarines.

The naval fleet provides the broader experience base for marine nuclear propulsion.

Key differences from commercial nuclear ships

Naval and commercial nuclear ships differ in:

• Regulatory framework: naval ships are governed by their own state’s military regulations, not by SOLAS.
• Reactor design: naval reactors are typically more compact, with higher power density.
• Crew complement: naval crews are typically larger and more highly trained.
• Fuel cycle: naval reactors often use highly enriched fuel for longer fuel cycle and compact size; commercial reactors use lower-enrichment fuel.
• Safety culture: naval safety culture is well-developed but typically not auditable by external authorities.
• Public information: naval nuclear ship operations are largely classified, in contrast to commercial transparency.

Lessons transferable

Despite the differences, naval nuclear experience provides:

• Reactor design techniques applicable to commercial reactors.
• Safety culture frameworks transferable to commercial operation.
• Maintenance and inspection methodologies.
• Crew training models.
• Decommissioning experience.

The transferability is particularly relevant for SMR ship development, where naval-derived reactor technology may form the basis of commercial designs.

Reactor types in marine applications

Pressurised Water Reactor (PWR)

The Pressurised Water Reactor (PWR) is the dominant reactor type in marine applications:

• NS Savannah, NS Otto Hahn, NS Mutsu: all used PWRs of various designs.
• Russian icebreakers: use PWR derivatives (OK-150, OK-900, KLT-40, RITM-200).
• Naval applications: most US, French, British and Chinese naval reactors are PWRs.

PWR characteristics:

• Primary loop: water under high pressure (typically 150 bar) circulated through the reactor core, removing heat.
• Secondary loop: lower-pressure water in steam generators converted to steam for the propulsion turbines.
• Containment: sealed barrier between primary loop and the rest of the ship, providing radiation shielding and accident barrier.
• Control: control rods inserted into the core for power adjustment.

PWRs benefit from extensive operational experience and a mature regulatory framework.

Boiling Water Reactor (BWR)

BWRs have been used in some Russian icebreaker designs, with simplified primary loops compared with PWRs. However, BWRs have largely been displaced by PWRs in marine applications because of:

• More complex containment requirements.
• Higher radiation levels in the propulsion machinery space.
• Lower operational flexibility.

Liquid Metal Cooled Reactor

Liquid metal cooled reactors (sodium or lead-bismuth coolant) have been investigated for ship applications:

• Soviet Alfa-class submarines: used lead-bismuth cooled reactors with good performance but corrosion issues.
• Liquid metal reactors for civil ships: under research as a future option.

Liquid metal reactors offer high power density but introduce coolant compatibility challenges.

Small Modular Reactor (SMR)

The next-generation Small Modular Reactors (SMRs) for ship application include:

• Integrated reactor design: primary loop entirely within the reactor pressure vessel, eliminating large external piping.
• Passive safety: gravity, natural circulation, and material properties drive safety functions without active operator intervention.
• Long fuel cycle: 5 to 10 years between refuelling, supporting voyage flexibility.
• Modular construction: factory-produced modules assembled in shipyard.

Specific SMR designs being considered for ships include:

• NuScale Power: 50 MWe modular reactor.
• Rolls-Royce SMR: 470 MWe (likely too large for most ships, but applicable to very large vessels).
• GE Hitachi BWRX-300: 300 MWe small BWR.
• BWX Technologies BWXT-300: small modular reactor.
• TerraPower Natrium: liquid metal cooled SMR.
• KAERI SMART: 100 MWe Korean SMR with marine application proposed.

These designs are at various stages of development, with first commercial deployments expected in the late 2020s to 2030s.

Crew training and certification

Specialised training

Nuclear ship crew training is substantially more demanding than conventional ship training:

• Reactor operators: fully trained in reactor operations, with theoretical and practical training equivalent to nuclear power plant operators.
• Reactor engineers: with engineering degrees plus specialised marine reactor training.
• Health physics specialists: trained in radiation protection.
• Crew radiation training: all crew receive basic radiation protection training appropriate to their roles.

The training requirements exceed STCW provisions for conventional ships and are typically met through national programmes.

Soviet/Russian Atomflot training

Atomflot operates a dedicated training facility for nuclear icebreaker crew:

• Reactor operator training: 2 to 3 year programme combining classroom and on-board training.
• Senior engineer training: 4 to 5 year programme.
• Continuous professional development: ongoing training during career.

The Atomflot training infrastructure has produced thousands of qualified nuclear ship officers since 1959, with current crew numbers around 800-1000 active at any time.

Future SMR ship crew

The crew requirements for SMR-powered merchant ships are expected to be:

• Fewer than current Atomflot model: SMR designs aim for simpler operation requiring fewer specialised personnel.
• Hybrid skill set: combining marine engineering with limited reactor-specific knowledge.
• Remote support: with shore-side specialists providing detailed reactor expertise via communications.
• Type-rating concept: similar to aviation, with crew qualified for specific reactor types.

The crew model is one of the open questions for commercial SMR ship deployment.

Port state acceptance

Historical port state issues

Nuclear ships have historically faced port state acceptance issues:

• NS Savannah: declined entry to several ports during her operational life.
• NS Otto Hahn: similar issues with some non-flag-state ports.
• NS Mutsu: faced significant Japanese domestic port acceptance issues.
• Russian icebreakers: have generally operated in Russian ports and Northern Sea Route, with limited foreign port calls.

The IMO Code of Safety for Nuclear Merchant Ships includes provisions to facilitate port state acceptance, but actual port acceptance depends on the port state’s national legislation and political environment.

Modern port state framework

Modern port state acceptance for nuclear ships is governed by:

• National nuclear ship legislation: each port state has its own legal framework.
• Bilateral agreements: between nuclear ship flag states and port states.
• Pre-arrival notification: typically 48 to 72 hours notice required.
• Port-specific arrangements: dedicated berths, monitored access.
• Emergency response coordination: with port state nuclear safety authorities.

For SMR-powered commercial ships, port state acceptance is one of the major unresolved regulatory issues.

IMO MSC consideration

The IMO MSC has recognised the port state acceptance challenge and has been considering:

• Standardised port state procedures for nuclear ships.
• Pre-acceptance agreements between flag and port states.
• Information sharing about ship safety performance.
• Public communication to address public acceptance concerns.

These considerations are part of the ongoing IMO discussion of nuclear ship regulation.

Decommissioning

Reactor removal at end of life

Nuclear ship decommissioning involves:

• Defueling: removal of spent fuel from the reactor for shipment to storage or reprocessing.
• System decontamination: cleaning of primary coolant loops to remove radioactive contamination.
• Reactor removal: physical extraction of the reactor pressure vessel and primary loop components.
• Disposal: of removed components either through deep-burial waste sites or through extended on-site storage.
• Ship recycling: of the remaining ship structure under conventional ship recycling rules (Hong Kong Convention).

Russian decommissioning experience

Russia has decommissioned multiple nuclear icebreakers:

• Lenin (decommissioned 1989): preserved as a museum ship with reactor removed.
• Arktika (decommissioned 2008): reactor removed, ship being scrapped.
• Sibir (decommissioned 1992): reactor removed, ship scrapped.

The decommissioning experience is concentrated in Russia, with limited transferable experience for other states.

Spent fuel management

Spent fuel from nuclear ships is typically:

• Removed from the reactor at refuelling intervals.
• Stored on board temporarily in shielded casks during transit to a fuel storage facility.
• Transferred to shore-based storage at specialised nuclear handling facilities (Russian fuel goes to Atomflot Murmansk; Western fuel typically goes to national storage).
• Reprocessed or stored long-term depending on the country’s nuclear waste policy.

Spent fuel management is a long-term commitment that extends well beyond the ship’s operational life.

Notable incidents

NS Mutsu coolant leak (1974)

The 1974 coolant leak on NS Mutsu produced no public radiation release but did prompt extended controversy and shutdown. The incident illustrated the political sensitivity of nuclear merchant ships and the regulatory caution that follows even minor incidents.

Soviet/Russian icebreaker incidents

The Russian nuclear icebreaker fleet has had a generally strong safety record over more than 60 years of operation. Specific incidents have been minor (component failures, primary loop minor issues) without significant radiation release. The cumulative operating experience is approximately 350 reactor-years, providing substantial empirical evidence for the safety case.

Comparison with naval nuclear safety

Naval nuclear ship safety records (US Navy, Russian Navy, French Navy, UK Royal Navy, Chinese Navy, Indian Navy) similarly show strong safety. The US Navy nuclear program has accumulated approximately 6,200 reactor-years without a single reactor accident with public radiation release. This experience supports the safety case for commercial SMR-powered ships.

Related Calculators

• SOLAS VIII - Nuclear ship crew radiation dose Calculator

See also

• SOLAS Convention parent article
• SOLAS Chapter VII: Carriage of Dangerous Goods (INF Code for nuclear cargo)
• SOLAS Chapter II-1: Construction, Subdivision, Stability, Machinery and Electrical Installations
• SOLAS Chapter XI-1: Special Measures to Enhance Maritime Safety
• SOLAS Chapter XIII: Verification of Compliance
• Polar Code (relevant for nuclear icebreakers in Arctic operations)
• Hong Kong Convention (ship recycling)

References

• IMO, International Convention for the Safety of Life at Sea (SOLAS), 1974, as amended, Chapter VIII.
• IMO Resolution A.491(XII) (1981), Code of Safety for Nuclear Merchant Ships.
• IAEA Safety Standards Series, multiple volumes covering nuclear ship operations.
• Paris Convention 1960 on Third Party Liability in the Field of Nuclear Energy, as amended.
• Brussels Supplementary Convention 1963.
• 1962 Brussels Convention on the Liability of Operators of Nuclear Ships (not in force).
• 1971 Convention Relating to Civil Liability in the Field of Maritime Carriage of Nuclear Material.
• US Maritime Administration documentation on NS Savannah.
• GKSS publications on NS Otto Hahn operational experience.
• Atomflot operational reports on Russian nuclear icebreaker fleet.
• IAEA INSAG (International Nuclear Safety Advisory Group) publications.
• World Nuclear Association reports on small modular reactors and marine applications.