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SMALL MODULAR REACTORS actors (MSRs) run hot at low pressure, though corrosion Security is a separate discipline from safety. It means and chemistry questions remain open. Lead-cooled fast re- protecting reactor, material and control systems against actors (LFRs) use low-pressure heavy-metal coolant but theft and sabotage through layered physical protection, bring fuel-cycle and safeguards complexity. Heat-pipe controlled access, cybersecurity and coordination with microreactors are passive and compact, but their limited ? ag, coastal and port authorities. Crews need combined output suits smaller vessels and auxiliary roles. High- nuclear and maritime competence, built on simulator- temperature gas-cooled reactors still need validation at based training.

merchant-ship scale. Fig. 2 shows the trade: advanced de- signs offer long refueling intervals, yet only the PWR is REGULATION IS THE REAL BOTTLENECK close to commercial maturity. Nuclear ships must satisfy maritime law and nuclear regulation at once. SOLAS Chapter VIII and the IMO’s

THE MOTHER-DAUGHTER IDEA 1981 Code of Safety for Nuclear Merchant Ships remain

Our central proposal tackles the most awkward prob- the operative international benchmark. In June 2025 lem: every port a nuclear ship visits must accept it. The the IMO’s Maritime Safety Committee tasked its Ship

Nuclear Mother-Daughter Transshipment Network (N- Design and Construction sub-committee with revising

MDTN) sidesteps this. A nuclear-powered mother vessel the Code in a technology-neutral way, drawing on IAEA sails long-haul trunk voyages between a few nuclear-en- standards. A work plan was agreed in January 2026, with abled gateway ports, while conventional daughter ves- adoption targeted for 2030 (a date that may change), so sels carry cargo onward to regional ports that never need the updated framework is not yet mandatory.

nuclear acceptance. Flag states need the capacity to license a nuclear in-

The logic mirrors existing mother-daughter distribu- stallation, and registration does not guarantee entry to tion systems, but it concentrates reactors, specialized foreign ports. Classi? cation societies must bridge marine crews, regulatory responsibility and emergency capability and nuclear standards, and liability and insurance need in one trunk service. That shrinks the number of ports provisions that conventional policies lack. International needing nuclear-speci? c preparedness and allows nuclear harmonization is a prerequisite for deployment, not a corridors to be introduced in phases. current condition.

Strict separation is the design rule. Daughter vessels handle cargo only, with no reactor fuel, coolant, radio- INDUSTRY AND GOVERNMENTS ARE MOVING active waste or access to nuclear machinery. Gateway Design work is accelerating. In October 2025 DNV terminals act as controlled zones with segregated cargo granted HD KSOE an Approval in Principle (AiP) for a operations, mooring safeguards, weather limits and emer- 15,000 TEU SMR-powered container ship designed for gency separation procedures. Safety cases must show that 24 knots. ABS and HD Hyundai agreed in March 2026 no transfer operation or feeder incident can compromise to design a 16,000 TEU ship with nuclear-linked electric reactor shutdown, decay-heat removal, containment propulsion. Lloyd’s Register granted an AiP on June 2 or emergency power. N-MDTN remains a prospective for a 7,000 CEU car carrier using a molten salt reactor, model, and moving energy between vessels would add and ABS followed in July with an AiP for a 15,000 TEU signi? cant technical requirements. ship with two such reactors. An AiP is a preliminary in- dependent assessment, not a nuclear license, an operating

SAFETY AND SECURITY AT SEA certi? cate or proof of commercial viability.

Ships add hazards that land plants never face: collision, Policy is following. In the U.S., the Maritime Adminis- grounding, ? ooding, ? re and blackout. Decay heat con- tration (MARAD) opened an SMR request for informa- tinues after shutdown, so the seawater cooling interface tion in May, then signed cooperation agreements with must fail safe. The marine-speci? c danger is common- the Port of Long Beach in July and with CORE POWER cause failure, where redundant systems sharing a com- in August. Days later the International Atomic Energy partment, cable run or sea intake fail together, so physi- Agency launched ATLAS, an initiative backed by 26 cal and functional separation is essential. Passive cooling countries to build licensing and safeguards frameworks helps, but passive features alone do not guarantee acci- for nuclear technology at sea.

dent tolerance.

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