Interest in nuclear power at sea is accelerating, from in-port power supply and floating barges to platforms for offshore activity and ship propulsion. Yet the one dedicated international reference for this domain, IMO's 1981 Code of Safety for Nuclear Merchant Ships, was written for a single reactor technology, has never been implemented commercially, and predates more than forty years of technology evolution and nuclear safety practice lessons of Chernobyl and Fukushima Daiichi events.
Nuclear-21 has prepared a Perspective report proposing a practical route to replace the Code without starting from a blank page.
Why the 1981 Code can no longer serve as-is
The Code itself anticipated the need for revision, citing technical progress, new ship types, changing risk profiles, evolving international standards and compatibility with other codes or conventions, conditions that are now clearly met. It was also built exclusively around pressurised water reactor propulsion, whereas today's projects span a wide range of small, advanced and micro reactor concepts using different coolants and serving uses well beyond propulsion. Its terminology, drawn from 1970s maritime and nuclear usage, no longer aligns with the vocabulary since standardised through the IAEA Safety Glossary, and its drafting style is often read as overly prescriptive at a time when design and licensing are moving toward goal-setting, risk-informed and performance-based approaches.
What a replacement needs to achieve
Nuclear-21's analysis points to a small set of conditions the new framework must satisfy:
- it must be technology-neutral, so it can accommodate whichever reactor concepts are eventually deployed at sea;
- it must preserve the international consensus that a mobile nuclear installation requires, unlike land-based plants which regulation is a purely national matter;
- and It must retain the Code's genuinely useful function, defining the boundary conditions which are an essential input for the designers involved in these activities, such as environmental and hazards, that a maritime nuclear safety case must address, rather than discarding this as mere prescription.
Our approach: extend, don't replace, the existing safety foundation
Rather than drafting a new code from scratch, Nuclear-21 proposes building directly on the body of IAEA Safety Fundamentals, Requirements and Guides that already underpins land-based nuclear licensing, and that is itself being updated to become more technology-inclusive through initiatives such as the SMR Regulators' Forum and the Nuclear Harmonization and Standardization Initiative (NHSI). A mapping of the 1981 Code's full table of contents against current IAEA standards shows that most of its themes, from site evaluation and design extension conditions to transport of radioactive material and the legal and regulatory framework for safety, are already covered, wholly or partly, by these updated standards. What remains is a genuinely maritime-specific residue: essentially the boundary conditions particular to a vessel or floating platform, such as sinking and seaway loads, that has no land-based equivalent and must be developed on top of the existing standards rather than duplicating them.
Two ways to close the gap
Nuclear-21 sees two realistic routes to formalise this maritime-specific layer:
- further extending the relevant IAEA Standards themselves to explicitly cover maritime applications,
- or developing dedicated “Standards Addenda” that sit alongside the existing standards and address the maritime needs specifically.
The Perspective favours the second route on grounds of simplicity and efficiency, while noting that the choice should be made collectively by the stakeholders involved. The same reasoning is expected to extend to nuclear security and safeguardability, using the corresponding IAEA publications as the starting basis.
Both these approaches would not preclude a review of International Conventions regulating the peaceful uses of nuclear energy that were predominantly designed for land based applications. A consistent and comprehensive framework should be ready for the deployment phase of the maritime nuclear application.
Why this matters now
A fully revised IMO Code is still several years away: revising an IAEA safety standard is itself a lengthy, consensus-driven process, and a maritime code requires an equivalent international agreement among the states that will host these vessels. Designers cannot wait for that process to conclude before advancing their projects. Working now to align emerging designs with the direction of travel of the safety standards, rather than only with the outdated 1981 text, reduces the risk of late-stage regulatory surprises and keeps nuclear maritime projects on a credible path to licensing, in acceptable economic conditions and with public confidence intact.
Nuclear-21 believes replacing the Code, built on the existing IAEA foundation rather than against it, is one of the conditions needed to keep these projects both robust and economically viable.
Next steps
Nuclear-21 has documented these proposals in a new Perspective (Executive Summary), together with a detailed mapping of the 1981 Code's full table of contents against current IAEA standards. The proposed next step is an in-depth, collective discussion among IAEA, IMO and other stakeholders to select between the two routes outlined above and to launch the corresponding drafting work.
Nuclear-21, drawing on its long-standing experience in nuclear licensing and its recent involvement in nuclear maritime projects, stands ready to support this effort.
Contact: Mr. Gian-Luigi Fiorini
