The design enables micro modular reactors (MMRs) to be combined with conventional diesel-electric systems for 73-metre and 90-metre amphibious stern landing vessel (SLV) designs.
The approval in principle (AiP) follows several years of close collaboration between Lloyd's Register (LR) and Seatransport. Together, they have demonstrated how licensable MMRs can be safely integrated with proven diesel-electric systems to deliver long-range vessels with significantly reduced fuel dependence and emissions.
A recently launched 73-metre stern landing vessel was used as the trial platform. Seatransport's stern landing vessel platform is already well established, with more than 25 years of successful operations. Sea trials of the conventionally powered stern landing vessel confirmed the design assumptions used in the MMR concept, providing strong technical assurance that the design is both practical and robust.
"By incorporating a hybrid nuclear-ready capability, the vessels gain effectively unlimited operational range, significantly reduced reliance on conventional fuels, and extended endurance for sustained missions," Lloyd's Register said. "This approach also enhances operational flexibility, delivers low-emission performance, and enables reliable operation in demanding environments, such as landing and logistic support on unprepared or remote beaches."
The MMRs under consideration range from 1.2 MW to 2.6 MW and are undergoing rigorous technical and regulatory assessment. Lloyd's Register said it was working closely with national authorities to ensure that safety, compliance and operational standards are fully addressed. Wider adoption is anticipated in the early 2030s.
Lloyd's Register said the approval in principle process offers technology developers an opportunity to lay out a roadmap for full regulatory compliance by focusing on key issues. By gaining approval in principle, developers can gain early confidence that their technology has the potential to satisfy regulatory requirements and that there are no major obstacles to future certification or classification. "An Approval in Principle is not a guarantee that, despite good engineering practice and judgement, the design will obtain regulatory approval or an assurance that a design can meet any code or standards requirements," it noted.
"Achieving Approval in Principle for hybrid nuclear power is an exciting step for LR and the wider maritime industry," said Jez Sims, Technical Authority for Nuclear, Lloyd's Register. "We are proud to provide independent technical assurance, drawing on decades of expertise in regulatory compliance, vessel design and nuclear safety. Our role is to help the industry move forward with confidence - turning pioneering ideas into safe, practical solutions."
Seatransport CEO Stuart Ballantyne added: "This AiP marks a pivotal moment for amphibious vessel design. By working closely with LR, we've integrated nuclear MMR capability into our proven SLV platform, future-proofing it for extended endurance, operational flexibility and low-emission performance. We do believe that for all shipowners, this is a paradigm shift in marine technology greater than sail to steam."
In April 2025, Seatransport and US-based Deployable Energy announced they were collaborating with Lloyd's Register to develop nuclear power generation for different applications, including strategic response vessels in remote areas. The project - led by Lloyd's Register - envisages using MMR technology, with two to five MMRs of 1 MWe capacity each powering a 73-metre amphibious vessel, designed for emergency response and disaster relief duties in remote areas. This will enable the vessel to operate for 8-10 years without refuelling, and it can feed power into the shore grid of affected areas and whenever docked at port.
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