Research and development on SMRs and MMRs, the micro modular reactors, is advancing rapidly. Their use could spread in other maritime sectors but must face regulatory development, safety concerns, waste management, and public perception
Nuclear propulsion in yachting is one of the hypotheses currently under investigation. Mini nuclear reactors are capable of generating significant volumes of energy that could potentially be applied not only in commercial shipping but also in other maritime sectors. To understand how far this research has progressed, we spoke with Lorenzo Pollicardo, Technical & Environmental Director of Sybass, the Superyacht Builders Association.
Dr. Pollicardo, what is the current status of the research?
We are facing a major technological evolution. Research and development of small modular reactors, SMRs, and micro modular reactors, MMRs, is advancing rapidly. In the case of SMRs, we can already envisage potential timelines for their application aboard ships. For MMRs, research is still at a much earlier stage, yet it is clear that the development of these propulsion systems represents a highly compelling objective.
In what sense?
SMRs deliver substantial power outputs—on the order of 300 megawatts. Their application would therefore be limited to vessels of no less than 100 metres in length. They are well suited to commercial shipping, which already employs nuclear propulsion in a limited number of non-conventional units, but they are difficult to adapt to yachting, except potentially for very large maxi yachts.
The scenario is quite different for MMRs, which could generate between 30 and 40 megawatts, power levels more compatible with comparatively smaller units. That said, MMRs are still in an early research phase, and significant validation is required before imagining realistic market deployment.
Nuclear propulsion is already used on some commercial vessels operating today. Is that correct?
Yes. The numbers remain limited, around 200 vessels, approximately 3% of global commercial traffic, and these are primarily non-conventional units. Nuclear propulsion is typically installed aboard icebreakers and polar support vessels. Their extended autonomy allows them to operate on routes where refuelling with traditional fuels is complex or impractical. Nuclear propulsion is also used in naval military fleets.
For the time being, nuclear technology is applied in sectors less exposed to public scrutiny than, for example, a hypothetical future use in passenger ships. Moreover, it is essential to distinguish between the operational and energy demand profiles of commercial shipping and yachting.
What are the differences?
In commercial shipping, excluding passenger ships, which are more comparable to yachts, around 90% of energy consumption is dedicated to propulsion, the so-called sailing load, with only 10% used for onboard services (hotel load). In yachting, the situation is reversed: the majority of energy demand is absorbed by hotel services.
What are the main areas of research focus? And what challenges remain?
Modularity is one of the key areas of focus. Modularity implies versatility and operational flexibility. Furthermore, this new generation of nuclear reactors operates at low pressure and offers significantly enhanced safety characteristics.
In Italy, Ansaldo Energia is among the most active companies in next-generation nuclear development. Currently, approximately fifty projects are under study, some involving Fincantieri and RINA. The United Kingdom is also strongly committed to this sector, arguably pushing most decisively in this direction. Rolls-Royce Nuclear is one of the most active players, and the Rolls-Royce name has long-standing maritime associations, particularly following its acquisition of MTU, a major manufacturer of marine propulsion systems.
What are the primary challenges nuclear research must address, and how are they being tackled?
It would be disingenuous to ignore the fact that the term “nuclear” still evokes apprehension among the general public, even in terrestrial applications. Beyond narratives often shaped by misconceptions and persistent myths, perceived safety remains an objective obstacle to broader research and real-world application in both shipping and yachting.
In addition, the international regulatory framework remains incomplete and fragmented.
What concrete steps are being taken to overcome this impasse?
Perceived safety depends largely on the level of public information, particularly regarding new-generation reactors, which operate at low pressure and incorporate enhanced safety systems. With the exception of Italy, where nuclear power remains prohibited following a national referendum, the technology is widely adopted in many countries worldwide and across Europe.
At the same time, the maritime regulatory framework must be redesigned. International institutions are currently working to establish updated regulations covering next-generation technologies and non-fossil fuels. Nuclear energy is included in this discussion.
What is the cost of next-generation nuclear propulsion? Is it possible to compare it with alternatives such as hybrid diesel, methanol, or hydrogen?
Cost comparisons are complex, particularly because SMRs have not yet entered full-scale production or commercialization. However, it is worth noting that an SMR can operate for 15 to 20 years without refueling. Once installed onboard, it requires no conventional bunkering. More relevant, perhaps, is the issue of sustainability and decarbonization.
What does that entail?
Sustainability is a broad concept encompassing economic factors as well as environmental performance relative to other propulsion solutions designed to reduce CO₂ and greenhouse gas emissions, such as hydrogen, biofuels, and methanol.
Current efforts focus on reducing TTW (tank-to-wake) emissions, direct greenhouse gases (CO₂, methane, nitrous oxide) released during onboard fuel combustion for propulsion and auxiliary systems. Conversely, WTW (well-to-wake) measures total lifecycle greenhouse gas emissions, from upstream fuel production (“well-to-tank”) through onboard combustion (“tank-to-wake”).
The maritime decarbonization pathway has been structured into short-, medium-, and long-term phases. For example, a fully electric propulsion system generates virtually zero tank-to-wake emissions during navigation. However, if the electricity used is produced by burning coal, well-to-wake emissions tell a very different story.
What are the practical implications?
In the short term, the objective is energy efficiency through consumption rationalization, measures that can reduce emissions by up to 30%, but no more. In the medium term, new fuels will be required to further reduce the emissions curve, with the long-term objective of achieving zero emissions, tentatively targeted by the United Nations for 2050.
How can this goal be achieved?
Biodiesel, methanol, and hydrogen are not currently zero-emission fuels, as their production processes generate emissions. Energy efficiency is therefore only a transitional solution while research advances toward truly clean energy generation. In this context, nuclear energy represents a potentially viable option.
Also, in terms of safety?
Yes, although the road ahead remains long and depends on more than technological development alone. Acceptance of nuclear propulsion will also require a narrative capable of moving beyond clichés and dispelling persistent myths surrounding the technology.
