Nuclear power has the potential to make a transformational impact on carbon emissions reduction across the electricity, industrial and transportation sectors. Its ability to provide clean alternative power generation options in shipping has already attracted attention and the journey to cleaner maritime energy is gaining momentum.
From the perspective of achieving IMO’s 2050 net-zero ambitions, it would be a mistake to ignore nuclear as a part of the fuel mix. However, progress will not happen without regulations that provide a foundational basis for how nuclear-powered systems in the maritime sector could look.
Nuclear energy has the potential to be a disruptor for the maritime sector. Enabling it to be successfully and safely integrated into the shipping industry requires a new kind of collaboration.
Nuclear power for ships holds out the prospect of using advanced small modular nuclear reactors as propulsion, while nuclear for future fuels includes scenarios where small modular nuclear reactors are positioned near shore to produce power for ports and support the production of alternative fuels.
Developing the systems that could power merchant vessels, provide shore power and generate clean fuels, means bringing together players in marine and offshore design with builders of nuclear systems to fill knowledge gaps and exchange ideas.
Both marine and offshore sectors represent high potential demand, sharing as they do an increased focus on clean energy usage. The offshore market exhibits immediate demand due to the power requirement created by ports and other industrial users.
The American Bureau of Shipping (ABS) is playing a leading role in helping government and industry. The industry’s first comprehensive rules for floating nuclear power plants were recently unveiled at a forum for nuclear industry leaders held jointly by ABS and Idaho National Laboratory (INL). The ABS Requirements for Nuclear Power Systems for Marine and Offshore Applications, provides the first classification notation for nuclear power service assets such as floating nuclear power plants or nuclear-powered floating production, offloading and storage units. Uniquely, the requirements are agnostic to specific reactor technologies technology and propose a framework for nuclear regulators to collaborate with Flag administrations and ABS for complete regulatory oversight and license.
This is one example of how ABS is helping industry work towards the adoption of advanced nuclear technology in commercial maritime, including key research with the US Department of Energy and multiple New Technology Qualification and Approval-in-Principal projects. The same event, for example, also saw publication of a detailed study from ABS and Herbert Engineering Corporation (HEC) modelling the design, operation and emissions of a floating nuclear power plant.
Exploring floating nuclear power
Nuclear energy’s potential in the maritime domain is much more than a reactor on a ship. Instead, nuclear energy can link demand across the electricity, industrial and transportation sectors to optimise energy generation and support decarbonisation of shipping and industry.
With advances in nuclear engineering and the development of many types of advanced nuclear reactors come opportunities to implement the technology floating nuclear power plant applications.
In addition to net zero emission electricity created by a small modular plant, the power barge concept could be extended towards production of alternative fuels such as pink hydrogen and pink ammonia for consumption by onshore and offshore facilities.
In the joint study by ABS and HEC reported at the INL event, a floating platform named Navigator was designed with supply to the shore grid in mind to increase the available power to support maritime decarbonisation in port. This study reviewed existing ports fitted with onshore power supply in the US and the typical energy consumption from large ships such as cruise vessels.
With these parameters in mind, a platform supplying a maximum of 70 MWe to the port’s electric grid was considered sufficient to meet the need of up to six visiting cruise ships at once. Also known as ‘cold-ironing’ this term encompasses the provision of shoreside electrical power to docked ships while their engines are turned off. The ability to deliver the floating platform to its site location and connect to the local grid from the pier can also ease many portside challenges of increasing available power for port operations.
To conceptualise the possible design, the design team invited a reputable small reactor designer to provide information regarding the use of their reactor design for
the Floating Nuclear Power Plant. This reactor design has been supported by the US Department of Energy’s Advanced Reactor Demonstration Program (DOE ARDP) to demonstrate the commercial viability of small modular reactors (SMRs).
The modular reactor philosophy can successfully be carried over to the floating platform design with significant advantages in terms of safety and cost. Furthermore, the modularity concept allows the power output to be reasonably flexible to adapt to the needs of large ports and their berthed vessels. Refuelling cycles of approximately five years allow the design to be compact and simple, with no need for fuel or high radioactive waste to be handled on board.
Feasibility study for an LNG carrier
ABS also worked with HEC on the high-level design of a standard LNG carrier to illustrate how one type of advanced nuclear fission technology could be applied for shipboard power in the future, with an emphasis on what aspects of ship and reactor design may require further investigation to guide the development of the integrated technology and regulatory framework.
The main conclusion of this study was that nuclear power would be a supportive means of drastically abating shipping emissions, but that significant hurdles remain in public perception and international regulations before this can be achieved.
The modular reactor philosophy imposes significant restrictions on ship design. The modularity concept imposes a fixed maximum SMR power output per reactor, corresponding to a set lifespan of its core.
It is advantageous if the nuclear power plant equipment and fuelling lifecycles align with the vessel’s life. Access to suitable shipyards or other support facilities and the physical removal of the reactors are key challenges, which would be simplest to avoid by addressing the issues in the design stages.
It is possible to operate an SMR at a lower constant power level such that its core will last longer. This may cause the reactor end-of-life to not line up with the ship’s standard drydocking schedule, thus imposing significant additional operational costs.
This means that SMRs would be better suited for just a few sizes per ship type (mostly larger ships). In the design presented in the study, the SMR is considered to have an output capacity of 17.5 MWe associated with a core lifespan of five years.
This matches well the total power requirement of a 147k m3 LNG carrier, imposing the use of two reactors and a core switch at each special survey. However, if the same SMR were considered for a QMax LNG Carrier (262k m3) with a total energy need of approximately 56 MW, four SMRs would be needed, operating at around 80% of their maximum power.
This would imply a core switch approximately every six years and three months, which would represent the primary driver for service scheduling. This SMR feature may impose limits to ship capacity that can be offered to the market.
At the same time, the ability of nuclear power plants to tolerate higher accelerations due to ship motions and vibrations can allow for flexibility in the overall design. While there are significant safety benefits to keeping the plants at midships, for specific vessel types like oil tankers and LNG carriers, the midships location would not be feasible or would significantly penalise cargo capacity.
The degree of redundancy required by a nuclear-powered vessel may be higher than a more conventionally powered vessel for safety, which causes a decrease in performance. The nuclear vessel design presented has two separate power, propulsion and steering plants, which provide a high level of redundancy compared to no redundancy typically accepted of single screw vessels driven by marine diesel engines. Opportunities for optimisation exist on many levels for future design iterations.
However, both this study of nuclear-powered commercial vessel designs and the nuclear-powered cold-ironing analysis also concluded that the maturity of advanced nuclear technologies that may be implemented for these applications is currently low. Therefore, the level of detail provided in the studies is limited to engineering information available from the design of terrestrial applications for engineering postulation and recommendations for future design optimisation.
Outlook for nuclear in marine applications
Nuclear energy has the potential to be a disruptor for the maritime sector. The ABS focus is on bringing together major players in marine and offshore design with designers of nuclear systems. ABS can help facilitate filling knowledge gaps that nuclear power companies may have around marine and offshore and vice versa.
With the feasibility demonstrated for small nuclear reactors onboard large container ships, gas carriers and offshore platforms, it is likely that regulation and reactor licensing will prove the primary driving force in realising full-scale projects.
With renewed interest in building new technologies that are feasible for the marine sector, it will be up to regulators to support the ambition of reducing carbon emissions by enough to meet 2050 targets.
While the regulatory landscape continues to develop, both modular system providers and vessel designers are encouraged to establish further joint industry projects that can further investigate both challenges and opportunities.
