ULSTEIN THOR ready to repower another vessel

Was maritime industry too quick to discard nuclear power? Emerging initiatives are proving it wrong.

The quest for zero-emission fuels is dominating the decarbonization narrative in the maritime industry today. Ammonia and hydrogen are at the top of the candidate list for the future fuel mix. However, there are numerous challenges in establishing a scalable production of green hydrogen and green ammonia, as well as overcoming safety challenges, and financing the construction of the massive infrastructure that is required.

ULSTEIN THOR ready to repower another vessel; Source: Ulstein

On the other hand, there is a solution that would not need such a massive infrastructural undertaking that is emission-free: nuclear power.

Nuclear power reactors have been in use in the naval industry for decades, and they have had a sound safety record. Switching to nuclear-powered ships would remove business uncertainty caused by fuel cost volatility, as they wouldn’t need to be refueled. This would further bolster costs and utilization since ships could sail at higher speeds (e.g., 30-35 knots) leading to reduced transit times and increased transport capacity.

The key obstacle to the wider implementation of the technology in commercial shipping has been public acceptance.

What people don’t realize is that nuclear-powered ships already call at ports around the world every day… and what’s more, they have been doing so since 1955,” Robert McDonald, Principal Engineer, Institute for Energy Technology (IFE).

“Today, there are around 100 maritime reactors in use, on a wide variety of vessels ranging from subs, to aircraft carriers and icebreakers. These are proven,” he stressed, “and safe.”

Robert McDonald, Principal Engineer, Institute for Energy Technology (IFE)

McDonald started his career on a nuclear submarine in the 1980s, and he is now working as a process expert in nuclear power at Norway’s IFE. His focus is on assisting researchers, developing scenarios, running simulations, and generally utilizing his practical experience to help unlock new innovation and understanding. For the last few years, Small Modular Reactors (SMRs) have been a key area of interest.

Safety has been one of the major concerns of the wider public when it comes to integrating nuclear power into commercial shipping. Potential radiation leaks or explosions caused by collisions have rendered the technology in commercial shipping unacceptable in the public eye.


Nevertheless, there has been a rise in initiatives aimed at exploring the potential of nuclear power in the sector, hinting that we might have been too quick to discard it as a pathway toward decarbonizing the industry.

Specifically, there is a new kid on the block: Thorium.

Industry, and society, need to talk about Thorium, McDonald.

As explained by McDonald, Thorium is abundant, naturally occurring metal that can serve as a clean, efficient fuel with extraordinary energy density.

Its byproducts are significantly safer than Uranium (Plutonium is not produced under fission) and, with shorter half-lives, degrade far faster. It does not need to be enriched and is not challenging to access. It is also a completely zero-emission fuel.

Norwegian company Ulstein has decided to put theory to practice. In April, Ulstein revealed a concept for the world’s first Thorium-powered ship – ULSTEIN THOR.

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This 149m Replenishment, Research and Rescue vessel design features a Thorium MSR, which works by dissolving Thorium into liquid salt, causing a chain reaction that produces steam to drive a turbine, creating huge amounts of clean electricity. Battery-operated vessels could then plug into this ‘floating power station’ and recharge anywhere in the world, effectively transferring maritime’s short-sea battery revolution to deep sea operations.

McDonald says this is “a fantastic idea” with what he deems to be “possibly one of, if not the, most feasible alternative future fuels for maritime.”

“A small modular reactor is a nuclear reactor with a power output of 10-300 MWe,” he explains. “They are efficient, easy to install – typically built in factories with the last 10% assembled on site – easily scalable, safe (with very few moving parts and almost zero maintenance) and, unlike other renewables, only require a very small footprint.

At the moment there are over 70 small and micro designs under development, with typical uses for applications such as district heating, desalination, general electricity generation and hydrogen production. Considering them for the maritime industry is a new idea… and one that’s very relevant. They could prove to be an essential piece of the zero-emission puzzle for a huge number of applications. In a way, they’re perfectly suited.”

IFE’s HAMMLAB (Halden Man Machine Laboratory) simulator, a leading nuclear research facility

McDonald explains that, in the case of Thorium MSRs, they almost never need to be refueled – with the salt removed from the reactor only every 3 to 7 years (dependent on its specifications). This would mean no bunkering, no regular stops, and operational windows that could be tailored to fit the task, rather than a vessel’s fuel tank capacity. For fishing trawlers, cruise ships, container carriers, or replenishment vessels such at THOR, a new world of opportunity would swing right open.

Waste is minimal and, in the case of MSRs, the old salt is simply reprocessed to remove the byproducts (primarily Uranium 235) which can then be used as a new reactor fuel.

It’s incredibly efficient,” McDonald notes. And although there’s no Thorium reactors up and running today it is a proven technology, with the earliest examples operating back in the 1950s and 1960s.

However, that also means, unlike Uranium, there’s currently no supply chain. But as Thorium is around three times more abundant in the Earth’s crust than Uranium – and there’s a lot here in Norway – it’s simply a matter of starting-up the mining process.

Every new energy source has to start somewhere. The barriers to utilizing Thorium are certainly not insurmountable.”

The greatest hurdle, however, probably won’t be accessing the fuel, or bringing the necessary SMR technology to market. It will, of course, be acceptance.

McDonald acknowledges that the word ‘nuclear’ has different connotations for different audiences, and not everyone’s associations are as positive as his. As such, the development of necessary regulations and a willingness within society (on a global basis) to embrace Thorium-powered ships will be crucial.

“The military follows regulations whereby they are expected to keep the reactors safe and ensure no unauthorized people gain access to it,” McDonald explains. “I expect those regulations would be the same in a commercial scenario. But remember, there’s no Plutonium produced in Thorium reactors – meaning the byproducts don’t have the same potential for weaponization – and why would anyone want to gain access? If the reactor is running you wouldn’t survive exposure.”

He added that any maritime reactor would be in a sealed, self-contained, lead-lined compartment that is built for complete security and containment. If there’s a loss of power they automatically shut down and even in the worst-case scenarios of crashes or the loss of a vessel – as the world saw with the nuclear submarine Kursk in 2000 – there is no reason to expect radiation leaks or spills.

“This is not a completely new solution, unlike some other alternative fuels, so we do have a good understanding of the risk picture,” McDonald notes.

Maritime momentum

IFE and Ulstein aren’t alone in their interest in Thorium and MSRs in the maritime context. Seaborg from Denmark is developing a floating power barge that could support grids, complement other renewables and be used for both sea- and land-based industry. IFE has also been approached by a trawler firm keen to investigate the potential of the reactors to charge its shrimp-fishing fleet, while offshore energy producers are apparently eager to look into ways MSRs could be utilized to satisfy the power needs of their remote operations.

Up until this year it seemed like MSRs and Thorium were areas of niche interest, whereas now momentum is really growing. Here at IFE we’ll aim to do everything we can to support industry and society in finding the best way forward to harness the huge potential of Thorium.

The arrival of the THOR concept has really supercharged interest and, in my opinion, this is just the start.

Expect to hear a lot more about Thorium in the near future,” he concluded.

The US has set sights on adopting nuclear propulsion on commercial vessels as well

Indeed, the U.S. is also looking into the potential of the technology. On Wednesday, the ABS classification society said that it won a contract from the U.S. Department of Energy (DOE) to research barriers to the adoption of advanced nuclear propulsion on commercial vessels.

The $800,000 research project – awarded by the DOE’s Office of Nuclear Energy last year and formally contracted through its U.S. Industry Opportunities for Advanced Nuclear Technology Development funding opportunity – will address challenges to adopting new reactor technology in commercial maritime applications.

As part of the research ABS will develop models of different advanced reactor technologies for maritime applications and develop an industry advisory on the commercial use of modern nuclear power. 

The Department of Energy’s National Reactor Innovation Center (NRIC), based at Idaho National Laboratory, will provide the advanced reactor framework to help propose how a maritime nuclear demonstration could take place. 

In a separate, smaller award, the DOE has also contracted ABS to support research into molten salt reactors being carried out by the University of Texas.

“Modern nuclear technologies are increasingly suggested as a potential solution to shipping’s decarbonization challenge. The technology certainly has potential both in terms of its contribution to emissions reduction and for U.S. shipyards and their supply chains to leverage national investment in terrestrial nuclear energy development. Nevertheless, many questions need to be answered and it is critical the industry is able to evaluate these technologies with a laser focus on safety,” said Patrick Ryan, ABS Senior Vice President, Global Engineering and Technology.

“The national lab system has powerful capabilities – when we partner with industry, we can jointly apply those to our energy challenges, and NRIC was created to make that happen faster,” said NRIC director Ashley Finan.

There’s a tremendous opportunity to reduce emissions in shipping, as well as growing interest from both the maritime and advanced nuclear sectors, and we’re pleased to be a part of this important work.”

ABS has a history with maritime nuclear energy sources dating back to 1959 with the NS Savannah which was the first merchant ship powered by a nuclear reactor and approved under ABS Rules.

Molten salt reactors have also sparked the interest of one of the world’s biggest shipbuilders: Samsung Heavy Industries (SHI).

Last year, SHI revealed that it had partnered up with Korea Atomic Energy Research Institute (KAERI) with an aim to develop nuclear-powered vessels. SHI plans to tap into the market of MSR-based floating nuclear power generation plants and nuclear-powered vessels. It is focusing on R&D within the project targeting a new future growth engine based on the MSR technology.

Furthermore, earlier this year SHI teamed up with Seaborg Technologies, a Denmark-based startup focused on nuclear reactor technology, to develop floating nuclear power plants based on Seaborg’s Compact MSR.

The agreement includes the development of hydrogen production plants and ammonia plants, as the CMSR is said to be an ideal power source for the supply of stable, clean, and safe electricity.

​The aim of the partnership is to manufacture and sell turn-key power plants, ready to be moored at industrial harbors and connected to the electric grid onshore. ​

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A modular MSR for vessels is also being developed by Core Power, a UK-based development company specializing in scalable atomic power technology for ocean transport and heavy industry.

The reactor will be capable of propelling ships and providing energy for manufacturing blue and green fuels. Measuring 3,5 x 3,5 x 7,5 meters and weighing 450 tons, it can be produced in factory-controlled conditions. The first prototype MSR reactor is due to start trials in 2025.

In May 2021, X-Press Feeders, the world’s largest independent common carrier, made an investment in Core Power together with six other partners.

The carrier has not disclosed the amount of the investment, saying only that it was part of its overall strategy aimed at reducing its carbon footprint in line with the IMO targets.

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