The Business Times

Going nuclear: Is it an option for merchant ships?

David Hughes
Published Tue, Aug 30, 2022 · 06:46 PM

Nuclear powered ships are not new. Many naval ships and submarines are nuclear powered, as are a number of icebreakers. However nuclear energy has not caught on. The US built a nuclear powered cargo ship, the Savannah, back in 1959. But she was deactivated in 1971 and is now a museum ship. The general view has been that nuclear is not a viable option for the world’s commercial fleet.

Could that be changing? Perhaps it could be. A few months ago, Norwegian shipbuilder Ulstein launched a vessel concept that it says could make “the vision of zero emission cruise operations a reality”. Its proposed project would see cruise passengers touring remote areas of the world in ships powered by batteries fed by floating nuclear power plants.

An Ulstein statement calls the use of thorium a “silver bullet discovery” that could solve the decarbonisation challenge for the shipping industry.

The Ulstein Thor design for a 149-metre replenishment, research and rescue design will feature a thorium molten salt reactor (MSR) to generate, Ulstein says, “vast amounts of clean, safe electricity”. It adds: “This enables the vessel to operate as a mobile power/charging station for a new breed of battery driven cruise ships.”

Ulstein also says its Thor project “may be the missing piece of the zero emissions puzzle for a broad range of maritime and ocean industry applications”.

To prove the feasibility of using the technology, Ulstein has also developed its SIF concept, a 100-metre long, 160 personnel-on-board capacity, zero emission expedition cruise ship. This Ice Class 1C vessel is intended to run on next generation batteries, using the Thor mother ship to recharge while at sea.


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Ulstein chief executive Cathrine Kristiseter Marti comments: “We have the goals, ambition and environmental imperative to switch to zero emission operations, but, until now, we haven’t had the solution. We believe Thor might be the answer we’ve been looking for. Thor is essentially a floating, multi-purpose power station that will enable a new battery revolution.”

She added: “Expedition cruise ships operate in increasingly remote, and environmentally fragile, areas. At the same time, the industry faces growing pressure from diverse stakeholders to preserve nature as it is and ban the environmental impact of cruising. Thor enables replenishment of energy and supplies on site, while also boasting the technology to facilitate rescue operations, as well as conducting research tasks. It is, in effect, a crucial piece of infrastructure to support sustainable and safer operations. Thor literally has the power to change our entire industry.”

Ulstein highlights that an expert in the field of thorium and nuclear power generation Jan Emblemsvag, professor at Norwegian University of Science and Technology supports the project. He says: “MSRs have enormous potential for enabling clean shipping. There is so much uncertainty over future fuels, but here we have an abundant energy source that, with the right approach, can be safe, much more efficient, cheaper, with a smaller environmental footprint than any existing alternative.”

He concludes: “From my perspective I see this as the most viable, and potentially the only credible, solution for a zero emission fleet that can operate under commercial terms and cost levels. The Thor concept is exactly the kind of innovation we need for sustainable success at sea.”

There certainly is something of a bandwagon building up to promote thorium. A couple of weeks ago, a press release from the same stable as Ulstein’s featured comments by Robert McDonald, principal engineer, Institute for Energy Technology (IFE), saying it is time “to shine the spotlight on the unique potential of thorium and MSRs”.

The press release make the main arguments put forward in favour of thorium. These are: “Its by-products 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.”

McDonald describes the Ulstein project as “hugely exciting”. He adds: “This is a conversation we need to have. Industry, and society, need to talk about thorium.”

“A small modular reactor is a nuclear reactor with a power output of 10 to 300 MWe,” Mc Donald explains. “They are efficient, easy to install – typically built in factories with the last 10 per cent 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.”

According to McDonald thorium’s suitability for use at sea relates to much more than the lack of greenhouse gas emissions. He says thorium MSRs, they almost never need to be refuelled – with the salt removed from the reactor only every 3 to 7 years. 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 by-products (primarily uranium 235) which can then be used as a new reactor fuel.”

There certainly has been a revival of interest in thorium recently, with China currently working on a pilot MSR. However the technology certainly has critics and if this project does start to move forward there are bound to be opponents trying to ensure the silver bullet is just a lead balloon.

I would suggest for anybody wanting read more about the realities using thorium, Nick Touran’s webpage on debunking the myths on thorium at, would be a good place to start.

Although he dismisses several of the claims made for thorium he does stress that “thorium is absolutely a viable and capable fuel, and some advanced nuclear reactors that use it are among the most exciting designs out there”.

That does not of course mean that going nuclear will be an economically viable option. How will it compare with the various alternative fuels currently being developed? For that matter how will it stack up against carbon capture technologies which are showing promise? So perhaps we can be allowed a degree of scepticism about the silver bullet claims. Nevertheless it is a technology worth keeping an eye on.


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