Why thorium could help achieve a green maritime future

Robert McDonald discusses the potential of thorium and small modular reactors

Why thorium could help achieve a green maritime future


Ulstein Thor is a conceptual design for what would be the first thorium-powered vessel

By Alex Smith |

Thorium is an abundant, naturally occurring metal that can be used as a clean, efficient fuel with high energy density, enabling one ton of thorium to produce the same energy as 3.5 million tons of coal. Its by-products are significantly safer than uranium and, with shorter half-lives, degrade far faster. It does not need to be enriched and is not challenging to access, and also produces no emissions.

Ulstein released a vessel concept in April 2022, Ulstein Thor, which would be the first thorium-powered ship in the world if built. The design features a Thorium Molten Salt Reactor, which works by dissolving thorium into liquid salt, causing a chain reaction that produces steam to drive a turbine and therefore generate electricity. Battery-operated vessels could then connect to the reactor at seas to recharge anywhere in the world.

“Thorium is now being considered as an alternative fuel for shipping and that’s hugely exciting,” says Robert McDonald, principal engineer for the Institute for Energy Technology (IFE). “Ulstein Thor is a fantastic idea, and possibly one of the most feasible alternative future fuels for maritime. This is a conversation we need to have. Industry, and society, need to talk about thorium.”

McDonald has been working with nuclear power since 1985 and with IFE for the last eight years. The Norwegian organisation conducts international energy research, with over 650 employees. Operating as a not-for-profit, IFE is funded through a combination of government grants and commercial contracts, working to support industry, society and a range of stakeholders in the investigation and development of more energy-efficient processes, renewable energy solutions and energy systems for the future.

McDonald’s focus is on assisting researchers, developing scenarios, running simulations and utilising his practical experience to help unlock new innovation and understanding. For the last few years, small modular reactors – of the same sort that Ulstein aims to deploy in Ulstein Thor – have been a key area of interest.

“A small modular reactor is a nuclear reactor with a power output of 10-300 megawatt electrical,” he explains. “They are efficient, easy to install, easily scalable, safe and, unlike other renewables, only require a very small footprint. 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.”

Thorium Molten Salt Reactors generally do not require refuelling in their lifespan, and salt only needs to be removed from the reactor every three to seven years, depending on a specific reactor’s specifications. Therefore, there would be no need for bunkering or regular stops and operational windows could be tailored to fit the task, rather than a vessel’s fuel tank capacity.

The old salt removed from a reactor can also be reprocessed to remove the by-products, primarily uranium-235, which can then be used as a new reactor fuel.

“It’s incredibly efficient,” says McDonald. “And although there are 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, it’s simply a matter of starting up the mining process. Every new energy source has to start somewhere. The barriers to utilising thorium are certainly not insurmountable.”

However, one of the biggest challenges in introducing thorium-powered vessels will be gaining public acceptance. McDonald acknowledges that the word ‘nuclear’ has different connotations for different audiences, and not everyone’s associations are as positive as his.

However, he points out that there are already around 100 maritime nuclear reactors in use today, on a wide variety of vessels ranging from submarines to aircraft carriers and icebreakers.

“The military follow regulations whereby they are expected to keep the reactors safe and ensure no unauthorised people gain access to it,” says McDonald. “I expect those regulations would be the same in a commercial scenario. But remember, there’s no plutonium produced in thorium reactors, meaning the by-products don’t have the same potential for weaponisation. And why would anyone want to gain access? If the reactor is running, you wouldn’t survive exposure.”

According to McDonald, any maritime reactor would be in a sealed, self-contained, lead-lined compartment that is built for containment. In the case of a loss of power, they automatically shut down. In the worst-case scenarios of crashes or the loss of a vessel – as happened with the nuclear submarine Kursk in 2000 – there have been no cases of leaks and spills.

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

IFE and Ulstein aren’t alone in their interest in thorium and Molten Salt Reactors 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.

“Up until this year it seemed like Molten Salt Reactors and thorium were areas of niche interest, whereas now momentum is really growing,” says McDonald. “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.”

More information about the IFE’s work is available at https://ife.no/en/

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