In the maritime industry’s quest for zero-emissions solutions, it’s often stated there’s no silver bullet. But proponents of thorium believe it is just that.
Thorium has been identified as having huge potential as a clean alternative maritime fuel. At Seatrade Cruise Global in April, Ulstein unveiled its 149-meter Ulstein Thor 3R (replenishment, research and rescue), a vessel with a thorium molten salt reactor (MSR) to generate vast amounts of clean, safe electricity. This would serve as a mobile power/charging station for a new breed of battery-driven cruise ships.
Robert McDonald, principal engineer at Norway’s Institute for Energy Technology (IFE), thinks it’s time to shine the spotlight on the potential of thorium and small modular reactors. He considers thorium a ‘fantastic idea … possibly one of, if not the, most feasible alternative future fuels for maritime.’
What is thorium?
Thorium is an abundant, naturally occurring metal with extraordinary energy density. One ton of it produces the same energy as 3.5m tons of coal. Its byproducts are significantly safer than uranium since plutonium (which is used in nuclear weapons) is not produced in fission. With a shorter half-life, it degrades faster. It does not need to be enriched. It is also a completely zero-emission fuel.
McDonald has been working with nuclear power since 1985 and with IFE for the last eight years. IFE is a frontrunner in international energy research with 650 employees from 38 countries. This nonprofit organization is funded through a combination of government grants and commercial contracts, and works to support industry, society and a broad range of stakeholders by investigating and developing more energy efficient processes, renewable energy solutions and future-orientated energy systems.
McDonald focuses on assisting researchers, developing scenarios, running simulations by channeling his experience to help unlock innovation and understanding. For the last few years, small modular reactors — of the same sort Ulstein aims to deploy in Thor — have been a key area of interest.
Small modular reactors
‘A small modular reactor is a nuclear reactor with a power output of 10-300 MWe,’ he explained, adding they are efficient, easy to install — typically built in factories with the last 10% assembled on site — easily scalable and safe, with very few moving parts and almost zero maintenance. Unlike other renewables, they only require a very small footprint.
McDonald said there are currently more than 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,’ he said. ‘In a way, they’re perfectly suited.’
Thorium MSRs rarely need to be refueled — with the salt removed from the reactor, only every three to seven years, depending on 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, this would open new opportunities.
Waste is minimal and, in the case of MSRs, the old salt is reprocessed to remove the byproducts, primarily uranium 235, which can then be used as a new reactor fuel.
‘It’s incredibly efficient,’ McDonald said. ‘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.’
Public acceptance the biggest hurdle
The greatest hurdle probably won’t be accessing the fuel or bringing the necessary MSR technology to market. It will be acceptance.
McDonald acknowledged that ‘nuclear’ has different connotations for different audiences, and not everyone’s associations are as positive as his. The development of necessary regulations and society’s willingness to embrace thorium-powered ships will be crucial.
He noted most people don’t realize nuclear-powered ships already call at ports around the world every day and have been doing so since 1955.
These are naval vessels, something McDonald knows a great deal about having started his career on a nuclear submarine in the 1980s. Today, there are around 100 maritime reactors in use on a wide variety of vessels ranging from submarines to aircraft carriers and icebreakers.
Regulations and safety
Military regulations are designed to keep the reactors safe and ensure no unauthorized people gain access to them. McDonald expects the same regulations would apply in a commercial scenario but added thorium reactors don’t produce plutonium, so 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 said.
McDonald was quick to add that any maritime reactor would be in a sealed, self-contained, lead-lined compartment. If there’s a loss of power, these reactors automatically shut down and even in the worst case scenarios of crashes or the loss of a vessel — as 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 said.
Maritime momentum
IFE and Ulstein aren’t alone in their interest in thorium and MSRs in the maritime context.
Denmark’s Seaborg is developing a floating power barge that could support grids, complement other renewables and be used for both sea- and land-based industry. IFE also has 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 looking into ways MSRs could be used 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,’ McDonald said. ‘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.’
He added: ‘The arrival of the Thor concept has really supercharged interest and, in my opinion, this is just the start.’
