Robert McDonald, Principal Engineer at Norway's Institute for Energy Technology (IFE), says it's time to shine the spotlight on the potential of thorium and small modular reactors (SMRs) for shipping.

The big picture: The concept would transfer the short-sea battery revolution to the deep sea, enabling ships to recharge anywhere in the world.

In April, the design for the world's first thorium-powered ship, Ulstein Thor, was launched.

• The project features a thorium molten salt reactor (MSR) that works by dissolving thorium into liquid salt, causing a chain reaction that produces steam to drive a turbine, creating large amounts of electricity.
• Battery-operated vessels could then plug into this floating power station and recharge anywhere, effectively transferring shipping's short-sea battery revolution to deep-sea operations.

McDonald describes Thor as "a fantastic idea" and posits that thorium is "possibly one of, if not the, most feasible alternative future fuels for maritime."

• The specialist has been working with nuclear power since 1985 and with IFE for the last eight years. His focus is on developing scenarios, running simulations and utilizing his experience to help unlock new innovation and understanding.
• For the last few years, SMRs have been a key area of interest for him.

An SMR is a nuclear reactor with a power output of 10-300 megawatts electric (MWe), McDonald explains, as he goes on to list what he believes are the key benefits of the technology.

• "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," he asserts.
• Also, McDonald notes that thorium MSRs almost never need to be refuelled, with the salt removed from the reactor only every 3 to 7 years.
• Waste is said to be 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.
• And although there are no thorium reactors up and running today, it is a proven technology, with the earliest examples dating back to the 1950s and 1960s.
• Furthermore, thorium is around three times more abundant in the Earth's crust than uranium, so even though there is currently no supply chain, it would simply be a matter of starting up the mining process.

Negative connotations

McDonald acknowledges that the word 'nuclear' has different connotations for different audiences and that the willingness within society to embrace thorium-powered ships will be crucial for it to be accepted.

To support his argument, McDonald points out that nuclear-powered naval vessels already call at ports around the world every day and have been doing so since 1955.

• Today, there are around 100 maritime reactors in use on a wide variety of vessels ranging from submarines to aircraft carriers and icebreakers. These are "proven", he stresses, adding: "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 that the military follow regulations whereby they are expected to keep the reactors safe and ensure there is no unauthorized access. "I expect those regulations would be the same in a commercial scenario," he adds.

• Also, plutonium is not produced in thorium reactors – meaning the byproducts do not have the same potential for weaponization.
• The maritime reactor would be in a sealed, self-contained, lead-lined compartment built for security and containment.
• And if there is a loss of power, the reactor automatically shuts down. In worst-case scenarios of crashes or the loss of a vessel, McDonald says there is no reason to expect radiation leaks or spills — citing the Kursk submarine disaster as an example (where the vessel's two reactors shut down automatically to prevent a nuclear meltdown).

Signs of maritime momentum?

IFE and Ulstein are not 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.
• And 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," McDonald says.

• "The arrival of the Thor concept has really supercharged interest and, in my opinion, this is just the start," he concludes.