Nuclear powered shipping – a golden future or unrealistic claims?

There was little in the way of caution at the conference, save for the odd nod to safety, seemingly when someone remembered there were members of the press in the room. But is atomic energy really the answer to decarbonising shipping? Underneath it all there was an undertone of not really believing what they were saying, and an element of ‘will they find out what we’re not saying’.

Nuclear scientists are split on the ability of fourth generation nuclear reactors to decarbonise shipping, but the drive for funds is leading to ever greater claims

Nick Savvides, Europe correspondent

Keeping politicians and politics away from the technical decisions necessary to develop nuclear power was how one professor described the path to nuclear nirvana.

Jan Emblemsvåg, a professor, speaker and organiser for a recent meeting on Nuclear Power for Shipping, at the Technical University of Norway (NTNU), believes that politicians will stymie the work of engineers.

But professor Emblemsvåg was, like his fellow delegates, very optimistic about the future of nuclear ships, as long as politicians kept their noses out of the technicians’ business. That gave the conference room an upbeat feel.

As it happened, a quick chat with Dr Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists in Washington, DC, and author of the April 2024 paper, “Five Things the ‘Nuclear Bros’ Don’t Want You to Know About Small Modular Reactors,” was certainly fuel for thought.

The paper outlined what the protagonists for nuclear energy, and in particular small modular reactors (SMR), didn’t want you to know. An SMR is defined as producing 300MW of power or less.

Unsurprisingly, Dr Lyman said: “Nothing has changed since 2024, the same challenges outlined then remain in the reactors of today.”

Dr Lyman’s report was written about land-based reactors, but he says it is just as pertinent for ship-based SMRs.

The report discusses the five major claims made for SMR technology; that they are more economical than larger reactors; they are safer; that they reduce radioactive waste; they are more reliable and resilient; and are more efficient than large reactors.

Economies of scale

Building SMRs should in theory be cheaper with lower capital costs, but that doesn’t mean they are more economical, argues Dr Lyman: “What matters more when comparing the economics of different power sources is the cost to produce a kilowatt-hour of electricity, and that depends on the capital cost per kilowatt of generating capacity, as well as the costs of operations, maintenance, fuel, and other factors.”

Economies of scale can also mean that larger units are more economical than smaller ones and SMR developers claim up to 80% cost reductions through the mass production of SMRs. Dr Lyman, however, cites a 2018 University of Cambridge, department of engineering study, that put cost savings due to mass production at 30% at most.

Safety

Safety is said to be a major advantage of SMR technology, they are smaller, have less radioactive material and generate less heat than their larger pressurised water cousins.

Not so, said Dr Lyman: “The so-called passive safety features that SMR proponents like to cite may not always work, especially during extreme events such as large earthquakes, major flooding, or wildfires that can degrade the environmental conditions under which they are designed to operate.”

Lack of testing

None of these reactors have been tested on land or at sea, but Dr Lyman told Seatrade Maritime News: ”The complex, issues associated with fluid flow, and heat transfer and heat distribution in these reactors, they have absolutely no idea that they would be able to operate safely on land, much less on a ship.”

He added: “I would not be comfortable with deploying SMR’s on ships, there are many more challenges at sea than on land.”

Moreover, some molten salt reactors can generate significant quantities of tritium, a radioactive isotope of hydrogen, which cannot be contained within the reactor and could “diffuse throughout your entire ship,” putting crew at risk and contaminating the cargo.

Early attempts to develop a molten salt reactor used charcoal absorption beds in an attempt to capture the tritium, which eventually led to the abandonment of the technology. The used charcoal had to be treated as nuclear waste and disposed of appropriately.

Waste, however, was an issue that was brushed aside as irrelevant by panellists at NTNU, who considered the costs associated with radioactive waste as “minimal”.

Radioactive waste disposal, “is something the nuclear industry promised they could solve 80 years ago, and it hasn’t happened yet,” noted Dr Lyman.

Finland is the one country where there has been “progress toward a geologic repository for very small amounts of fuel,” said Dr Lyman, but no other country has achieved that. In fact Finland has consent to build the Onkalo repository a geologic repository on Olkiluoto Island.

It has a capacity for 6,500 tonnes, stored in copper canisters for 100,000 years at a depth of 400-450m. After 100 years the repository will be permanently sealed.

Storing radioactive waste

No other country has the capacity to sustainably store radioactive waste, “Is stored where it’s being generated,” explained Dr Lyman, “So it’s unrealistic for them to brush off the issue of waste. Any shipping company that is going to start using nuclear reactors is going to have to have a plan and a programme for the long-term management of waste.”

Moreover, some fuel types, such as TRISO will generate as much as 10 times the volume of waste compared to a light water reactor.

“Any shipping company that claims it’s going down this path without having the parallel commitment for management and storage of waste, which would generally require a license, in whatever country that storage facility is going to be, is just, they’re living in fantasy land,” claimed Dr Lyman.

Neither could those costs be mitigated by leasing a reactor as some industry figures have suggested, companies might be suggesting that they will collect spent fuel and handle the waste, but unless they have a credible plan for dealing with that waste it is not a realistic option.

Dr Lyman pointed out that spent fuels are initially stored in “swimming pool type structures” where the waste is cooled, this is expensive and can take five to 10 years to cool. Following that the costs for dry storage are comparatively small, but monitoring will continue indefinitely, so the expense will be ongoing.

Eventually the cost of storage will likely fall on the taxpayer, but even there it is uncertain whether governments are willing to take on the cost of storage.

“In the United States, the law requires the federal government to take title of spent nuclear fuel after a certain period of time. And, you know, the US government famously reneged on its commitment to take over [waste management] in 1998.It has not happened yet.”

Ultimately, the utility companies that continue to store spent fuel have sought damages from the federal government for the hundreds of millions of dollars that they have spent over nearly three decades in storing nuclear waste.

Reactor designs are yet to be proven

None of the proposed SMR designs have yet been tested and proven, though the US Department of Energy launched a Reactor Pilot Program that is meant to “Expedite the testing of advanced reactor designs”.

Launched in 2025 the programme that aims to test three designs which will go critical outside the Idaho National Laboratory on 4 July this year.

To achieve the aim of going critical Dr Lyman points out that no company has built a reactor.

“These aren’t actual power producing machines. They’re just really an array of fuel in an experimental apparatus,” explained Dr Lyman, but that’s not the hard part.

“The hard part is the engineering, the power conversion system, understanding the thermal hydraulics and all the other effects, all those take time, and if you’re trying to do that quickly, especially with novel concepts and materials, it’s a recipe for failure,” he concluded.

According to Lyman the Reactor Pilot Program is a rushed job that the Trump administration is pushing, but he says it lacks durability.

Moreover, the high-assay low-enriched uranium, known as HALEU, is uranium enriched to contain between 5% and 20% of the fissile isotope U-235, these fuels need more mined uranium to produce the fuel.

Uranium mining uses in situ leaching methods where a solution of water, sulphuric acid and hydrogen peroxide is used to dissolve uranium, before purifying and drying the fuel into a concentrated powder known as yellowcake.

More conventional mining methods crush uranium ore into a slurry before dissolving the uranium with sulphuric acid.

Uranium mining is ecologically unsustainable, and costly, particularly in lives lost with some 7,800 uranium miners dying of lung cancer according to data from the Pooled Uranium Miners Analysis.

Effectively, from mine to wake to waste nuclear energy must clean up its act, and it needs to take safety and security seriously too if it is to achieve the kind of break through its proponents claim.

Currently, added Dr Lyman, “There’s no path between the situation today and what you would need to do to have an international safety and security regime for shipboard SMRs and commerce,” noted Dr Lyman.

No modern SMR has been built or tested, there is no regulatory regime and issues such as safety and security remain open, with International Atomic Energy Agency monitoring needed to make certain that nuclear fuels “are not diverted”.

Existing SMR companies, “Need to attract capital to be able to actually build their reactors. And now you have this multiplicity of vendors who are all competing, and that’s compelling them to make more and more unrealistic claims to try to attract attention and making promises and ambitions that are not realistic,” claimed Dr Lyman.

Responding to professor Emblemsvåg’s claim that politicians were the roadblock for developing nuclear powered ships Dr Lyman argued that politicians were critical to the future of nuclear-powered ships. “The only way nuclear is going to get accepted is if politics drives the process, which is what we’re seeing now [with the Reactor Pilot Program]….There has to be massive government support, that’s the only way some of these plans are going to happen.”