NUCLEAR power for shipping is having a moment. But why?

Class societies are pushing out more analysis, Greek shipowners are working with MIT, and the International Maritime Organization is hosting workshops on how to join up different parts of the industry to develop the regulation alongside the technology.

Those reports — or at least the press summaries of them — use words like “viable” to describe nuclear, despite there being no civilian commercial ships commissioned in more than 40 years.

We are told that new Small Modular Reactors (SMRs) could work like atomic batteries, which could let a ship sail as fast as it pleases, with no emissions and little refuelling.

Class societies don’t disguise the challenges.

Sentences like the following, from DNV, stand out: “The operation of the reactor continually generates spent fuel and radioactive waste which must be actively managed on board and regularly removed from the ship.”

Several countries have experimented with SMR technology, which has not avoided nuclear’s trademark delays and cost blowouts.

“The three operating SMRs worldwide, which are located in Russia and China, exceeded their original cost estimates by 300% to 400%,” the Financial Timesreported on October 5, in a piece warning the technology “could prove too costly to be viable”.

Molten salt reactors, like those hyped by maritime start-up Core Power, are still far from commercial adoption.

Their problems include how to handle wear and tear on components in contact with the highly corrosive and radioactive reactor environment.

“The design and manufacturing of certain components, for which little prior experience is available, are among the key challenges that SMRs pose,” the International Atomic Energy Agency said in a 2023 paper.

Making long-lasting parts such as circulation pumps, heat exchangers, valves and flanges that are in contact with the harsh salt system would require great effort, the IAEA said, and instruments to monitor their status were “yet to be developed and demonstrated”.

The IAEA added: “Solid structural materials in direct contact with the salt or the graphite moderator ... can be strongly contaminated.

“Since they will be irradiated at the same time, their limited lifespan can result in a substantial stream of intermediate- to high-level waste.”

This isn’t to say these problems can’t be fixed, but they highlight that this technology is nowhere near a done deal.

A big goal for new nuclear is reprocessing or recycling spent nuclear fuel. But this has faced strong objections because of the risk of proliferation, according to DNV’s white paper this week.

“As a result, this process is only pursued by a few countries, even though it is a prerequisite for some technologies, especially advanced ones, to be industrially and commercially viable,” DNV’s report said.

It added: “The process is relatively complicated as, in most cases, the spent fuel must be handled remotely or with strong shielding, with inherent risk of release.”

That doesn’t sound like a Jetsons-style, set-and-forget nuclear battery, does it?

Costs are hard to predict, but they will be vastly higher than those of diesel engines. Nuclear ships will probably require much larger crews, increasing operating costs.

Dr Tristan Smith, who leads UCL’s green shipping research team, said SMR technology was “highly academic and hard to rationalise relative to the attention it is getting”.

Nuclear ships would need to run between countries with bilateral agreements in place, and stop for repairs only at specially equipped ports. What about emergencies in the middle of nowhere?

Lawyers and insurers have said states will probably have to underwrite their risks, since the potential liability goes far beyond anything insurers could cover.

Where would they get the money?

Either governments would have to pay for all this development directly, or the IMO levies a pollution tax and uses the proceeds to subsidise the technology.

The first option is unlikely, and the second would never fly.

During the run-up to the last IMO green talks, Middle Eastern and African states complained that a carbon levy would in practice siphon cash from the poor world to tech firms in the rich world.

Where would the funds for nuclear ships go? Only the likes of the US, China, Russia, the UK and France have the sort of big nuclear industries that would qualify. The IMO won’t vote for it.

We would also presumably say goodbye to open registries, and to transits of places like the Strait of Hormuz without naval escorts. This would not be a commercial shipping industry as we know it today.

Sure, dealing with the emissions of only a few hundred of the very biggest cargoships would tackle most of shipping’s climate impact. But the emissions of the rest of the world fleet will still need tackling somehow.

Then there’s protecting a reactor against the risk of grounding, hijack, capsize, cyberattack, piracy... These aren’t the sort of engineering problems shipping professionals prefer. 

So why are we talking about this?

It may be that the industry has simply exhausted the debate on whether ammonia, methanol and other alternative fuels are worth chasing, or will ever happen.

Hydrogen-based e-fuels involve staggering efficiency losses, from converting electricity to hydrogen, to ammonia and back to electricity. Their economics are horrible, and I’m far from sure they will ever happen at scale.

Nuclear has no such problem with energy density, and far less need of refuelling (though exactly how much is an important detail to come). It could be amazing, in theory.

But SMRs are not expected to arrive on land until the 2030s, and not at sea until well after.

The technology is in its infancy. Its regulatory, legal, insurance, and PR challenges (Chernobyl anyone?) mean it’s little more than a distant fantasy, and a distraction from the situation today.

Lest we forget, last week the US, Saudi Arabia and others torpedoed IMO’s best hope of a global carbon price. The Net-Zero Framework has not been pronounced dead yet, but most think it may as well be.

That leaves no present threat to fossil fuels globally.

Supporting nuclear is therefore easy; it looks like having a decarbonisation strategy, but it’s just a licence for business as usual.

The sad irony is that it still might be among the best options to decarbonise big ships, such is the near-hopeless state of play in 2025.