Nuclear transport: is atomic energy really a viable path to reaching net zero?
Image credit: Seaborg Technologies
Forthcoming regulations will pave the way for a nuclear-powered merchant fleet in the UK, but is atomic energy really a viable path to reaching net zero, and can innovative reactors overcome long-standing safety and security concerns?
As governments around the world recognise the urgent need to decarbonise, nuclear power looks set to make a resurgence as advocates of the technology position it as a key component in the energy mix over the coming decades.
Significant resource and investment is being channelled into the development of small modular reactors (SMRs), mini versions of power stations made in factories and capable of powering up to a million homes each.
Politicians including US President Joe Biden and UK Prime Minister Boris Johnson are backing the concept, while companies including EDF, the world’s biggest operator of atomic plants, Rolls-Royce and TerraPower, a nuclear innovation firm backed by tech billionaire Bill Gates, all have prototype reactors in development.
SMRs started life as propulsion systems for submarines and ice breakers, and the next generation of small reactors will be installed in commercial vessels as part of efforts to decarbonise one of the most polluting sectors on the planet.
Recognising the opportunity, the UK government consulted in 2021 on new merchant shipping regulations for nuclear ships, which would transpose international safety legislation into UK law. The intention is to establish a new legal framework for nuclear ships to flag in the UK, as well as for visiting foreign nuclear ships (none currently sail under the UK flag or visit UK ports), potentially paving the way for entire fleets of such ships in British waters.
The argument for nuclear ships is compelling. With shipping responsible for churning out almost 3 per cent of the world’s carbon dioxide emissions, according to the International Maritime Organisation (IMO), the zero-emissions fuel could put a significant dent in the UK’s target to reach net zero by 2050. Alternative clean fuels like LNG, hydrogen or ammonia either fail to eliminate greenhouse gases entirely or face technical hurdles, such as the need for reliable sources of renewable energy for their manufacture.
Nuclear propulsion is also an established technology, and the fuel is so long-lasting it can power vessels for up to a decade without the need to refuel, resulting in major operational cost and time savings.
However, the words ‘nuclear energy’ also triggers thoughts of disasters like Chernobyl and Fukushima and a legacy of radioactive waste that could remain for thousands of years. Environmental campaigners question the safety and security risks and what would happen if nuclear ships are hijacked and the technology gets into the hands of terrorists or non-nuclear states.
Jan Haverkamp, nuclear expert at Greenpeace Central and Eastern Europe, tells E&T: “Over the years, nuclear shipping has had its fair share of incidents;there was the whole Kursk affair (a nuclear sub that sank in an accident in the Barents Sea in 2000, killing all 118 personnel on board) and a host of reactor problems, including during construction and maintenance. Norway is investing hundreds of millions of euros to help Russia take apart its decommissioned ships to reduce the risk of radioactive pollution.”
Shipping is currently the only form of transport, apart from spacecraft, considered viable for nuclear propulsion due to the relatively large scale of vessels and the long distances travelled. The safety risks are arguably less severe compared to land-based vehicles, which are close to buildings and people.
Britain currently has no legislation that applies to merchant nuclear ships. The government’s proposed regulatory framework will translate into law Chapter VIII of SOLAS, the international maritime treaty for safety, which sets out the basic requirements for nuclear-powered merchant ships.
It pays particular attention to radiation hazards and provisions under the IMO’s Code of Safety for Nuclear Merchant Ships, also known as the Nuclear Code.
Gwilym Stone, assistant director for ship standards at the Maritime and Coastguard Agency, an executive agency of the Department for Transport, told E&T: “Previous international regulations were entirely based on the assumption that any maritime nuclear reactor design would be a form of pressurised water reactor. This excluded recent developments in nuclear technology that may provide better solutions.”
The government consultation ended in October 2021 and the regulations were due to be introduced into law in December, but this has now been delayed until some point in early 2022.
The case for nuclear-powered vessels has grown in recent years for various reasons and the consultation document pinpoints the potential as a zero-emissions alternative to polluting heavy fuel oil currently used by most ships. UK domestic shipping emitted 5.0Mt of CO2 equivalent in 2017, amounting to 1 per cent of all UK emissions; domestic and international shipping together were responsible for 13.87MtCO2e of UK emissions
If shipping is going to truly decarbonise, and keep the planet within safe temperature limits, it will need to ditch reliance on fossil fuels entirely. LNG is the sector’s most strongly supported ‘green’ fuel at present, but is only capable of a 23 per cent reduction in greenhouse gases, compared to current oil-based marine fuels.
Another option is to adopt ‘synthetic’ fuels like hydrogen, or fuels made from it, such as ammonia or methanol. Yet to eliminate emissions they must be made using green hydrogen, produced from renewable energy through the electrolysis of water. This is currently expensive and at present able to produce just 0.1 per cent of all hydrogen supplies.
Ammonia, meanwhile, only has 40 per cent of the energy content of diesel, so vessels would need to accommodate larger storage tanks, potentially eating into cargo space. The fuel is also toxic, so engine rooms would need additional safety equipment.
Nuclear reactors avoid all these drawbacks and generate zero emissions at the point of use.
Ian Adams, managing director at IMA Marine, a consultancy specialising in bunker fuels, says: “LNG isn’t a realistic solution in any way, shape, or form when trying to stamp out emissions. Hydrogen is a possibility, but it’s not there yet, we’re still developing the technology. However, nuclear technology is mature and ready to go.” However, at present, nuclear power is not listed in the UK Clean Maritime Plan.
Nuclear propulsion offers other advantages, such as very long intervals between refuelling (up to 10 years in naval vessels), so there would be fewer delays at ports, and operational cost savings. Having all the fuel contained inside the reactor removes the need for fuel storage space, exhaust stacks or combustion air intake.
The prospect of rapid decarbonisation and efficiency gains are attractive, but anti-nuclear campaigners and certain maritime experts remain unconvinced of a future role for atomic power in merchant shipping.
Unlike static nuclear power stations, ships are in constant motion and exposed to external factors such as temperature oscillation, wind and water resistance, collision, corrosion, etc, which may increase the risk of an accident. Some point to the risks of nuclear proliferation or terrorism should the technology get into the wrong hands, for example after a hijacking.
Nuclear ships and submarines have historically suffered various incidents, including reactor problems. Another drawback is decommissioning at the end of the vessel’s life, a major task requiring the defuelling and land burial of the reactor. The ‘low-level’ contaminated material and components have no options for reuse and must remain secure for hundreds of years.
The Soviet Union got around this problem for decades by using the remote Kara Sea as a dumping ground for nuclear waste. Official figures show the Soviet military used the sea to dispose of 17,000 containers and 19 vessels with radioactive waste, plus 14 nuclear reactors, five of which contain hazardous spent fuel. International funds have donated billions to support Russia’s nuclear clean-up efforts in the region.
“The world has been looking to deal with radioactive waste for 70 years and we still don’t have an acceptable solution on the table,” says Greenpeace’s Haverkamp. “Even Finland’s idea for deep geological disposal doesn’t have a proven safety case and there are technical problems. The UK is far away from that and has an ever-growing stockpile of spent fuel. You cannot solve a problem like radioactive waste by producing more radioactive waste; it’s very simple.”
These are valid concerns, but proponents of nuclear point to the fact it is now an established technology and reactor designs have developed and improved in reliability over time. The next generation of advanced pressurised water reactors and small modular reactors currently in development were designed not only to ratchet up performance, but specifically with safety at the ‘core’.
A consortium led by nuclear innovation company TerraPower, chaired by Microsoft founder Bill Gates, and involving UK-based Core Power, is working on the concept of a marine molten salt reactor for use in merchant ships and other applications.
The prototype reactor will melt chemically purified salt at high temperature and blend it with an oxide powder containing non-
weapons-grade fissile material enriched from uranium-235. This makes it capable of exceptional fuel efficiency, Core Power claims, with over 95 per cent of energy in the fuel consumed, versus less than 1 per cent in a conventional reactor.
Most accidents in conventional reactors are caused by a loss of coolant that triggers a chain reaction generating explosive heat. However, if the molten salt reactor malfunctions and the temperature starts to rise, drain plugs melt and the entire load of liquid core fuel is poured into passive drain tanks linked to a heat sink, keeping them cool and unreactive. According to Mikal Bøe, chairman and CEO of Core Power, this makes a loss-of-coolant accident, such as the one that befell Fukushima in Japan, physically impossible because the fuel itself is locked into the coolant.
Furthermore, the reactor’s high fuel efficiency minimises the amount of radioactive waste generated and can be configured to run on spent nuclear fuels, extending the fuel cycle to further minimise waste.
“[When a vessel is decommissioned] after 30 years the reactor can be drained and the fuel used in the next generation of reactors,” says Bøe. “Theoretically, if there were thousands of ships installed with these reactors, the fuel would continue to operate in subsequent generations of ships.”
The prospect of fleets of atomic ships and their associated supply chains could help resolve previous problems around decommissioning, says Professor Michael Fitzpatrick, pro-vice-chancellor for engineering, environment and computing at Coventry University, and an expert in the field of nuclear energy: “If this was a global industry, and a significant proportion of the cargo fleet was nuclear-powered, the supply chain would develop. So those sorts of issues would become less obstructive. There would be dockyards devoted to decommissioning nuclear ships on a regular basis.”
Another company adapting SMRs for the maritime sector is Danish firm Seaborg Technologies, which has designed a series of modular power barges that could be towed to their final destination to provide clean electricity either by plugging into the grid at a port or powering the production of hydrogen and ammonia for ships.
The barges will use conventional engines for propulsion and come fitted with either two, four, six, or eight compact molten salt reactors able to deliver up to a total of 800MW of electricity or 2,000MW of thermal energy. The aim is to bring the first barge into service in 2026.
According to a spokesperson at the firm, a key innovation is the use of molten sodium hydroxide, also known as lye and caustic soda, as the moderator in the reactor, which facilitates a more compact design.
“We use a uranium-based fluoride fuel salt as coolant, which gives us several prominent features,” says the spokesperson. “It cannot melt down or explode, it cannot release radioactive gases to air or water, and it cannot be used for nuclear weapons.”
Also active in the field is Samsung Heavy Industries, which last year partnered with the Korea Atomic Energy Research Institute to develop molten salt reactors to power ships and offshore power plants.
The past and future of nuclear merchant ships
The dawn of nuclear propulsion came in the 1940s and the first nuclear merchant ships started development in the 1950s, but vessels put into service have not overall been commercially successful.
The US-built demonstration ship NS Savannah was launched in 1962 but decommissioned eight years later. The German-built cargo ship Otto Hahn launched in 1969 and ran successfully for 10 years but ultimately proved too expensive to operate and in 1982 was converted to diesel. The only nuclear merchant ship still in service is the NS Sevmorput, commissioned in Russia in 1988 and recently refitted as an ice breaker.
The advent of more reliable and efficient small modular reactors (SMRs), currently in development, could reinvigorate the technology’s reputation and, according to the World Nuclear Association, is immediately promising to provide power for:
Large bulk carriers that go back and forth on routes between dedicated ports;
Cruise liners, with power needs equivalent to a small town, in which case a 70MW unit could give baseload and charge batteries, with a smaller diesel unit supplying the peaks;
Nuclear tugs, to pull conventional ships across oceans;
Certain types of bulk shipping where speed is essential.
Major supporters of SMR technology include the World Nuclear Transport Institute, which in 2021 announced the launch of a working group to discuss and develop rules and frameworks for the deployment of next-generation reactors at sea. This covers nuclear propulsion, floating nuclear power plants, offshore SMRs used for hydrogen production, and the maritime transport of SMRs.
Some experts believe nuclear’s main role in shipping is to provide a green source of power to produce hydrogen and ammonia fuels. According to one estimate, 2,300TWh per year would be required to produce enough ammonia to fuel the world’s container ships and bulk carriers, almost as much as total nuclear generation today and more than total wind generation.
Even if safety concerns and misconceptions around the risks of nuclear-powered ships can be sufficiently addressed, other factors may prevent the technology from taking hold.
Economic viability is a challenge given that nuclear vessels feature highly specialised propulsion systems and require additional protection from collision, grounding, or impact. Crews are typically highly skilled and highly paid and more of them are needed onboard than on conventional ships.
The government admits in its consultation that the relatively high costs and unique features mean that nuclear is “not expected to be widely rolled out for traditional shipping”.
Furthermore, the repair and maintenance of atomic ships would require specialised docks, yet conventional ports have historically shied away from allowing visits by nuclear-powered ships even if they have the necessary permissions and security certificates.
Ports may need to reassess their involvement with nuclear ships in future, explains Mark Simmons, director of policy and external affairs at British Ports Association. “UK ports are legally obliged to accept ships carrying legal cargo, so we would probably need to look in some detail at what powers harbour masters have regarding nuclear ships – do they want these vessels coming in and do they have any choice?”
Other potential legal barriers include conflicting national policies on nuclear shipping, which may be at odds with the ship’s flag-state authority, and policies on how and where nuclear waste from ships can be transported and disposed of.
The widespread uptake of atomic vessels also implies a major shake-up of maritime supply chains. With vessels able to travel much faster on nuclear fuel (some estimate up to 50 per cent faster), far fewer ships would be needed than at present. And with reactors providing virtually free power after upfront investment, what would become of the approximately 40 per cent of the global fleet currently devoted to transporting fuel, and the vast network of fuel bunkering facilities in ports?
Much like the atom, opinion on the future of this controversial but highly efficient clean fuel remains split. Time will tell if it can make an explosive impact on the world of commercial shipping.
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