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Disarming the deterrents to nuclear propulsion (part 1)

With shipping poised to tackle the decarbonisation question head on, is it time to renew the discussion about nuclear power? In the first of a two part analysis Gavin Lipsith looks at the technology developments, both from a safety and efficiency perspective and asks whether nuclear could be an accepted solution in the future

Opposition to Russia’s new floating nuclear power station underlines the obstacles to using atomic energy for marine applications. But advances in reactor design and safety – as well as an urgent environmental imperative – are bringing the prospect of nuclear shipping closer than ever.

In mid-September, Akademik Lomonosov and its two 35 MW nuclear reactors will arrive at a remote peninsula on Russia’s long Arctic coastline. The floating nuclear power plant – the first purpose built facility of its kind – will replace a land-based power station supplying the town of Pevek.

Greenpeace’s response to the deployment of the floating power plant highlights some of the main obstacles to nuclear propulsion. In 2018 when Russian nuclear agency Rosatom had the vessel towed from St Petersburg to Murmansk for testing, the environmental group’s nuclear expert Jan Haverkamp complained that the power station brought “the threat of a nuclear catastrophe into fragile Arctic waters”.

Public opposition

It is valid to note Russia’s sometimes chequered history of operating nuclear vessels and submarines safely. But three decades have now passed since the last notable marine nuclear reactor accident, a fatal explosion onboard a Russian submarine in Chazma Bay in 1985. Since then Russia has accrued many thousands of incident-free operation hours on its fleet of nuclear icebreakers and naval vessels.

Nevertheless, the concerns underline the challenges facing any attempt to expand the use of nuclear power into the civil maritime sector. In a 2014 paper (just three years after the disastrous overheating at Japan’s Fukushima nuclear power station), Dr Spyros Hirdaris of Aalto University presented the concept of a nuclear-powered Suezmax tanker. He noted: “The impact of more recent nuclear incidents has refreshed the level of public and political opposition… It must be anticipated that this will be reflected in any proposals to use nuclear power at sea in commercial applications.”

There have been a handful of nuclear-powered merchant ships built, one of which – Russian nuclear-powered icebreaking barge carrier and container ship Sevmorupt, built in 1988 – remains in service. As shipping looks for a path to decarbonise, nuclear propulsion is once again being given serious consideration.

As Dr Hirdaris suggests: “Recent advances in nuclear technology and the continuous development of the nuclear regulatory framework may result in this tide of scepticism turning as pressure to reduce dependence on fossil carbon increases.”

Restricted movement

But public opinion is not the only hindrance. The movement of nuclear-powered ships is tightly restricted. The UN Convention on the Law of the Sea gives states the right to confine foreign nuclear vessels to sea lanes or traffic separation schemes. Other regional legislation including the New Zealand Nuclear Free Zone, Disarmament, and Arms Control Act 1987 and the South Pacific Nuclear-Free Zone Treaty also prevent the transit of nuclear ships.

A 2007 study concluded that it would cost at least €522,000 to secure permits for Sevmorupt to sail from Rotterdam to the Far East. Even then, political negotiations and in some cases new policies would need to be created to allow unfettered sailing.

In 2012 Lloyd’s Register and the University of Southampton proposed modular vessels where the nuclear plant can be separated from the vessel outside territorial waters. Another design, the abovementioned Suezmax, features an integral reactor but relies on the fact that the vessel would perform cargo operations outside of ports and so may not be as restricted as other ship types.

Reactor designs

Both designs are enabled by the introduction of a new type of reactor offering more flexibility than the pressurised water reactors that have powered marine nuclear applications until now. Small modular reactors (SMR) use less nuclear fuel, deploy more passive safety features and can fit in a shipping container. This allows the reactor to be used like a ‘plug-in nuclear battery’ that can be replaced once the core is depleted.

Further developments in SMR technology could make merchant shipping applications of nuclear power more likely. In particular, the use of thorium instead of uranium is expected to offer longer periods between refuelling and avoid the use of highly enriched nuclear fuel (which is restricted under international agreements limiting nuclear proliferation). A major study published earlier this year explored the development of a reactor for civil marine applications that uses a ‘duplex fuel’ consisting of thorium and low enriched uranium.

There have also been dramatic improvements in reactor safety design, notably the introduction of passive safety features that do not require electricity or human intervention for shutdown in case of emergency. These include coolants and reactor designs that slow the atomic reaction automatically to overheating, as well as electrically suspended control rods that drop into the reactor if electricity fails.

Business case

The financial case for nuclear powered merchant ships remains an obstacle, with researchers regularly citing capital costs of up to three times that of a conventional vessel. The modular containerships proposed by Lloyd’s Register could be feasible for vessels with a power demand of more than 65 MW according to a study published last year, but the business models may prove challenging.

Brazil’s Instituto de Pesquisas Energéticas e Nucleares suggested that a separate enterprise should own ship’s nuclear reactors and take responsibility for reactor production, operation, refuelling, maintenance, emergency response, and fuel disposal. The enterprise would then rent the power plant to shipowners. The world of aviation is familiar with the concept of ‘power-by-the-hour’, by which airlines hand back responsibility for availability and upkeep of their engines to OEM. But the model is largely unknown in shipping.

The wealth of recent research suggests a renewed interest in nuclear propulsion. Underpinning this is the need for clean energy sources as shipping looks to IMO’s 2050 greenhouse gas emission reduction targets. But while technical and safety advances make the prospect of nuclear propulsion in mainstream shipping more likely, they will only bear fruit if they lead to a less restrictive regulatory regime which, in turn, makes nuclear power more competitive.

Part two of this article, exploring the environmental advantages and challenges of nuclear propulsion, will be published later this month.

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