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Preparations are under way for nuclear reactors to make a major comeback in commercial shipping.
Although shipping is already highly energy efficient, pressure has come on the industry to lower emissions. There is the potential for market-based measures for controlling carbon dioxide emissions, while the entry into force of strict International Maritime Organization controls in 2020 provides a firm deadline against which the industry can weigh the benefits of a range of technology enhancements and fuel options. But with no clear technological fix to lower emissions using traditional diesel or LPG fuels, nuclear energy is emerging as a practical option.
This trend has been developing quickly in recent years and the recent announcement of a major joint research project on the topic is the most significant to date.
Marine and energy consultants BMT Group and Enterprises Shipping and Trading have joined with start-up small reactor firm Hyperion and Lloyd's Register to "investigate the practical maritime applications for small modular reactors."
"We will see nuclear ships on specific trade routes sooner than many people currently anticipate," said Lloyd's Register CEO Richard Sadler. The organization has been an independent service provider to the shipping industry for 250 years.
In response to its members' interest in nuclear propulsion Lloyd's Register has recently rewritten its 'rules' for nuclear ships, which concern the integration of a reactor certified by a land-based regulator with the rest of the ship. A draft of the rules was put before Lloyd's technical committee two weeks ago and this represents a further step towards an international regulatory regime to ensure worldwide safety in a potential nuclear shipping sector.
Nuclear options
Cruise liner
A luxury liner has the power demand curve of a town, including peaks at morning and evening mealtimes. Conceivably a 100 MWe nuclear power system could take the base-load role with smaller diesels for peak load and back-up.
Bulk carrier
Transporters moving large cargoes like raw materials on point-to-point routes could run much faster with the extra power and low emissions from a nuclear reactor. A frequent service could be run by fewer vessels, mitigating the extra capital cost.
Supertug
Existing conventionally powered vessels could attach to a nuclear-powered tug for emissions-free passage across oceans.
What about the ports?
Nuclear powered vessels could be the subject of controversy and this would seem to make a nuclear cruise liner concept difficult due to passenger and port acceptance. However, a point-to-point cargo service would need only agreement from two states and the supertug could remain in international water. Another idea is to create a large nuclear vessel with a conventionally powered detachable section to take cargo to port.
Vince Jenkins of Lloyd's Register told World Nuclear News: "National maritime regulators have little nuclear capability, so land based nuclear regulators will be needed in support. Since there are no internationally traded nuclear powered merchant vessels today, our nuclear powered ship rules have suggested a framework which may allow nuclear powered shipping to operate. Within this suggested framework, we have developed the area where it is felt that a ship classification society can add value and confidence to the safety of nuclear powered vessels, the integration of the reactor plant into the ship."
The new program of joint research is meant to produce "a concept tanker ship design based on conventional and modular concepts," said Lloyd's. It noted that "Special attention will be paid to analysis of a vessel's lifecycle cost as well as to hull-form designs and structural layout, including grounding and collision protection."
Nuclear power looked set for a maritime role in the 1960s thanks to early vessels like the Savannah and Otto Hahn, although in the end the Savannah worked for only ten years and the Otto Hahn was repowered with diesel engines after nine years. The Japanese-built Mutsu operated from 1970 until 1992 but none of these ships was a commercial success.
A notable exception has been the icebreaker fleet that works Russia's trade routes in the Arctic Ocean. These vessels number only seven, but one is a cargo vessel and small reactors of the same type are currently being fitted to the Akademik Lomonosov, the world's first floating nuclear power plant, set for deployment in Russia's far east.
Nevertheless, there remain about 200 small reactors at sea in military fleets but this technology cannot easily be transferred to the civil sector due to the requirement of using low-enriched uranium (LEU). In the military sector of recognised nuclear weapons states, high-enriched uranium allows more compact reactor designs with weight and controllability benefits.
The reactor of the Hyperion system uses LEU and measures about 1.5 meters by 2.5 meters. It would produce about 70 MWt - enough for about 25 MWe for propulsion. Its 'battery' design simplifies refuelling to a swap-out operation every 8-10 years with the possibility of managed lease arrangements similar to aircraft engines.
However, incorporation of any reactor in a ship would require extensive radiation shielding, consideration of impact protection. A step change in crew training would be required and there is a strong case for crew to be supplied by reactor vendors.
Similar to nuclear power on land, the additional capital cost of nuclear compared to fossil fuels is a significant obstacle despite the fact that savings on fuel and potential emissions charges would make nuclear economic in the long run. One of the most effective ways for a diesel-powered vessel to save fuel and emissions is to travel more slowly and avoiding this practical constraint could make nuclear vessels particularly attractive for certain cargoes and routes.
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