New research by C-Job Naval Architects shows that nuclear energy could be applied as marine propulsion in the future, with the molton salt reactor as the most likely candidate. According to the ship design company, nuclear technology has seen several interesting developments making it worth considering.
Based on the research, C-Job concludes that the molten salt reactor has the most potential in the long term. The combination of passive safety, high burn-up, and the future potential to use the thorium cycle make it the best fit for maritime application. With thorium, the high-level nuclear waste longevity can be reduced from more than 10,000 years to approximately 300 years.
Molten salt reactor concepts have a built-in passive safety system due to the salt being used as the coolant and fuel, and the strong negative temperature coefficient, indicating that upon temperature increase the reactivity drops strongly. This prevents problems with stability and makes the reactor follow load. Burn-up is an effectivity measure indicating how much thermal energy the reactor can extract from a given quantity of nuclear fuel. A higher burn-up is favourable as it reduces the amount of required nuclear fuel and produced waste per power produced.
The thorium cycle has proliferation resistance, meaning it is a very unattractive route to create nuclear weapons out of it. This make makes the weaponisation potential very low, as it is difficult to weaponise the respective material, which is largely consumed in the reactor.
98 per cent CO2 reduction
The research was carried out by Koen Houtkoop, Msc. Marine Technology graduate at TU Delft, on behalf of C-Job. He says: ‘Developments in nuclear energy have mostly been focused on land-based applications. However, a number of aspects make them of interest for maritime application. In particular, the significant reduction in harmful emissions. Compared to conventional fuel-based systems, my research showed that there can be up to a 98 per cent reduction in CO2 emissions. Furthermore, the air pollution emissions, such as SOx, PM and NOx, are eliminated completely.’
The stated reduction of up to 98 per cent regards CO2 equivalent emissions for the entire life cycle. The amount of produced nuclear waste (high level, intermediate level, low level, and tails) is listed separately in the report as no universally accepted method for direct comparison is yet available.
‘There are obvious concerns with nuclear energy such as nuclear waste as well as societal perception. Additionally, we should be mindful that regulations for marine application are outdated and require significant effort for a successful application,’ Houtkoop adds.
Lighter and more compact
The research identified large ocean-going vessels as having the most potential for nuclear propulsion. By creating four different concepts (bulk, container, tanker, and offshore), key items were analysed, including the mass and volume of the energy storage and power generation system. It shows that, even though the shield around the reactor is a significant portion of the respective mass and volume of the nuclear power generation system, in most cases, the nuclear option is lighter and more compact than the conventional marine diesel option.
While nuclear marine propulsion has a high capital expenditure (CAPEX), the research shows it to be cost-effective within five to fifteen years depending on fuel cost and the vessel’s operational profile. Furthermore, nuclear marine propulsion offers the potential to consider higher design speeds, making the ship more profitable. This is because fuel cost (operational expenses, OPEX) only grows marginally with higher speeds where ultimately the main limiting factor would be the CAPEX of the installation with more power.
Not mature enough yet
C-Job has previously been at the forefront of researching and applying alternative maritime fuels.
Niels de Vries, Lead Naval Architect at C-Job: ‘We’re not one to shy away from the unconventional. Where maritime applications for ammonia, hydrogen, and methanol have advanced, nuclear energy so far has not been widely considered to be a viable option. As with other energy sources, appropriate safety measures must be in place and the technology must be developed further before it’s mature enough to be implemented, but nuclear technology has serious potential. More research is needed to fully understand the design, operation, and life cycle.’