China reveals molten-salt nuclear reactor-driven 24,000-TEU box ship design

Chinese media outlets have reported that the Chinese state-backed shipyard group proposed the design of a nuclear-powered ultra-large container ship that would rival the largest currently in existence.

The vessel would be powered by a molten-salt reactor (MSR), likely using a metal called thorium as fuel. Thorium, an abundant, naturally occurring metal is a clean, efficient fuel with extraordinary energy density. One tonne of it produces the same energy as 3.5M tonnes of coal. Its byproducts are significantly safer than uranium (in that plutonium is not produced under fission) and, with shorter half-lives, degrade far faster. It does not need to be enriched and is not difficult to access. Reports said China has large reserves of thorium. It is also a completely zero-emissions fuel.

“The ultra-large nuclear container ship is designed to truly achieve zero emissions during the ship’s operating cycle,” China State Shipbuilding Corporation said on Weibo.

Nuclear power and, more recently MSRs, have been at the fringes of discussions around decarbonising shipping for many years. In 2022, design firm Ulstein launched a thorium-based concept for zero-emission cruises in polar regions.

Proponents of MSRs say the reactors are safe, efficient and operationally proven solutions. They work by dissolving thorium in liquid salt. The ensuing chain reaction heats the salt, producing steam to drive a turbine and create electricity. Although developments of MSRs on land are well documented, its potential for delivering clean maritime power is still untested in real-world scenarios.

Speaking about the suitability of thorium MSRs as an energy source for maritime applications, Norwegian University of Science and Technology professor Jan Emblemsvåg, an expert in the field of thorium and nuclear power generation, noted, “MSRs have enormous potential for enabling clean shipping. There is so much uncertainty over future fuels, but here we have an abundant energy source that, with the right approach, can be safe, much more efficient, cheaper, and with a smaller environmental footprint than any existing alternative.  From my perspective I see this as the most viable, and potentially the only credible solution for a zero-emissions fleet that can operate under commercial terms and cost levels."

Nuclear use for vessels took another step towards commercial reality in October 2023 with the beginning of pumped-salt operations in the integrated effects test (IET) - part of the development of MSR technology for maritime applications. 

The project brings together American gas and electric utility firm Southern Company; Core Power, a startup that focuses on nuclear power for maritime applications; and TerraPower, a company developing a nuclear reactor. A team previously completed mechanical, electrical and controls verification and commissioned all systems at an IET facility installed at TerraPower’s laboratory in Everett, Washington. 

The idea of combining fuel and coolant in a reaction using molten salt fuels was first conceived in the 1940s, with a functional MSR test running in 1954 at Oak Ridge National Laboratory in Tennessee, USA.

As with so many technological breakthroughs, it had its origins in military applications. The original plan was an aircraft reactor experiment with the idea of powering warplanes that could stay in the air for very long periods. The reactor successfully generated power, but the introduction of inter-continental ballistic missiles ended the project. In 1962, work began on the construction of an experimental test reactor called the molten salt reactor experiment and a reactor was successfully started within four years, with work on the project ending in 1969 due to funding cuts.