The horizon of international maritime transport is set for a profound transformation with China's announcement of a nuclear-powered cargo ship of an entirely new kind. This project, led by the Jiangnan Shipbuilding Group, relies on the use of an alternative fuel, thorium, and a reactor architecture radically different from conventional systems. This initiative could well redefine the standards for autonomy and sustainability for the global merchant fleet, marking a significant step in the decarbonization of the sector.
The design of this sea giant, capable of carrying 14,000 containers, incorporates an innovative energy approach. Its core is a Thorium Molten Salt Reactor (TMSR) delivering a thermal power of 200 MW. A fundamental particularity of this system lies in its energy conversion mode: the generated heat is not used to produce steam driving turbines, but powers an advanced supercritical carbon dioxide cycle. This technological choice allows for unprecedented performance and compactness for marine propulsion.
Illustration image Pexels An energy technological breakthrough
The electricity generation process used constitutes a notable leap forward. The supercritical carbon dioxide system, operating on the Brayton cycle principle, converts heat into electricity with an efficiency between 45% and 50%. This efficiency far exceeds that of conventional pressurized water reactors, which generally plateau around 33%. This optimization results in the production of 50 electrical megawatts, a power sufficient to ensure the ship's propulsion for very long periods without requiring fuel replenishment.
The intrinsic safety of the system represents another pillar of this innovation. The use of thorium, an element more abundant than uranium, is accompanied by a more docile reactor physics. The fuel, dissolved in molten salts, operates at atmospheric pressure, eliminating the risk of explosion linked to overpressure. Furthermore, the reactor has a negative temperature coefficient, a self-regulating mechanism that naturally slows the nuclear reaction in case of temperature increase, thus preventing any core runaway.
The design incorporates several passive safety barriers. In case of failure, the liquid fuel would flow by gravity into retention tanks located under the reactor, where it would solidify, confining the radioactive materials. The entire reactor block is designed as a sealed module, replaced entirely after an operational lifespan of 10 years. This "plug-and-play" approach minimizes fuel handling in port environments and considerably reduces the risks of human error or leakage.
An industrial and geopolitical strategy
This cargo ship project is part of a broader Chinese energy strategy, aimed at securing the country's supply. China possesses significant thorium reserves, notably in the Bayan Obo deposit in Inner Mongolia. Developing a nuclear sector based on this domestic resource would allow China to reduce its dependence on uranium imports, thereby strengthening its energy sovereignty. This ambition is supported by substantial investments in research and development of fourth-generation reactors.
The technical feasibility of the process was recently consolidated by a major breakthrough. Chinese researchers have demonstrated for the first time the successful conversion of thorium into fissile uranium-233 within an experimental molten salt reactor located in the Gobi Desert. This achievement validates the thorium fuel cycle and constitutes an essential proof of concept for the entire sector, beyond the sole maritime application.
Beyond this cargo ship, the Chinese roadmap includes the development of other civilian nuclear vectors. A Suezmax-class tanker, using a lead-bismuth cooled reactor, and a floating power plant are also under study. These projects aim to demonstrate the maturity and versatility of advanced nuclear technologies, with the stated objective of positioning the country as a leader in the global market for reactors and decarbonized propulsion systems for heavy transport.
Article author: Cédric DEPOND