The Case for Nuclear Power in Shipping

In 2022, shipping accounted for 10% of global transport-related greenhouse gas emissions:

Having observed many vessels at sea, I've noted their heavy reliance on pollution-generating fuels. A typical 24,000 TEU container ship consumes over 400 tons of heavy fuel oil daily at maximum speed (approximately 25 knots). The International Maritime Organization has been exploring nuclear solutions to mitigate these emissions.

Despite its public commitments to reducing greenhouse gases, China's heavy reliance on coal-fired power plants raises questions about its dedication to curbing maritime emissions. While thorium reactors have historically been linked to military applications, there is potential for civilian use, which may explain China's reluctance to disclose details about this thorium reactor while promoting it for commercial shipping.

Advantages of Thorium Reactors

Thorium reactors fall under the category of molten salt reactors (MSRs), which offer several advantages over traditional uranium reactors:

• MSRs feature built-in safety mechanisms; in case of a power loss, the fuel salt can be drained into a passively cooled system, preventing meltdowns.
• They utilize a negative temperature coefficient of reactivity and allow for significant temperature increases to avert criticality incidents. The thorium-232 isotope can be transformed into fissile uranium-233, allowing for a more efficient process than the enrichment needed for conventional uranium reactors.
• The nuclear waste produced is generally less hazardous, containing fewer long-lived trans-uranic elements, which could mitigate nuclear proliferation threats.

Consequently, thorium reactors are safer and more compact than the enriched uranium reactors commonly used in military vessels. Moreover, thorium is nearly four times more prevalent in the Earth's crust than uranium, making it an economically viable option, especially since China possesses ample thorium resources, and its extraction is less damaging to the environment compared to uranium mining.

Understanding Thorium Reactor Technology

In a thorium fuel cycle, thorium dioxide (ThO²) is bombarded with neutrons to generate fissile materials such as uranium-233.

> "Thorium dioxide can serve as a ceramic fuel in nuclear reactors, typically encased in rods clad with zirconium alloys. Although thorium itself is not fissile, it is fertile, allowing for the breeding of fissile uranium-233 under neutron bombardment." (Wikipedia)

Reflecting on my childhood visits to my aunt's farm, I recall her using gas lights with mantles containing ThO². Even in the 1980s, a substantial portion of ThO² produced was utilized for lighting purposes, showcasing its historical significance.

The technology behind thorium reactors is intricate yet advantageous. The radioactive fuel is blended with molten salt and circulated through the reactor core, which contains thorium in a closed loop. Reports suggest that Chinese developments in this area require less cooling water than their uranium counterparts, although this is a broad assertion.

There are three primary types of MSRs, categorized based on the relationship between the salt, fuel, and coolant. The design options include: - Circulating fuel-salt MSRs where salt serves both as fuel and coolant. - Dual fluid reactors using salt for fuel and metal for cooling. - Fluoride salt high-temperature reactors with solid fuel but salt as the coolant.

Specifics about the design chosen by the Chinese research team remain unknown.

In the proposed ship, the generator depicted would be absent; instead, steam turbines would power the ship’s propeller via a gearbox, though electric motors might also be an option.

Technical Hurdles

The implementation of thorium reactors presents challenges, notably the elevated operational temperatures associated with liquid salt coolant. The corrosive nature of high-temperature liquid salt necessitates stringent material requirements compared to conventional pressurized water reactors. Furthermore, consideration must be given to the ship's disposal post-service, as traditional scrapping methods may not be feasible.

Competitive Landscape

While various nations are testing thorium reactors, China is the first to announce a practical commercial design. Other countries, including Japan, the U.S., South Korea, and European nations, have proposed thorium-powered container ships, but none match the scale of China's initiative. Russia operates nuclear-powered icebreakers with conventional reactors, classified as civilian vessels.

Historically, the U.S. built a prototype cargo ship (NS Savannah) in 1956, followed by Japan and Germany, but these were not economically viable.

Future Prospects

Thorium reactors could reshape the economics surrounding nuclear-powered cargo shipping, garnering continued interest. Lloyd's Register, a leading authority in shipbuilding standards, is revising its construction guidelines to accommodate these emerging reactors, essential for insurance purposes, as commercial operation hinges on having adequate coverage. Nuclear vessels face significantly higher civil liability standards than conventional ships.

China's shipbuilding sector has rapidly expanded, currently accounting for over 60% of global new ship orders. While the practicality of thorium reactor technology remains uncertain, it is likely that any advancements will primarily benefit China's military interests for the foreseeable future.