Jiangnan Shipyard recently released the design of the world's first 24,000TEU nuclear-powered container ship at the 2023 China International Maritime Technology Academic Conference Exhibition, demonstrating that China has mastered the design and construction technology of nuclear-powered surface ships. Although the container ship is not a nuclear-powered aircraft carrier, it is an important milestone for China's shipbuilding industry. Through this project, Jiangnan Shipyard has not only obtained the construction qualification and safety certification of nuclear-powered ships, but also made full preparations for the construction of nuclear-powered aircraft carriers in the future.
The nuclear-powered container ship plan released by Jiangnan Shipyard has aroused people's attention to nuclear-powered ships. This type of container ship uses a molten salt reactor as the propulsion system, which is significantly different from the pressurized water reactor mainly used in modern nuclear-powered aircraft carriers. A molten salt reactor mixes nuclear fuel with fluoride salts and achieves heat exchange through a heat exchanger. Compared with pressurized water reactors, molten salt reactors are smaller in size and weight, and have higher heat exchange efficiency. In addition, molten salt reactors are solid at room temperature, so they are safer, less prone to nuclear leakage, and have relatively low requirements for safety systems.
However, there are also some problems with molten salt reactors. Due to the effects of molten salt and radiation on reactor tubing, molten salt reactor tubing is susceptible. The meltability of molten salts can also adversely affect heat exchangers and tubes. In addition, the graphite elements of molten salt reactors have a short lifespan and need to be replaced in less than 5 years, resulting in higher maintenance and operating costs.
Considering the differences between military and civilian nuclear propulsion systems, as well as the requirements of the service time of nuclear-powered aircraft carriers, PWRs may still be the preferred power system for domestic nuclear-powered aircraft carriers at this stage. PWRs have made great strides in reliability and high power, and have achieved longer maintenance and safeguards. At present, the S9G nuclear reactor used by the Virginia-class attack nuclear submarine of the US Navy only needs to be replaced once in 30 years, and the service life of the attack nuclear submarine is also 30 years, and there is no need to replace the nuclear fuel during the entire service cycle, which greatly saves time and costs.
In order to make the nuclear reactor service life of the domestic nuclear-powered aircraft carrier reach 50 years, the aircraft carrier does not need to be refueled and overhauled during the service period, and the cost is lower, China's shipbuilding industry needs to continue to carry out technological innovation. Although there is no urgent need to build a nuclear-powered aircraft carrier at this stage, postponing the construction of a nuclear-powered aircraft carrier and selecting a conventionally powered aircraft carrier as the next ship will provide the People's Republic of China Navy with a rapid maritime deployment capability and buy more time and conditions for the development of a new generation of nuclear-powered aircraft carriers.
The maintenance and security of nuclear-powered aircraft carriers is a huge challenge. It takes 3-4 years for the US Nimitz-class nuclear-powered aircraft carrier to change the reactor fuel at a time, and the cost is close to $3 billion. Such a long construction period and huge cost led to the limited number of aircraft carriers in the US Navy, and even twice tried to abandon the refueling and overhaul of the aircraft carrier and directly decommissioned the aircraft carrier. Therefore, the trend of modern nuclear-powered aircraft carriers is to increase the life and reliability of reactors.
In order to reduce the maintenance cost of aircraft carriers and reduce the impact on the deployment of naval forces, domestic nuclear-powered aircraft carriers need longer maintenance guarantees. Ideally, the reactor service life should be consistent with the service life of the aircraft carrier, and there is no need to replace nuclear fuel. For domestic nuclear-powered aircraft carriers, pressurized water reactors are still an ideal choice. Considerable progress has been made in the development of PWRs, which enable longer maintenance cycles and allow aircraft carriers to be deployed and used for longer periods of time. The replacement cycle for Nimitz-class aircraft carriers is 25-30 years, while it is said that Ford-class aircraft carriers can reach 50 years without replacing nuclear fuel.
In general, although China has made some progress with nuclear-powered ships, at the moment, molten salt reactors are not ideal for domestic nuclear-powered aircraft carriers. It is likely that domestic nuclear-powered aircraft carriers will still use traditional pressurized water reactors as propulsion systems to achieve longer-term maintenance guarantees and lower operating costs.