Nuclear energy has been used to power ships since the 1950s, and today, more than 150 vessels are powered by small nuclear reactors. Nuclear marine propulsion is the propulsion of a ship or submarine with heat provided by a nuclear reactor. This type of energy is particularly suitable for ships, which need to be at sea for long periods without refueling, or for powerful underwater propulsion. The United States Navy operates about 100 nuclear ships, ranging from submarines to aircraft carriers.
The atoms in the nuclear reactor divide, releasing energy in the form of heat. This heat is used to create high-pressure steam, which turns the propulsion turbines that provide the power needed to turn the propeller. Nuclear energy is highly efficient and allows these submarines to operate at high speed for longer periods than conventional diesel-electric submarines. The environmental benefits of nuclear energy are indisputable, however, they are not widespread for several reasons.
Nuclear waste can cause serious water pollution, destroying marine life and, as a consequence, also human life. In addition, nuclear-powered ships are much more expensive than those with conventional (petroleum-based) power sources. The dismantling of nuclear-powered submarines has become an important task for both the United States and Russia. A set of standards refers to a detailed and comprehensive Safety Code for nuclear merchant ships, which was approved by the IMO Assembly in 1981. More specifically, if there is a reactor on a ship, the entire crew is automatically considered to be working in radiation and should not be exposed to more than 5 rems per year.
Nuclear technology has also helped increase navigation in the Arctic from two to ten months a year, and year-round in the Western Arctic. In the future, restrictions on the use of fossil fuels in transportation may cause marine nuclear propulsion to become more widespread use. Some small modular reactors (SMR) are similar to marine propulsion reactors in terms of capacity and some design considerations, and therefore, nuclear marine propulsion (whether civil or military) is sometimes proposed as an additional niche market for SMRs. The advantages of using nuclear-powered ships are clear: they are highly efficient and can operate at high speeds for long periods without refueling; they have environmental benefits; and they can help increase navigation in the Arctic. However, there are also drawbacks: they are expensive; they produce nuclear waste; and they require strict safety regulations.
Despite these drawbacks, nuclear-powered ships remain an important part of naval warfare and will likely continue to be used in the future.