Nuclear submarines generate oxygen through the use of onboard oxygen generators or by utilizing a process called electrolysis. Here's an overview of each method:
Oxygen Generators: Some nuclear submarines are equipped with onboard oxygen generators, also known as oxygen candles. These generators typically contain a solid chemical compound, such as sodium chlorate (NaClO3), which releases oxygen when heated. By igniting the compound, oxygen is produced as a result of the chemical reaction. The generated oxygen is then circulated throughout the submarine's internal atmosphere to provide breathable air for the crew.
Electrolysis: Another method employed by nuclear submarines to generate oxygen is through the process of electrolysis. Electrolysis involves the decomposition of water (H2O) into hydrogen (H2) and oxygen (O2) gases using an electric current. A device called an electrolyzer is used for this purpose. The electrolyzer consists of electrodes submerged in water, and when an electric current is passed through the water, it splits into hydrogen and oxygen. The oxygen produced in this process is captured and supplied to the submarine's atmosphere for the crew's breathing needs.
It's worth noting that while oxygen generation methods are employed on nuclear submarines, these vessels also carry onboard stores of compressed oxygen as a backup in case of emergencies or system failures. This ensures the availability of breathable air for the crew during extended periods underwater when contact with the surface is limited.