Nuclear power allowed submarines to operate for about twenty years without the need for refueling. Food supply became the only time limit for a nuclear submarine at sea. Nuclear submarines can operate underwater for three or four months in a row and cross oceans with ease. While some conventional submarines can withstand distance, none have comparable submarine resistance.
Navy nuclear submarines can remain submerged for long periods of time. Air is not a problem, as they produce their own oxygen and keep the air clean. The limits for how long they can stay underwater are food and supplies. Submarines generally have a 90-day food supply, so they can spend three months underwater.
At the height of the Cold War, approximately five to ten nuclear submarines were being commissioned at each of the four Soviet submarine yards (Sevmash in Severodvinsk, Admiralteyskiye Verfi in St. the engines are practically silent. Nuclear power proved to be ideal for the propulsion of strategic ballistic missile (SSB) submarines, greatly improving their ability to remain submerged and undetected. That said, if appearing on the surface of the water is so dangerous for a submarine and its crew, why does it have to resurface? I mean, what prevents a submarine from being submerged indefinitely? Can't you stay underwater for the entire mission? Nuclear reactors are quieter, do not consume air and produce greater energy production, allowing nuclear submarines to remain submerged for months instead of days while traveling at higher speeds underwater.
While AIP ships may not be able to do everything a nuclear submarine can do, having a larger fleet of submarines would be very useful for hunting opposing ships and submarines for control of the seas. The nuclear reactor also supplies energy to other subsystems of the submarine, such as for maintaining air quality, producing fresh water by distilling salt water from the ocean, regulating temperature, etc. Nuclear submarines still have a clear advantage in terms of resistance over AIP ships, remote patrols. The weakness of nuclear submarine stealth technology is the need to cool the reactor even when the submarine is not moving; about 70% of the reactor's output heat dissipates into seawater.
The British figures are a little more conservative, but it is also true that the Royal Navy has been and continues to be under considerable financial pressure and has neither the funds nor the personnel to steer its nuclear ships any longer than expected. In 1960, the second nuclear submarine in the United Kingdom was commissioned from Vickers Armstrong and, equipped with the Rolls-Royce PWR1 nuclear plant, the HMS Valiant was the first British nuclear submarine. From the late 1950s to the end of 1997, the Soviet Union, and later Russia, built a total of 245 nuclear submarines, more than all other nations combined. A nuclear submarine can stay and operate underwater for a couple of decades, as long as it has enough supplies and rations for its crew on board to survive for so long.
However, keep in mind that AIP submarines are mostly small or medium-sized vessels with crews of around 30 and 60 respectively, while nuclear submarines are usually larger with crews of 100 or more. The construction of the world's first nuclear submarine was made possible by the successful development of a nuclear propulsion plant by a group of scientists and engineers from the United States in the Naval Reactors Branch of the Bureau of Ships and the Atomic Energy Commission. .