
Nuclear submarines, unlike diesel-electric boats, can be used underwater. They are more costly and larger. They usually require two years of on-site maintenance before they can be reopened for service. They will also need a storage area for used fuel.
Nuclear submarines typically use highly enriched uranium (HEU) as their fuel. HEU is one of the most dangerous metals on earth. It is also one which is the easiest to work. HEU is not required to be replaced throughout the life of a submarine. It is possible that the fuel can contain poisons. Normally, this would decrease the efficiency of the fuel. In some cases, the poisons can be burnt off.
There have been many types of reactors used in nuclear submarines. PWRs were one of the earliest, and were constructed by Westinghouse. Rolls-Royce further developed these PWRs. The cores were created for Royal Navy submarines. They are built to last between 30-40 years.

Later, submarines could be built using lead-bismuth-cooled reactors. These designs were used on the K-27, an experimental predecessor of the Alfa class. However, the experimental reactors were found to have problems, and the submarine was laid up at Gremikha Bay.
Long-range anti-submarine ballistic missiles were first developed in the 1960s. These were submerged to launch them and were made to hit targets far away. They had a range of approximately 2,500 miles.
The United States has had over 100 nuclear submarines in service. The submarines of the US Virginia-class are usually equipped with high-enriched uranium (HEU). The US's other submarines, such as the Virginia, Skipjack, and Dreadnought, use high-enriched uranium. You can also add a toxic substance to the core to increase its durability. The US and Britain are the only countries that use HEU in naval reactors.
The United States has been involved with Australia and the UK in security alliances over the past few years. This alliance seeks to counter China. These three countries share a common point of view in security matters. A new security pact was signed to create a security alliance. This agreement will allow Australia become the seventh world-class nuclear-powered submarine. It will also allow Australia to become the second country to receive US technology.

Australia will cancel its multi-billion dollar submarine contract with France, and will enter a new security pact with the United States and the United Kingdom. This agreement will make Australia the second country to receive US nuclear submarine technology.
Australia will also receive diesel powered submarines. They are believed to be a complement technology to the US’s nuclear subs. These submarines will work together with the UK and US, as Australia does not have a current nuclear power industry. It is anticipated that the subs' majority of work will be done overseas.