Nuclear fuel is non renewable source of energy but nuclear fission is also considered as alternative source of energy , why ?

Even nuclear fuel is non renewable source of energy , nuclear fission is alternative source of  energy because this energy is used by some countries only in this world so they help to reduce energy crisis. 

Uranium is the main fuel for nuclear reactors, and it can be found in many places around the world. In order to make the fuel, uranium is mined and goes through refining and enrichment before being loaded into a nuclear reactor.The main nuclear fuels are uranium and plutonium. In a nuclear power station, nuclear fuel undergoes a controlled chain reaction in the reactor to produce heat - nuclear energy is converted to heat energy: heat is used to change water into steam in the boiler.Used nuclear fuel can be recycled to make new fuel and byproducts. More than 90% of its potential energy still remains in the fuel, even after five years of operation in a reactor.

Nuclear fission, subdivision of a heavy atomic nucleus, such as that of uranium or plutonium, into two fragments of roughly equal mass. The process is accompanied by the release of a large amount of energy. Nuclear fission. key people.In order to initiate most fission reactions, an atom is bombarded by a neutron to produce an unstable isotope, which undergoes fission.