Uranium rods are allowed to interact with each other in the core of the reactor. As the rods interact, the radioactive uranium atoms decay and release great amounts of heat. The heat is used to change water into steam. The steam is forced through pipes until it reaches giant turbines. The steam pressure turns the turbines which drive giant electrical generators.
Nuclear power is a very expensive source of energy.
First of all, that uranium used for fuel is not found in nature in its elemental form. It is always found bonded with other substances. Once this uranium compound is mined, the uranium must be separated from the other substances. The uranium compound is sent to an enrichment plant where it can be purified. The purification process is very complicated and involves many complex machines and procedures.