I'm not sure I understand the question properly.
The reaction of uranium produces heat. This reaction is called fission. It heats water to obtain work by a turbine, then electricity by an alternator.
Nearly any heavy atom would make heat by splitting ("fission"). Uranium and plutonium are special because they split easily by absorbing neutrons, and their fission emits enough neutrons, so their fission can be a chain reaction. Making enough neutrons would be difficult by other means: this would consume more energy than uranium fission produces.
Uranium fission needs no initial heat. The only condition for a "chain reaction" is that more neutrons are produced than lost. This condition is not easy.