explain why do we use uranium for nuclear energy

it is not all uranium isotopes that is used in nuclear energy but an isotope of uranium, ²³⁵U  it is naturally fissible  and fertile; meaning it can sustain a nuclear chain reaction and fertile meaning it can produce another fisssible atom( plutonium-238).

 the uranium-235 is fissible by fast neutron, uranium 233 has high cross-section with slow neutron  therefore with sufficient amount of the above we can have a sustained nuclear chain reaction.

 with the fissible uranium-235 and the fissionable uranium-238 we can maintain a self-sustained nuclear chain reaction capable of sufficient nuclear energy .