Before we get to know the pros and cons of nuclear energy , let's make you know about nuclear energy before. nuclear energy is generated through the process of nuclear fission. Nuclear fission is a nuclear reaction in which a heavy nucleus splits spontaneously or through collision with another particle and releases energy. The raw material used in nuclear plants is uranium, and plutonium is also sometimes used as an alternative. In a nuclear plant, uranium is collided with uranium to start the nuclear fission reaction which then continues uninterrupted.