For a start a nuclear bomb can be either fusion or fission. To create a fusion reaction you need an enormous amount of energy to initiate the process. This is why fusion is not a viable from of energy. On the other hand, fission reactions are much easier to achieve, because the material is already unstable and only requires a small amount of energy to create a reaction. Thus, fusion will never be a viable form of energy and is just an excuse for a bunch of greeny nut cases to expend billions of government dollars on useless research. See my post – Spin plus aether equals matter – for further explanation.