It can’t be denied that he peaceful use of nuclear energy has always suffered from the stigma of being associated with warfare. The first nuclear reactor was developed by Fermi and Leo Szilard during the Manhattan Project with the aim of showing how a fission chain reaction works. The design of the most common reactor of our days, the LWR, is based on the reactors developed for nuclear submarines. On the other hand, the initial expansion of nuclear energy went hand in hand with the growth of the nuclear superpowers. The USA, Russia, France and the UK simultaneously built power plants in order to generate electricity and produce a nuclear arsenal. Two processes that can be used both to obtain nuclear fuel and as a raw material for atomic warheads and are uranium enrichment and the reprocessing of fuel used in a reactor. Let’s see why.