The consequences of igniting a small fissionable pellet by laser-beam or relativistic electron-beam induced high density implosion-compression on future reactor technology are discussed. It is shown that with this method a highly efficient reactor system becomes possible by direct magnetohydrodynamic conversion of the expanding fireball into a magnetic cavity. The method not only will lead to an “absolutely” safe fast breeder reactor but by using hybrid pellets consisting of a combination of both fissionable and fusionable materials in addition will also lead to a combined fission-fusion energy producing system. In such a fission-fusion hybrid system, whereby the fission process produces a large amount of heat and the fusion process produces a large number of neutrons, the bootstrap coupling between the fission and fusion processes greatly increases the rate of the ensuing chain reaction and hence energy output enhancing substantially the energy yield of the micro-explosions.