Hybrid Reactor Performances to Optimize the Nuclear Fission Fuel Cycle

The neutronic performance of a hybrid in analysed on the basis of a set of lumped parameters which properly characterize the main features of the hybrid, as energy multiplication or fissile breeding. This analysis enables one to identify the parametric ranges or design windows where a specific hybrid objective can be met. It is shown that fissile fuel production to feed fission reactors requires a set of parameters totally different from that of an energy amplifier hybrid. The latter can be designed to maintain a high factor of energy multiplication for very long burnups. The former reaches the maximum capability to feed fission reactors in the limit of fission-suppressed hybrids, which requires the fertile capture cross section to be as high as possible as compared to the fissile fission cross section. Upper limits of the magnitudes characterizing the neutronic performance are identified.