Transmutations of nuclear waste in accelerator-driven subcritical systems

The physical preconditionings of transmutations are analysed. It has been suggested that one of the most viable incineration concepts is a symbiotic nuclear-energy system, consisting of a transmuter and a number of co-operating light-water reactors (LWRs). Closing of the fuel cycle is not easily achievable, since the minor actinides (MAs), unavoidably then produced in significant quantities, show disadvantageous safety properties (positive void reactivity coefficients). Accelerator-driven subcritical systems (ADSSs), distinct by their remoteness from super prompt criticality, have been attracting more and more attention. The superiority of subcritical ones is shown by comparing their behaviours in the case of a rapid reactivity insertion that brings no risk, in contrast to the fast critical ones. Finally, research problems and difficulties are mentioned. Any form of closed fuel cycle cannot avoid dealing with large quantities of radioactive materials. Yet, a definitive elimination of actinides, with the use of the enormous released energy, is worth this price. Summarising, the concept of nuclear transmutations in accelerator-driven subcritical systems significantly heightens the safety of nuclear-power systems.