Numerical simulations of an innovative decay heat removal systems

The general interest in innovative forms of nuclear energy from fission leads many industrial companies and research institutions to develop ambitious projects to design an innovative reactor fleet. Often such new designs are based on innovative reactor coolants and imply as a consequence a complete change of the technology know how. Among the main characteristics of such developments, safety demonstration plays a central role. Safety systems of such newly developed designs must meet different requirements respect to those designed for reactors currently in operation. One good example is the case of the lead fast reactor, where primary coolant freezing must be considered. The paper reports an excursus of what has been done over the past few years on ALFRED reactor decay heat removal system, reporting the history of the safety system from the preliminary configuration up to the present, together with an innovative idea of a passive system to delay lead freezing. Finally, ongoing activities for the experimental qualification of such safety system are presented, together with support and pretest calculations.