Design of a complementary scram system for liquid metal cooled nuclear reactors

Generation IV (GEN IV) reactors promise higher safety levels compared to current generation II or III reactors, one of the most important safety aspects of any reactor is the ability to shutdown the reactor in any condition. The shutdown mechanism in current designs of liquid metal cooled Gen IV reactors is based on absorber rods. Although these rod based systems are duplicated to provide redundancy, they all have a common mode of failure as a consequence of their identical operating mechanism; possible causes being a largely deformed core or blockage of the rod guidance channel. To achieve the goal of higher safety, a complementary scram system is desirable. In this paper an overview of existing solutions of such a complementary system is given and a new concept based on absorber particles and the existing solutions is proposed. This original system, which is not rod based, is under investigation and its feasibility is verified both by experiments and simulations.