IMPROVED FAST REACTOR SAFETY BY PASSIVE SHUT-DOWN

摘要

This paper presents a simple device for passive shut-down of liquid metal cooled fast reactors (LMR) during unprotected transients. It uses enhanced thermal expansion of control rod drive lines (CRDL) to provide for automatic scram and forced control rod insertion when pre-fixed coolant temperatures are exceeded. In this way the reactor is brought into a safe permanently subcritical state and temperatures are kept well below the boiling point of the coolant. A prototype of such a device called ATHENa (German for: Shut-down by THermal Expansion of Na) has been manufactured and tested. The paper presents the principle, design features and thermal characteristics of ATHENa as well as results of the experiments and reactor dynamics calculations of unprotected loss of flow and transient overpower (ULOF, UTOP) accidents for the European Fast Reactor (EFR) equipped with enhanced thermal expansion devices.