Modeling and transient simulation of the PB-AHTR using RELAP5

The Pebble Bed Advanced High Temperature Reactor (PB-AHTR) is a liquid fluoride-salt cooled reactor that uses TRISO coated particles in the form of fuel pebbles. The baseline reactor design produces a power output of 900 MWth and operates with an average coolant temperature of 650 deg. C. The reactor design also includes various passive and active safety systems designed to protect the core from overheating under a variety of transient and accident scenarios. A number of transients have been studied using the thermal hydraulics code RELAP5-3D with the goal to determine appropriate design parameters of the safety systems in order to satisfy peak coolant temperature requirements and to test the performance of multiple safety systems under a variety of postulated events. (authors)