Quantitative Evaluation of the Post Disassembly Energetics of a Hypothetical Core Disruptive Accident in a Sodium Cooled Fast Reactor

Analyses of Hypothetical Core Disruptive Accidents (HCDAs) play a fundamental role in the safety assessment of Sodium Fast Reactors (SFRs). The accident sequence is typically subdivided into different phases according to dominant phenomena. The phase dealing with an upward discharge of the pressurized hot fuel/steel mixture from the core region is referred as the Post-Disassembly Expansion (PDE) phase. It is characterized by massive sodium vaporization due to Fuel-Coolant Interaction (FCI) in the upper sodium pool, which displaces and accelerates the surrounding liquid sodium resulting in potential significant loads on internal structures and vessel. The present paper - based on KIT simulations with the SIMMER code including dedicated parametric studies - identifies and evaluated the main PDE phenomena and event paths enhancing or mitigating the mechanical work potential. (author)