Development of CRONO: A System Code for Safety-Informed Design of Liquid Metal-Cooled Fast Reactors

The design of innovative liquid metal-cooled fast reactors (LMFRs) is driven by the need to comply with high safety and reliability standards, while maintaining economic competitiveness through compactness and modularity. Owing to the complexity and limited accessibility of most existing system-level codes, ENEA is developing CRONO: a flexible system code to support safety-informed core design, i.e., a designoriented system code. The code couples neutron kinetics, solved with the point kinetics approximation, with simplified thermal-hydraulic models of the core and the reactor coolant system components. Emphasis is placed on modularity and computational efficiency. This paper presents the governing equations for each component, the overall code architecture, and the adopted numerical solution strategy. A preliminary benchmark against the system codes RELAP5 and SIM-LFR and the fuel performance code TEMIDE has been performed for an unprotected transient of overpower scenario, showing good agreement in predicting reactor power and core temperature evolution during the transient. The developed tool is intended to support design via system-level accidental transients studies, stability analyses and sensitivity and uncertainty evaluations of LMFRs.