[en] As part of a collaboration between KAERI and CEA France, the fast reactor neutronics analysis system, ECCO/ERANOS-2.1, developed by CEA has been used by KAERI to study the properties of metallic fueled fast reactor cores. This code system has been extensively validated for sodium-cooled mixed oxide cores, in particular through the analysis of many experiments and the operating experience of the Phenix and Super Phenix power reactors. However, it has not been validated for metallic fueled cores with a harder neutron spectrum. The main purpose of this study is to analyze the metallic uranium fueled BFS-73-1 and -75-1 experiments with ECCO/ERANOS-2.1 in order to evaluate the applicability of the code to a future Sodium Cooled Fast Reactor core design