Starting point, keys and milestones of a computer code for the simulation of the behavior a nuclear fuel rod

The BaCo code ('Barra Combustible') was developed at the Atomic Energy National Commission of Argentina (CNEA) for the simulation of the behavior of a nuclear fuel rod under irradiation conditions. We present in this paper a brief description of the code and the strategy used for the development, improvement, enhancement and validation of a BaCo during the last 30 years. Extreme case analysis, parametric (or sensibility), probabilistic (or statistic) analysis plus the analysis of the fuel performance (full core analysis) are the tools developed in the structure of BaCo in order to improve the understanding of the burnup extension in the Atucha I NPP and the design of advanced fuel elements as CARA and CAREM .The 3D additional tools of BaCo can enhance the understanding of the fuel rod behavior, the fuel design and the safety margins. The modular structure of the BACO code and its detailed coupling of thermo-mechanical and irradiation-induced phenomena make it a powerful tool for the prediction of the influence of material properties on the fuel rod performance and integrity. (Author)