The presentation emphasized the critical role of nuclear safety across all phases of a nuclear facility's lifecycle, highlighting the necessity of robust simulation processes for ensuring safety in normal, incidental, and accidental reactor operations. Key topics included legislative requirements for nuclear safety, particularly the 2012 decree on Basic Nuclear Installations, which mandates the use of validated methods and tools for safety demonstrations. Vaglio-Gaudard discussed the general approach for tool qualification within the French nuclear sector, a process formalized in the ASN's 2017 guide. This approach involves a comprehensive VVQI process, ensuring tools can accurately calculate relevant physical quantities within acceptable uncertainties for safety studies. Examples from the ASTRID project and the Jules Horowitz Reactor (RJH) illustrated the practical application of VVQI principles, underscoring the importance of continuous and iterative modeling and simulation processes in the nuclear industry. The presentation concluded by highlighting the significance of ongoing research and development to enhance the formalization of the VVQI process, especially for multi-disciplinary applications in nuclear safety.