Contribution to the analysis of thermodynamic transients in a pressurized water reactor. Assessment of the SIRENE 3 code and elaboration of the one-dimensional module of the FLICA 4 code

The first part of this research thesis addresses the SIRENE 3 code (a calculation code aimed at the analysis of thermodynamic transients in a pressurized water reactor) and the calculations performed with this code on operation transients in the LOFT test loop. Thus, the author presents the SIRENE 3 code, its modelling approach and equations, and domain of validity, and the LOFT installation, its geometry and modelling by means of the SIRENE 3 code. He reports the calculation of the LOFT test (experiment, parameters adjustment in permanent and transient conditions, sensitivity studies). The objective is to assess the code validity by comparing its results with experimental results. This raised the question of the difficulties of interpretation of experimental results and of the necessity to extend the calculation domain to the treatment of two-phase flows. This issue is addressed in the second part of the thesis with a presentation of FLICA 4 code, and a detailed presentation of the TUYAU module: equations and models (mass and momentum conservation, energy assessment), resolution algorithm (resolution of the energy assessment). The last part reports tests, the obtention of permanent regimes and transient calculations