• control rod ejection
• BEPU
• licencing
• Atucha-II

This thesis work has been carried out within the cooperation between the GRNSPG-UNIPI and NA-SA for the preparation of the final safety analyses report (FSAR) of the Atucha-II nuclear power plant (NPP). For the first time a “best estimate plus uncertainty” (BEPU) approach was adopted for the analysis of all the considered accidents. The candidate cooperated in several activities to improve and qualify the evaluation model based on RELAP5-3D. Key contributions deal with the improvement of two nodalizations; the improvement and qualification of the coupling between RELAP5-3D and the Dynetz code (derived from NLOOP) to simulate the plant I&C; the improvement of the coupling between RELAP5-3D and NESTLE. Then the candidate contributed in the BEPU analyses of the control rod accident and in writing the related FSAR section. Noticeably, the uncertainty quantification was performed with two fundamentally different methods to provide a method-to-method validation of the results. Noticeably, the reference uncertainty method, CIAU-TN, has been used for the first time in a licensing context. The contributions of the candidate in two activities to show the importance the I&C modelling in BEPU analyses and to propose an idea to foster the best estimate code verification and validation methods are also show.