KV-Scaling Analysis to support the Validation of Atucha-II Best Estimate Evaluation Model A. Petruzzi, M. Cherubini Nuclear and INdustrial Engineering (NINE), Via della Chiesa XXXIII, 759, Lucca, Italy Nuclear Engineering and Design, Volume 363, July 2020, Article number 110609

Abstract — In the frame of the licensing process of the Atucha-II PHWR (Pressurized Heavy Water Reactor) the BEPU (Best Estimate Plus Uncertainty) approach has been selected for issuing the Chapter 15 of FSAR (Final Safety Analysis Report) dealing with accident analysis. Approaches based on Best Estimate Plus Uncertainties (BEPU) to perform accident analysis of a Nuclear Power Plant (NPP) for licensing purposes request the availability of validated tools and specific procedures suitable for the analysis of accident conditions envisaged in the concerned NPP. This implies the necessity to adopt and to prove an adequate quality of the so-called Evaluation Model (EM), i.e. the ensemble of data, assumptions, codes and nodalizations developed and validated to be used for carrying out the safety analysis. The purpose of the present paper is to outline key aspects and results of one of the steps of the BEPU process concerning the qualification of the     Atucha-II PHWR Evaluation Model for the licensing process. A special procedure, named “Kv-Scaled Analysis + Countepart Test Calculations” have been developed to take into account the specificities of Atucha-II NPP (CNA-2) and the fact that Atucha-II has not a prototype integral test facility. The proposed procedure uses a set of facilities which share some similar geometrical features and ranges of variations of relevant physical quantities for some subsystems or components of CNA-2, taking into account the different kind of accidents addressed in the Chapter 15 of the Final Safety Analysis Report (FSAR) of Atucha-II NPP. The final goal of the procedure is to qualify separately systems/sub-systems of the nodalization of the Atucha-II NPP while keeping the features of a full system analysis involving the whole NPP nodalization. A total of nine tests performed in six different scaled facilities have been considered and analyzed.