Development and Verification of Calculation Models for the Accident Analysis in Nuclear Power Plants

This report presents the activities performed in the frame of LP1, Objective A (Acquisition, development and validation of methods and codes for sustainable and safety studies and analyses), Task A3.1&2 of PAR2013, ADP ENEA-MSE. New plenum temperature models are under development to refine the accuracy of the TRANSURANUS code under steady-state and accident conditions (LOCA, RIA). For the purpose, a 2D transient heat transfer model and a finite elements model have been developed. In this frame, ENEA has introduced in TRANSURANUS the FRAPCON–3 plenum temperature model. Furthermore, pre-test analysis of debris bed reflooding experiments have been performed with the ICARE/CATHARE code to support the PEARL experimental program at IRSN and verify the capability of the new 2D porous media model implemented in the last version of the code. Moreover, the calculation of degraded core reflooding scenarios has been performed with the ASTEC code in the frame of the TMI-2 Benchmark Exercise promoted by the OECD. Besides the important achievements in code model development, improvement and verification, these activities contributed to strengthen research collaborations with foreign partners at international level and acquire tools and their knowledge for safety analysis applications to the existing nuclear power plants located near the border of our country.