Best-estimate LOCA simulation in a PWR-W containment building with a detailed 3D GOTHIC model

The design-basis accidents in a PWR-W containment building are usually simulated with a lumped parameter model, normally used for license analysis. Nevertheless, some phenomenology is difficult to be simulated with a lumped model: the condensation rate in each structure, stagnant water areas, temperature in different compartments, sumps and recirculation pumps disabled because of lack of water, etc. Therefore, for the detailed study of the thermal-hydraulic (TH) behaviour in every room of the containment building could be more appropriate to do it with a detailed 3D representation of the containment building geometry. The main objective of this project has been to build a 3D PWR-W containment model with the GOTHIC code to analyze the detailed behavior during a design basis accident. In the process of the 3D GOTHIC model development some previous steps were necessary: a detailed CAD model of the containment, followed by a simplified model adapted to the GOTHIC geometric capabilities. Once the geometry has been adapted to the GOTHIC requirements, the 3D model is created with this information. A design-basis accident has been simulated with the 3D model (LBLOCA), and the local TH behaviour is analysed. The results show that in comparison with a lumped parameter model, high temperatures are reached locally. Nevertheless the average pressure behaviour is found to be similar to that given by a lumped parameter model. The present paper demonstrates that is possible to build a 3D PWR-W model with the GOTHIC code with enough resolution to analyse the TH behaviour in each one of the containment rooms but at the same time with reasonable computing time. Once the GOTHIC model has been created a new road is opened enabling the simulation of other accidents such as MSLB, a SBLOCA or even a long-term SBO sequence. This document is made up of an abstract and the slides of the presentation. (authors)