MA von J. Miró Olivé, 2005

Titel

Analysis of the Performance of the Passive Containment Cooling System of the ESBWR

(MA: Escola Tècnica Superior d'Enginyeria Industrial de Barcelona)

Betreuung

Prof. W. Kröger; Dr. M. Andreani (PSI)

Abgabe

April 2005

Abstract

The European Simplified Boiling Water Reactor (ESBWR) is an evolutionary design in Boiling Water Reactors (BWRs), the key feature of which is to apply simple passive systems to enhance safety and to reduce costs. One of these systems is the Passive Containment Cooling System (PCCS), the performance of which will be studied throughout this report. The purpose of the PCCS is to remove residual heat from the reactor to the secondary water pool outside the containment, and thus mitigate the pressure increase inside the containment.
The PCCS performance can be degraded by the presence of non-condensable gases in the steam. These gases hinder the transport of steam to the condensing surfaces, reducing the condensation rate and consequently the efficiency of the condensers (Bandurski et aL, 2001). The effect of non-condensable gases on the PCCS performance was studied in TEMPEST project. The main aim of the TEMPEST project was to improve advanced modeling methods for evaluating pressure safety margins of BWR containment buildings.
One of the most important phenomena that were observed within the TEMPEST T-Series Tests included several temperature inversions in the PCC tubes caused by gas flow reversals that appeared after the helium injection started.
In this work, part of the database obtained from the TEMPEST project was used to simulate the PCCS performance in PANDA T1.2 test using GOTHIC containment code. The aim of the thesis was to assess if the code was capable to predict the response of PCC2 and PCC3 during the helium injection phase, with especial focus on the aforementioned phenomena. Additionally, the influence of the condensation model in the simulation results was analyzed. For that purpose, four simulations were carried out, i.e. two simulations for each one of the PCCs, since two different condensation models (MAX and DLM-FM) were used.
The simulations showed several flow reversals in some of the tubes but with different patterns to the ones observed in the experiment. For three of the cases, the simulation also failed to predict the complete condensation inside the PCC when only residual air was present in the steam (before helium injection). However, the results obtained for PCCS with DLM-FM condensation model showed a good prediction of this condensation process.