Numerical analysis of thermal-hydraulic safety for a reactor containment in the event of a main steam line break

Abstract

The present work demonstrates the development of a numerical thermal-hydraulic (TH) model for the containment module of the PRABHAVINI code which is an in-house severe accident analysis computer code used for the analysis of Indian pressurized heavy water reactors (PHWRs). The model, for the analysis of the TH behavior of the containment under a postulated main steam line break (MSLB) situation inside it, incorporates the effect of nonlinear coupling among different heat and mass transfer chronologies such as heat transfer within the containment and through its walls, wall and interface condensations, condensation due to over saturation of the air and evaporation. The TH model accounts for the thermodynamic non-equilibrium between the air–vapor mixture inside the containment and the water likely to be accumulated at the bottom of the containment. For the comparison of the TH model developed, a more conservative case study is undertaken where a single containment is analyzed for an MSLB accident ceasing the possibility of any kind of leakage from it. The results obtained from the model developed are compared with those obtained from the RELAP5. Next, the model is extended for more realistic TH analysis of the multi-volume containment incorporating the possibility of uni- or bi-directional inter-volume leakages as well as leakages from the containment volumes to the atmosphere. The analysis demonstrates the effect of different heat and mass transfer phenomena on the critical TH field variables of the reactor containment for the MSLB situation under consideration. © 2022