Heat transfer to the building structures of the Ignalina NPP accident localisation system

The performed thermal-hydraulic analysis of the Accident Localisation System (ALS) has shown, that in the case of a Maximum Design Basis Accident (MDBA), in the long term, a significant amount of energy (∝40%) is transferred to the building structures. Therefore, special attention should be paid to the correct simulation of the building structures and heat transfer processes. Free convection, forced convection, condensation and conductivity are the phenomena, which are connected with the heat transfer to the building structures and should be investigated. In this paper, the heat transfer models available in the COCOSYS code, which is applied for the analysis, are discussed. The influence of the heat transfer models on the behaviour of thermal-hydraulic parameters in ALS compartments during MDBA is investigated. (orig.)