Research on the Steam-Gas Pressurizer With Non-Condensable Gas

Abstract

The thermal-hydraulic characteristics of a steam-gas pressurizer are considered as one of the most important factors which affect the safe operation of the small and medium reactor. Since the steam and non-condensable gas are used to sustain the pressure in the steam-gas pressurizer, the pressurizer would experience very complicated thermal-hydraulic phenomena with the non-condensable gas. A steam-gas pressurizer model was developed to investigate thermal-hydraulic characteristics of a steam-gas pressurizer. The governing equations in the model include the phasic continuity equations, momentum conservation equations and energy conservation equations. The pressurizer model was verified with the results from the insurge experiments performed at Massachusetts Institute of Technology. In addition, a wall condensation model with non-condensable gas was introduced to consider the effect of non-condensable gas on the heat and mass transfer during the steam condensation. The calculations results which were performed in the Relap5 code had a great agreement with the experiment results. It’s indicated that the non-condensable gas played a key role in the pressure transient process in the steam-gas pressurizer and it’s necessary to consider the effect of non-condensable gas in the steam-gas pressurizer model. With different kinds and mass fraction of non-condensable gas, the pressure transient in the steam-gas pressurizer would be significant different. The accuracy of model would be also different with different mass fraction and kinds of non-condensable gas.