Experimental analysis of steam mixing and thermal stratification phenomena related to small steel containment studies

To study the mixing and thermal stratification caused by the plumes or buoyant jets in the small steel containment during the LOCA or MSLB accidents, temperature was measured experimentally. Using steam as the working medium, the experiments were conducted with various jet inlet temperatures and spray water flow rates to identify their influence on the thermal stratification phenomena. Temperature distributions with height are given to illustrate the thermal stratification in containment. The performed analysis shows that recirculating stratified fluid existed in only lower part of containment while steam mixing and temperature homogenization happened in upper part of containment. Rayleigh-Benard convection, which is often neglected in big steel containment stratification, and convection caused by negatively buoyant jet and plume entrainment are considered to be the major factors causing steam mixing. It is suitable to consider such thermal stratification and steam mixing in developing a more accurate and detailed model for small steel containment and system design of SMRs.