Modeling and Validation of Hydrogen Deflagration in Computer Code for Severe Accident Analysis

Hydrogen release inside the containment which is generated during metal water reaction under certain postulated accident condition may challenge the integrity of the containment as the hydrogen with air in the containment can form flammable or even explosive mixture. The high pressure that can rise in the containment with hydrogen combustion is the main concern in nuclear reactor containments. It may cause structural damage of the containment structures and results in release of radioactivity to outside environment. Further, thermal and pressure loads due to the combustion of hydrogen might lead to the failure of safety related equipment, which is the another major concern. Other possible concerns are internal missile generation and secondary fires. Thus, calculations for the change in the containment pressure and temperature along with the changes in the hydrogen concentration following hydrogen deflagrations need to be performed to assess the containment behaviors following accident. These became the input for PSA (Probabilistic Safety Analysis)-Level-II studies. Post Accident Containment System Response (PACSR-SI-2.0) is a containment thermal hydraulic analysis computer code and it can be used for the calculation of hydrogen distributions in the containment. This paper discusses the incorporation of the modeling of hydrogen deflagration /combustion into computer code PACSR-SI-2.0 so that this model can be used for multi compartmental hydrogen distribution analysis along with deflagration /combustion and its effect on containment functionality and large early release to the environment for PSA Level-II study.