Computer simulations to study interaction between burning rates and pressure variations in confined enclosure fires

Fires in nuclear facilities constitute a significant threat to nuclear safety. A major concern when dealing with safety assessments in nuclear facilities is the confinement of nuclear material by dynamic confinement. Therefore, pressure variations within compartments in case of fire are important to consider. This paper focuses on the capability of a zone model (CFAST) and a field model (ISIS) to predict the interaction between mass loss rate and total relative room pressure or oxygen concentration in case of under-ventilated fire conditions. Results are obtained using as input the mass loss rate measured during the experiment and the mass loss rate measured in free atmosphere. A sensitivity study has also been performed for the field model to analyse the influence on the outputs of soot production, radiation modelling, wall emissivity, turbulence modelling and branch flow resistance.

► A major concern is the confinement of nuclear material by dynamic confinement.
► Interaction between mass loss rate & oxygen concentration for under-ventilated fires.
► Sensitivity study performed for the field model to analyse the effects on the outputs.