Aerosol Behavior During a Postulated Severe Accident in a 540-MW(electric) PHWR Containment

One of the important issues in severe reactor accident scenarios is the containment integrity and the characteristics of the source term that governs the ultimate radioactive releases to the environment. The releases are in the form of aerosols that are generated by the condensation of volatile fission products released from fuel, within the containment, during the severe accident. A loss-of-coolant accident with simultaneous failure of the emergency core cooling system has been postulated for a study of such aerosols. For the aerosol behavior in the containment, various removal mechanisms, such as gravitational settling, diffusional plate-out, and diffusiophoresis, and growth processes such as agglomerations and condensation have been included. The transport process such as leakage from the containment has also been modeled. This paper discusses the results of the studies carried out to estimate aerosols' behavior in the Tarapor Atomic Power Station (TAPS)-3&4 containment following their release during the postulated accident condition. It was found that the gravitational settling is the major aerosol removal mechanism following the postulated severe accident.