Three-Dimensional Modelling of Aerosol Transport from a Flashing Two-Phase Jet in Containment

Abstract

Under postulated loss-of-coolant accident (LOCA) conditions in a CANDU (CANada Deuterium Uranium) reactor, aeroeols containing radioactive fission products could be released from a rupture in the primary heat transport system (PHTS) into the containment, The fate of these aerosols is of concern to safety analysts who must assess the potential hazards of such accidents to public safety and health. Simulations of the transport of aerosols in a containment LOCA environment are possible, but some knowledge of the local thermalhydraulic conditions is required to solve the aerosol transport equations. At the Whiteshell Laboratories, these are done using the coupled computer code CATHENA/PACE: three-dimensional CATHENA thermalhydraulic calculations of a flashing two-phase jet in a given enclosure simulating a containment structure are coupled with the PACE code, which solves the equations describing the transport behaviour of the unflashed aerosols in the enclosure. To gain insight into the transport behaviour of aerosols in containment, some preliminary computations have been performed of the concentration of aerosols in suspension, of surface deposition of the aerosols in the enclosure, and of percent aerosol leakage through postulated vents as a function of a number of conditions, such as the thermalhydraulic conditions upstream from a simulated break, the break size, and the initial size of the aerosol distribution released. In this paper, these results are presented and discussed, with emphasis on the significance of break and initial aerosol size on aerosol concentration and deposition in the enclosure.