Aerosol release experiments in the Fuel Aerosol Simulant Test Facility. Undersodium experiments

The release of uranium dioxide (UO2) aerosols from pools of sodium was studied in a series of ten experiments in the Fuel Aerosol Simulant Test (FAST) facility at Oak Ridge National Laboratory. The experiments were designed to provide a mechanistic basis for evaluating the radiological source term associated with a postulated, hypothetical core-disruptive accident (HCDA) in a liquid-metal fast breeder reactor (LMFBR). Aerosol was generated by capacitor discharge vaporization of UO2 pellets that were submerged in a sodium pool under an argon cover gas. Measurements of the pool and cover gas pressures were used to study the transport of aerosol contained by vapor bubbles within the pool. Cover gas samples were filtered to determine the quantity of aerosol released from the pool. Trace amounts of UO2 aerosol (<0.3% of the total pellet mass) were detected in the cover gas samples suggesting that the bulk of aerosol was trapped within bubbles confined by the pool. The report contains: (1) a description of the experiments; (2) data records for the pool pressure, the cover gas pressure, and the UO2 aerosol concentration in the cover gas; and (3) an analysis of the experimental findings using simplified models of bubble behavior. 23 refs., 25 figs., 7 tabs