Equilibrium considerations in aerosol formation during sodium combustion

Combustion of liquid sodium is of interest in the safety assessment of liquid metal cooled fast breeder reactor systems. In the present study, a detailed thermodynamic analysis of sodium-air system has been carried out for equivalence ratios in the range of 0.1–1.9 and for flame temperatures ranging from 1100 to 1950 K. In addition to this, decomposition calculations presented for product aerosols such as sodium oxide (Na₂O), sodium dioxide (Na₂O₂) and sodium hydroxide (NaOH) in normal oxygen and oxygen-deficient conditions (which are some form of phase diagrams of these aerosols) are used rigorously to find out the predominant aerosol that should be present in and outside the burn pan for a pool fire of liquid sodium. The conditions of occurrence of various sodium oxides under two different fire conditions namely pool and jet fires have been worked out. It is established that heterogeneous reactions involving sodium oxide are responsible for the formation of sodium dioxide and sodium hydroxide. It is necessary to take account of the rates of these heterogeneous reactions as well as the equivalence ratio-dependent decomposition calculations to correctly estimate the aerosol product mix in practical situations.