Numerical investigation of jet agitation in a nuclear liquid waste storage tank

Radioactive liquid waste is often stored in a large capacity (150 m3) horizontal cylindrical tanks. It is necessary to keep the contents of the tank agitated to prevent the settling of fine solids in the tank. In extreme cases, solids settled at the tank base may invoke the system malfunction. This paper deals with the Computational Fluid Dynamic (CFD) modeling of the agitation mechanism considering the turbulent dispersion effects. The simulations are conducted on a standard tank geometry to arrive the optimum jet velocity required to suspend the settled solid particles thoroughly. The distribution of volume phase fraction, velocity magnitude, turbulence kinetic energy (TKE) and eddy dissipation of each phase for different inlet jet velocities (v = 10-25 m/s) have been presented. The spatial variation of these quantities are measured at three different planes in the vessel mainly in the vicinity of the nozzle exit. The results indicate that the jet velocity is a significant parameter that influences the particle suspension. Parametric studies have also been carried out for four different particle sizes, viz. dp  = 5, 10, 50 and 100 μm. The present study revealed that, for the range of parameters covered, the smallest (dp  = 5 μm) and the largest (dp  = 100 μm) particle sizes has least effect in terms of solids suspension.