(146b) Mixer Pump Operations for Hanford Waste Tanks

The Hanford Site’s double-shell tanks (DSTs) contain supernatant and undissolved solid waste from previous plutonium production. This waste needs to be removed from the tanks and immobilized through vitrification. For efficient vitrification, a relatively homogenous feed with specified solid concentrations from the tanks is required. An in-tank settling and decanting process can be used to concentrate the solid waste. After being concentrated, the remaining liquid would be used to mobilize and suspend the solid particles with mixer pumps for removal from the tanks with a transfer pump. Computational fluid dynamics (CFD) simulations can be used to investigate the settling/decanting process and optimize the mixer and transfer pump specifications and conditions of operation. The CFD simulations provide key input to the planned scaled experimental testing and scale-up methods that will be used to demonstrate, verify, and provide the final recommendations for the equipment configuration and operation of the system. A CFD model of the waste tank has been constructed which includes the rotating mixer pumps with variable nozzle sizing. In this work, the CFD model is used to optimize mixing performance by evaluating the effects of mixer pump nozzle diameter and flowrate on upward flow velocity in specific regions of the tank.