Masters Theses

Date of Award

5-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Chemical Engineering

Major Professor

Joseph J. Perona

Committee Members

R.M. Counce, M.G. Hansen

Abstract

The Melton Valley Storage Tanks (MVSTs), which are located at the Oak Ridge National Laboratory, are used for the collection and storage of remote-handled radioactive liquid wastes. These wastes, which were typically acidic when generated, were neutralized with the addition of sodium hydroxide to protect the storage tanks from corrosion, but this caused the transuranic and heavy metals to precipitate. These wastes will eventually need to be removed from the tanks for ultimate disposal. The objective of the research activities discussed in this thesis is to support the design of a pipeline transport system between the MVSTs and a treatment facility. Since the wastes in the MVSTs are highly radioactive, a surrogate slurry was developed for this study. Rheological properties of the simulated slurry were determined in a test loop in which the slurry was circulated through three pipeline viscometers of different diameters. Pressure drop data at varying flow rates were used to obtain shear stress and shearrate data.

Twelve runs were made with the test loop using MVST surrogates that contained suspended solids concentrations ranging from 23 to 34 wt %. The experiments were divided into four categories. The first three categories explored two variables: (1) concentration of dissolved and suspended solids and (2) temperature of the slurry. The objective of the fourth category was to determine the minimum transport velocity for the slurry.

The runs were successfully completed with few difficulties. The data were analyzed, and the slurry rheological properties were analyzed by the Power Law model and the Bingham plastic model. The surrogate slurry developed for this study worked well. The plastic viscosity and yield stress data obtained from the rheological tests were used as inputs for a piping design software package, and the pressure drops predicted by the software compared well with the pressure drop data obtained from the test loop.

The minimum transport velocity was determined for the slurry by adding known nominal sizes of glass spheres to the slurry. The density of the glass spheres was similar to the density of the suspended solids, but the size of the glass spheres was selected to be conservatively large to predict the minimum transport velocity. However, it was shown that the surrogate slurry exhibited hindered settling, which may substantially decrease the minimum transport velocity. Therefore, it may be desired to perform additional tests with a surrogate that does not undergo hindered settling (i.e., a surrogate with a lower concentration of suspended solids) to determine the minimum transport velocity.

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