Vessel Erosion

DOE-HDBK-1132-99

Vessel Erosion allowance should be factored into the hold vessel design,

based on the feed material and the mixing system potential to abrade the tank

wall.

Feed to Melter . Like the sampling system, the melter feed system moves

2.14.8

homogeneous feed from the hold tank to the melter. Also as noted earlier,

selecting a pumping system similar to the one from the sampling system will

provide some degree of consistency between the samples and the actual feed

to the melter. The feed system should consider the need for flushing and

plug-clearing capabilities, particularly at the melter discharge point.

Experience has shown the potential for high temperatures to dry out and

accumulate feed material at this point.

Acceptable Glass Compositions . Acceptable glass compositions with

2.14.9

respect to melter behavior are those compositions exhibiting properties

amenable to proper melter operation and longevity. These properties include

glass viscosity at operating temperature, liquidous temperature, glass

electrical resistivity at operating temperature, and glass transition temperature.

The actual values for these parameters depend on the melter technology

employed. In addition, the following compositions should be avoided: those

that exhibit behaviors such as foaming in either the cold cap during drying or

in the glass melt pool and those with unfavorable Redox behavior (i.e.,

precipitation of metals during melting) or explosive gas generation (i.e.,

hydrogen evolution).

Acceptable glass properties and behaviors should be generally identified early

in the project and promulgated through the process development phase.

Melters and Melter Behavior . Melters vary in size, configuration, and heating

2.14.10

source. The large-scale, high-level waste melters in the DOE system are joule

heated, by passing current through the actual glass melt. RF and gas-fired

melters have also been proposed. The melter' configuration usually requires

two chambers.

The first is a refractory chamber surrounding a glass melt " ool,"where some

mixing occurs either by natural convection or as enhanced with air bubblers;

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