and D&D projects. For example, considerations related to electrical power,
radiation shielding, structural integrity, and work process controls, are
discussed in the preceding section on D&D projects.
Introduction . The process of vitrification is the melting and fusing of
materials to produce a glass. It is one of the preferred treatment options for
many types of hazardous and radiological waste. The general design
considerations in developing a vitrification plant are discussed below.
General Vitrification Processes and Steps to Consider . Waste composition
may make material more or less amenable to the use of vitrification as a
treatment technique. It affects pretreatment required and influences the
transport of material within a vitrification plant. Characteristics to consider
include the following:
Physical Characteristics . Physical characteristics of the waste material,
including whether the material is in solution, a slurry, or a solid, influences
transport within the plant and the material' ability to form a homogenous
mixture with glass formers. Imposed constraints on transport, mixing, melting
the material, and the need for pre-treatment are all considerations subject to
physical characteristics of the waste.
Chemical Characteristics . Certain chemicals (notably sulfur) are
incompatible with vitrification and if present influences the amount of final
waste produced. Other chemicals may be volatile and very difficult to retain in
the glass product. Factors like pH may complicate the process of mixing a
final feed material, due to rheological considerations or corrosion.
Radiological Characteristics . The radiological characteristics dictates
shielding requirements, remote operations, off-gas processing, and possibly, a
requirement for criticality controls.
Waste Extraction from Tanks . Waste extraction from tanks is the first step
in the actual vitrification process. (Some in situ vitrification techniques
eliminate this and many other steps discussed below, but this technology is