Consistency of Waste Feed

DOE-HDBK-1132-99

Consistency of Waste Feed should be considered in developing sampling

plans and systems. The feed make up process will generally require accurate

measurement of all species significant to melter and possibly waste form

behavior. The feed make-up, as discussed above, is generally a batch

process; the vessel in which the feed is being prepared should be well mixed

to avoid composition errors that could damage the melter.

Feed Make-up and Chemical Addition . Feed make-up and chemical

2.14.6

addition may require concentration and then addition of chemicals needed to

meet target melter feed compositions. If the feed material is very well

characterized and homogeneous, the chemicals can be added in advance and

provided in the form of glass frit. If there is potential for variation, a chemical

batching system that can handle specific recipes is required. The system may

need to handle solids, liquids, and slurries, depending on the target feed

composition. Generally, the chemical additions should be made up in a

separate tank and batch-transferred into the feed tank. This recommendation

derives from unique requirements for contamination control and batch quality

control for high-level waste vitrification. There may be more innovative

approaches for other waste types.

Accurate measurements of tank volumes and fluid density have proven very

important in the feed make-up process. Special attention should be given to

these areas for batch make-up tanks.

Feed Holding . Melters generally perform longer and best when operated as

2.14.7

close to steady-state as possible. Enough feed should be prepared to support

that objective while the next batch of feed is being prepared. Vessel sizing

should consider the potential throughput, as well as the time necessary to

prepare batches. In estimating those times, analytical turnaround times for

process samples should not be discounted. They can and have been a large

part of the time required to make feed.

Mixing the feed holding tank is a necessary design feature to maintain

consistent feed material to the melter.

Re-suspension should be considered when developing the mixing system.

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