Chemical Processing cont'd

DOE-HDBK-1132-99

Two different types of chemistry are generally employed for plutonium

processing: the aqueous chemical process and pyrochemistry. Aqueous

processes that are common to the plutonium production and chemical analysis

are: dissolution, precipitation, liquid-liquid extraction, and oxidation-reduction

reactions.

The purex process, which has been the typical aqueous process used in

plutonium production, involves the extraction and purification of plutonium with

tributyl phosphate. Other processes are the production of plutonium

tetrafluoride (PuF4) and the reduction of PuF 4 using calcium and iodine. The

purex process should include design features to deal with the use of flam mable

liquids, the potential for radiolysis, the iron catalysis of hydrogen peroxide

decomposition, and the potential generation of a large volume of plutonium-

contaminated wastes.

The design of facilities that employ an aqueous chemical process should

consider the following features:

Systems, structures, and components for aqueous processing should be

resistant to highly corrosive liquid and entrained vapors. Depending on

the process to be used, stainless steel components are acceptable for

nitrate-based systems. Because stainless steel is incompatible with

chlorides, special coatings for gloveboxes (e.g., KynarTM ) should be

considered, along with TeflonTM or derivative polymer piping, valves,

pump bodies, and vessels in systems that employ chloride chemistry.

Selection of in-line process controls should consider materials

compatibility. Automated ion-exchange systems have been used at Los

Alamos with great success.

The sizing of process equipment is necessarily small to accommodate

nuclear criticality requirements. In-process storage of feed solutions is

efficiently handled in slab tanks or hollow cylindrical tanks. Pencil tanks

have also been used; however, the array of such tanks is more

complicated and subject to leaks. Selection of gasket, pump, and valve

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