Provisions should be made for crucibles and molds removed or no longer
serviceable to be processed to recover or remove residual plutonium
before they are discarded.
Design should provide for the need to process plutonium scrap and
residue before any subsequent disposition action is taken. Aqueous
(chloride or nitrate system) and pyrochemical processing are required.
Stabilization optimally involves separation of plutonium from matrix
material in order to minimize the volume of material to be stored.
Likewise, separation of plutonium from waste matrices will minimize the
amount of transuranic waste to be shipped and placed in a waste
repository. The final form of the concentrate should be a stable (but not
necessarily highly purified) oxide or metal. The process includes acid
dissolution (hydrochloric or nitric), some degree of purification (e.g., ion
exchange), precipitation (typically as oxalate), calcining (to decompose
the oxalate and produce plutonium oxide), and packaging. If a metal form
is required as the end point, the temperature at which the oxalate is
calcined should be kept as low as practical. Metal can be produced by
direct oxide reduction with elemental calcium in a molten salt medium
(calcium chloride). Means to regenerate the calcium chloride salt medium
should be included in the process design.
Characterization, Control and Accounting . Chemical sampling and analyses
should be provided to support process and operations in the process area of the
PPHF. Techniques employed for the characterization of plutonium include:
metallography, electron microscope, X-ray diffraction, chemical analysis, thermal
analyses, and isotopic. The most common detection technique employed is the
nondestructive assay detection system, which includes (1) radiation detection
which measures the heat output of the radioactive materials.
Several pyrochemical processes are likely to be used in plutonium processing.
Molten salt extraction is used to separate americium from plutonium in aged
plutonium items. A " altless"extraction process has been developed at Los