Patent Number: 043942695
Section: summary

The 30% tri-n-butyl phosphate (TBP), 70% dodecane solution used in nuclear fuel reprocessing undergoes degradation in use, forming monobutyl phosphate and dibutyl phosphate which then form complexes with small quantities of plutonium, uranium, and their fission products that are not removed from the solution in the primary nuclear fuel reclaiming process. Recycle of TBP solvent for further use requires the removal of these degradation products, and various methods have been proposed for this purpose, including washing the solvent with Na.sub.2 CO.sub.3 or N.sub.2 H.sub.4.H.sub.2 CO.sub.3 solutions or passing the solvent through a column containing solid adsorbents such as macroreticular resins, hydrous TiO.sub.2, and mixed SiO.sub.2 and PbO.sub.2. The use of Na.sub.2 CO.sub.3 produces large amounts of waste material that causes a disposal problem. The N.sub.2 H.sub.4.H.sub.2 CO.sub.3 method presents problems in the preparation and storage of the N.sub.2 H.sub.4.H.sub.2 CO.sub.3 solution used therein. A resin adsorbent works well only with acid-free solvents. TiO.sub.2 is presently used only on an experimental scale, and mixed SiO.sub.2 and PbO.sub.2 have only been reported as being used for secondary removal of degradation products from solutions previously treated by standard wash solutions. SUMMARY OF THE INVENTION It is therefore an object of this invention to provide an efficient and convenient method for decontaminating a nuclear metal extracting solution containing a hydrocarbon diluent, tri-n-butyl phosphate or tri-2-ethylhexyl phosphate, and a degradation product of one of the named phosphates. Another object of the invention is to clean a TBP solution without producing waste products that are difficult to dispose of. These objects and other advantages are achieved, in accordance with the invention, by contacting a contaminated actinide metal extracting solution with silica gel having alkali metal ions such as sodium or lithium adsorbed thereon, thereby adsorbing impurities in the solution on the gel, which can then be disposed of as an easily handled solid or which can be washed and recycled for further use as a cleaning medium.