Recent Developments in the Purex Process for Nuclear Fuel Reprocessing: Complexant Based Stripping for Uranium/Plutonium Separation

Abstract

In order to recycle potentially valuable uranium and plutonium, the Purex process has been successfully used to reprocess spent nuclear fuel for several decades now at industrial scales. The process has developed over this period to treat higher burnup fuels, oxide as well as metal fuels within fewer solvent extraction cycles with reduced waste arisings. Within the context of advanced fuel cycle scenarios, there has been renewed international interest recently in separation technologies for recovering actinides from spent fuel. Aqueous fuel processing research and development has included further enhancement of the Purex process as well as the development of minor actinide partitioning technologies that use new extractants. The use of single cycle Purex solvent extraction flowsheets and centrifugal contactors are key objectives in the development of such advanced Purex processes in future closed fuel cycles. These advances lead to intensified processes, reducing the costs of plants and the volumes of wastes arising. By adopting other flowsheet changes, such as reduced fission product decontamination factors, U/Pu co-processing and Pu/Np co-stripping, further improvements can be made addressing issues such as proliferation resistance and minor actinide burning, without adverse effects on the products. One interesting development is the demonstration that simple hydroxamic acid complexants can very effectively separate U from Np and Pu in such advanced Purex flowsheets.

A review of the demonstration of innovative solvent extraction processes for the recovery of trivalent minor actinides from PUREX raffinate

“…With some modifications, neptunium can also be recovered (advanced PUREX) [3][4][5]. Up to now, solvent extraction processes have been the reference technology for fuel processing at commercial scale for more than 60 years and the reasons for this are multiple.…”

Lanthanides and Actinides in Ionic Liquids

“…CPMO is the extractant in the TRUEX process (TRUEX ) transuranium extraction). 144 Because of the ionic nature of ionic liquids, the partitioning equilibriums in solvent extraction systems involving ionic liquids are not necessarily identical to those involving conventional organic solvents. The equilibriums often involve cation or anion exchange between the aqueous phase and the ionic liquid phase.…”

“…The PUREX process uses tri-n-butyl phosphate (TBP) as a 30% solution in kerosene as the extractant in the solvent extraction step. 144 There are some technical and safety problems related to the PUREX process. First of all, tri-n-butyl phosphate is not very stable against radiolysis.…”

“…The first step in commercial processes like the plutonium-uranium separation by extraction (PUREX) process consists of oxidative dissolution of the UO 2 pellets in a concentrated aqueous HNO 3 solution. 155,156 After the spent fuel elements have been dissolved in the nitric acid solution, the acidic solution is contacted with a waterimmiscible organic solution, which can selectively extract the desired elements. The PUREX process uses tri-n-butyl phosphate (TBP) as a 30% solution in kerosene as the extractant in the solvent extraction step.…”

Determination of the Constants of Formation of Complexes of Iron(III) and Acetohydroxamic Acid

“…The potential role of such hydroxamate siderophores in the mobilisation of actinide ions within the environment has also been considered (John et al,2001). More recently, XHAs have also been identified as useful reagents for the control of Pu and Np in advanced PUREX and UREX processes proposed for the processing of spent nuclear fuel (Birkett et al,2005). In such separation processes, U, Np and Pu are separated according to oxidation state specific aqueous/non aqueous solvent extraction in the presence of acetohydroxamic acid (AHA) (Carrott et al,2007).…”