Actinide Separation from MAW Process Streams via Ion-Exchange Techniques

Abstract

AbstiactTreatment of medium activity waste (MAW) solutions generally includes a concentration step followed by a chemical treatment to remove radioactive materials. The latter can be returned in an appropriate manner to the process or stabilized in a suitable matrix. Presently, mostly precipitation methods are considered for the decontamination of MAW concentrates. However, more recent developments suggest that specific decontamination steps can be successfully carried out in various process streams of well defined composition by using Chromatographie techniques, especially ion-exchange systems. Such a process stream originates, e. g., from the basic sodium carbonate Solution which is used for the removal of organic degradation products from the organic extraction medium before the latter is returned to the process. Düring this procedure actinides, such as uranium, neptunium, and plutonium, which were previously bound in the organic phase, are reextracted in form of their water-soluble carbonato-complexes. In order to develop a technique to separate these actinides from the aqueous Solution in a chemical form in which they can be returned to the process, several ion-exchange systems were tested. It was found that the uranium retention reached a maximum of about 300 g U/kg ion-exchange resin in the case of Bio-Rex-5 in a stoichiometric Solution of uranyl and carbonate ions. The presence of organic degradation products did not affect the retention; however, a large excess of carbonate ions tends to reduce the amount of retained uranium. A further advantage of this ion-exchange system is that the uranium can be -quantitatively eluted with approximately three column volumes of elution Solution (NH4NO3). Similar results were obtained in experiments with neptunium and plutonium ions. Other MAW streams are the nitric acid solutions from the first and following solvent extraction cycles, from which the actinides were separated by using a strong base anionic exchanger, and the Pu-oxalatecontaining Solution from the nuclear fuel fabrication, from which Pu was removed via fixation preferentially on ion exchanger with phosphonic acid groups.

Separation of Cesium from Acid ILW-Purex Solutions by Sorption on Inorganic Ion Exchangers

“…However, from recent developments it appears, that specific decontamination steps can be successfully carried out on various process streams of well defined compositions, as postulated in the second concept, by using chromatographic techniques, especially ion exchange systems [1,2].…”

Liquid-liquid extraction of plutonium and americium by cekanoic acid from alkaline medium

“…Horwitz et al [1] and Singh et al [2] removed the activity after acidifying the scrub solution. Using carbonate solution as it is, Ali and Ache [3] loaded U, Pu and Np on the organic resin, Bio-Rex-5, and eluted with 4 M HNO 3 . Kennedy et al [4] used hydrated titanium oxide to remove Pu(IV), ruthenium, zirconium and niobium whereas Pius et al [5] studied the loading of Pu(IV) on Alumina, silica gel and hydrous titanium oxide.…”

Selective separation of europium using polymer‐enhanced ultrafiltration

“…Among the many types of ionic radioactive species found in liquid radioactive wastes, actinides are important owing to their high radiotoxicity and long half-lives (Ali and Ache, 1984).…”