Uranium/technetium separation for the UREX process – synthesis and characterization of solid reprocessing forms

Abstract

In the context of the demonstration of the UREX (uranium extraction) process, a separation of uranium and technetium using an anion exchange resin was performed on a simulant solution containing 98.95 g/L of 238U and 130.2 mg/L of 99Tc. After sorption on the resin, TcO4 − was eluted with NH4OH, the eluting stream was treated, and the technetium converted to Tc metal (yield=52.5%). The purity of the compound was analyzed: it contains less than 23.8 μg of 238U per gram of 99Tc. Tc metal was characterized by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) spectroscopy; EXAFS analysis clearly confirms the hexagonal structure of the metal obtained after treatment. Uranium was converted to ammonium diuranate and to U3O8 in a yield of 88.2%, analysis indicates that the compound contains less than 0.16 μg of 99Tc per gram of ammonium diuaranate.

Separation of Pertechnetate from Uranium in a Simulated UREX Processing Solution Using Anion Exchange Extraction Chromatography

“…We previously reported using steam reforming of tetrabutylammonium pertechnetate to produce Tc metal. [11] The Ar flow exiting the quartz tube passed through another water bubbler before being exhausted into the hood. The tube furnace was programmed to heat to 950 • C at 10 • C/min, remain at 950 • C for 12 h and then cool to room temperature.…”

“…This is a much sharper elution than that observed with Reillex HP where 15-18 BV were needed to recover a similar amount of the loaded Tc. [11] The Tc elution profiles (Fig. 4) "ammonium hydroxide" solutions can more rapidly penetrate the protonated, anionloaded Alamine 336 layer (R 3 NH + /NO 3 − ) to neutralize the protonated sites and release the bound anions.…”

“…Results from testing of Reillex TM HP to recover TcO 4 − from a surrogate UREX U/Tc product solution were reported. [11] As noted above, the large molar excess of nitrate present in the UREX product solution competes for the anion exchange sites on the resin and limits the loading with TcO 4 − to about 2-3% of the theoretical anion-exchange capacity of the Reillex TM HP resin.…”

“…[7][8][9][10] We previously evaluated a number of commercial anion exchange resins, especially weak-base anion exchangers, for TcO 4 − binding and elution in surrogate UREX product streams. [11] These tests indicated that the most promising commercial resin for a loading-elution process was Reillex TM HP, a weak-base anion exchanger built from a vinylpyridine-divinylbenzene copolymer. The most useful eluent solution tested was ammonium hydroxide (i.e., NH 4 OH) because it gave relatively efficient removal of the Tc and the eluent solution could be distilled to give a concentrated product solution and ammonium hydroxide condensate for recycle.…”

Anion Exchange Resins for the Selective Separation of Technetium from Uranium in Carbonate Solutions

“…8 The recovered 99 Tc can subsequently be converted to metal or into other waste forms suitable for long-term storage or geological disposal. 9 Despite the evolutions of advanced PUREX processes, these technologies have some significant shortcomings, such as radiolytic degradation of the organic solvents, that other reprocessing technologies hope to improve upon. 10−12 One alternative revolutionary approach is to use alkaline solutions for the dissolution of UNF.…”