Distribution Coefficient Model for Zirconium and Technetium Extraction from Nitric Acid Solution

Abstract

Technetium and zirconium are two of the most problematic fission products in the PUREX process due to their complex extraction behaviors. Although there are several published works related to the calculation of Tc and Zr distribution coefficients, the reliability of those methods must be validated carefully, and further knowledge in this area is still needed. This work is, therefore, devoted to developing technetium and zirconium distribution coefficient models for predicting their distribution between nitric acid solution and tributyl phosphate in diluent for solutions containing uranium, technetium, and zirconium. The distribution coefficient model for zirconium is based on the organic nitric acid concentration, rather than the free TBP concentration. An improved technetium distribution coefficient model, in the absence of other metals, is also developed. The coextraction of technetium and zirconium or uranium is calculated by ligand exchange mechanisms. The validation results demonstrate that the distribution coefficient models developed in this work are more accurate than established models.

Novel 90Sr analysis of environmental samples by Ion-Laser InterAction Mass Spectrometry

“…Under conditions of Zr concentrations below 0.01 M (910 ppm) and 1-4 M HNO 3 , the monomer with the general formula Zr(OH) m (NO 3 ) 4 À m is the main component and the number of NO 3 À bound to the Zr ions increases with nitric acid concentration. 23 In our case, the sample solutions were made with 10 mL of 8 M HNO 3 and, Zr concentrations were lower than 910 ppm (4 ppm in the moss-soil, 3 ppb in the animal bone, and 11 ppm in the Syrian soil), suggesting that the monomer represented by the general formula was the main component in the sample solution. There is the possibility that Zr(OH) m (NO 3 ) 4 À m forms a complex with DtBuCH18C6 and was sorbed onto the resin like Sr, suggesting that Zr could be further separated if the optimum condition could be determined to Zr separation with Sr resin.…”

Radiolytic evaluation of a new technetium redox control reagent for advanced used nuclear fuel separations

“…Multiple efforts to date have provided a quantitative foundational, understanding of technetium chemistry under UNF reprocessing conditions. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] However, the challenges of technetium management have been amplified by more recent efforts to simplify the traditional PUREX process, motivated by economics, plutonium proliferation concerns, and neptunium management. [26][27][28] Some iterations of the PUREX process use hydrazine-stabilized ferrous and uranous nitrates for the reduction and separation of plutonium and neptunium (transuranics) from uranium-loaded organic phases.…”