Volume 101, Issue 3 -

The complexation of Np(IV) with gluconic acid (GLU) under alkaline conditions was investigated in the absence of Ca by carrying out a series of sorption experiments. The decrease of Np(IV) sorption on the sorbing material at increasing concentrations of GLU was interpreted as the formation of Np(IV)-GLU aqueous complexes. The modelling of experimental data according to the Schubert method [1] confirmed the formation of a complex with a Np : GLU ratio 1 : 1. The stoichiometry of the complex Np(OH) 4 GLU − was proposed based on the experimental observation that no proton exchange occurred during the course of the complexation reaction and that Np(OH) 4 (aq) was the predominant hydrolysis product in the absence of GLU. A log * β 1,4,1 0 = −2.92 ± 0.30 for the formation reaction Np 4+ + 4H 2 O + GLU − ⇔Np(OH) 4 GLU − + 4H + was calculated based on the conditional stability constants determined from sorption experiments and using the Np(IV) thermodynamic data selected in the NEA reviews [2]. Linear free energy relationships (LFER) confirmed that the stoichiometry and stability of the Np(IV)-GLU complex characterized in this work are consistent with data available for Th(IV)-, U(IV)- and Pu(IV)-GLU complexes.

The complexation of uranium(VI) with bioligands found in human biological fluids, viz , urea and uric acid in aqueous solutions, has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO 4 ) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with average stability constants of log β 110 = 4.67 ± 0.29 for uric acid and log β 110 = 3.79 ± 0.15 and 2.12 ± 0.18 for relatively low and relatively high urea concentrations, respectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g. , human urine was also discussed.

Optical spectroscopic measurements in the UV-Vis and IR ranges were performed in model solutions of aqueous and organic phases of the PUREX process for spent nuclear fuel (SNF) reprocessing. Chemometric processing of the spectral data with PLS (partial least squares) regression allowed simultaneous quantification of several key components (uranium, neptunium, plutonium, nitric acid) in these mixtures in an effective and elegant way. The content of all key components was quantitively determined with mean relative errors not exceeding 10%. It was shown that the employment of the whole spectra or their certain continuous regions for a PLS calibration enables to decrease the analytical errors compared to the use of a single wavelength in an ordinary least squares approach. The results of this research imply that the development of on-line techniques for SNF reprocessing monitoring is fully possible and can be based on optical spectroscopy methods combined with multivariate data processing techniques.

Within the framework of the European collaborative project ACSEPT, a new SANEX partitioning process was developed at Forschungszentrum Jülich for the separation of the trivalent minor actinides americium, curium and californium from lanthanide fission products in spent nuclear fuels. The development is based on batch solvent extraction studies, single-centrifugal contactor tests and on flow-sheet design by computer code calculations. The used solvent is composed of 6,6´-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo-[1,2-4]trizazin-3-yl)-[2,2´]-bipyridine (CyMe 4 BTBP) and N , N , N ´, N ´-tetraoctyldiglycolamide (TODGA) dissolved in n -octanol. A spiked continuous counter-current test was carried out in miniature centrifugal contactors with the aid of a 20-stage flow-sheet consisting of 12 extraction, 4 scrubbing and 4 stripping stages. A product fraction containing more than 99.9% of the trivalent actinides Am(III), Cm(III) and Cf(III) was obtained. High product/feed decontamination factors >1000 were achieved for these actinides. The trivalent lanthanides were directed to the raffinate of the process with the actinide (III) product stream being contaminated with less than 0.5 mass-% in the initial lanthanides.

A novel extraction chromatographic resin was prepared by impregnating CMPO-RTIL (C 8 mim + ·NTf 2 − ) on Chromosrob-W for the removal of trivalent actinides from aqueous solution and its behaviour was compared with previously reported CMPO- n -dodecane resin. Under identical condition, the K d value of Am(III) by CMPO-RTIL resin ( K d at 3 M HNO 3 = 5805 ± 525) was one order magnitude higher than that obtained with CMPO- n -dodecane resin ( K d at 3 M HNO 3 = 610 ± 55). The sorption reaction of Am(III) followed a first-order rate law with both the resins. The metal sorption capacities for Eu(III) at 3 M HNO 3 were found to be 18.95 ± 1.13 mg and 20.52 ± 1.25 mg/g of CMPO-RTIL and CMPO- n -dodecane resins, respectively. The analysis of the sorption data by different models supported the hypothesis that the sorption of Eu(III) on the resins was actually limited by the saturation of the CMPO complexing sites on the resin. The free energy for the sorption of Eu(III) obtained from D–R isotherm was 17.67 ± 1.63 kJ/mol and 16.51 ± 2.05 kJ/Mol for CMPO-RTIL and CMPO- n -dodecane resins, respectively. The sorption free energy is an indication of chemisorption monolayer mechanism. The monolayer sorption mechanism was also confirmed by the theoretical approach calculated based on the sorption kinetics.

DTDGA solvent system was evaluated for hydrolytic and radiolytic stabilities to ascertain its application in separation and recovery of palladium from High Level Liquid Waste (HLW) solutions. Hydrolysis of DTDGA solvent system was not observed when it was kept in contact with 3.0 M nitric acid solution for two weeks. Moreover, contrary to other ‘S’ donor extractants used for the said purpose, the oxidation of thioetheric sulphur to sulphoxide or sulphones was also not observed. On the other hand, radiolysis of DTDGA solvent system was notably observed, which was found to increase with increase in absorbed dose. At gamma radiation dose of 0.2 MGy, no significant loss of DTDGA was observed. Aliphatic diluent namely n -dodecane was found to have sensitization effect on degradation of DTDGA. The degradation products were identified by GC-MS, the major ones were found to be formed by cleavage of thioetheric and amidic bonds of DTDGA molecule. The liquid–liquid extraction studies of palladium with irradiated solvent indicate that there was no significant change in D Pd up to an absorbed dose of 0.2 MGy above which it decreases gradually. Further, the radiolysis does not affect the stripping behavior of palladium. Extraction studies of Simulated High Level Liquid Waste (SHLW) elements with irradiated solvent system showed that, except palladium, any other element is hardly extracted thus retaining its remarkable selectivity.

This work was carried out with the aim to establish the effect of some impurities on the coprecipitation of gadolinium with calcium phosphate and gypsum. The tests were performed using the radioactive tracer technique to monitor the fate of gadolinium in various phosphoric and sulpho-phosphoric media containing fluoride and silicate ions as impurities. In 10 −2 to 10 −1  M NH 4 H 2 PO 4 solution, the Gd(III) at a concentration of 10 −4  M is almost entirely precipitated as amorphous phosphate. However, the presence of H 2 SO 4 at C H 2 SO 4 ≥ 0.1 M, reduces the coprecipitation to less than 8 at. %, on average. The fluoride ions in solution, even at C HF ≤ 0.1 M, induce a reduction of coprecipitation of 10 to 30% according to HF concentration. In the media containing 10 −2 to 10 −1  M NH 4 H 2 PO 4 and 10 −1  M H 2 SO 4 , the effect of HF is almost negligible in the absence of Si(IV); nevertheless, the presence of fluorosilicate in solution may contribute to the enhancement of the coprecipitation of the REE. The sulphuric acid (0.1 M) in phosphoric media (0.74 ≤ C H 3 PO 4 ≤ 4.44 M), leads to a significant coprecipitation of the REE (1.3 ± 0.2 ≤ D Gd ≤ 3.1 ± 0.5), whilst the addition of HF (0.1 M) to these media enhances the solubility of the REE (〈 D Gd 〉= 0.06 ± 0.01). XRD, IR spectroscopy and elemental analyses of the solid phases in conjunction with the variation of the distribution coefficient D indicate that the coprecipitation of the REE is likely controlled by heterovalent substitution of REE in gypsum and its precipitation as phosphate or fluorosilicate.

This paper describes an electrochemical method for the preparation of 55 Fe sources, utilized in the calibration of low energy X-ray detectors. In this process, electrodeposition of 55 Fe containing 185 MBq (∼5 mCi) of activity on a small circular cross sectional flat surface area (∼0.07 cm 2 ) within a cylindrical Cu metal rod was carried out at a current density of 20 mA/cm 2 at 18 ºC for 4 h using sulphate bath maintained at pH ∼ 2. The electrolytic cell, the experimental set up used and the process of 55 Fe deposition were described. The effect of various experimental parameters influencing the electrodeposition of 55 Fe were identified and optimized. The texture and morphology of the electrodeposited samples were examined by X-ray diffraction (XRD), SEM and EDS techniques. The quantity of deposited 55 Fe activity was assayed in a calibrated ion chamber. Quality control tests were carried out to ensure nonleachability, uniform distribution of activity and stability of the sources.

This paper describes a facile and effective method to prepare 133 Ba source exploiting the intrinsic properties of the anodized titanium to electro-deposit 133 Ba from an aqueous solution. The process consists of anodization of Ti rod [4.8 mm ( ∅ )  ×  10 mm ( l )] to create a reactive surface to permit cathodic electrodeposition of 133 Ba from an aqueous solution. The factors that influence the electrodeposition of 133 Ba onto the anodized titanium substrate were identified and a careful control has been exercised to ensure optimum deposition of 133 Ba activity onto the substrate. The morphology of the electrodeposited samples were examined by SEM and EDS analyses. Sources containing ∼ 3.7–11.1 MBq (0.1–0.3 mCi) 133 Ba were prepared, encapsulated successfully in titanium capsules and subjected to quality control tests to ensure compliance with mandatory regulatory safety requirements.