Band 99, Heft 2 -

This paper describes the development of a radioanalytical procedure to separate Am 3+ and Cm 3+ that relies on chromatography with the TRU ® resin available from Eichrom Technologies, Inc. Although the TRU chromatographic materials are not currently recommended for the separation of the trivalent actinides from each other, our work demonstrates their suitability. We explored parameters such as nitric acid concentration, column length, and flow rate; standard chromatographic parameters such as resolution, theoretical plates, and total separation time are reported for each variable. The advantages of the method described herein include use of a commercially available product and no application of an organic solvent during elution. Optimal resolution between the Am 3+ and Cm 3+ was achieved with the slowest flow rate.

The interaction between neptunium(V) and a natural argillaceous rock (Opalinus Clay (OPA), Mont Terri, Switzerland) has been investigated in batch sorption experiments by varying pH (6–10), Np(V) concentration (10 −12 –10 −4  M), solid-to-liquid ratio (2–20 g/L), and partial pressure of CO 2 (10 −3.5 and 10 −2.3  atm) under aerobic/anaerobic conditions in saturated calcite solution. All batch experiments were carried out using well characterized aerobic and anaerobic dry powders of OPA. The results show a great influence of pH on Np(V) sorption. Under aerobic conditions sorption increases with increasing pH until maximum sorption is reached between pH 8–9. At pH>9 sorption decreases due to the formation of negatively charged Np(V)-carbonate complexes. By increasing p CO 2 from 10 −3.5 to 10 −2.3  atm, the sorption edge is shifted ≈0.5 units to lower pH values. Under anaerobic conditions stronger sorption of 8×10 −6  M Np(V) was found, possibly due to partial reduction of Np(V) to Np(IV). The sorption of 8×10 −6  M Np(V) under aerobic conditions at pH 8.2 in saturated calcite solution increases continuously with increasing solid-to-liquid ratio of OPA in the range of 2–20 g/L with a constant K d value of 126±13 L/kg. The sorption isotherm was measured over seven orders of magnitude in Np(V) concentration using 239 Np as tracer. The sorption isotherm could be divided in a part of linear sorption behaviour between 10 −13 –10 −9  M Np(V) and non-linear behaviour in the range of 10 −9 –10 −4  M Np(V).

Understanding the mechanism(s) of uranium-mineral dissolution is crucial for predictive modeling of U mobility in the subsurface. In order to understand how pH and type of cation in solution may affect dissolution, experiments were performed on mainly single crystals of curite, Pb 2+ 3 (H 2 O) 2 [(UO 2 ) 4 O 4 (OH) 3 ] 2 , becquerelite, Ca(H 2 O) 8 [(UO 2 ) 6 O 4 (OH) 6 ], billietite, Ba(H 2 O) 7 [(UO 2 ) 6 O 4 (OH) 6 ], fourmarierite Pb 2+ 1−x (H 2 O) 4 [(UO 2 ) 4 O 3−2x (OH) 4+2x ] ( x = 0.00–0.50), uranophane, Ca(H 2 O) 5 [(UO 2 )(SiO 3 OH)] 2 , zippeite, K 3 (H 2 O) 3 [(UO 2 ) 4 (SO 4 ) 2 O 3 (OH)], and Na-substituted metaschoepite, Na 1−x [(UO 2 ) 4 O 2−x (OH) 5+x ] (H 2 O) n . Solutions included: deionized water; aqueous HCl solutions at pH 3.5 and 2; 0.5 mol L −1 Pb(II)-, Ba-, Sr-, Ca-, Mg-, HCl solutions at pH 2; 1.0 mol L −1 Na- and K-HCl solutions at pH 2; and a 0.1 mol L −1 Na 2 CO 3 solution at pH 10.5. Uranyl mineral basal surface microtopography, micromorphology, and composition were examined prior to, and after dissolution experiments on micrometer scale specimens using atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Evolution of etch pit depth at different pH values and experimental durations can be explained using a stepwave dissolution model. Effects of the cation in solution on etch pit symmetry and morphology can be explained using an adsorption model involving specific surface sites. Surface precipitation of the following phases was observed: (a) a highly-hydrated uranyl-hydroxy-hydrate in ultrapure water (on all minerals), (b) a Na-uranyl-hydroxy-hydrate in Na 2 CO 3 solution of pH 10.5 (on uranyl-hydroxy-hydrate minerals), (c) a Na-uranyl-carbonate on zippeite, (d) Ba- and Pb-uranyl-hydroxy-hydrates in Ba-HCl and Pb-HCl solutions of pH 2 (on uranophane), (e) a (SiO x (OH) 4−2x ) phase in solutions of pH 2 (uranophane), and (f) sulfate-bearing phases in solutions of pH 2 and 3.5 (on zippeite).

The chemical investigation of E113 is likely to become soon feasible. The determination of chemical properties of carrier-free amounts of the lighter homologues of element 113, especially indium and thallium, allows designing experimental set-ups and selecting experimental conditions suitable for performing these studies. Here, we present investigations of the interaction of indium species with quartz and gold surfaces. Deposition temperatures as well as enthalpies of adsorption were determined for indium T dep =739±20 °C (−Δ H ads (In)=227±10 kJ mol −1 ) and for indium hydroxide T dep =250±20 °C (−Δ H ads (InOH)= 124±10 kJ mol −1 ) respectively, on quartz. In case of adsorption of indium on a gold surface only a lower limit of the deposition temperature was established T dep >980 °C (−Δ H ads (In)≥315±10 kJ mol −1 ). Investigations of macroscopic amounts of indium in thermosublimation experiments at similar experimental conditions were instrumental to establish a tentative speciation of the observed indium species.

This paper describes an electrochemical method for the preparation of 57 Co source to be used in quality evaluation of nuclear fuel rods. The electrolytic cell, the experimental set up used and the process of deposition are described. The effect of various parameters such as pH of the electrolyte, bath temperature, current density, content of cobalt in the bath, electrolyte volume in the cell and deposition time were investigated and optimized for maximum deposition. The texture and morphology of the electrodeposited samples were examined by X-ray diffraction (XRD), SEM and EDS analyses. Sources containing ∼370 MBq (10 mCi) 57 Co on a circular copper foil of 4 mm diameter could be prepared and encapsulated in an aluminum capsule. Quality assurance tests performed to ensure non-leachability, uniform distribution of activity and stability of the sources gave satisfactory results.

An industrial liquid–liquid extraction process for reprocessing of spent nuclear fuel will inevitably lead to radiolysis of the phases, since the process streams contain highly radioactive species. Solvents containing one of the BTBP (6,6′-bis(5,6-dialkyl-[1,2,4]-triazin-3-yl)-2,2′-bipyridine) molecules intended for the separation of trivalent actinides (An) from lanthanides (Ln), the so called C5-BTBP, have shown a dramatic decrease in both distribution ratios and An/Ln separation factor when irradiated; hence, the molecule is highly unstable towards radiolysis. HPLC-, APCI(+)-MS and LC-MS analyses were performed on irradiated solvents containing initially 0.005 M C5-BTBP dissolved in either hexanol or cyclohexanone. The decrease in concentration of starting molecule as well as the increase in concentration of various degradation products were studied with quantitative and semi-quantitative measurements. Structures were suggested for the degradation products produced in highest yields and these were compared to previously proposed structures for the same products.

A procedure was developed for determining 241 Pu activity in environmental samples. This beta emitter isotope of plutonium was measured by ultra low level liquid scintillation, after several separation and purification steps that involved the use of a highly selective extraction chromatographic resin (Eichrom-TEVA). Due to the lack of reference material for 241 Pu, the method was nevertheless validated using four IAEA reference sediments with information values for 241 Pu. Next, the method was used to determine the 241 Pu activity in alpine soils of Switzerland and France. The 241 Pu/ 239,240 Pu and 238 Pu/ 239,240 Pu activity ratios confirmed that Pu contamination in the tested alpine soils originated mainly from global fallout from nuclear weapon tests conducted in the fifties and sixties. Estimation of the date of the contamination, using the 241 Pu/ 241 Am age-dating method, further confirmed this origin. However, the 241 Pu/ 241 Am dating method was limited to samples where Pu-Am fractionation was insignificant. If any, the contribution of the Chernobyl accident is negligible.