Volume 102, Issue 11

The MARS beamline at the SOLEIL synchrotron is dedicated to the characterization of radioactive material samples. One great advantage of the beamline is the possibility to characterize about 380 radionuclides by different X-ray techniques in the same place. This facility is unique in Europe. A wide energy range from around 3.5 keV to 36 keV K-edges from K to Cs, and L3 edges from Cd to Am and beyond can be used. The MARS beamline is optimized for X-ray absorption spectroscopy techniques (XANES/EXAFS), powder diffraction (XRD) but x-ray fluorescence (XRF) analysis, High Energy Resolution Fluorescence Detected -XAS (HERFD-XAS), X-ray Emission (XES) and μ -XAS/XRD are also possible. A description of the beamline as well as its performances are given in a first part. Then some scientific examples of XAS studies from users are presented which cover a wide variety of topics in radiochemistry and nuclear materials.

Studies for chromatographic separation of Th, U(VI) and Pu(IV) were carried out using mandelic acid as an eluent. The different chromatographic conditions like concentration of mandelic acid, pH of the mobile phase, presence of MeOH and effect of ion interaction reagent (IIR) were studied. The method was optimized for the separation of Th, U(VI) and Pu(IV). At pH < 3.5 of mobile phase, Pu(IV) was more retained compared to U(VI) whereas at pH > 3.5, reverse trend was observed. The optimized parameters were employed for the separation and determination of Th, U(VI) and Pu(IV) in a dissolved solution of irradiated (Th, Pu)O 2 . Sample treatment was optimized to minimize loss of Pu and Th during chromatographic determination. Studies were carried out using two IIRs to understand the anomalous chromatographic behavior of Pu(IV). Retention behavior of different oxidation states of Pu viz. Pu(III), Pu(IV) and Pu(VI) was also studied in mandelic acid.

We have examined the sorption of aqueous Pu(IV) and intrinsic Pu colloids to goethite across a Pu concentration range that spans the solubility of Pu(IV) hydrous oxide, at 25 and 80 ℃, and after equilibration for over 100 days. The strong affinity of aqueous Pu(IV) for the goethite surface is explained by the epitaxial growth of bcc Pu 4 O 7 nano-particles on goethite. The 3–5 nm Pu 4 O 7 nano-particles are strictly associated with goethite, widely dispersed across the goethite surface, and stable over the timescale of months at both 25 and 80 ℃. There is no indication that the sorbed Pu 4 O 7 nano-particles alter to PuO 2 over time. Intrinsic Pu colloids were identified by TEM as 3–5 nm PuO 2 nano-particles. They exhibit a weaker association with the goethite surface. Aggregation of PuO 2 nano-particles was observed. There is no indication that the PuO 2 nano-particles, once formed, will alter to Pu 4 O 7 on goethite. Based on supernatant Pu concentrations, PuO 2 nano-particle aggregation behavior is consistent with Pu(IV) hydrous oxide precipitation.

An attempt was made to select thermodynamic data with uncertainties and to evaluate the solubility of radioelements with uncertainties considering the uncertainties of the thermodynamic data and variation in groundwater chemistry. The thermodynamic data were selected by reviewing the JAEA-TDB released in 2012 from the viewpoint of consistency of the data selection process, the conservativeness of the solubility evaluation and testing up-to-date data. A Monte Carlo-based probabilistic solubility calculation code, PA-SOL, was used for the uncertainty analysis of the solubility. The uncertainty analysis for the solubility of 13 elements showed large uncertainties for Nb, Tc and U. The variations in pH, pe and total carbonate concentration assumed in this study induce significant uncertainties to the evaluated solubility. The reactions whose log  K 0 with uncertainties induce significant uncertainties to the evaluated solubilities were identified.

The extraction behavior of U(VI) in the PUREX solvent namely 1.1 M tri- n -butyl phosphate (TBP) in n -dodecane ( n -DD) was studied in the presence and absence of the ionic liquid, tri- n -octylmethylammonium bis-(2-ethylhexyl)phosphate ([A336] +  [DEHP] – ). The discrepancy in the extraction behavior observed in these systems was probed by measuring the distribution ratio of U(VI) as a function of various parameters. The distribution ratio of U(VI) in 0.03 M [A336] +  [DEHP] – / n -DD decreased with increase in the concentration of nitric acid. The extraction of U(VI) was accompanied by the extraction of nitric acid leading to the formation of ionic liquid constituents namely tri- n -octylmethylammonium nitrate ([A336] +  [NO 3 ] – and bis(2-ethylhexyl)phosphoric acid (HDEHP). Therefore, the distribution ratio of U(VI) in the PUREX solvent was measured in the presence of these constituents also. The study revealed that extraction of U(VI) was controlled essentially by the synergistic contribution of TBP and the constituents of ionic liquid.

Most of the procedures developed for the extraction of cobalt, strontium and cesium by solid phase extraction do not employ simultaneous extraction of them. In this study, rapid simultaneous removal of Co 2+ , Sr 2+ and Cs + on microcrystalline naphthalene as solid-phase extractant was investigated. These ions were allowed to form chelates with oxine and then adsorbed on freshly microcrystalline naphthalene from aqueous solutions. The solid phase extraction procedure (SPE) was optimized by using model solution containing Co 2+ , Sr 2+ and Cs + in batch system. The effects of different parameters such as variation in pH, reagent concentration, standing time, naphthalene solution concentration and contact time on the simultaneous removal of these ions was studied. The obtained results indicated that, sorption was found to be rapid, and the percentage removal of Co 2+ , Sr 2+ and Cs + was found to be 98, 79 and 68% within 10 min, respectively. The kinetics of the sorption process was investigated to understand the kinetic characteristics of sorption of metal chelates onto microcrystalline naphthalene. The developed procedure has been successfully applied to the removal and recovery of 60 Co and 134 Cs from liquid radioactive waste. The parameters can be used for designing a plant for treatment of wastewater economically.

Dinitrogen pentoxide has aroused significant interest in atmospheric chemistry because of its importance in the night time chemistry of nitrogen oxides to influence the tropospheric oxidation capacity. We have used an established method of 13 N production to synthesize 13 N labeled N 2 O 5 for the first time in order to study N 2 O 5 uptake kinetics on aerosol particles. 13 N is produced via the 16 O( p ,  α ) 13 N reaction in a gas target attached to the IP2 endstation of the Injector 2 cyclotron at PSI. The 13 NO produced in the gas target is transported to a laboratory where it is mixed, under dry conditions, with non-labeled NO and O 3 in a gas reactor, giving 13 NNO 5 . The N 2 O 5 thus produced is fed into an aerosol flow tube together with a humidified aerosol gas flow. The gaseous species present in the resulting gas flow are selectively separated via a narrow parallel plate diffusion denuder system, while aerosol particles can be trapped on a particle filter placed at the end of the denuder system. The activity of the 13 N labeled species trapped on the denuder plates and in the particle filter can be monitored via scintillation counters. A system for the routine online production of 13 N labeled N 2 O 5 has been assembled and used to assess the conformity of the results by kinetic modeling of gas phase N 2 O 5 chemistry, showing good agreement. A few exemplary experiments of uptake of labelled N 2 O 5 to ammonium sulfate and citric acid particles are presented that are in good agreement with results obtained with other methods reported in the literature.

In this study, zinc-62 was prepared at radiopharmaceutical grade (for 62 Zn/ 62 Cu generator production) using nat Cu( p ,  xn ) reaction with the production yield of 5.9 mCi/ μ Ah at 30 MeV proton energy (radiochemical separation yield >95%, radionuclidic purity >99% and radiochemical purity >99%). In the next step, rituximab was successively labeled with [ 62 Zn]-ZnCl 2 after conjugation with p-SCN-Bz-DOTA followed by molecular filtration and determination of the average number of DOTA conjugated per mAb (6:1) by spectrophotometric method. Radiochemical purity (>97%, measured by ITLC and HPLC), integrity of protein after radiolabeling (gel electrophoresis) and stability of [ 62 Zn]-DOTA-rituximab (in final formulation, and human serum) were determined 1–8 h as well as biodistribution studies in wild-type rats followed by coincidence imaging for 6 h. However, the accumulation of the radiolabeled antibody was not consistent with the former reported rituximab conjugates. [ 62 Zn]-labeled monoclonal antibodies and fragments can be prepared as potential in vivo PET generators for molecular imaging however, the search for application of stable zinc complexes must be continued.

Mono-and poly- iodinated peptides form frequently during radioiodination procedures. However, the formation of a single species in its mono-iodinated form is essential for quantitative studies such as determination of tissue concentration or image quantification. Therefore, the aim of the present study was to define the optimal experimental conditions in order to exclusively obtain the mono-iodinated form of L-maurocalcine (L-MCa). L-MCa is an animal venom toxin which was shown to act as a cell-penetrating peptide. In order to apply the current direct radioiodination technique using oxidative agents including chloramine T, Iodo-Gen ® or lactoperoxidase, an analogue of this peptide containing a tyrosine residue (Tyr-L-MCa) was synthesized and was shown to fold/oxidize properly. The enzymatic approach using lactoperoxidase/H 2 O 2 was found to be the best method for radioiodination of Tyr-L-MCa. MALDI-TOF mass spectrometry analyses were then used for identification of the chromatographic eluting components of the reaction mixtures. We observed that the production of different radioiodinated species depended upon the reaction conditions. Our results successfully described the experimental conditions of peptide radioiodination allowing the exclusive production of the mono-iodinated form with high radiochemical purity and without the need for a purification step. Mono-radioiodination of L-Tyr-MCa will be crucial for future quantitative studies, investigating the mechanism of cell penetration and in vivo biodistribution.