Volume 99, Issue 6 -

The excitation functions of proton induced nuclear reactions on nat Te were measured using the stacked-foil technique up to 14.5 MeV. Samples of thin uniform layers of nat Te on Ti-backing were prepared by electro-deposition. Nuclear reaction cross sections for the formation of 120g,121,123,124,125,126,128,130(m+g) I were determined and their theoretical thick target yields were calculated. The obtained data were compared with the previously published experimental results and the values obtained theoretically using the ALICE-IPPE computer code.

The retention behaviour of uranium, thorium, americium and lanthanides has been investigated, using a reverse phase C 18 column modified with 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine ( n -Pr-BTP) with the aim of investigating rapid lanthanide-actinide separations by HPLC technique. Nitric acid and α -hydroxy isobutyric acid ( α -HIBA) have been employed as the mobile phase. The influence of mobile phase pH and concentration on the retention of metal ions has been studied. The aim of this study is to investigate the use of BTP coated reverse phase columns as analytical columns for the fast separation of the minor actinides from the lanthanides in the high-level waste (HLW), and to explore whether such columns can be used on a preparative scale for the purification and the recovery of minor actinides from the high-level waste (HLW). It was observed that reverse phase columns modified with BTP showed greater affinity for actinides but exhibited no retention for lanthanides and the lanthanide-actinide separations could be achieved in nitric acid mobile phase, without the need for complexing agents. Americium was separated from the lanthanides with good peak profile and baseline resolution in both nitric acid as well as α -HIBA as the mobile phase. Based on this, the separation of americium from the lanthanides in the HLW was also demonstrated. The retention of a significant amount of thorium by the column in breakthrough studies also indicated that these columns can be used for preparative scale purification of the actinides.

Uranium ores and yellow cake samples of known geographic origin were investigated for their n ( 236 U)/ n ( 238 U) isotope abundance ratio. Samples from four different uranium mines in Australia, Brazil and Canada were selected. Uranium was separated by UTEVA ® Resin and was measured by Accelerator Mass Spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA). The measurement of the isotope abundance ratio n ( 236 U)/ n ( 238 U) will be used to investigate possible correlations between the original mineral (uranium ore) and the intermediate product (yellow cake). Such correlations are useful indicators for nuclear forensic or for non-proliferation purposes.

The thermodynamic quantities (Δ G c , Δ H c and Δ S c ) for formation of Th(IV) complexes with dicarboxylic ligands, namely, malonate, succinate, glutarate and adipate were determined using potentiometry and calorimetry. The protonation constants of the dicarboxylate ligands were determined by potentiometric titration of the ligand solution, while the corresponding enthalpy values were taken from the literature. In the case of Th(IV)-malonate, multiple species (ML j , j =1–3) were revealed from the potentiometric data, while in the case of higher homologues, the data for only 1:1 complex could be obtained owing to precipitation at higher ligand concentration. The effect of chain length on the thermodynamic parameters of Th(IV)-dicarboxylate complexation was studied. All the complexation reactions were found to be highly entropy driven, which is the characteristic of the hard acid (metal ion) and hard base (ligand) interactions. The T Δ S c values for 1:1 complexes were found to be nearly constant while the Δ H c values increased from malonate to glutarate and then leveled off in adipate. The thermodynamic data of Th(IV) have been compared with corresponding data for U(VI) and rare earths.

The sorption behavior of neptunium(V) onto the clay mineral kaolinite was studied in batch experiments under different experimental conditions: [Np(V)]=7 × 10 −12 –8 × 10 −6  M , solid-to-liquid ratio 2–20 g L −1 , I =0.1 and 0.01 M NaClO 4 , pH=6–10, ambient air and Ar atmosphere. The short-lived isotope 239 Np ( T 1/2 =2.36 d) was used instead of 237 Np ( T 1/2 =2.14 × 10 6  a) to study the sorption behavior of Np(V) at environmentally-relevant concentrations, i.e. , 7 × 10 12  M Np. In addition, 239 Np(V) served as tracer to measure sorption isotherms over six orders of magnitude in Np concentration (4.8 × 10 −12 –1.0 × 10 −4  M). The results show that Np(V) sorption on kaolinite is strongly influenced by pH, CO 2 , and ionic strength. The sorption of 8 × 10 −6  M Np(V) at pH 9.0, and ionic strength of 0.1 M NaClO 4 was proportional to the solid-to-liquid ratio of kaolinite in the range of 2–10 g L −1 . In the absence of CO 2 , the Np(V) uptake increased continuously with increasing pH value up to 97% at pH 10. Under ambient CO 2 , the sorption of Np decreased above pH 8 up to zero at pH 10. An increase of Np(V) concentration from 7 × 10 −12 to 8 × 10 −6  M resulted in a shift of the sorption pH edge by up to one pH unit to higher pH values. The ionic strength influenced the Np(V) sorption onto kaolinite only in the presence of ambient CO 2 . Under Ar atmosphere the sorption of Np(V) was independent from ionic strength, indicating the formation of inner-sphere complexes of Np(V) with kaolinite. Time-dependent batch experiments at pH 9.0 under ambient CO 2 showed that the sorption of Np(V) on kaolinite is fast and fully reversible over six orders in Np(V) concentration.

The proton rich 97 Ru, a potential candidate for nuclear medicine, was produced for the first time through the nat Nb( 7 Li,3 n ) 97 Ru reaction. A natural Nb foil of 20ߙmg/cm 2 thickness was irradiated with 32ߙMeV 7 Li beams to attain the yield of ∼1ߙMBq/μAߙh for 97 Ru. The no-carrier-added 97 Ru was separated from the bulk niobium by liquid–liquid extraction (LLX) and solid–liquid extraction (SLX) techniques. Liquid cation exchanger, di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane was used in LLX and solid cation exchanger, DOWEX-50 was used for SLX in HCl. The LLX technique was found to be superior to the SLX technique with respect to radiochemical yield and purity of the radionuclide 97 Ru.

The visualization of cyclin-dependent kinases (CDKs), which are overexpressed in multiple tumor types, with radiolabeled CDK inhibitors by means of positron emission tomography in vivo is a promising approach for tumor imaging. Pyrido[2,3- d ]pyrimidines belong to a class of inhibitors, which bind with high affinity to CDK4 and CDK6. 1-(3-[ 18 F]Fluoropropyl)-4-(4-nitrophenyl)piperazine and 1-(3-[ 18 F]fluoropropyl)-4-(6-nitropyridin-3-yl)piperazine represent structural elements of the appropriate CDK inhibitors and were therefore chosen as model compounds for the incorporation of fluorine-18 into pyrido[2,3- d ]pyrimidines. Three methods are known for the preparation of tertiary 3-[ 18 F]fluoropropyl-amines: 1) the direct substitution of a good leaving group, 2) the two-step reaction synthesizing a 3-[ 18 F]fluoropropyl intermediate, and 3) the utilization of aziridinium or azetidinium salts. In general, radiofluorinations using azetidinium salts lead to excellent radiochemical yields in short periods of time. For these reasons, we developed a synthesis route to tosylated piperazine precursors and established a radiolabeling approach based on the incorporation of fluorine-18 into open-chained tosylates as well as the respective azetidinium spiro compounds to yield the desired radiofluorinated piperazines successfully.