Band 101, Heft 2 -

Excitation functions of the reactions nat Te( p , xn ) 123,124,126,130 I were measured from their respective thresholds up to 17 MeV. The conventional stacked-foil technique was used where the samples for irradiation were prepared by a sedimentation process. The measured excitation functions were compared with both the data available in the literature and the results of theoretical calculations using the codes TALYS-1.2 and ALICE-IPPE. The present experimental data show good agreement with TALYS-1.2 calculations but some deviations from ALICE-IPPE results. From the experimental data the integral yields of the investigated radionuclides were calculated as a function of the proton energy. The most dominating product is 130 I.

The present paper describes the speciation of Am(III)/Eu(III) sorbed on γ -alumina, and its evolution with changing metal ion concentration, studied using batch sorption experiment, time resolved fluorescence spectroscopy (TRFS), extended X-ray absorption fine structure (EXAFS) and surface Complexation modeling (SCM). Though numerous studies exist in the literature on the speciation of trivalent actinides and lanthanides on alumina surface, the mechanism of sorption at high metal ion concentrations is not yet fully understood. Batch sorption experiments of Am(III) on γ -alumina under varying condition of pH (3–10), ionic strength (0.005–0.1 M NaClO 4 ) and metal ion concentration (10 −7 –10 −4  M) were performed. Higher metal ion concentration was achieved by the addition of Eu(III) considering it as an analogue of Am(III). Time resolved fluorescence spectroscopy (TRFS) study of Eu(III) sorbed on γ -alumina at the metal ion concentration of 5.0 × 10 −5  M was carried out over pH 4 to 7. TRFS showed the presence of two surface species, with distinctly different fluorescence decay life times. The shorter lifetime value and its changing pattern with pH indicate the surface species corresponding to this component to be monodentate species >AlOAm 2+ and its hydrolyzed forms. The sorbed Eu 3+ species corresponding to the longer lifetime value has 2–3 water molecules in its first coordination sphere and is multidentate in its binding on alumina surface. Extended X-ray absorption fine structure (EXAFS) measurement of Eu: γ -Al 2 O 3 sorption systems at pH 6.18 and 7.15 corroborate the existence of two surface complexes. Further it suggests the edge sharing bidentate binding of Eu on AlO 6 octahedra as the co-ordination mode of the higher lifetime component. Surface Complexation Modeling (SCM) of Am(III)/Eu(III) sorption onto γ -alumina at pH ≤ 7 has been carried out using these two surface species. 2-p K surface complexation modeling coupled with constant capacitance model for surface charge, revealed monodentate surface speciation as the predominant species at 10 −7 –10 −6  M, while at 10 −5  M, above pH 5.5, bidentate surface species starts to compete with monodentate speciation, and becomes the predominant surface species of Am(III)/Eu(III) on alumina surface at 10 −4  M.

The present study describes a correlation that is developed from retention of lanthanide and actinide complexes with the stability constant. In these studies, an ion-pairing reagent, camphor-10-sulphonic acid (CSA) was used as the modifier and organic acids such as α -hydroxy isobutyric acid ( α -HIBA), mandelic acid, lactic acid and tartaric acid were used as complexing reagent for elution. From these studies, a correlation has been established between capacity factor of a metal ion, concentration of ion-pairing reagent and complexing agent with the stability constant of metal complex. Based on these studies, it has been shown that the stability constant of lanthanide and actinide complexes can be estimated using a single lanthanide calibrant. Validation of the method was carried out with the complexing agents such as α -HIBA and lactic acid. It was also demonstrated that data from a single chromatogram can be used for estimation of stability constant at various ionic strengths. These studies also demonstrated that the method can be applied for estimation of stability constant of actinides with a ligand whose value is not reported yet, e.g. , ligands of importance in the lanthanide–actinide separations, chelation therapy etc. The chromatographic separation method is fast and the estimation of stability constant can be done in a very short time, which is a significant advantage especially in dealing with radioactive elements. The stability constant data was used to derive speciation data of plutonium in different oxidation states as well as that of americium with α -HIBA. The elution behavior of actinides such as Pu and Am from reversed phase chromatographic technique could be explained based on these studies.

N , N ´-dimethyl- N , N ´-dioctyl-2,(2´-hexyloxyethyl) malonamide (DMDOHEMA) has been synthesized by a relatively simpler route with a better yield than the conventional procedures for the synthesis of pentaalkyl substituted diamides. The proposed route replaces the use of acid chlorides and brominating agents (corrosive in nature) by acid diester and p -toluene sulphonyl (tosyl) chloride, respectively. The later easily replaces hydrogen from primary OH group of the 3-oxanonyl side chain and relatively less corrosive. The synthesized product has been tested for the extraction behavior of 241 Am, Np, Pu as pure tracers as well as under Pressurized Heavy Water Reactor (PHWR) Simulated High-Level Waste (SHLW) conditions. The stoichiometries of extracted species of Np(IV), Pu(IV), and Am(III) from 3 M HNO 3 using varying concentrations of DMDOHEMA in n -dodecane has been determined. The effect of the nature of mineral acid ( viz. HCl, HNO 3 , and HClO 4 ) on the extraction of Am(III) has also been investigated employing DMDOHEMA and N , N ´-dimethyl- N , N ´-dibutyl-tetradecyl malonamide (DMDBTDMA) as extractants and explained in terms of the aggregation behavior of diamides. The performance of DMDOHEMA has been evaluated vis-à-vis other proposed extractants for actinide partitioning under PHWR-SHLW conditions.

A layered double hydroxides (LDH) hydrotalcite-pyroaurite solid solution series (Mg 1− x Fe(II) x ) 3 Al 1 Cl 1 · n H 2 O with variable x Fe solid = Fe 2+ /(Fe 2+ +Mg 2+ ) iron mole fractions were studied in co-precipitation experiments at T = 25, 40, 45, 50, 55 and 60 ºC and pH = 10.00 ± 0.05. The compositions of the solids and reaction solutions were determined using ICP-OES, EDX (Mg, Al, Fe) and TGA techniques (Cl − , OH − , H 2 O). Powder X-ray diffraction was applied for phase identification and determination of unit-cell parameters a o = b o and c o from Bragg evaluation. Syntheses products containing x Fe solid > 0.13 display additional X-ray patterns attributed to the mixture of iron oxides and hydroxides. On the other side, precipitates with 0 ≤ x Fe solid ≤ 0.13 show only X-ray reflexes typical for pure LDH compositions. Moreover, in this case unit-cell parameters a o = b o as a function of x Fe solid follow Vegard's law corroborating the existence of a continuous solid solution series. TGA data demonstrated the temperatures at which interlayer H 2 O molecules and Cl − -anions are lost, and at which temperatures dehydroxylation of brucite-like layer occurs. Based on detailed analyses of TGA curves it was established that the increase of x Fe solid does not result in a visible change of the thermal stability of hydrotalcite-pyroaurite solids. From the chemical analyses of both the solids and the reaction solutions after syntheses, preliminary Gibbs free energies of formation were estimated by using GEMS-PSI code package. Values of G º f (Hydrotalcite) = −3619.04 ± 15.27 kJ/mol and G º f (Pyroaurite) = −2703.61 ± 191.93 kJ/mol were found at 298.15 K. A comparison of our estimate with G º f value −3746.90 ± 11.00 kJ/mol for CO 3 2− -bearing hydrotalcite presented in our previous studies, denotes the effect of intercalated anion on the aqueous solubilities of LDH when Cl-containing solids have to be more soluble than CO 3 2− -bearing substances. Estimation of the standard molar entropy of the hydrotalcite end-member by applying Helgeson's methods and using results of co-precipitation experiments at variable temperatures let us to conclude that derivation of more precise S º f values would require calorimetric measurements.

This paper presents the experimental determination of the stability constant for the citrate complexes with TcO(OH) + and TcO(OH) 2 0 at different ionic strengths (NaCl), using a solvent extraction method. Data show that the stability constants for the formation of TcO(OH)Cit 2− and TcO(OH) 2 Cit 3− are 10 7.5 ± 0.2 and 10 2.8 ± 0.2 , respectively, at zero ionic strength, with an average of 10 6.5 ± 0.3 and 10 2.8 ± 0.2 , respectively, in the 1.0–3.0 M ionic strength range. PHREEQC calculations based on these stability constants show that the TcO(OH)Cit 2− is the predominant species between pH 3 and 8 and that 50 mM citrate leads to a Tc(IV) solubility of 2 × 10 −5  M at pH 5.

The complexation of rhenium, to the polyamino-polycarboxylate EDTA was investigated using Raman spectroscopy. Complexation occurred when Re VII O 4 - was placed in the presence of a Sn(II) reducing agent and EDTA. Rhenium complexation was confirmed by the Raman and UV/Vis spectra of the solution samples. Binding modes were assigned using the Raman spectra of a solid-phase sample. Three complexes are proposed, a six-coordinate dimer H 4 [Re 2 (μO) 2 (EDTA) 2 ], a seven-coordinate monomer H 2 [ReO(EDTA)(OH 2 ) 2 ] and a mono-oxorhenium [ReO(EDTA)] 2- . The solubility of Re(IV)-EDTA complexes is greater than that of ReO 4 . If this behaviour is analogous to Tc, it is proposed that complexation to EDTA by Tc(IV) may increase the solubility and enhance the environmental transport of 99 Tc from geological repositories.

The aim of this study is to radiolabel ganciclovir, known as having selective antiviral properties against thymidine kinase, with technetium tricarbonylcore ( 99m Tc(CO) 3 + ) and to investigate the biological behavior of this complex in vitro and in vivo . Commercially provided Ganciclovir (GCV) was radiolabeled with 99m Tc(CO) 3 + . Initially, optimum radiolabeling conditions were determined by analyzing factors such as temperature, pH and time. Quality control of the radiolabeled compound was performed. The radiolabeling yield was found to be 97%. The 99m Tc(CO) 3 -GCV complex also displayed good in vitro stability during the 24 h period. In vitro cell uptake studies showed that the 99m Tc(CO) 3 -GCV complex is highly uptaken in A-549, PC-3, HeLa cell lines according to the control group 99m Tc(I)-tricarbonyl core. The knowledge gained from in vivo and in vitro studies of 99m Tc(CO) 3 -GCV could contribute to the development of a new HSV1-tk gene imaging agent.

The thin layer activation (TLA) technique was applied to study the surface erosion of zircaloy clad material during laser ablation process by producing a suitable γ -ray emitting radioisotope in the clad surface using 40 MeV α -particles. This paper reports the rate of surface erosion of zircaloy as a function of deposited laser energy in the range of a few hundred of millijoules to a few kilojoule. The minimum detection limit was found to be 80 ± 25 nm in the measurement of surface loss of material due to laser exposure by TLA technique.