Volume 109, Issue 7

The (n,α) and (n,p) cross-sections and their isomeric ratios ( σ m / σ g ) were measured at 13–15 MeV for 92 Mo and 95 Mo by activation and off-line γ-ray spectrometry. The activated Mo samples combined with Al foils were used to obtain the cross-section values and the neutron flux, generated using the 3 H( d,n ) 4 He reaction. The cross-sections of the ground states were obtained using the metastable state absolute cross-sections and the residual nuclear decay rule. The excitation functions, total cross-sections, and isomeric ratios for the 92 Mo(n,α) 89m,g Zr and 95 Mo(n,p) 95m,g Nb reactions were calculated using the TALYS-1.95 software. 92 Mo(n,α) 89m + g Zr and 95 Mo(n,p) 95m + g Nb reaction excitation functions were obtained using the EMPIRE-3.2.3 package. These simulation results were compared with the corresponding experimental data and with the evaluated data from the ENDF/B-VIII.0, JEFF-3.3, CENDL-3, and ROSFOND libraries. Only partial agreements were observed.

75 Se (T 1/2  = 120 d), 73g Se (T 1/2  = 7.1 h) and 72 Se (T 1/2  = 8.4 d) are important radioisotopes of selenium, being used in tracer studies, PET investigations and as a generator parent, respectively. Cross section data for the formation of those radionuclides in proton and deuteron induced reactions on 75 As were critically analyzed up to about 70 MeV. A well-developed evaluation methodology was applied to generate the statistically fitted cross sections, based on the critically analyzed literature experimental data and the theoretical cross section values of three nuclear model codes ALICE-IPPE, TAYLS 1.9, and EMPIRE 3.2. Using the fitted cross sections the integral yield of each radionuclide was calculated. For the estimation of impurities, the integral yield of each radionuclide was compared with the yields of the other two radionuclides over a given energy region, and therefrom the energy range was suggested for the high purity production of each of the radionuclides 75 Se, 73 Se and 72 Se. For production of the very important non-standard positron emitter 73 Se via the 75 As(p,3n) 73 Se reaction, the optimum energy range was deduced to be E p  = 40 → 30 MeV, with a thick target yield of 1441 MBq/μAh and the 72,75 Se impurity level of <0.1%.

Plutonium(IV) sorption onto quartz in carbonate solutions was systematically investigated under anaerobic conditions to analyze the sorption behaviors of Pu(IV) with a non-electrostatic model (NEM). Pu(IV) sorption data was obtained from batch sorption experiments as a function of pH and carbonate concentration. The Pu(IV) sorption onto quartz showed similar tendencies to Th(IV), which is considered to be chemically analogous as a tetravalent actinoid. The distribution coefficient, K d , of Pu(IV) onto quartz showed inverse proportionality to the square of the total carbonate concentration under the investigated pH conditions of 8–11. The modeling study, however, revealed a Th(IV) sorption model, which is ≡SOTh(OH) 4 − and ≡SOThOH(CO 3 ) 2 2− , could not be applied to simulate the Pu(IV) sorption onto quartz. It was inferred that the electrostatic repulsion between negatively charged ligands limited the formation of ≡SOM(OH) 4 − and ≡SOMOH(CO 3 ) 2 2− for Pu(IV) with smaller ionic radii than Th(IV). The Pu(IV) sorption model was developed as ≡SOPu(OH) 3 and ≡SOPu(OH) 4 − . In addition, data of Pu(IV) sorption onto muscovite was obtained in order to be compared with data for quartz.

The complexation of Cm(III) with the recombinant human serum albumin (rHSA) (characterized by single deletion of residue Asp-1), is studied in dependence of pH and rHSA concentration using time-resolved laser fluorescence spectroscopy (TRLFS). A Cm(III) rHSA species is formed between pH 6.4 and 10.0 with the conditional stability constant being logK = 6.47 at pH = 7.4. Competition titration experiments with Cu(II) and Zn(II) confirm complexation at the N-terminal binding site (NTS) of rHSA and exclude the involvement of the Multi-Metal Binding Site (MBS). Comparison with a previous study on Cm(III) interaction with native albumin, HSA, points out, that residue Asp-1 is involved in Cm(III) binding to HSA but is not crucial for Cm(III) complexation at the NTS. The results are of major importance for a better understanding of fundamental actinide-protein interaction mechanisms which are highly required for the identification and characterization of relevant distribution pathways of incorporated radionuclides.

The optimization and validation of a procedure for the determination of tritium from gaseous effluents from a nuclear power plant is described. Optimization included performance assessment of silica gel and a molecular sieve as a material for the adsorption of water moisture from air for continuous tritium sampling. In addition, the usability of such a system for monitoring tritium in laboratory air for low-level tritium measurements was assessed. The molecular sieve showed better performance, with an average desorption efficiency of 95% compared to 78% achieved with silica gel. The memory effect was also lower and more reproducible for the molecular sieve, amounting to 7% on average compared to 35% attained for silica gel. Measurement of low-level tritium in air showed the importance of prior checks of intrinsic tritium levels in the molecular sieve as due to that erroneous results could be produced.

From extraction experiments, the exchange extraction constants corresponding to the general equilibriums M + (aq) + NaL + (org) ⇔ ML + (org) + Na + (aq) or M + (aq) + CsL + (org) ⇔ ML + (org) + Cs + (aq), which take place in the two-phase water–nitrobenzene extraction system (M +  = Li + , H 3 O + , Ag + , K + , NH 4 + , Tl + , Rb + ; L = calix[4]arene-bis crown5(1,3- alternate ), 26,28-dipropoxycalix[4]arene-crown-5(1,3- alternate ), 11,23-dibromo-25,28-dipropoxycalix[4]arene-crown-5 (1,3- alternate ) and 1,3- alternate -25,27-dihydroxycalix[4]arene-crown-5; aq = aqueous phase, org = organic phase), were evaluated. The stability constants of the NaL + and CsL + complexes were calculated from the extraction of the respective picrates in the system of water–nitrobenzene solution of L. Further, the stability constants of the ML + complexes in nitrobenzene saturated with water were determined. High selectivities were found in some systems under study.

18 F-fluorination using aluminum-fluoride ([ 18 F]AlF) chelate technique has been reported to give a low-to-moderate radiochemical yield, between 5 and 20%. Therefore, the work described here outlines the optimum 18 F-fluorination condition for the formation of [ 18 F]AlF 2+ and [ 18 F]AlF-NOTA-NHS complex with the radiochemical yield (RCY) and purity (RCP) of more than 90% as a prerequisite step before proceeding with the radiopharmaceutical preparation using the [ 18 F]AlF-bifunctional chelator technique. As well as being simple, the suggested method is practical and relevant for beginners interested in 18 F-fluorination with [ 18 F]AlF-chelate complex technique or also for a researcher who aims to proceed on an extensive scale.

This study presents development and characterization of a radiotracer, [ 125 I]iodonefiracetam ([ 125 I]iodoNEF). Labeling with high yield and radiochemical purity was achieved through the formation of a [ 125 I]iodoNEF radiotracer after investigating many factors like oxidizing agent content (chloramines-T (Ch-T)), substrate amount (Nefiracetam (NEF)), pH of reaction mixture, reaction time and temperature. Nefiracetam (NEF) is known as nootropic agent, acting as N -methyl- d -aspartic acid receptor ligand (NMDA). The radiolabeled compound was stable, and exhibited the logarithm of the partition coefficient (log p ) value of [ 125 I]iodonefiracetam as 1.85 (lipophilic). Biodistribution studies in normal mice confirmed the suitability of the [ 125 I]iodoNEF radiotracer as a novel tracer for brain imaging. High uptake of 8.61 ± 0.14 percent injected dose/g organ was observed in mice