RESUMO
In this study, distillation, precipitation, and ion-exchange methods were chosen for the separation of the long-lived ß-emitters 129I, 36Cl and the α-emitters 154Dy, 148Gd, 150Gd, and 146Sm from Ta targets irradiated with protons up to 2.6 GeV to determine their production cross sections. Measurements of 129I/127I and 36Cl/35Cl ratios were performed with accelerator mass spectrometry. After separation of the lanthanides, the molecular plating technique was applied to prepare thin samples to obtain highly resolved α-spectra. Autoradiography and focused ion beam/scanning electron microscopy techniques were used to characterize the lanthanide deposited layer. Experimental cross-section data are compared with theoretical predictions obtained with INCL++ and ABLA07 code, and a satisfactory agreement is observed.
RESUMO
Accelerator driven fast nuclear reactors cooled by lead-bismuth eutectic (LBE) are developed for transmuting long-lived radionuclides in spent nuclear fuel. Due to the nature of the coolant, operating the reactor will result in a production of 210Po by neutron capture. Understanding the behavior of this highly radiotoxic nuclide in the event of a failure of the window separating the evacuated proton beam guide from the reactor core is required for safety assessments. The present work aims at acquiring this knowledge by studying the evaporation of polonium from neutron-irradiated LBE and its deposition in a scaled down model of the beam tube. Experimental results along with Monte Carlo simulations indicate that polonium adsorbs as a single species with an adsorption enthalpy of approximately -156 kJ/mol.
RESUMO
BACKGROUND: 161Tb is an interesting radionuclide for cancer treatment, showing similar decay characteristics and chemical behavior to clinically-employed 177Lu. The therapeutic effect of 161Tb, however, may be enhanced due to the co-emission of a larger number of conversion and Auger electrons as compared to 177Lu. The aim of this study was to produce 161Tb from enriched 160Gd targets in quantity and quality sufficient for first application in patients. METHODS: No-carrier-added 161Tb was produced by neutron irradiation of enriched 160Gd targets at nuclear research reactors. The 161Tb purification method was developed with the use of cation exchange (Sykam resin) and extraction chromatography (LN3 resin), respectively. The resultant product (161TbCl3) was characterized and the 161Tb purity compared with commercial 177LuCl3. The purity of the final product (161TbCl3) was analyzed by means of γ-ray spectrometry (radionuclidic purity) and radio TLC (radiochemical purity). The radiolabeling yield of 161Tb-DOTA was assessed over a two-week period post processing in order to observe the quality change of the obtained 161Tb towards future clinical application. To understand how the possible drug products (peptides radiolabeled with 161Tb) vary with time, stability of the clinically-applied somatostatin analogue DOTATOC, radiolabeled with 161Tb, was investigated over a 24-h period. The radiolytic stability experiments were compared to those performed with 177Lu-DOTATOC in order to investigate the possible influence of conversion and Auger electrons of 161Tb on peptide disintegration. RESULTS: Irradiations of enriched 160Gd targets yielded 6-20 GBq 161Tb. The final product was obtained at an activity concentration of 11-21 MBq/µL with ≥99% radionuclidic and radiochemical purity. The DOTA chelator was radiolabeled with 161Tb or 177Lu at the molar activity deemed useful for clinical application, even at the two-week time point after end of chemical separation. DOTATOC, radiolabeled with either 161Tb or 177Lu, was stable over 24 h in the presence of a stabilizer. CONCLUSIONS: In this study, it was shown that 161Tb can be produced in high activities using different irradiation facilities. The developed method for 161Tb separation from the target material yielded 161TbCl3 in quality suitable for high-specific radiolabeling, relevant for future clinical application.