Search Results
Abstract
The k 0-method of standardisation for instrumental neutron activation analysis (INAA) has been used at the OPAL research reactor to determine the elemental composition of three certified reference materials: coal fly ash (SRM 1633b), brick clay (SRM 679) and Montana soil (SRM 2711). Of the 41 certified elements in the three materials, 88 percent were within five percent of the certified values and all determinations were within 15 percent of the certified values. The average difference between the measured and certified values was 0.1 percent, with a standard deviation of 4.1 percent. Since these reference materials are widely used as standards in the analysis of archaeological ceramics by INAA, it has been concluded that the INAA facility in Australia is particularly well-suited for nuclear archaeometry.
Abstract
The radiochemical separation of the different radionuclides (64Cu, 67Cu, 67Ga, 66Ga, 56Ni, 57Ni, 55Co, 56Co, 57Co, 65Zn, 196Au) induced in the Ni supported Cu substrate — 68Zn target system, which was bombarded with the 29.0 MeV proton beam, was performed by ion-exchange chromatography using successive isocratic and/or concentration gradient elution techniques. The overlapped gamma-ray spectrum analysis method was developed to assess the 67Ga and 67Cu content in the 64Cu product and even in the post-67Ga production 68Zn target solution without the support of radiochemical separation. This method was used for the assessment of 64+67Cu radioisotope separation from 67Ga, the quality control of 64Cu product and the determination of the 68Zn (p,2p)67Cu reaction yield. The improvement in the targetry and the optimization of proton beam energy for the 68Zn target based 64Cu and 67Ga production were proposed based on the stopping power and range of the incident proton and on the excitation functions, reaction yields and different radionuclides induced in the target system.
Abstracta
The preparation of the OASIS®-HLB sorbent based solid phase extraction (SPE) resins and their application for the 177Lu radioisotope separation were investigated. Di-(2-ethylhexyl) orthophosphoric acid (HDEHP) impregnated OASIS-HLB sorbent based SPE resins (OASIS-HDEHP) were successfully developed from this investigation. The wettable porosity structure of the moderately extractant impregnated OASIS-HDEHP resins is favorable for the effective diffusion of polar and ionic solutes giving good separation performance. Its good wetting ability offers ease of packing into conventional chromatographic columns. Their off-gassing-free operation makes OASIS-HDEHP columns good for long term use with highly consistent elution dynamics (several dozens of separations perfectly achievable on the same column). The simple method for the capacity factor (k’) evaluation was developed to facilitate the characterization of the SPE chromatographic resin column. A competent procedure using OASIS-E30RS resin (one member of the OASIS-HDEHP resin group) for the separation of no-carrier added (n.c.a) 177Lu from the bulk amount of Yb target was developed. This separation procedure has showed very good performance with several prominent advantages such as the much shorter separation time (5–6 hours) and high reproducibility. Its high adsorption capacity for Yb and Lu makes it ideal for the separation of the bulky sample (50 mg Yb target for the 20 g weight resin column) for the production of the several Ci of 177Lu radioactivity.
Alternative chromatographic processes for no-carrier added 177Lu radioisotope separation
Part I. Multi-column chromatographic process for clinically applicable
Abstract
The conventional multi-column solid phase extraction (SPE) chromatography technique using di-(2-ethylhexyl)orthophosphoric acid (HDEHP) impregnated OASIS-HLB sorbent based SPE resins (OASIS-HDEHP) was developed for the separation of no-carrier added (n.c.a) 177Lu from the bulk quantity of ytterbium target. This technique exploited the large variation of lutetium metal ion distribution coefficients in the varying acidity of the HCl solution-OASIS-HDEHP resin systems for the consecutive loading-eluting cycles performed on different columns. The production batches of several hundred mCi n.c.a 177Lu radioisotope separated from 50 mg Yb target activated in a nuclear reactor of medium neutron flux (Φ = 5·1013 n·cm−2·s−1) were successfully performed using the above mentioned separation technique. With the target irradiation in a reactor of thermal neutron flux Φ = 2·1014 n·cm−2·s−1 or the parallel run of several separation units, many Ci-s of n.c.a 177Lu can be profitably produced. The OASIS-HDEHP resin based multi-column SPE chromatography technique makes the separation process simple and economic and offers an automation capability for operation in highly radioactive hazardous environments.
Alternative chromatographic processes for no-carrier added 177Lu radioisotope separation
Part II. The conventional column chromatographic separation combined with HPLC for high purity
Abstract
HPLC technique combined with the simple conventional column solid phase extraction (SPE) chromatography using di-(2-ethylhexyl)orthophosphoric acid (HDEHP) impregnated OASIS-HLB sorbent based SPE resins (OASIS-HDEHP) was developed for the separation of no-carrier added (n.c.a) 177Lu from the bulk quantity of ytterbium target. This combination strategy was based on combining the advantages of the better resolution of HPLC separation of n.c.a 177Lu from the few milligram level Yb target with the high capacity of the OASISHDEHP column for the separation of 177Lu from the bulk Yb target. The production batches of several hundred mCi activity of n.c.a 177Lu radioisotope separated from 50 mg Yb target activated in a nuclear reactor of medium neutron flux (Φ=5·1013 n·cm−2·s−1) were successfully performed using this combined separation technique. With the target irradiation in a reactor of higher thermal neutron flux or with the parallel run of several separation units, several Ci-s of n.c.a 177Lu can be profitably produced on a commercial production basis.
Nucleophilic [18F]-fluorination reactions traditionally include a drying step of the labeling agent in order to achieve a successful substitution. This passage extends the time and complexity required for the whole radiotracer production, with increased hardware and detrimental effects on the radioactive recovery of such a short-lived (t ½=109 min) isotope. Because the performance of radiofluorination reactions conducted under microfluidic flow conditions have been demonstrated to be more effective in terms of reaction time and yields, we have tested the tolerance to water present in this specific reaction condition, in view of eliminating the drying step in the process. To this purpose, we tested different substrates selected from typical radiofluorination intermediates. Our results show that water could be tolerated in a microfluidic environment; in particular, we observed a slight decrease in the labeling of aromatic precursors and a significant increase for iodonium salts, whereas the radiochemical yields of the other compounds studied were virtually unchanged. These findings may open the way to the possibility of simpler and faster processes for the production of new 18F-fluorinated positron emission tomography tracers.
Abstract
The positron density distributions in C60 and K6C60 have been evaluated using the positron lifetime and Doppler-broadening spectroscopy for the annihilation radiation.In C60, positrons are distributed in the interstitial sites between the C60 molecules,which has been demonstrated by measurements of the temperature dependence of the Doppler-broadening of the annihilation radiation. On the other hand, the positron density distribution must be greatly changed in K6C60, because positrons are repelled by Coulomb interactions by the positively charged K atoms. It has been observed that there is an extremely short lifetime and a small Doppler-broadening component for the positron annihilation in K6C60. This component is considered to reflect the positron annihilation inside a C60 molecule.
Abstract
Neutron activation analysis, inductively coupled plasma emission spectrometry(ICP-ES) and atomic absorption spectroscopy (AAS) have been used to determineactual daily dietary intakes of minerals and trace elements in the Iranianpopulation. This article deals with the trace elemental analysis of dailydiets of the Iranian population differentiated with respect to food habits,geographical variability, literacy and income. Three study groups in fiveregions were defined. Thirty total daily diet samples were prepared basedon the method of dietary records. Also a few samples representing the intakesof two other study groups, males and females, were prepared by the duplicatediet method. Therefore, this study not only covered representative dietarypatterns of almost all adult people in Iran in a pilot study, but it alsopermitted to check the validity of the sampling methodology for total mixeddiet simulation.
Abstract
Acid leaching of uranium deposits is not a selective process. Sulfuric acid solubilizes iron(III) and half or more of the thorium depending on the mineralog of this element. In uranium recovery by solvent extraction process, uranium is separated from iron by an organic phase consisting of 10 vol% tributylphosphate(TBP) in kerosine diluent. Provided that the aqueous phase is saturated with ammonium nitrate or made 4–5 M in nitric acid prior to extraction. Nitric acid or ammonium nitrate is added to the leach solution in order to obtain a uranyl nitrate product. Leach solutions containing thorium(IV) besides iron are treated in an analogous fashion. Uranium can be extracted away from thorium using 10 vol% TBP in kerosine diluent. The aqueous phase should be saturated with ammonium nitrate and the pH of the solution lowered to 0.5 with sufficient amount of sulfuric acid. In other words, the separation of uranium and thorium depends on the way the relative distributions of the two materials between aqueous solutions and TBP vary with sulfuric acid concentration. Thorium is later recovered from the waste leach liquor, after removal of sulfate ions. Uranium can be stripped from the organic phase by distilled water, and precipitated as ammonium diuranate.
Abstract
Three Iranian natural zeolites were characterized and evaluated for their abilities to take up Ba+2, Ca+2, K+ and Na+ from radioactive waste waters. The distribution coefficient values (K d ) of the cations were measured and investigated as a function of pH. Four different cationic forms (Na, K, NH4, and Ca) were also prepared and theirK d values were determined. Some cations such as potassium presented highK d values both in natural and exchanged zeolites. In sodium and ammonium exchanged forms theK d values increased between 7 to 100 times with respect to the untreated zeolite.
