Application of mercury isotopes and their production

Mercury isotopes are now broadly applied in various fields of science and technology. They are used in medicine, nuclear physics investigations, RF standards, nuclear gyroscopes, mercury analysing devices etc. One of the most promising applications is the use of weakly enriched (up to 3%) isotope¹⁹⁶Hg in fluorescent lamps for enhancing their light efficiency. Besides, the application of²⁰¹Hg and²⁰²Hg as the target material for the production at low-energy cyclotrons of one of the most consumed²⁰¹Tl isotope in medicine seems to be perspective. Various methods were proposed and examined for the separation of mercury isotopes. There are: electromagnetic, photochemical, centrifugal, laser, photoionizing method etc. But only two of them were effective for the mercury isotope separation: electromagnetic and photochemical ones. This paper presents a review of the experimental results on separation of various mercury isotopes by different methods.     

Cross-section calculations of proton induced (p,n) and (p,2n) reactions for production of diagnostic 67Ga, 81Rb, 111In, 123,124I, 123Cs and 123Xe radioisotopes

Investigation of pre-equilibrium (PEQ) and equilibrium (EQ) effects on proton induced reactions for production of radioisotopes are very important. Therefore, in this study, we have calculated the PEQ and EQ cross-sections for ⁶⁷Zn(p,n)⁶⁷Ga, ⁶⁸Zn(p,2n)⁶⁷Ga, ⁸²Kr(p,2n)⁸¹Rb, ¹¹¹Cd(p,n)¹¹¹In, ¹¹²Cd(p,2n)¹¹¹In, ¹²³Te(p,n)¹²³I, ¹²⁴Te(p,2n)¹²³I, ¹²⁴Te(p,n)¹²⁴I and ¹²⁴Xe(p,2n)¹²³Cs reactions for production diagnostic radioisotopes. Calculations have been performed by using the hybrid model, geometry dependent hybrid model and full exciton model of PEQ reaction mechanism with 1–40 MeV proton incident energy. We have also investigated the EQ effects on these reactions using the Weisskopf–Ewing model in the same energy range. The excitation functions including the PEQ and EQ effects on these reactions are evaluated by using the ALICE/ASH (2006) and the TALYS 1.4 (2011) codes. Our results have shown that using these codes is suitable for production diagnostic isotopes mentioned above. To obtain excitation functions for producing the diagnostic radioisotopes the PEQ mechanism has been found more dominant than that of the EQ. The results are discussed and compared with the available experimental data.     

Reaction mechanism for target-like products from197Au target bombarded with12C ions of energies above 100 MeV/u

Target-like products, that is,^191–200Au,^185–200Pt, and^183–195Ir, from¹⁹⁷Au target bombarded with¹²C ions at the energies of 180, 230, and 400 MeV/u were measured by using off-line gamma-ray spectrometry combined with chemical separation procedures. Spallation systematics by Rudstam reproduces well the measured cross sections for formation of platinum and iridium isotopes. It was found that the cross sections of gold nuclides increase with increase of the incident energy in the range studied and they are enhanced if compared with the reported proton-induced reaction of gold at a similar incident energy. It is suggested that the electromagnetic dissociation process plays a role for production of such gold nuclides.     

Separation of arsenic from germanium oxide targets by dry distillation

Positron-emitting isotopes of arsenic, ⁷⁰As (T _1/2 = 53 min), ⁷¹As (T _1/2 = 64 h), ⁷²As (T _1/2 = 26 h), and ⁷³As (T _1/2 = 17.8 d) are of interest in biomedical investigations using PET. A fast and simple method for their production using low-energy proton and deuteron reactions on enriched Ge-targets is presented. Dry distillation of GeO₂ at 1105 °C during 2 hours provides a separation efficiency of more than 60%. The loss of target material is less than one per cent and the irradiated targets can be used several times. The method allows production of diagnostically useful amounts of positron-emitting arsenic isotopes using accelerators commonly available at PET-centres.     

2,4-Difluoro anisole: a promising complexing agent for boron isotopes separation by chemical exchange reaction and distillation

Although methods of boron isotopes separation were intensively pursued about 60 years, the chemical exchange distillation is the only method that has been applied in industrial scale production of ¹⁰B. The present anisole BF₃ system suffers from the drawbacks like high melting point, relatively low separation coefficient and instability under reaction conditions, which demand a continuous search for more effective and efficient donors for boron isotope separation. A series of fluoro-substituted anisole derivatives were screened in this paper, among which 2,4-difluoro anisole exhibited good properties compared with anisole. Studies on the boron trifluoride and 2,4-difluoro anisole adduct, its thermodynamic and physical properties related to large-scale isotopic separation is reported. The results showed that 2,4-difluoro anisole is better than anisole in separation coefficient, freezing point and stability under pyrolysis conditions, which suggest a further detailed investigations on boron trifluoride and 2,4-difluoro anisole adduct.     

Preparative scale mass spectrometry: A brief history of the calutron

Calutrons were developed in the laboratory of E. O. Lawrence at the University of California at Berkeley. They were a modification of the cyclotrons he had invented and used in his Noble Prize winning investigations of the atomic nucleus. At the time their construction was undertaken, calutrons represented the only certain means of preparing enriched uranium isotopes for the construction of a fission bomb. The effort was successful enough that every atom of the 42 kg of ²³⁵U used in the first uranium bomb had passed through at least one stage of calutron separation. At peak production, the first stage separators, α tanks, yielded an aggregate 258-g/d ²³⁵U enriched to about 10 at. % from its natural abundance level of 0. 72 at. %. The second stage separators, β tanks, used the 10 at. % material as feedstock and produced a total 204-g/d ²³⁵U enriched to at least 80 at. %. The latter, weapons grade, material was used in fission bombs. Under typical operating conditions, each α tank operated at a uranium beam intensity at the collectors of approximately 20 mA and each β tank at a beam intensity of approximately 215 mA at the collectors. Bulk separation of isotopes for bomb production ceased in 1945. Since that time calutrons have been used to separate stable isotopes, but on a more limited scale than wartime weapons production. Stable isotope separations since 1960 have taken place using one modified beta tank.     

Preparative scale mass spectrometry: A brief history of the calutron

Calutrons were developed in the laboratory of E. O. Lawrence at the University of California at Berkeley. They were a modification of the cyclotrons he had invented and used in his Nobel Prize‐winning investigations of the atomic nucleus. At the time their construction was undertaken, calutrons represented the only certain means of preparing enriched uranium isotopes for the construction of a fission bomb. The effort was successful enough that every atom of the 42 kg of ²³⁵U used in the first uranium bomb had passed through at least one stage of calutron separation. At peak production, the first stage separators, α tanks, yielded an aggregate 258‐g/day ²³⁵U enriched to about 10 at. % from its natural abundance level of 0.72 at. %. The second stage separators, β tanks, used the 10 at. % material as feedstock and produced a total 204‐g/day ²³⁵U enriched to at least 80 at. %. The latter, weapons grade, material was used in fission bombs. Under typical operating conditions, each α tank operated at a uranium beam intensity at the collectors of approximately 20 mA and each β tank at a beam intensity of approximately 215 mA at the collectors. Bulk separation of isotopes for bomb production ceased in 1945. Since that time calutrons have been used to separate stable isotopes, but on a more limited scale than wartime weapons production. Stable isotope separations since 1960 have taken place using one modified β tank.     

Stable isotope enrichment capabilities at Oak Ridge National Laboratory

The Oak Ridge National Laboratory (ORNL) and the US Department of Energy—Nuclear Physics Program have built a high-resolution electromagnetic isotope separator (EMIS) as a prototype for reestablishing a US-based enrichment capability for stable isotopes. ORNL has over 60 years of experience providing enriched stable isotopes and related technical services to the international accelerator target community, as well as medical, research, industrial, national security, and other communities. ORNL is investigating the combined use of electromagnetic and gas centrifuge isotope separation technologies to provide research quantities (milligram to several kilogram) of enriched stable isotopes. In preparation for implementing a larger scale production facility, a 10 mA high-resolution EMIS prototype has been built and tested. Initial testing of the device has simultaneously collected greater than 98 % enriched samples of all the molybdenum isotopes from natural abundance feedstock.     

Neutron activation analysis of tin in biological materials and their ash using123Sn and125Sn

Tin has been determined in biological materials by NAA of the γ-emitting 40-min¹²³Sn and 9,7-min¹²⁵Sn isotopes at the sub-ppm level. For¹²³Sn, samples are wet-ashed after irradiation, whereas to allow fast radiochemistry for¹²⁵Sn, the samples are dry-ashed prior to the irradiation. Both separation techniques rely on selective solvent extraction of tin(IV) iodide, and NaI(TI) counting. Comparative analyses of several materials by both methods gave good agreement, indicating that tin is not lost on dry-ashing and that simple dissolution of the ash in an HCl?HI mixture is complete. Results by both techniques are presented for the standard materials Bowen's Kale and NBS Orchard Leaves, and for some other materials.     

The influence of distribution coefficients on the separation factor of lithium isotopes

The influence of distribution coefficients on the separation factor of lithium isotopes was studied with Dowex 50W-X8, 200–400 mesh, ammonium form, strongly acidic cation exchanger by changing the pH and EDTA concentration of the eluent. It was found that the larger the EDTA concentration in the buffer solution, the smaller the distribution coefficients were. The separation factor was increased with decreasing EDTA concentration. The separation factor of lithium isotopes linearly increased up to a distribution coefficient value of 30, and gradually increased above 30. The optimum value of distribution coefficient of lithium to separate litihium isotopes was about 30. The distribution coefficient was increased with increasing pH, but the separation factor of lithium isotopes has no relation with pH.⁶Li concentrated on the resin phase, and⁷Li in the solution phase.     

123I production at the Milan AVF cyclotron

The production of¹²³I from enriched¹²⁴Te is described. Preliminary experiments on a distillation separation of iodine from the Te target have been performed and the method seems promising in comparison to the time-consuming chemical separation technique.     

Experiences in the routine production of123I via the124Te(p, 2n)123I reaction with a low energy cyclotron

This paper deals with the results and experimental observations obtained in routine production of¹²³I via¹²⁴Te(p, 2n)¹²³I reaction, using the low energy cyclotron (protons, E_max=22 MeV) at the German Cancer Research Center in Heidelberg. The reaction was studied during the past 4 years using¹²⁴TeO₂ targets with various levels of enrichment. The purpose of the study was to determine which target material provided the highest quality and most economical production of¹²³I. A viable routine production was defined as one in which¹²³I could be conveniently and reproducably prepared in reasonable purity while maintaining a low cost for the entire process. Different methods of sublimation of¹²³I activity from the¹²⁴TeO₂ target were examined to determine the optimal conditions for recovery of radioactivity and recycling of target material. A rapid method is described which permits quantitative separation of¹²³I while allowing only a negligible loss of¹²⁴TeO₂.     

An ion chromatographic separation method for the sequential determination of <Superscript>90</Superscript>Sr, <Superscript>241</Superscript>Am and Pu isotopes in a urine sample

A radiobioassay method has been developed for the sequential determination of ⁹⁰Sr, ²⁴¹Am and Pu isotopes in a urine sample. Unlike the existing methods using multiple extraction chromatographic cartridges, this work demonstrates an application of an automated ion chromatographic (IC) system for the separation of these radionuclides on a single IC column. The method meets the bioassay performance criteria for relative bias and relative precision as recommended by ANSI/HPS N13.30-2011. The detection limits for the radionuclides are found to be satisfactory for medical intervention in case of an accidental exposure scenario. Sample preparation time is less than 11 h.     

Anion-exchange and solvent extraction studies on the separation of radioiodine with particular reference to the production of 123I via proton irradiation of 123Te metal target

The separation of radioiodine was investigated using two wet chemical procedures, namely anion-exchange and solvent extraction. Some factors affecting the separation, such as HCl, NaOH and tetrabutyl ammonium bromide (TBAB) concentrations, used solvents ethyl acetate, benzene and carbon tetrachloride and different quaternary ammonium salts were studied. For each procedure the optimum conditions were deduced. The separation of ¹²³I was effected from proton-irradiated ¹²³Te target under the optimized conditions of the two procedures. The yield of ¹²³I obtained using the Dowex 21k anion-exchanger and tetrabutyl ammonium bromide solution as eluting agent was 88±3%; the radionuclidic purity was high and the time needed was 60 minutes. In solvent extraction process using TBAB in ethyl acetate as the extracting agent, the yield of ¹²³I was low (47±3%), the radionuclidic purity was not as good as in the anion-exchange method, and the time needed was 150 minutes. Therefore, the anionexchange method is preferable. A comparison of this wet chemical method of separation of ¹²³I with the commonly used dry distillation method is given. The wet method appears to be more suitable when a ¹²³Te metal target is used.     

Yields of Photo-Proton Reactions on Nuclei of Nickel and Separation of Cobalt Isotopes from Irradiated Targets

Nowadays, cobalt isotopes ⁵⁵Co, ⁵⁷Co, and ^58mCo are considered to be promising radionuclides in nuclear medicine, with ⁵⁵Co receiving the most attention as an isotope for diagnostics by positron emission tomography. One of the current research directions is dedicated to its production using electron accelerators (via photonuclear method). In our work, the yields of nuclear reactions occurring during the irradiation of ^natNi and ⁶⁰Ni by bremsstrahlung photons with energy up to 55 MeV were determined. A method of fast and simple cobalt isotopes separation from irradiated targets using extraction chromatography was developed.     

Effect of humic acid,pH and ionic strength on the sorption of Eu(III) on red earth and its solid component

A highly sensitive separation procedure has been developed to investigate uranium and thorium activities and their isotopic ratios in environmental water samples in Tokushima, Japan. Uranium and thorium isotopes in environmental water samples were simultaneously isolated from interfering elements with extraction chromatography using an Eichrom UTEVA™ resin column. After the chemical separation, activities of U and Th isotopes coprecipitated with samarium fluoride (SmF₃) were measured by α-spectrometry. It has been confirmed that uranium isotopes are isolated successfully from thorium decay chains by analyzing a test aqueous solution as a simulation of an environmental water sample. The separation procedure has been first applicable to the determination of U and Th activities and their isotopic ratios in a drinking well water named “Kurashimizu” in Tokushima City, Japan. The specific activities of ²³⁸U and ²³²Th in “Kurashimizu” were deduced to be within the upper limits of <0.31 and <0.19 mBq/l, respectively.     

Rapid determination of actinides in urine by inductively coupled plasma mass spectrometry and alpha spectrometry: A hybrid approach

A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are split between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3 h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6 h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. ²³⁹Pu, ²⁴²Pu, ²³⁷Np, ²⁴³Am, ²³⁴U, ²³⁵U and ²³⁸U were measured by ICP-MS, while ²³⁶Pu, ²³⁸Pu, ²³⁹Pu, ²⁴¹Am, ²⁴³Am and ²⁴⁴Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred instead. Multiple vacuum box locations may be set-up to supply several ICP-MS units with purified sample fractions such that a high sample throughput may be achieved, while still allowing for rapid measurement of short-lived actinides by alpha spectrometry.     

Rapid column extraction method for actinides and 89/90Sr in water samples

Summary The SRS Environmental Laboratory analyzes water samples for environmental monitoring, including river water and ground water samples. A new, faster actinide and ^89/90Sr separation method has been developed and implemented to improve productivity, reduce labor costs and add capacity to this laboratory.This method uses stacked TEVA Resin^ò, TRU Resin^òand Sr-Resin^òcartridges from Eichrom Technologies (Darien, IL, USA) that allows the rapid separation of plutonium, neptunium, uranium, americium, curium and thorium using a single multi-stage column combined with alpha-spectrometry. By using vacuum box cartridge technology with rapid flow rates, sample preparation time is minimized. The method can be used for routine analysis or as a rapid method for emergency preparedness. Thorium and curium are often analyzed separately due to the interference of the daughter of ²²⁹Th tracer, actinium (²²⁵Ac) on curium isotopes when measured by alpha-spectrometry. This new method also adds a separation step using DGA Resin^ò, (diglycolamide resin, Eichrom Technologies) to remove ²²⁵Ac and allow the separation and analysis of thorium isotopes and curium isotopes at the same time.     

Production of123I and28Mg by high-energy nuclear reactions for applications in life sciences

The advantages of high energy cyclotrons as compared to small compact cyclotrons for the production of special radionuclides are outlined. The routine production of¹²³I (T=13.3 h) and²⁸Mg (T=21.1 h) by means of high energy nuclear reactions at the Jülich Isochronous Cyclotron is described. The reaction¹²⁷I(d,6n)^{123 123}I at 78 to 64 MeV is used for the production of¹²³I with thick target yields of 8 mCi/μAh and high radionuclidic purity. The practical experience in the application of this process, which is well suited for the production of Na¹²³I and for¹²³Xe-exposure labelling techniques, is reported.²⁸Mg is produced by the²⁷Al(α, 3p)²⁸Mg reaction at E_α=140 to 30 MeV with thick target yields of 40 μCi/μAh. The carrier-free²⁸Mg is separated from the matrix activities by coprecipitation and anion exchange with chemical yields of 80%.     

Simultaneous determination of Al,V, Mn and Cu from neutron-activated saline matrices by precipitation with poly-5-vinyl-8-hydroxyquinoline

Neutron Activation Analysis is a sensitive technique for the determination of more than seventy elements at the trace concentrations. The NAA analysis of biological and environmental matrices suffers from interferences caused by the presence of high concentrations of activated salts in these matrices. The high gamma-ray activities of these activated salts mask the low gamma-ray activities of short half-lived isotopes (e.g.,⁶⁶Cu,⁵⁶Mn,²⁸Al and⁵²V) necessitating the rapid separation of trace metals from high concentrations of salts. Poly-5-vinyl-8-hydroxyquinoline has been used to develop a new method to rapidly and quantitatively precipitate aluminum, copper, vanadium and manganese from neutron-activated biological and environmental matrices.