Preparation of99Mo,132Te isotopes and99mTc,132I generators

Adsorption and desorption of⁹⁵Zr−⁹⁵Nb,⁹⁹Mo,¹⁰³Ru,¹³²Te and²³⁹Np in a HCl-alumina system were studied in order to purify⁹⁹Mo and¹³²Te obtained by the cation-exchange separation of fission products and to prepare highly pure^99mTc and¹³²I generators.⁹⁹Mo and¹³²Te, of which radionuclidic purity was over 99.99% and 99.999%, respectively, could be obtained by passing the cation-exchange separated Mo and Te fractions through alumina columns, by washing with HCl and finally by eluting⁹⁹Mo with 1M NH₄OH and¹³²Te with 3M NaOH. In order to raise the recovery of⁹⁹Mo and¹³²Te from the alumina columns, they should be eluted as quickly as possible after the adsorption. The direct use of the alumina column containing⁹⁹Mo or¹³²Te as the generator allowed milking of^99mTc or¹³²I, of which radionuclidic purity was over 99.999%. Milking yields of^99mTc with 0.1M HCl and¹³²I with 0.01M NH₄OH were 77% and 90%, respectively. The latter value was much higher than that in usual performance of the generator.     

Elution of 235U fission products through a calcined hydrotalcite-packed column

Calcined hydrotalcite packed columns were utilized to sorb ²³⁵U fission products and their decay products. The elution behavior of some radionuclides was studied after washing the columns, either with distilled water or 0.5% NaCl solution. Afterwards, fission products and their decay products were eluted using 0.5% NaCl solution. It was found that no matter the washing process, ^99mTc, the b^--decay product of ⁹⁹Mo, was easily separated from ⁹⁹Mo which was strongly retained on the hydrotalcite. ¹³²I, the b^--decay product of ¹³²Te, was eluted slowly and was separated from ¹³²Te which was retained on the column. ¹³¹I and ¹⁴⁰Ba were eluted together with ^99mTc and ¹³²I, although in smaller proportions.     

Determination of gamma impurities in fission product99Mo

The methodology is given for determination of very low quantities of gamma impurities:⁹⁵Zr,⁹⁵Nb,¹⁰³Ru,¹³¹I,¹³²Te,¹³²I,¹⁴⁰Ba,¹⁴⁰La,¹⁴¹Ce,¹⁴⁴Ce in⁹⁹Mo produced by separation from other fission products, by means of different measurement conditions such as initial activity, decay time and attenuation with lead.Presented as a poster at the International Conference on Nuclear and Radiochemistry, Beijing, P.R. China, September, 1986.     

Measurement of absolute intensity of 1001 keV gamma-ray of 234mPa

The sorption behavior of ²³⁵U fission fission products ⁹⁹Mo and ¹³²Te was studied through batch and dynamic experiments when they were dissolved in 1 to 7M HNO₃ solutions. It was found that ⁹⁹Mo is always totally adsorbed on hydrated SnO₂, while ¹³²Te is rather weakly adsorbed, therefore they can be separated from each other although ¹³²Te in the solution still remains contaminated with other radionuclides as well as ⁹⁹Mo does in the solid.     

Solvent extraction studies using tetracycline as complexing agent

The behaviour of tetracycline as an extracting agent for strontium, iodine, barium, molybdenum, technetium, zirconium, niobium, cesium, ruthenium, tellurium and uranium has been studied and the influence of the acidity of the aqueous phase upon extraction of the elements mentioned has been examined. Experiments have been made to determine whether or not the species extracted into the organic phase is the complex formed between tetracycline and the elements considered as well as to determine the time of shaking necessary so that the equilibrium between the phases is attained. As a practical application, the possibility of using the tetracycline-benzyl alcohol system for separating the fission products¹³⁷Cs,¹⁴⁰Ba,¹⁴⁰La,¹⁴¹Ce,¹⁰³Ru,⁹⁵Zr and⁹⁵Nb from each other and from uranium is presented. The same study has been made for¹³¹I,^99mTc,⁹⁹Mo,¹³²Te,²³⁹Np and uranium and the steps necessary for the separation of these elements are proposed.From a thesis submitted by I. I. L. CUNHA to the Instituto de Pesquisas Energéticas e Nucleares-University of São Paulo in partial fulfillment of the requirements for a Doctor of Science's Degree. Work supported by Comissão Nacional de Energia Nuclear.     

Determination of uranium fission interference factors for INAA

Instrumental neutron activation analysis (INAA) is a very suitable technique for the determination of several elements in different kinds of matrices. However, when the sample contains high uranium concentration this method presents interference problems of uranium fission products. The same radioisotopes used in INAA are formed in uranium fission. Among these radioisotopes are ¹⁴¹Ce, ¹⁴³Ce, ¹⁴⁰La, ⁹⁹Mo, ¹⁴⁷Nd, ¹⁵³Sm and ⁹⁵Zr. The purpose of this study was to evaluate uranium fission interference factors to be used in the INAA of environmental and geological samples containing high levels of U. The obtained interference factors agreed with literature reported values. The results point to the viability of using these experimentally determined interference factors for the correction of uranium fission products.     

Transmutation of 239 Pu with spallation neutrons

Incineration studies of plutonium were carried out at the Synchrophasotron of the Joint Institute for Nuclear Research (JINR), Dubna, using proton beams with energies of 0.53 GeV and 1.0 GeV. Solid lead targets (8 cm in diameter and 20 cm long) were surrounded with 6 cm thick paraffin as neutron moderator and then irradiated. The transmutation of ²³⁹ Pu and the associated production of fission products ⁹¹ Sr, ⁹² Sr, ⁹⁷ Zr, ⁹⁹ Mo, ¹⁰³ Ru, ¹⁰⁵ Ru, ¹²⁹ Sb, ¹³² Te, ¹³³ I, ¹³⁵ I and ¹⁴³ Ce were studied in the present work. The plutonium samples (each 449 mg) were placed on the outer surface of moderator. For 1.0 GeV proton beam, the fission rate of ²³⁹ Pu is 0.0032 atoms per proton in one gram plutonium samples, for 0.53 GeV proton, this value is 0.0022. The experimental uncertainty is about 15%. The experiments are compared to two theoretical model calculations with moderate success, using the Dubna Cascade Model (CEM) and the LAHET code. The practical incineration rate of ²³⁹ Pu is very high. For example: if one uses 10 mA, 1 GeV proton beams under the same (fictive) experimental conditions, the incineration rate of ²³⁹ Pu via fission is 3 mg out of the 449 mg sample per day. For 0.53 GeV protons the corresponding rate is 2 mg per day.     

Multielement analysis of uraniferous rocks by INAA: Special reference to interferences due to uranium and fission of uranium

The presence of uranium in a sample enhances the true values of La, Ce, Nd, Sm determined by INAA if appropriate corrections are not made for the interference. The enhancement of the true values comes about because the (n, γ) activation products of these elements, viz.¹⁴⁰La,¹⁴¹Ce,¹⁴⁷Nd,¹⁵³Sm, are also produced from the fission of²³⁵U (～0.72% natural isotopic abundance) even when La, Ce, Nd, Sm are totally absent in the given sample. In a 5 hour irradiation 1 μg of U is found to be equal to 0.28 μg of Ce and 0.23 μg of Nd while the equivalent La is found to be dependent upon the delay from end of irradiation to sample counting time. A numerical procedure is given to correct for these interferences. Spectral interferences from fission and (n, γ) β products of uranium in the determination of other trace elements by INAA is also investigated. Uranium is found to be determined best using the 278 keV gamma-ray of²³⁹Np.     

Intereferences from uranium fission in neutron-activation analysis in an Argonaut-type Low Flux Reactor

The interferences by uranium fission on the determination by neutron activation analysis of Zr, Mo, Ru, La, Ce, Nd and Sm are investigated for the Argonaut-type Low Flux Reactor at ECN, Petten, The Netherlands. In addition, the spectral interference of the determination of Sm by²³⁹Np is considered. The experimental values for fission yields are found to be in good agreement with calculated values based on recent cross-section compilations.     

Radiochemical separation of99Mo from natural uranium irradiated with thermal neutrons

⁹⁹Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of⁹⁹Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and⁹⁹Mo was back-extracted from the organic phase with NH₄OH solution. The percent recovery from the organic phase was 91% and the purity of⁹⁹Mo was more than 99%. Pure^99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of⁹⁹Mo from¹³¹I and other fission products (10% HDEHP on kieselguhr bed).¹³¹I and other isotopes were quantitatively eluted with 0.1M H₂SO₄,⁹⁹Mo was eluted using a mixture of 0.5 M HCl and 30% H₂O₂.     

INAA of Zr,La, Ce and Nd in geological samples in the presence of different uranium concentratios

Rock samples which contain relatively high concentrations of uranium may create problems of interference produced by fission products, when instrumental neutron activation analysis is used. The isotopes⁹⁵Zr,¹⁴⁰La,¹⁴¹Ce, 143Ce and 147Nd, which are commonly used in the neutron activation analysis of the corresponding elements, are also produced as fission products of²³⁵U. For each of these radioisotopes, a contribution factor is calculated theoretically and meaured experimentally using geological samples with different uranium contents.     

Neutron activation analysis of pure uranium: Preconcentration of impurity elements

We have developed a radiochemical neutron activation analysis technique (RNAA) of pure uranium with using extraction chromatographic separation of ²³⁹Np from impurity elements in TBP-6M HNO₃ media. The estimation of influence of fission products of ²³⁵U on the results by radiochemical neutron activation analysis has been carried out. For it we have performed NAA with preconcentration of impurity elements. Experiments show that in this case the apparent concentration of Y, Zr, Mo, Cs, La, Ce, Pr, Nd exceeds the true concentration by 2500–3000 times. Therefore, determination of these elements is not possible by RNAA. This technique allowed to use the determination of 26 impurity elements with detection limit 10⁻⁵–10⁻⁹% by mass. This developed technique may be used for the determination of impurities in uranium and its compounds.     

Determination of americium-243 through its daughter product neptunium-239

The extraction of Np(IV), Zr, Nb, Cs, Ce(III) and Am(III) from nitric acid solutions containing oxalate and phosphate ions by solutions of 1-phenyl-3-methyl-4-benzoylpyrazolon-5 (PMBP) and tri-n-butyl phosphate (TBP) in benzene has been investigated. A solution 0.1M in respect to PMBP and 0.25M in respect to TBP was found to extract 99% of neptunium from aqueous solutions 1M in respect to H₃PO₄ and 0.5M in respect to HNO₃. Under these conditions, the extraction of the other investigated elements does not exceed 0.1%. Based on this finding, a procedure was developed to determine²⁴³Am through its daughter product²³⁹Np in solutions containing large quantities of curium and its fission products. The sensitivity of the procedure is 1·10⁻⁷ mg of²⁴³Am in the sample. The²⁴³Am content is obtained by calculation from measurements of the γ-activity of the extracted²³⁹Np. The purification ratio of²³⁹Np is∼10⁵ from Zr, Nb and Ru, ∼10⁸ from Ce and Cm and >10¹² from Cs.     

Separation of trace impurities of131I from99Mo obtained by extraction from fission products of uranium

The radioisotope⁹⁹Mo was separated from a mixture of²³⁵U fission products in the presence of Hg²⁺ by sorption on a chromatographic column filled with Al₂O₃ and elution with 1M NH₄OH. Trace impurities of¹³¹I in the molybdenum fraction were eliminated by selective sorption on silver iodide or by repeated sorption of⁹⁹Mo on Al₂O₃.     

Neptunium distribution in a high acid first cycle Purex Process

This work deals with the extraction behavior of neptunium in a high acid Purex Process. The composition of PWR fuel type with 3.2% enrichment, 500 MWd/t burn-up and 100 d cooling time was considered. Two consecutive cold runs were performed in a mock-up facility at IPEN-CNEN/SP with simulated feed solutions containing: 3M HNO₃; 1M U; 455 g²³⁷Np labeled with²³⁹Np; 15 mg Zr l^–1, 12 mg Ce l^–1, 7 mg Ru l^–1 and 13 mg Mo l^–1 traced with active isotopes⁹⁵Zr,¹⁴¹Ce,¹⁰³Ru and⁹⁹Mo as FP. A 30 vol% TBP/n-dodecane was used as solvent. Countercurrent experiments were carried out using two 16 stages plexiglass mixer-settlers, at 25°C, during 21 h continuous operation, with O/A ratio of 2 in the extraction section and 9 and 13 in the 1st and 2nd scrubbing sections, respectively. For a 65% organic loading, ca. 77% of neptunium remains in the waste stream, without any Np valence adjustment.     

Sequential separation of transuranic elements and fission products from uranium metal ingots in electrolytic reduction process of spent PWR fuels

A sequential separation procedure has been developed for the determination of transuranic elements and fission products in uranium metal ingot samples from an electrolytic reduction process for a metallization of uranium dioxide to uranium metal in a medium of LiCl-Li₂O molten salt at 650 °C. Pu, Np and U were separated using anion-exchange and tri-n-butylphosphate (TBP) extraction chromatography. Cs, Sr, Ba, Ce, Pr, Nd, Sm, Eu, Gd, Zr and Mo were separated in several groups from Am and Cm using TBP and di(2-ethylhexyl)phosphoric acid (HDEHP) extraction chromatography. Effect of Fe, Ni, Cr and Mg, which were corrosion products formed through the process, on the separation of the analytes was investigated in detail. The validity of the separation procedure was evaluated by measuring the recovery of the stable metals and ²³⁹Pu, ²³⁷Np, ²⁴¹Am and ²⁴⁴Cm added to a synthetic uranium metal ingot dissolved solution.     

The determination of fission products in irradiated uranium by electrophoretic focussing of ions

Electrophoretic focussing of ions was applied to the separation of fission products present in solutions of nuclear uranium fuel irradiated in various European reactors. By combining two separation methods, all the long-lived fission products could be determined individually and quantitatively by counting with a NaI(T1) and a GM detector of known detection efficiency. Radiography and autoradiography were used for semi-quantitative purposes. The concentrations of²³⁵U and²³⁸U were determined from a short post-irradiation of the fuel solution and counting of¹⁴⁰Ba−¹⁴⁰La and²³⁹Np, respectively. An iterative calculus method is presented which allows calculation of the irradiation history of the fuel solution from the above analyses. without any a priori knowledge.     

Separation of iodine produced from fission with a porous metal silver column in99Mo production

In Argentina, at the Ezeiza Atomic Center,¹³¹I is produced by wet distillation of natural tellurium dioxide irradiated with thermal neutrons in a pool-type reactor. In order to recover the¹³¹I present in the production process of fission⁹⁹Mo obtained by irradiation of UAL_x/Al targets (with 90% enriched uranium) a separation method was developed. Iodine isotopes can be separated from a sodium hydroxide solution containing fission products using a column filled with alternate beds of glass microspheres and porous metal silver. Tests with tracers were performed in radiochemical laboratory. Following this results, a series of tests with higher activities (3 TBq of⁹⁹Mo and 0.7 TBq of¹³¹I) were carried out in hot cells. Molybdenum passes through the silver column, while¹³¹I retention was 92–97% in tracer test and 90% in optimised hot cell tests. This result depends on several facts that are discussed. An initial separation of iodine isotopes diminishes radiation damage on ion-exchange resin used in the subsequent molybdenum purification, improving its retention and elution yield.     

Interference in neutron activation analysis of rocks by uranium fission

Interferences by uranium fission for⁹⁵Zr,⁹⁹Mo,¹⁰³Ru,¹⁴⁰La,¹⁴¹Ce and¹⁴⁷Nd have been studied using a single comparator method with two monitors. The effect of the neutron energy spectrum on the interference factor was examined by using the effective activation cross section. All the activities of¹⁴⁰La produced during neutron irradiation of uranium were included in the calculation of the factor for lanthanum. The calculated and experimental interference factors are in good agreement within 10% deviation. The results have been applied for the analysis of several rock samples containing uranium in a wide concentration range.