Yields of fission products with masses A=131 to 135 for the fast neutron induced fission of U-238

Yields of eleven fission products with masses A=131 to 135 have been determined for the reactor neutron induced fission of²³⁸U by means of radiochemical separation combined with high-precision Ge(Li) -ray spectrometry. The charge distribution in the isobaric chains 131 to 134 and the isotopic distribution of₅₂Te have been studied.     

A fast radiochemical procedure for separating iodine from fission products

The iodine isotopes produced by thermal neutron fission of²³⁵U were separated by a fast chemical procedure, with a separation yield of 95%. The gamma-ray energies and relative intensities in the decay of¹³¹I,¹³²I,¹³³I,¹³⁴I and¹³⁵I were determined using a Ge(Li) detector.     

Cluster emission and chemical reactions in oxygen and nitrogen ices induced by fast heavy-ion impact

Two ices, O2 and a mixture of O2 and N2, are bombarded by 252Cf fission fragments (FF) (approximately 65 MeV at target surface); the emitted positive and negative secondary ions are analyzed by time-of-flight mass spectrometry (TOF-SIMS). These studies shall enlighten sputtering from planetary and interstellar ices. Three temperature regions in the 28-42-K range are analyzed: (1) before N2 sublimation, in which hybrid chemical species are formed, (2) before O2 sublimation, in which the TOF mass spectrum is dominated by low-mass (O2)p cluster ions and (3) after O2 sublimation, in which (N2)p or (O2)p cluster ions are practically inexistent. In the first region, four hybrid ion series are observed: NOn-1+, N2On-2(+/-), and N4On-4(-). In the second region, two positive and negative ion series are identified: (O2)pO(+/-) and (O2)pO2(+/-). Their yield distributions are fitted by the sum of two decreasing exponentials, whose decay constants are the same for all series. It is observed that the cluster ion desorption from solid oxygen is very similar to that of other frozen gases, but its yield distribution oscillates with a three- or six-atom periodicity, suggesting O3 or 3O2 units in the cluster structure, respectively.     

Absolute fission yields in the fast neutron induced fission of 233U by track etch combined with gamma-ray spectrometry

The absolute fission yields of twenty seven fission products were determined in the fast neutron induced fission of ²³³U, employing track etch in combination with gamma-ray spectrometry. The total number of fissions was measured by registering the fission tracks on a small strip of lexan, a solid state track detector. The fission products were analysed by gamma-ray spectrometry. The measured yield values were compared to the ENDF/B-VI compilation and show a good agreement.     

Advanced system for separation of rare-earth fission products

A microprocessor-controlled radiochemical separation system, which has been developed at the INEL, has been further advanced to separate individual rare-earth elements from mixed fission products in times of a few minutes. The system was composed of an automated chemistry system fed by two ∼300μg²⁵²Cf sources coupled directly by a He-jet to transport the fission products. Chemical separations were performed using two high performance liquid chromatography columns coupled in series. The first column separated the rare-earth group by extraction chromatography using dihexyldiethylcarbamoylmethylphosphonate (DHDECMP) adsorbed on Vydac C₈ resin. The second column isolated the individual rare-earth elements by cation exchange chromatography using Aminex A-9 resin with α-hydroxyisobutyric acid (α-HIBA) as the eluent. Significant results, which have been obtained to date with this advanced system, are the identification of several new neutron-rich rare-earth isotopes including¹⁵⁵Pm (T=48±4 s) and¹⁶³Gd (T=68±3 s). In addition a half-life of 41±4 s is reported for¹⁶⁰Eu. Work supported by the U.S. Department of Energy under DOE Contract No. De-ACO7-76IDO-1570.     

A new method for the radiochemical separation of copper from fission products

A new method for obtaining radiochemically pure⁶⁷Cu from highly active fission product solutions is described. The method is based on the solvent extraction of the Cu(II)-diethyldithiocarbamate complex in n-butyl acetate in the presence of hold-back carriers for Ni, Co, Mn, Mo, rare earths, Cd, Te and Sb, and subsequent purification steps involving scavengings for Ag, Ba, Sr and Fe followed by an anion-exchange purification step for decontamination from Te. Copper is finally extracted as the α-benzoin oxime complex in which form it is mounted and counted. The method has several advantages over other methods in that decontamination is very high and it is sufficiently fast considering the stringent radiochemical purity achieved. The⁶⁷Cu separated by this procedure from a one-day-old mixture of fission products arising from 10¹⁰ fissions was found to be completely free of any contamination.     

Chemical behavior of antimony and tellurium fission products in aqueous solutions

The oxidation states of antimony and tellurium fission products formed in the aqueous solutions of²³³U and²³⁵U irradiated in a reactor were studied by means of anion exchange method. Results were corrected for the thermal reactions such as radiation induced reactions using double tracers for each element. In hot reactions, the isotopes formed independently by fission take their reduced states almost completely, whereas the isotopes formed by β-decay of their precursors favor their oxidized states. The fractions of the tellurium isotopes in the oxidized state depend on the β-decay energy of their precursors, whereas those of the antimony isotopes are nearly constant irrespective of the β-decay energy. The different behaviors between those two elements would reflect the chemical properties of their precursors.     

Use of isooctyl thioglycolate for the separation of tin and antimony

The extraction characteristics of isooctyl thioglycolate (IOTG), a chelating agent, in various diluents has been studied with respect to the metal ions, tin(IV) and antimony(III), in hydrochloric acid medium. It is concluded that antimony(III) can be separated from tin(IV) with 85% yield and with a decontamination factor of at least 1·10⁵ using IOTG diluted with petroleum ether and 3M HCl medium. Tin(IV) can be separated conveniently from antimony(III) in 2M HCl with 95% yield and with a decontamination factor greater than 7·10⁵ using IOTG diluted with carbon tetrachloride.     

Liquid-liquid microbatch extraction system for rapid mutual separation of fission products

The liquid-liquid microbatch extraction system (LMES) was developed for rapid separation of short-lived metal ions. The equipment is composed of three simple extraction cells for phase mixing, phase separation, and collection of a solvent. Metal separation can be completed in a single operation, lasting only a minute, from solvent extraction to preparation for gamma-ray spectrometry. As a demonstration of the rapid operation of the LMES, fission products were each separated into several categories after three stages of operation. The extractability in the LMES was comparable to that of traditional methods, and the developed method was feasible for rapid separation.     

Yields of tin and antimony isotopes in the vicinity of the closed shell N = 82 from reactor neutron induced fission of 232Th

The independent yields of the isotopes ^131,132Sn and ^131–133Sb from the reactor neutron induced fission of ²³²Th were measured. Tin and antimony were chemically separated as hydrides and the decay or the growth and decay of their γ-ray spectra were followed. The independent yields of ^131,132Sn and ^132,133Sb were obtained by a direct measurement, while the yield of ¹³¹Sb was derived from the corresponding measured isobaric yield and the respective chain yield. An enhancement of yield of ∼70% was found for the closed neutron shell nucleus (¹³²Sn) while the other measured nuclei showed either an enhancement or a decrease, i.e. a proton odd-even effect of ∼30%. The contribution of the data to the fission yields system of Z = 90–98 is discussed. The odd-even systematics is discussed according to previous studies, while the neutron shell effect is examined with regard to the primary mass split and the neutron emission probabilities.     

Efficient triplet pair separation from intramolecular singlet fission in dibenzopentalene derivatives

In intramolecular SF(iSF), the strong coupling nature and confinement of diffusional separation of ~1(TT) limits the extraction and harnessing of triplet energy. In order to investigate the possible ~1(TT) separation and the role of molecular parameters on it, a series of iSF-capable dibenzopentalene derivatives(DBPs) have been synthesized and their photoinduced dynamics are monitored. iSF takes place in DBPs, accompanied by consecutive ~1(TT) separation in polycrystalline film with almost ~100% yield. It is suggested the strong intermolecular coupling provided by the closely packing configuration in the film facilitates the disentanglement of correlated ~1(TT). Highly efficient triplet pair separation to yield free triplets makes one step forward for utilizing triplet energy from iSF materials for further optoelectronic applications.     

Application of neutron activation analysis in a fission molybdenum separation study

The separation of⁹⁹Mo from low-enriched uranium (LEU, 19.5%²³⁵U) targets was evaluated using natural uranium (NU) and non-radioactive tracers. Neutron activation analysis was used to determine (1) the efficiency of molybdenum recovery and (2) the decontamination factor of numerous fission product elements from the molybdenum product. Using NU and non-radioactive elements simplified procedures and allowed tests to be completed in a fume hood instead of a shielded cell. During activation of the non-radioactive tracers, uranium fission occurs, which can interfere with subsequent gamma-ray analysis. A comparison was made of the interferences caused by these fission products from both NU and LEU.     

Utilization of cyclotron produced fast neutrons in the activation analysis for oxygen

The possible application of cyclotron-produced fast neutrons to activation analysis for oxygen based on the¹⁶O(n, p)¹⁶N reaction has been investigated. Neutrons were produced by bombarding a thick beryllium target with 22 to 45 MeV deuterons. It was found that the sensitivity increases rapidly with the energy of the deuterons. Using 45 MeV deuterons and a 10 μA beam current a sensitivity of about 20 counts per 1 μg oxigen could be achieved, enabling the determination of less than 1 μg oxigen. In a direct comparison it was experimentally established that the sensitivity for cyclotron-produced neutrons assuming a deuteron beam of about 10 μA, is up to two orders of magnitude higher than that achievable for 14 MeV neutrons with a flux of about 10¹⁰ n/s. The interference of fluorine is at about the same level for both the cyclotron-produced and 14 MeV neutrons. Using cyclotron-produced fast neutrons in the investigated energy range, sodium and magnesium can also interfere, but only to a very much lower extent.     

Preparatory investigations of fast separation for heavy ion reaction products

A method for separation and chemical identification of products formed in nuclear reactions or nuclear decay is to slow down the recoil products in a gas and to transport them to a trap, where a detecting system is arranged. The sources for the recoil products are²⁵²Cf and²²⁴Ra. As transport phase we used nitrogen or argon and added chemical reagents such as methyl and ethyl radicals, chlorine, oxygen, carbon monoxide or methane. The chemical additives lead to selective and fast separation of certain elements. As examples the results of two experiments are presented:²²⁴Ra with ethyl radicals, and²⁵²Cf with chlorine-oxygen-nitrogen mixtures. The registration of the recoil products at the trap was measured as a function of temperature, pressure and composition of the reactive gas.     

Radiochemical separation of antimony and tellurium in isotope production and in radionuclide generators

A potentially useful radionuclide generator for PET studies is based on ¹¹⁸Te/¹¹⁸Sb. A novel single-step approach using anion-exchange chromatography was developed to separate the ¹¹⁸Te parent activity from proton-irradiated targets. The average yield of radiotellurium using this method was 88%, with no detectable radioantimony contamination. A generator system employing activated carbon as a column chromatography adsorbent was studied. An ¹¹⁸Sb elution yield of 87%, with a radiotellurium breakthrough of less than 0.1%/ml, was achieved. Oxidation state studies indicate that approximately 39% of the ¹¹⁸Sb formed in the decay of ¹¹⁸Te is in the form of Sb(V). Details of these separations are presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

A molecularly imprinted monolith for the fast chiral separation of antiparasitic drugs by pressurized CEC

Molecularly imprinted polymer (MIP) monoliths with (S)‐ornidazole ((S)‐ONZ) as the template molecule have been designed and prepared by the simple thermal polymerization of methacrylic acid, 4‐vinylpyridine, and ethylene dimethacrylate in the presence of a binary porogenic mixture of toluene and dodecanol. The influences of polymerization mixture composition on the chiral recognition of ONZ have been evaluated, and the imprint effect in the optimized MIP monolith has been clearly demonstrated. The new monolithic stationary phase with optimized porous property and good selectivity was used for the chiral separation of ONZ by pressurized CEC. The pressurized CEC conditions were also optimized to obtain the good chiral separation. The enantiomers were rapidly separated within 9 min on the MIP‐based chiral stationary phase, whereas the chiral separation was not obtained on the nonimprinted polymer. Additionally, the proposed method has been successfully applied to the chiral separation of ONZ in tablet samples by injection of the crude sample. The cross‐selectivity for similar antiparasitic drug was investigated. The results indicated that the chiral separation of secnidazole could also be obtained on the optimized MIP monolith within 14 min.     

Ultrasound- assisted emulsification microextraction for separation of trace amounts of antimony prior to FAAS determination

We describe a simple and rapid method for the ultrasound-assisted microextraction of antimony using the solidified floating organic drop method. The effects of pH, type and volume of the extractant, time of sonication, amount of chelating agent, type and amount of surfactant were investigated and optimized. Bromopyrogollol red is acting as the chelating agent. Antimony(III) ion was extracted into finely dispersed droplets of undecanol after ion-pair formation with the water soluble chelator and the cationic detergent benzyldimethyltetradecylammonium chloride. Flame atomic absorption spectrometry was used for the detection. The resulting calibration is linear in the concentration range from 4.0 to 900?ng?mL^-1 of Sb(III) with a correlation coefficient of 0.9981. The enrichment factor is 67, the detection limit is 0.62?ng?mL^-1, and the relative standard deviation is?±?3.6% (at 100?ng?mL^-1; for n?=?10). The method was successfully applied to the determination of antimony in water samples.