Nuclide analysis of a tantalum target irradiated with high-energy protons

First results of γ-spectrometric measurements of radionuclides produced in a tantalum target irradiated for 500 days with 800 MeV protons are presented. The activities of the γ-ray-emitting nuclides measured after a cooling period of 2–4 years differ by more than four orders of magnitude. Within this cooling period about 95% of the activity of the target is determined by¹⁷²Lu,¹⁷³Lu,¹⁷⁴Lu,¹⁷²Hf (daughter nuclide of¹⁷²Lu) and¹⁸²Ta nuclides. These highly active nuclides, together with some other medium-active nuclides, were measured with good precision by γ-ray spectrometry directly in the sample solution. Weakly active nuclides could not be measured in this way because of the high Compton background in the γ-ray spectrum. For the sensitive measurement of many other nuclides present in weaker activities a simple chemical separation procedure was developed to separate Lu, Hf and Ta. With the separation of these elements and simultaneously of the high-active nuclides, the Compton background in the γ-ray spectra could be drastically reduced and many weakly active nuclides additionally measured.     

Production of carrier-free scandium radioisotopes from a neutron-irradiated potassium titanium oxalate target

Summary Extraction of scandium and calcium radioactivities with 1% HDEHP in benzene from nitric acid solution was investigated. The effect of potassium titanium oxalate concentration on the extraction from 1.5M nitric acid was studied. From the data obtained, two procedures based on batch solvent extraction and extraction chromatography were developed for separation and production of radioscandium from a neutron-irradiated potassium titanium oxalate target. The radiochemical purity of the separated scandium radioactivities was more than 98%.

---

Zusammenfassung Die Extraktion der Aktivitäten des Scandiums und Calciums aus salpetersaurer Lösung mit 1% Diäthylhexylphosphorsäure in Benzol wurde untersucht. Der Einfluß der Kalium-Titanoxalat-Konzentration auf die Extraktion aus 1,5-m Salpetersäure wurde geprüft. Auf Grund der Ergebnisse wurden zwei Verfahren zur Trennung und Gewinnung von Radio-Scandium aus einem neutronenbestrahlten Kalium-Titanoxalat-Target ausgearbeitet, die auf einmaliger Extraktion mit dem Lösungsmittel bzw. auf Extraktionschromatographie beruhen. Die radiochemische Reinheit der Sc-Aktivitäten war besser als 98%.

     

Inorganic ion-exchangers for the removal of zirconium,hafnium and niobium radioisotopes from aqueous solutions

Studies were made on the uptake of zirconium, hafnium and niobium isotopes onto zeolites and amorphous zirconium phosphate. Ion exchange capacities and distribution coefficients were determined and the influence of pH examined. Kinetic experiments were made to determine the rates of uptake of the radioisotopes on the exchangers and to measure the leaching of isotopes from preloaded exchangers by synthetic sea water, simulated pond water and distilled water.     

Chemical separation procedure for the nuclide analysis of a tantalum target irradiated for 500 days with 800 MeV protons

A rapid radiochemical separation procedure has been developed for the determination of long-lived and stable nuclides produced by spallation and activation in a tantalum target irradiated for 500 days with 800 MeV protons. In this procedure the matrix element tantalum and simultaneously the¹⁸²Ta activity, built-up by activation of the matrix with themalized spallation neutrons is removed from many elements. About 50 mg of the sample is dissolved in a mixture of concentrated nitric and hydrofluoric acid. After dilution tantalum is extracted with a solution of 0.2M tetrahexylammonium bromide in methyl isobutyl ketone (MIBK). The residual amount of tantalum and the remaining¹⁸²Ta activity are 0.0003% and the recoveries of 27 investigated elements are in the range of 96.0–99.9%. A further 22 elements are quantitatively separated according to their chemical behavior. In the final aqueous fraction the separated long-lived and stable nuclides of 49 elements can be measured with high sensitivity by -ray spectrometry and mass spectrometry (ICP-MS).     

Separation of NCA 88Zr from proton irradiated natY target: a novel approach using low cost bio-sorbent potato peel charcoal

Separation of no-carrier-added (NCA) ⁸⁸Zr from natural yttrium target irradiated with proton beam has been studied using nature-resourced material, potato peel, which is a commonly available domestic waste. Here, an attempt has been undertaken to exploit natural resource as separating agent. Good separation of NCA ⁸⁸Zr from bulk Yttrium target could be achieved at 0.01 M HCl concentration, when extraction was carried out using 20 mg potato peel charcoal—a natural bio-sorbent. ⁸⁸Zr was extracted in the solid phase leaving behind bulk Y in the aqueous phase.

     

Simultaneous determination of tantalum and hafnium in silicates by neutron activation analysis

A neutron activation procedure suitable for the routine determination of tantalum and hafnium in silicates is described. The irradiated sample is fused with sodium peroxide and leached, and the insoluble hydroxides are dissolved in dilute hydrofluoric acid-hydrochloric acid. After LaF₃ and AgCl scavenges, tantalum and hafnium are separated by anion exchange. Tantalum is obtained radiochemically pure; ²³³Pa and ⁹⁵Zr contaminants in the hafnium fraction are resolved by γ-ray spectrometry. The chemical yield of the procedure is detemined after counting by re-irradiation. Values for the 8 U.S. Geological Survey standard rocks are reported.     

On-line separation of short-lived tungsten isotopes from tantalum,hafnium and lutetium by adsorption on ion exchangers from aqueous ammonia solution

The title goal was achieved using a DOWEX 50Wx8 cation exchange column saturated with La(OH)₃ and ammonia solution as eluent. Hf, Ta and Lu were adsorbed on this column, whereas W remained in the solution. This chemical system may be used for fast on-line separations of element 106.     

Preparation of carrier-free group tracers from a gold target irradiated by high-energy heavy ions

A rapid radiochemical separation procedure has been finished by using of radiochemical separation and -spectrum measurement methods. In this isolation procedure, tantalum nuclides produced by the irradiation of natural tungsten targets with 14 MeV neutrons were extracted by methyl isobutyl ketone (MIBK) in the system of HF-HNO₃ mixed solutions. It has been found that tantalum was rapidly and efficiently separated in the isolation procedure and the decontamination factors of tungsten were more than 10⁴. The procedure is simultaneously used to separate tantalum from tungsten bombarded with intermediate energy (47 MeV/u)¹⁸O beams. The measured -spectra showed that tantalum can be separated from most elements produced in the nuclear reactions except for a few elements.     

Separation of bulk Pb and Bi from proton irradiated lead bismuth eutectic (LBE) target by DGA-N and TK-200 resins

Journal of Radioanalytical and Nuclear Chemistry - Poly (vinyl alcohol)-ethylene glycol (PVA-EG) composites were geared up using casting method. The PVA-EG composite films have been irradiated at...     

Synthesis of zirconium, hafnium, and tantalum complexes with sterically demanding hydrazide ligands

The bulky hydrazine t-BuN(H)NMe2 was synthesized via hydrazone and t-BuN(H)N(H)Me intermediates as the major component in a 90:5:5 mixture consisting of t-BuN(H)NMe2, t-BuN(Me)N(H)Me, and t-BuN(Me)NMe2. Reacting the mixture with n-BuLi followed by distillation and fractional crystallization led to the isolation of the ligand precursor LiN(t-Bu)NMe2. Lithium hydrazides, LiN(R)NMe2, were reacted with metal chlorides to afford the hydrazide complexes M(N(Et)NMe2)4 (M = Zr or Hf), MCl(N(R)NMe2)3 (M = Zr, R = i-Pr or t-Bu; M = Hf, R = t-Bu), and TaCl3(N(i-Pr)NMe2)2. The X-ray crystal structures of [LiN(i-Pr)NMe2]4, [LiN(t-Bu)NMe2.THF]2, ZrCl(N(R)NMe2)3 (R = i-Pr or t-Bu), and TaCl3(N(i-Pr)NMe2)2 were determined. The structural analyses revealed that the hydrazide ligands in ZrCl(N(R)NMe2)3 (R = i-Pr or t-Bu) and TaCl3(N(i-Pr)NMe2)2 are eta2 coordinated.     

Production of carrier free192,193Hg and192,193Au in16O irradiated tantalum target and their separation by liquid-liquid extraction

Carrier-free radionuclides of mercury and gold^192,193Hg and^192,193Au have been produced by heavy ion activation of tantalum target with 95 MeV¹⁶O⁵⁺ beam obtained from an ECR ion source. An effective radiochemical separation scheme has been developed to isolate gold and mercury radionuclides from the tantalum target matrix.     

Determination of metal traces in tantalum by proton activation analysis

Procedures for determining traces of calcium, titanium, vanadium, chromium, iron, copper, niobium, molybdenum and tungsten in tantalum are described utilizing 11 MeV proton activation. The instrumental method of analysis with the use of a Ge(Li) detector and the radiochemical separation of the corresponding fractions are described. The formula for the calculation of the concentration of traces with the use of thick target yields is given. Experimental data on the thick target yields of radioisotopes⁴⁴Sc,⁵²Mn,⁵⁶Co,⁶⁵Zn,^93mMo,⁹⁶Tc are presented. Based on the experimental data, the detection limits are estimated at 1–10 ppb for the above mentioned metal traces in tantalum. The successful solution of the task of the simultaneous determination of nine elements in tantalum confirms the wide applicability of proton activation analysis.     

Separation of carrier-free lutetium-177 from neutron irradiated natural ytterbium target

Neutron irradiation of naturally occurring Yb produces small amounts of carrier-free¹⁷⁷Lu activity. Cation exchange chromatography in the displacement development mode using Dowex-50X8, 200–400 mesh resin, and Zn²⁺ as the separating ion was used to separate¹⁷⁷Lu produced in a neutron irradiated Yb target. 0.04M -hydroxyisobutyric acid at pH 4.6±2 and temperature 26±1°C was used to elute carrier-free¹⁷⁷Lu in 70% yield and at a radionuclidic purity greater than 99%.     

Production of carrier-free radioisotopes from targets irradiated with deuterons or alpha particles in the U-120 Cracow Cyclotron

The results of experiments on the preparation of carrier-free lanthanides from some targets irradiated in the U-120 cyclotron are presented. In the reactions¹⁵¹Eu(α, n)^154m,154Tb,¹⁵¹Eu(α, 2n)¹⁵³Tb,¹⁵⁵Gd(α, 2n)¹⁵⁷Dy,¹⁶⁹Tm(α, n)¹⁷²Lu and¹⁶⁹Tm(α, 2n)¹⁷¹Lu, the isotopes^154m,154+153Tb,¹⁵⁷Dy and^172+171Lu were obtained. These were seaprated by means of ion-exchange chromatography. Part II: see Ref. 2     

Atomic layer deposition of hafnium oxide from hafnium chloride and water

Hafnium oxide (HfO2) is a leading candidate to replace silicon oxide as the gate dielectric for future generation metal-oxide-semiconductor based nanoelectronic devices. Atomic layer deposition (ALD) has recently gained interest because of its suitability for fabrication of conformal films with thicknesses in the nanometer range. This study uses periodic density functional theory (DFT) to investigate the mechanisms of both half-reactions occurring on the growing surface during the ALD of HfO2 using HfCl4 and water as precursors. We find that the adsorption energy and the preferred site of adsorption of the metal precursor are strong functions of the water coverage. As water coverage increases, the metal precursor preferentially interacts with multiple surface adsorption sites. During the water pulse the removal of Cl can be facilitated by either a ligand exchange reaction or the dissociation of Cl upon increase in coordination of the Hf atom of the precursor. Our predicted potential energy surface indicates that a more likely mechanism is hydration of the adsorbed Hf complex up to a coordination number of 7, followed by the dissociation of a chloride ion that is stabilized by solvation. Born-Oppenheimer molecular dynamics (BOMD) simulations of an adsorbed metal precursor in the presence of a multilayer of water shows that Cl dissociation is facile if sufficient water molecules are present to solvate the Cl(-) anions. Hence, solvation plays a crucial role during the water pulse and provides an alternative explanation for why ALD growth rates for this system decrease at high temperatures.     

Recovery of uranium from U3O8 irradiated with thermal neutrons

The extraction of uranium with different concentrations of HDEHP in n-hexane from varying concentrations of nitric acid solutions was investigated. Uranium in the organic phase was quantitatively stripped with a solution containing 8M H₂SO₄ and 6M HCl, the partition coefficient was determined by X-ray fluorescence and U. V. spectrophotometry. The assay of⁹⁵Zr,⁹⁵Nb,²³⁹Np and other gamma-emitters was made with a Ge(Li) detector coupled to a 4096 multichannel analyzer.     

Application of on-line HPLC-ICP-MS for the determination of the nuclide abundances of lanthanides produced via spallation reactions in an irradiated tantalum target of a spallation neutron source

An analytical procedure has been developed for the determination of spallation nuclides in an irradiated tantalum target using HPLC coupled on-line to ICP-MS after dissolution and separation of the tantalum matrix. Pieces of tantalum were taken from different locations of the irradiated tantalum target which had been used as the target material in a spallation neutron source. Tantalum was dissolved in a HNO₃/HF mixture and the tantalum matrix was separated by liquid-liquid extraction so that only the spallation nuclides were left in the sample solutions. The major fraction of the spallation nuclides in the tantalum target are lanthanide metals in the μg g^–1 concentration range determined in the present study. Additional reaction products are formed by the irradiation of trace impurities in the original tantalum target. The nuclide abundances of the lanthanide metals measured in the tantalum target differ significantly from the natural isotopic composition so that a lot of isobaric interferences of long-lived radionuclides and stable isotopes in the mass spectrum are to be expected. Therefore, all the lanthanide metals had to be separated chemically prior to their mass spectrometric determination. The separation of all rare earth elements was performed by ion chromatography on-line to ICP-MS. The nuclide abundances of each lanthanide were determined using a sensitive double-focusing sector field inductively coupled plasma mass spectrometer. The nuclide abundances of the lanthanides in the irradiated tantalum target calculated theoretically and the experimental results obtained by on-line HPLC-ICP-MS proved to be in good agreement.