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).     

Recovery of hafnium radioisotopes from a proton irradiated tantalum target

The^178m2Hf nucleus, with its long half-life (31 y) and high-spin isomeric state (16⁺) is desired for new and exotic nuclear physics studies. The Los Alamos Radioisotope Program irradiated a kilogram of natural tantalum at the Los Alamos Meson Physics Facility in early 1981. After fifteen years of decay, this target was ideal for the recovery of^178m2Hf. There was more than a millicurie of^178m2Hf produced during this irradiation and there has been a sufficient period of time for most of the other hafnium radioisotopes to decayed away. Traditionally, separation techniques for recovering hafnium isotopes from tantalum targets employ solvent extractions with reagents that are considered hazardous. These techniques are no longer condoned because they generate a mixed-waste (radioactive and hazardous components) that can not be treated for disposal. In this paper we describe a new and unique procedure for the recovery of hafnium radioisotopes from a highly radioactive, proton irradiated, tantalum target using reagents that do not contribute a hazardous waste component.     

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.     

Simulation of the interactions of galactic cosmic ray protons by irradiation of a thick stony target with 1.6 GeV protons

A thick spherical target (R=25 cm) made of gabbro was irradiated isotropically with 1.6 GeV protons at the Saturne cyclotron at Laboratoire National Saturne (LNS)/CEN Saclay in order to simulate the interaction of galactic cosmic ray (GCR) protons with meteoroids in space. During a 2 weeks irradiation a proton-dose of 1.32 · 10¹⁴ cm^–2 was received, which is equivalent to a cosmic-ray exposure age of 1.4 Ma. Production rates were measured by X- and gamma-spectrometry, by low-level counting and by conventional and accelerator mass spectrometry (AMS). Up to now, more than 200 target-product combinations were investigated. Theoretical production rates were derived on the basis of spectra of primary protons, secondary protons and secondary neutrons calculated by Monte Carlo techniques and thin-target cross sections of the underlying nuclear reactions. The model calculations excellently describe the production depth profiles in the artificial meteoroid, if reliable crosss sections are available. The thus validated model calculations allow for the interpretation of cosmogenic nuclide abundances in stony meteorites and lunar samples in terms of their exposure history and of the history of the radiation itself.Dedicated to R. Berndt on the occasion of his retirement.     

Photoluminescence study of silicon solar cells irradiated with large fluence electrons or protons

In order to investigate the anomalous degradation of space silicon solar cells which was found in large fluence region, photoluminescence measurements are carried out for the cells irradiated with 1 MeV electrons with a fluence exceeding 1×10¹⁶ e/cm² and 10 MeV protons with a fluence exceeding 1×10¹³ p/cm². For both irradiation, the intensity of boron-related bound exiton line decreases with fluence and it disappears at the fluences where the anomalous degradation occurs. The dominant defect is a complex of an interstitial carbon and an interstitial oxygen (C_I–O_I). The generation of five-vacancy-defects was also observed for the proton irradiation. Variations of photoluminescence line intensity are discussed in terms of displacement damage dose calculated based on non-ionizing energy loss (NIEL).     

Effect of ultraviolet radiation on polyethylene naphthalate films irradiated with high-energy heavy ions

The effect of UV radiation in the spectral range of 280–400 nm on polyethylene naphthalate (PEN) films has been studied. Changes in the optical absorption spectra of PEN after exposure to accelerated ions and UV radiation have been revealed. Changes in the surface properties have been explored, and the depth of the degraded polymer layer after long-term UV irradiation in air has been measured. Depending on the treatment time, the depth has made 0.1–0.9 μm. The photoablation rate and the quantum yield of monomer unit removal due to UV irradiation of the PEN films have been estimated at ~0.7 × 10^?4 molecule/photon. The possibility of the formation of asymmetric pores in PEN films using controlled photooxidative degradation has been shown.     

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.     

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.     

Spectrographic analysis of tantalum pentoxide

Summary The mutal influence of Fe, Si, Mo, Nb, Cr, Al, Ti, Ni on the spectrographic determination of these elements as trace impurities in tantalum pentoxide matrix has been investigated. In a preliminary experiment designed according to Plackett and Burman the influence of Fe and Al proved to be insignificant. Consequently both elements were excluded from further investigations. Based on experiments carried out on standard samples whose compositions resulted from factorial plans 2ⁿ, 3ⁿ, rotatable composite design and conventional calibration methods, the mathematical models of interference effects were fitted. In all the cases studied it was found that the correction of analytical results for the interference effects by means of polynomial models containing concentrations of interferents, was more effective than by means of conventional calibration methods. Those models in which a logarithmic analytical function was applied, proved to be most effective.

---

Spektrographische Analyse von Tantalpentoxid Eine Untersuchung der Störeffekte

     

Quantitative ultratrace distribution analysis of tantalum wires with SIMS

Summary The potential of SIMS for multielement ultratrace bulk analysis in refractory metals has already been shown in previous publications [1, 2]. In this paper it will be demonstrated, that the high sensitivity of SIMS can be used advantageously for high resolution distribution analysis. Due to the high useful yield (0.5 to 10^–5) it is possible to perform distribution analysis in the ng/g range with a sample consumption of about 1 pg per data point. A good lateral resolution of about 1 m and the variability of the sputtering rate over 3 orders of magnitude allow an optimization of the measurement parameters with respect to the sample geometry. This is of special importance in our work, because small lateral dimensions, high total sputtering depth (300 m) and crooked surfaces have to be considered. In this paper also the technical significance of sensitive high resolution distribution analysis of tantalum wires, which are used for microelectronic applications, will be discussed.

---

Quantitative Ultraspuren-Verteilungsanalyse von Tantaldrähten mit Hilfe von SIMS

---

Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Analytical capabilities of X-ray emission induced in heavy elements by high-energy protons and alpha-particles

The possibility of using high-energy ion beams for analytical purposes is explored. The most promising field is the identification of medium-weight elements by detection of K X-rays following alpha-particle and proton bombardment, where a sensitivity well bellow 1 ppm was predicted. In the case of heavy elements, interferences are possible because of competition of nuclear reactions. In the case of rare earths, the method is interference free, quantities of 0.1 mg/cm² can be determined.     

Solvent extraction of no-carrier-added 103Pd from irradiated rhodium target with a-furyldioxime

Summary Solvent extraction of no-carrier-added ¹⁰³Pd was investigated from irradiated rhodium target with a-furyldioxime in chloroform from diluted hydrochloric acid. Extraction yield was 85.3% for a single extraction from 0.37M HCl and ¹⁰³Pd purity was better than 99%.     

Determination of impurities in tantalum by a radiochemical neutron activation analysis

A radiochemical separation method using Dowex 1×8 (200–400 mesh) has been applied to two tantalum metals of 99.9% purity. While tantalum was still retained on the resin, the elements Na, K, Cr, Mn, Fe, Co and Zn were separated with 2M HF and subsequently the elements Sc, As, Zr, Mo, Eu, W and Hf with a mixture of 0.5M HF and 3M HCl. The separation yields for all impurities was 98–100%. Elemental contents were calculated by a single comparator method using two monitors.     

The molecular-topological structure and thermal stability of Ftorplast F-2M polyvinylidene fluoride irradiated with 1-MeV protons

Pelletized polyvinylidene fluoride (PVDF) of the Ftorplast F-2M brand is a semicrystalline diblock polymer, and its topological structure remains almost unchanged after bombardment with 5 × 10¹⁴ proton/cm². The glass transition temperature of the irradiated polymer is reduced by 2°C, but the melting point of the crystalline polymorph and the flow temperature of the polymer significantly increase (from 35 to 137°C and from 132 to 151°C, respectively); the mass fraction of the crystalline modification also increases (from 0.12 to 0.70). As a result of fluorine abstraction by fast protons to form HF, the fluorine content of the polymer decreases and the carbon content increases. The irradiation has no substantial effect on the onset temperature of intense gas evolution or the composition of the gas released during heating the polymer to 300°C.     

Yields of photonuclear reactions for photon-activation analysis with high-energy bremsstrahlung

Experimental reaction yields have been determined for various types of photonuclear reactions, induced in 52 elements by means of Bremsstrahlung irradiation with maximum energies ranging from 30 to 72 MeV, and of detection of the resultant activities with a lithium-drifted germanium detector. From the results obtained, sensitivities in photon-activation analysis were evaluated and the reactivity of high-energy photons with nuclei in a wide range of atomic number is discussed. Some nuclear considerations in photon-activation analysis, involving the relative probability of forming each product as a result of the (gamma,xnyp) reactions are also given.     

Spectroscopic analysis of irradiated erythrocytes

The aim of the present work is to study the effect of gamma radiation on the lipid part of the erythrocyte membrane, and to test the efficiency of lipoic acid as a radioprotector. This effect was evaluated using electron paramagnetic resonance (EPR), and Fourier transform infrared (FT-IR) spectroscopy. The results showed an increase in the number of spin density by 14%, 22% and 65% after exposure to 25, 50 and 100 Gy respectively; whereas there was a decline in the obtained density after incubation with lipoic acid by a factor of approximately 32%. The FT-IR spectra of the irradiated erythrocytes samples showed a marked decrease in the intensity of all characteristic peaks, which increased as the irradiation dose increased. The second-derivative of these spectra, allow the conformationally sensitive membrane acyl chain methylene stretching modes to be separated from the protein (mostly hemoglobin) vibrations that dominate the spectra of intact cells. The 2850 cm⁻¹ band showed changes in the band shape and position after exposure to 50 and 100 Gy. Therefore it can be concluded that the band at 2850 cm⁻¹ only is useful in monitoring the radiation effect of the lipids cell membrane intact cells.     

Pore formation in polyimide irradiated by high-energy ions and the properties of the obtained membranes

The optimum conditions are determined for etching latent Kr tracks in sodium hypochlorite solution to prepare polyimide track membranes (PI-TMs) with cylindrical pores and the electrosurface properties of the membranes are investigated. The stability of the porous structure of PI-TMs is studied at elevated temperatures (up to 250°C) in aggressive media (pH 1–12). It is shown that the porous structure of PI-TMs is characterized by enhanced chemical and thermal stability.