In the course of an investigation of an electrostatic precipitation technique as a sampling method for airborne dust particles, elevated concentrations of As were found in the data collected during New Years Eve celebrations in Vienna. The original study confirmed the applicability of the new sampling device as a useful sampling method, showing elevated values for the elements Na, Mg, Al, Si, S, K, Cu, As, Br, Rb, Sr, Sb, Te and Ba, all associated with the use of pyrotechnics. The measured values for As could not be explained as a impurity in some other substances used. Thus, several unburned pyrotechnic products were investigated to find the source of As in the dust collected. The results showed only one product with higher than expected As contents (1.4 μg g−1), leading to the assumption of intentional—but illicit—use of arsenic compounds in pyrotechnics as a colouring agent for the production of blue light.

The impact of Chicxulub (Yucatan, Mexico) was a global event exhibiting a short-time (fallout) and a long-time (boundary clay) sedimentation of the K/T-boundary [1]. The fallout is mainly characterized by iridium, Ni-Cr-rich magnesia-ferrite spinels (K/T-spinels), spherules, as well as shocked quartzes. The amount of the sediments and their distribution depend on the distance from the impact crater. The Cretaceous/Paleogene (K/T) boundaries at three different locations namely Caravaca (Spain), Cerbara (Italy), and Bjala (Bulgaria) have been well analyzed. About 65 million years ago, they were located at the distances from the impact crater ∼6000 km, ∼7500 km, and ∼8800 km, respectively. The boundary clay is characterized by transported minerals like quartzes and feldspars, authigenically formed minerals, as well as biominerals like Mg-calcites and greigites (Fe3S4). The samples were analyzed by scanning X-ray diffractometry (Bruker Analytical X-ray System), scanning electronic microscopy (XL30, ESEM-Philips), neutron activation analyses, DeltaC and DeltaO analyses, and the determination of nannofossils and foraminifera. Owing to the Earth’s rotation, the analyzed samples lie along a great circle (crossing the equator under an angle of ∼23 ) which covers Chicxulub, Caravaca, Cerbara, and Bjala indicating the existence of only a single impact. The study of this K/T-boundary by means of high resolution scanning X-ray diffractometry in combination with the scanning electron microscopy and neutron activation analyzes revealed the time dependency of the K/T-event in the fallout as well as in the boundary clay. The biomineralization of sulfatereducing bacteria by greigites provided the duration of the sulfuric acid rain. The reoccurrence of algae is indicated by the appearance of Mg-calcite at the end of the boundary clay. The K/T-spinels were formed on the nucleus of metallic iridium [2]. They were built in the mesosphere (in a height of about 100 km) and grew during the fall to the Earth’s surface by forming ferrimagnetic twins, which were etched by the H2SO4 content of the atmosphere. We developed an extensive mathematical model incorporating all relevant physical effects (particle growth, pressure dependence of the atmosphere, fluid resistance, centrifugal and coriolis forces, etc.) in order to study the development of the particles during the fall. For Caravaca, the shortest flight time for the Iridium fallout is approximately 6.5 days, while the shortest flight time for the ejecta near Chicxulub last only a few hours.

A system for Automatic NAA is based on a list of specific saturation activities determined for one irradiation position at a given neutron flux and a single detector geometry. Originally compiled from measurements of standard reference materials, the list may be extended also by the calculation of saturation activities from k 0 and Q 0 factors, and f and a values of the irradiation position. A systematic improvement of the SRM approach is currently being performed by pseudo-cyclic activation analysis, to reduce counting errors. From these measurements, the list of saturation activities is recalculated in an automatic procedure.

Combining the powers of a fast pneumatic transport system and the Automatic Activation Analyzer (AAA) of the Atominstitut in Vienna with the newest version of the IAEA k(0)-Software, the application of the k(0)-method to the determination of short-lived radionuclides becomes easily possible. By calculating Asp-values with the IAEA software, the often expensive and time-consuming measurement of Asp-values using certified reference materials is reduced to quality control checks. Measurements clearly show that the two approaches are equivalent, especially since both take self-absorption and neutron self-shielding into account. In this way it is possible to expand the library of the AAA with many hitherto unobtainable Asp-values. At the same time, using highly accurate Asp-values already measured for many short-lived radionuclides, k(0)-values for those can be produced with a simple procedure.

Automatic activation analysis (AAA) is rendered possible by a unique neutron activation analysis facility for short-lived isomeric transitions based on a fast rabbit system with sample changer and sample separation, and an adaptive digital gamma-spectrometer for very high counting rates of up to 10 6 cps. The system is controlled by a computer program performing irradiation control, neutron flux monitoring, and gamma-spectrometry with real-time correction of counting losses, spectra evaluation, nuclide identification and calculation of concentrations in a fully automatic procedure. As spectrometry is done by means of hundreds of sequentially measured pairs of concurrently recorded loss-corrected and non-corrected spectra, concentrations are derived from an optimally weighted average of all individual occurrences in this sequence of spectra which also enable the separation of isomeric transitions with coinciding energies but different half-lives such as 116m2 In (162.4 keV, T 1/2 = 2.2 s) and 77m Se (162.2 keV, T 1/2 = 17.4 s). To clear up repeatedly voiced misconceptions concerning the errors of loss-free counting our findings of 1978 and 1981 are reiterated, namely that the counting error of a peak in a corrected spectrum may be derived consistently from the error of the same peak in the respective non-corrected spectrum and from the error of weighting factors in the corresponding region of interest, according to the principle of propagation of errors. Experimental proof is provided for conditions of stationary as well as rapidly varying counting rates and spectral shapes.

A system for rapid automatic neutron activation analysis is governed by software performing irradiation control, neutron flux monitoring and gamma-spectrometry with real-time correction of counting losses as well as spectra evaluation, nuclide identification and calculation of concentrations in a fully automatic flow of operations. 1,2 Elemental concentrations are derived from a list of experimentally determined specific saturation activities. To expand this list, the “k0_IAEA” software 3 is presently under evaluation and will be reported on in this paper. At a Triga reactor, reactor pulse activation may enhance the sensitivity for very short half-lives, 4 and will be presented in our paper.

For the practical application of large sample activation analysis, an extensive characterization of the irradiation facility and of the measurement system — of sample size, flux-gradient, maximum count rate, size of irradiation and counting containers, estimation of created activity after irradiation and dose rate — is required.The term, “large samples” is not unequivocal. Here the consideration is restricted to samples from several grams to 100 or 200 grams, which can be irradiated in existing irradiation facilities. Calculations were performed for about 1200 organic samples divided into 18 groups. The results are in about 400 tables. The effective Z number, Z/A ratio, mass attenuation for several gamma lines, the relative contribution of the main absorbing elements in the sample for effective cross sections and for gamma transmission are calculated for each sample. All these data have been calculated for various sizes of irradiation and measuring containers. Macroscopic thermal, epithermal, scattering and transport cross sections were used for calculation of self-shielding by five different methods. Owing to the limited space only a selection of the most pertinent values characterizing each group of samples is presented and discussed.The main differences of Large Sample NAA to other nuclear analytical methods are self-shielding and gamma attenuation in the sample. The main object of this paper is to show up problems that may arise in LS-NAA through self-shielding and gamma attenuation.

Exhaust systems of modern cars contain catalysts for the reduction of CO, NOx and hydrocarbons. These catalysts are made of ceramic materials with a large surface on which platinum metals catalyse the oxidation. The catalysts contain approximately 2 g of platinum and 0.4 g of rhodium. Recently platinum is being replaced by palladium. During driving the platinum-group elements (PGEs) are expelled from the tip in fine particles and are deposited in the environment. For a projected study of emissions from cars driven on streets and highways it is important to know which elements can be measured by short time activation analysis without any chemical procedure.

Dubbed "Analyzer" because of its simplicity, a neutron activation analysis facility for short-lived isomeric transitions is based on a low-cost rabbit system and an adaptive digital filter which are controlled by a software performing irradiation control, loss-free gamma-spectrometry, spectra evaluation, nuclide identification and calculation of concentrations in a fully automatic flow of operations. Designed for TRIGA reactors and constructed from inexpensive plastic tubing and an aluminum in-core part, the rabbit system features samples of 5 ml and 10 ml with sample separation at 150 ms and 200 ms transport time or 25 ml samples without separation at a transport time of 300 ms. By automatically adapting shaping times to pulse intervals the preloaded digital filter gives best throughput at best resolution up to input counting rates of 10(6) cps. Loss-free counting enables quantitative correction of counting losses of up to 99%. As a test of system reproducibility in sample separation geometry, K, Cl, Mn, Mg, Ca, Sc, and V have been determined in various reference materials at excellent agreement with consensus values.

Anthropogenic activity is one of the causes of contamination in the human environment: contamination of air, water, top soils, plants and food products has complex effects on human health problems. Wear and abrasion of various surfaces are constant processes in daily life, and commonly include interaction between human fingers and surfaces of every conceivable material. New methods for investigation of trace transfer processes by human fingers are described. Results of transfer for commonly used metals such as gold, silver, zinc, cadmium, tin, cobalt, nickel, chromium and iron are presented. Relationship between transfer of metals by touch and the general problem of purity in analytical activities is briefly discussed.

A simple but highly effective rabbit system is made from an aluminum in-core part, inexpensive plastic tubing and an industrial compressed air generator. Large sample containers have a volume of 25 ml. Smaller containers of 5 ml automatically separate from a transport capsule. A transport time of below 0.5 second enables fast neutron activation analysis (FNAA). A software implementation of a Loss-Free Counting multi-channel analyzer, storing immediately into the multi-megabyte memory of a low-cost 486 or Pentium type PC, enables the real-time control of a rabbit system as well as the collection of up to 1000 pairs of simultaneously recorded loss-corrected and non-corrected spectra of 16 k channels each, in a true sequence without time gaps in between, at throughput rates of up to 200 kc/s. By automatically adapting the noise filtering time to individual pulse intervals, the Preloaded Digital Filter (PLDF) combines low- to medium-rate resolutions comparable to those of high-quality Gaussian amplifiers with throughput rates of up to 100 kc/s, and high-rate resolutions superior to those of state-of-the-art gated integrator systems. The combination of rabbit system, PLDF and software based multi-channel analyzer provides a low-cost but powerful solution for NAA at Triga reactors in developing countries.

Instrumental neutron activation analysis was utilized for the multielemental determination of elements in the roots of Ageratum conyzoides , a tropical medicinal plant that is used locally for the cure of various diseases in Nigeria. The concentrations of Al, Ba, Br, Ca, Co, Cr, Fe, K, Mg, Mn, Na, Rb, Sc, Sr, V and Zn were analyzed with the 250 kW Triga Reactor at the Atominstitut, Vienna. The essential elements K, Na, Ca, Fe, Mg, Mn and Zn and the non-essential elements Al, Ba, Sr and Rb are present in significant concentrations. Other elements including Co, Cr, Sc and V are present at trace levels. The likely implication of these elements in restoring and maintaining good health is discussed. Quality control on the measurements was carried out by analyzing standard reference materials alongside the samples.

A software implementation of a loss-free counting multichannel analyzer, storing immediately into the multimegabyte memory of a low-cost 486 or Pentium type PC, enables the real-time control of a rabbit system as well as the collection of up to 1000 pairs of simultaneously recorded loss-corrected and non-corrected spectra of 16 k channels each, in a true sequence without time gaps in between, at throughput rates of up to 200 kc/s. 1 Intended for activation analysis of short-lived isomeric transitions, the system renders possible peak to background optimizations and separations of lines with different half-lives without an a priori knowledge of sample composition by summing up appropriate numbers of spectra over appropriate intervals of time. By automatically adapting the noise filtering time to individual pulse intervals, the Preloaded Digital Filter (PLDF) combines low- to medium-rate resolutions comparable to those of high-quality Gaussian amplifiers with throughput rates of up to 100 kc/s, and high-rate resolutions superior to those of state-of-the-art gated integrator systems. In contrast to commercially available digital filters, the PLDF in its new implementation performs pulse shortening as well as pole zero cancellation in the analog domain. This not only results in a simpler digital core but also, for the first time, makes possible the use of a low-cost ADC in a spectrometric application. 2 A simple but highly effective rabbit system is made from an aluminum incore part, inexpensive plastic tubing and an industrial pressurized air generator. Large sample containers have a volume of 25 cm 3 . Smaller containers of 5 cm 3 are automatically separated from a transport capsule. A transport time of below 0.5 s enables activation analysis of short-lived isomeric transitions. The combination of rabbit system, PLDF and software based multichannel analyzer provides a low-cost but powerful solution for NAA at Triga reactors in developing countries, a forthcoming research project of the IAEA, Vienna.

In 1991, a Cretaceous-Tertiary (K-T) boundary was discovered in Bulgaria in marine sediments on the coast of the Black Sea near the city of Bjala, 35 km south of Varna. At the Bjala 2b site, rhythmic sedimentation under hemipelagic conditions from the Late Cretaceous (30 m below the K-T boundary) to the early Paleogene (70 m above the K-T boundary) resulted in the deposition of 100 m of marly limestone and intercalated marl. In these strata, 200 marly limestone beds correspond to precessional Milankovitch cycles of an average duration of 22.5 k.y. An absolute geological time scale over 4 m.y. is obtained from the number of limestone beds of the measured magnetic polarity zones (chronozones 29R to 27R). The reference age (65.0 Ma) is assumed to correspond to the level with the maximum Ir and Ni-rich spinet content in the K-T profile.The process of geomagnetic polarity reversals is relatively short (5-10 k.y.) compared to the geomagnetic polarity zones between the reversals (0.2-1.2 m.y.). The sediments show CaCO3 minima of the marly limestone beds and maxima of magnetic susceptibility in the geomagnetic polarity reversals. In addition to the magnetic minerals such as greigite, extraterrestrial ferrimagnetic spinels composed of Ni-rich magnesioferrites with high Cr contents were found at the polarity reversals. These extraterrestrial spinels are similar in their composition to the K-T spinels of the K-T impact at Chicxulub, but without etched pits on the octahedral faces of the spinet crystals.The K-T boundary profiles at Bjala are characterized by fallout sedimented within a short time, overlapped by boundary clay sedimented over a long time, and some partially reworked sediments. Names of extinct species, of survivors, and first occurrences of new species at Bjala 2b (chronozone 29R) are given.

Based on a Preloaded Digital Filter operating on a 20% n-type HpGe detector with transistor reset preamplifier, and on a software implementation of a loss-free counting MCA, storing immediately into the multi-megabyte main memory of a low-cost 486-type PC, the new system enables the collection of up to 120 pairs of simultaneously recorded loss-corrected and non-corrected spectra of 16 k channels each, in a true sequence without time gaps in between, at a throughput rate of up to 140 kc/s. Intended for activation analysis of short-lived isomeric transitions, the system for the first time makes possible peak to background optimizations and even separations of lines with different half-lives without an a priori knowledge of sample composition by summing up appropriate numbers of spectra over appropriate intervals of time. The speed of this programmable system also made possible the direct comparison of two methods of real-time correction of counting loss. by simultaneous recording of LFC-corrected, ZDT(tm)-corrected and non-corrected spectra together with their corresponding weighting factor distributions.

The new measurement system for high-resolution, high-rate gamma -spectrometry consists of a 20% n-HPGe detector with a transistor reset preamplifier, a PLDF-system, and a software implementation of an LFC-multichannel analyzer allowing the continuous registration of 120 pairs of 16k channel gamma -spectra, pile-up and dead-time corrected, and uncorrected [3, 4]. Thus, it is possible to obtain the total information contained in the gamma -spectra of short- and medium-lived radionuclides after a short neutron irradiation. The new gamma -spectrometry system was tested by activation of a mixture of In, Se, and Ba. This enables the optimal analysis of radionuclides by selecting the optimal summation range simultaneously with a quality assurance of the data by plotting the decay curves of the respective radionuclides.

The usual mass of samples for activation analysis is in the range of several milligrams to several hundred milligrams. An improvement of the detection limit by three orders of magnitude is attainable by use of a larger sample size. Limitations of the method due to thermal effects, neutron self-shielding and gamma-ray attenuation during activation and measuring of large organic samples are discussed.

Fields in which progress has been achieved at the Atomic Institute Vienna are discussed briefly. The use of short and medium lived nuclides for activation analysis (AA). Construction of out-core parts of a fast transfer system. Combined sample catcher sample-changer for AA allowing cyclic and pseudocyclic AA. A system for discontinuous or continuous irradiation of liquid samples. Counting with an anticompton shield and quantitative correction of random coincidences. Screening analyses with the fast irradiation and measurement system. Improved peak-evaluation of gamma-spectra, Epithermal AA by a neutron converter. Following short-lived nuclide measurement, automatic sample transfer into a well-type detector enabling sensitive counting of nuclides with short half-lives. Use of large samples to increase the detection limits of ng to pg at activation with moderate neutron flux. Flux determination by liquid scintillation counting.