Special spectrum regions, like around the annihilation peak at 511 keV, the boron peak at 478 keV, the Ge-triangles, as well as complicated multiplets or heavily distorted intense peaks require ...special attention when evaluating prompt gamma activation analysis (PGAA) spectra. A computer code and the related analytical practice of the Budapest PGAA facility is presented to improve the spectroscopy of these cases beyond the past practice relying on the well-known Hypermet-PC software.
This paper discusses the current status of the European research reactor (RR) fleet and identified opportunities for its utilization. The data for this analysis was collected through a specific ...questionnaire from which a database of the European RR fleet was created. The questionnaire was designed to assess the degree of exploitation of different RR applications and to identify gaps and opportunities for future utilization. The results indicate that the European RR fleet is older compared to the world average, with no new research reactors built in Europe since 1992. The majority of RRs reported low levels of exploitation across all applications, and a desire to expand utilization was expressed by 78% of respondents. Lack of manpower, finance, and customers were identified as the main obstacles preventing expansion, while the need for more nuclear engineers was identified as a clear opportunity to attract people to the field. The findings of this study emphasize the need for actions to be taken to combat future needs and to improve the utilization of the European RR fleet. Overall, this study provides valuable insights for policymakers, industry professionals, and researchers working in the field of nuclear energy.
We present here Monte Carlo computer simulations to broaden the scope of the prompt-gamma activation analysis (PGAA) from the elemental composition measurement of ideal, point-like, homogeneous ...samples towards non-homogeneous or heterogeneous but still regularly-shaped samples. The successful correction for the negative matrix effect related to the neutron self-shielding and gamma self-absorption is a key step in the quantitative analysis of layered metal structures. This geometry is relevant to practical cases where corrosion layer, patina, paint, coating, gilding, or segregation are present on the surface of a core metal. Linear neutron attenuation coefficients are measured in a polychromatic neutron beam by radiography, while the gamma attenuation calculations by MCNP6 simulations were validated by gamma transmission measurements. Finally, the method was successfully applied to correct for the PGAA matrix effect in double- and triple-layer metal stacks and a real structured numismatic sample.
Results of geant4 Monte Carlo simulations carried out on the Budapest PGAA detector are presented in this paper. A complete set of detector response functions, i.e. the gamma spectra corresponding to ...incremental gamma-ray energies up to 12 MeV, were obtained by simulations and used to unfold the experimental gamma spectra of60Co and152Eu. The unfolding successfully removed the continuous Compton-background and the escape peaks related to a full-energy peak but preserved the shape and area of the peak itself. We finally demonstrated the applicability of this approach in determining the total radiative neutron capture cross-sections of the14N(n, γ) reaction, where an excellent agreement with literature data was found.
The analysis workflow of Prompt gamma activation analysis (PGAA) at the Budapest Neutron Centre’s PGAA and NIPS-NORMA facilities, at the MLZ FRM II PGAA station, and other centers worldwide relied on ...the use of the Hypermet-PC gamma spectrometry software and the ProSpeRo concentration calculation Excel macro. The sustained interest of our user community amid the reduced availability of multiple large-scale neutron sources worldwide called for more efficient utilization of the operational PGAA facilities. The present paper addresses both measurement and data evaluation bottlenecks of the analysis procedure to achieve higher productivity and superior spectroscopic performance.
Discussed are the recent experimental and theoretical results on palladium‐based catalysts for selective hydrogenation of alkynes obtained by a number of collaborating groups in a joint multi‐method ...and multi‐material approach. The critical modification of catalytically active Pd surfaces by incorporation of foreign species X into the sub‐surface of Pd metal was observed by in situ spectroscopy for X=H, C under hydrogenation conditions. Under certain conditions (low H2 partial pressure) alkyne fragmentation leads to formation of a PdC surface phase in the reactant gas feed. The insertion of C as a modifier species in the sub‐surface increases considerably the selectivity of alkyne semi‐hydrogenation over Pd‐based catalysts through the decoupling of bulk hydrogen from the outmost active surface layer. DFT calculations confirm that PdC hinders the diffusion of hydridic hydrogen. Its formation is dependent on the chemical potential of carbon (reactant partial pressure) and is suppressed when the hydrogen/alkyne pressure ratio is high, which leads to rather unselective hydrogenation over in situ formed bulk PdH. The beneficial effect of the modifier species X on the selectivity, however, is also present in intermetallic compounds with X=Ga. As a great advantage, such PdxGay catalysts show extended stability under in situ conditions. Metallurgical, clean samples were used to determine the intrinsic catalytic properties of PdGa and Pd3Ga7. For high performance catalysts, supported nanostructured intermetallic compounds are more preferable and partial reduction of Ga2O3, upon heating of Pd/Ga2O3 in hydrogen, was shown to lead to formation of PdGa intermetallic compounds at moderate temperatures. In this way, Pd5Ga2 and Pd2Ga are accessible in the form of supported nanoparticles, in thin film models, and realistic powder samples, respectively.
Find the beauty on the inside: Recent work is reviewed that shows how the modification of Pd surfaces by incorporation of foreign species X in the sub‐surface of Pd metal (X=H, C, Ga) can be developed into a design tool for hydrogenation catalyst development.
By using state-of-the-art experiments and theoretical calculations, we unravel mechanistic details of HCl oxidation on the industrially relevant RuO2/SnO2 catalyst. On the extensively chlorinated ...surface, oxygen activation is the rate determining step. Display omitted
► RuO2/SnO2 Deacon catalysts consist of two major RuO2 morphologies, (2–4nm particles) and 1–3ML epitaxial RuO2 films. ► Steady state Deacon kinetics indicates a medium-to-strong positive effect of reactants (HCl, O2) partial pressures. ► There is strong product inhibition by water and chlorine. ► On the extensively chlorinated surface, oxygen activation is the rate-determining step. ► DFT-based micro-kinetic modeling suggests that the reaction is structure sensitive.
Rationally designed RuO2-based Deacon catalysts can contribute to massive energy saving compared to the current electrolysis process in chemically recycling HCl to produce molecular chlorine. Here, we report on our integrated approach between state-of-the-art experiments and calculations. The aim is to understand industrial Deacon catalyst in its realistic surface state and to derive mechanistic insights into this sustainable reaction. We show that the practically relevant RuO2/SnO2 consists of two major RuO2 morphologies, namely 2–4 nm-sized particles and 1–3-ML-thick epitaxial RuO2 films attached to the SnO2 support particles. A large fraction of the small nanoparticles expose {110} and {101} facets, whereas the film grows with the same orientations, due to the preferential surface orientation of the rutile-type support. Steady-state Deacon kinetics indicate a medium-to-strong positive effect of the partial pressures of reactants and deep inhibition by both water and chlorine products. Temporal Analysis of Products and in situ Prompt Gamma Activation Analysis strongly suggest a Langmuir–Hinshelwood mechanism and that adsorbed Cl poisons the surface. Under relevant operation conditions, the reactivity is proportional to the coverage of a specific atomic oxygen species. On the extensively chlorinated surface that can be described as surface oxy-chloride, oxygen activation is the rate-determining step. DFT-based micro-kinetic modeling reproduced all experimental observations and additionally suggested that the reaction is structure sensitive. Out of the investigated models, the 2ML RuO2 film-covered SnO2 gives rise to significantly higher reactivity than the (101) surface, whereas the 1ML film seems to be inactive.
Non-destructive characterization of decorated porcelain artifacts requires the joint use of surface-analytical methods for the decorative surface pattern and methods of high penetration depth for ...bulk-representative chemical composition. In this research, we used position-sensitive X-ray Fluorescence Spectrometry (XRF) and Prompt-gamma activation analysis (PGAA) for these purposes, assisted by 3D structured-light optical scanning and dual-energy X-ray radiography. The proper combination of the near-surface and bulk element composition data can shed light on raw material use and manufacturing technology of ceramics.
PDF
