Milan Štefánik

Fast neutron irradiation effects on two Fe-based metallic glasses, Fe₇₉Cu₁Nb₇B₁₃ and Fe₇₈Si₉B₁₃, were investigated up to integral fluences of 3 × 10¹⁶ n/cm². Structural characterization by total scattering and pair distribution function analysis revealed no irradiation-induced crystallization and only negligible modifications of the short- and medium-range atomic order. Mössbauer spectroscopy confirmed the amorphous character of both alloys after irradiation and showed that hyperfine parameters such as mean isomer shift and mean hyperfine field remained essentially unchanged. The most pronounced effect was a reorientation of the net magnetic moment towards the in-plane direction after irradiation. These results demonstrate that Fe-based metallic glasses are structurally stable under fast-neutron exposure, with irradiation primarily influencing their magnetic microstructure.

Recent Tc 91 , 92 , 93 activation for deuterons incident on Mo nat has become a challenge for the nuclear level density (NLD) angular-momentum dependence. Actually, replacement of the moment of inertia rigid-body value I r by half of it, within a given NLD parameter set, demands a change of the rest of NLD parameters significantly beyond their fitted limits. The corresponding uncertainty of calculated cross sections versus the NLD parameter accuracy is also higher, while use of either the same or distinct compound-nucleus and preequilibrium emission spin distributions becomes significant at higher incident energies. Nevertheless, the current way to describe experimental isomeric cross sections by using at most half of I r values provides agreement of the measured and calculated data at the price of less and less correct NLDs. The moment of inertia relevance for the NLD correctness also emphasizes the value of a direct method to endorse it. Further measurements of average resonance spacings of s -wave neutrons and protons, corresponding to different spins of the same nucleus, are therefore highly demanded.

At the Department of Nuclear Reactors of the Faculty of Nuclear Sciences and Physical Engineering of the Czech Technical University (FNSPE CTU) in Prague, there is a need to implement a neutron activation analysis as a tool for the separation of uranium foils depending on various 235U and 238U contents. Experiments were carried out on the training reactor VR-1 “Sparrow”, which is operated at the institute mentioned above. The uranium foils were analysed using the neutron activation analysis and gamma-ray spectrometry, and were separated into two groups, the first group contained foils of depleted uranium and the other contained natural uranium foils. The uranium foils can be further used for educational purposes or experimental applications, such as the measurement of neutron spectral indexes, neutron activation analysis of uranium ore, or delayed neutron analysis. The neutron activation analysis has been extended to determine whether foils contain natural or depleted uranium.

The high complexity of deuteron-nucleus interactions is due to (i) a variety of reactions induced by nucleons that follow the deuteron breakup (BU), owing to the deuteron weak binding energy, and (ii) the specific stripping and pickup direct reactions (DRs) in addition to the statistical processes of preequilibrium emission (PE) and evaporation from the compound nucleus (CN). Moreover, an update of the limited experimental deuteron database is needed, and there is an incomplete theoretical framework for deuteron activation analysis. Accurate new measurements of low-energy deuteron-induced reaction cross sections for natural Mo target are intended to enhance the related database and provied a consistent account of BU, DR, PE, and CN involved reaction mechanisms. The activation cross sections for Tc 91 – 97 , 99 , 101 residual nuclei in deuteron-induced reactions on Mo were measured by the stacked-foil technique and high-resolution gamma spectrometry using the U-120M cyclotron of the Center of Accelerators and Nuclear Analytical Methods (CANAM) infrastructure of the Nuclear Physics Institute of the Czech Academy of Sciences (NPI CAS), at energies up to 20 MeV, and using the Neutrons for Science (NFS) SPIRAL2/GANIL facility at energies up to 40 MeV, where a single-foil technique and a dedicated transport system were used for short-lived isotopes. Their extended analysis, including all available data for deuteron interactions with Mo isotopes up to 50 MeV, considered every process from elastic scattering until CN evaporation, with particular attention paid to BU and DR mechanisms. The newly measured activation excitation functions have improved substantially the deuteron database for molybdenum, which is a major constituent of large-scale facilities using deuteron beams. Concurrent analysis of all available data has brought forward questions concerning their consistentcy. The suitable description of nuclear mechanisms involved within deuteron-induced reactions on Mo, especially the BU and DR processes, is validated by overall agreement of the calculated and measured cross sections including the new data at low energies. The analysis of many isomeric-state activation data in this work provides also a quite useful analysis of the CN+PE spin distribution effects. Published by the American Physical Society 2025

Described research work is focused on the study of environmental pollution in the Czech Republic using an instrumental neutron activation analysis (INAA). The samples of mosses and alluvial soils were irradiated at the VR-1 training reactor utilizing a nondestructive (instrumental) method of NAA at the Czech Technical University in Prague. Subsequently, the gamma-ray spectra of investigated samples were measured at a semiconductor high purity germanium (HPGe) detector. A qualitative and quantitative analysis of the samples of alluvial soils and mosses from nine regions in the Czech Republic was performed. The presence of Na, K, Ti, V, Al, Au, Mn, Fe, and others was revealed in the studied samples. Apart from these, Ba, Br, As, or Hg were found using qualitative analysis. Depending on the obtained production rates, the amount of Na, K, Al, Au, As, Ti, V, and Fe was determined. Based on the results, it can be verified that the VR-1 training reactor is a suitable device for identifying the composition and concentration of the environmental samples. In the future, more data utilizable for environmental pollution monitoring can be obtained.