The impact of chronic gamma irradiation (8 days, dose rate 12 μcGy/s, absorbed dose 8.29 cGy) on Pseudomonas aeruginosa strains IMV 9024, IMV 9095, and IMV 9096 was investigated. Irradiation of phytopathogenic strains IMV 9024 and IMV 9096 enhanced their phytotoxic activity, whereas in strain IMV 9095, it primarily promoted bacterial growth. In addition, irradiation stimulated pigment biosynthesis, notably the production of pyocyanin (in all examined strains, with the strongest effect in IMV 9024) and pyomelanin (in IMV 9024 and IMV 9096, most prominently in IMV 9024). The persistence of elevated phytotoxic activity across multiple bacterial generations following infection suggests the involvement of epigenetic regulatory mechanisms sustaining virulence factor expression. Collectively, these findings demonstrate that chronic low-dose irradiation can induce substantial alterations in plant–phytopathogen interactions.
This study investigated using of silicon photomultiplier (SiPM) for scintillation γ-spectrometry with CdWO4, CsI(Tl), and NaI(Tl) crystal scintillators. At room temperature, CsI(Tl) crystal scintillator provides the best performance, while the achievable energy resolution is lower compared to that obtained with conventional photomultiplier tube (PMT) with green-enhanced photocathode. These findings highlight the potential of SiPMs as a compact and cost-effective alternative to PMTs in nuclear physics applications, particularly for light portable spectrometers, such as radiation monitoring systems based on small unmanned aerial vehicles.
The surveillance program is an important source of information on the change in the properties of the metal of the water-water power reactor pressure vessel during operation. The regular program carried out at the power units of the Ukrainian NPPs provides material science support for the safe operation of the VVER-1000 pressure vessel until the end of the designated service life. Therefore, regulatory documents in force in the nuclear power industry of Ukraine require the development and implementation of additional surveillance programs, which would, first of all, ensure the earlier irradiation of surveillance specimens compared to the reactor pressure vessel. To solve this problem, the programs for modernization of single-floor container assemblies with specimens that are irradiated at regular locations in the VVER-1000 reactors have been developed. The transition of Ukrainian NPPs to Westinghouse nuclear fuel requires updating these programs. For now, one of the programs for the modernization of single-floor container assemblies has been implemented at one of the power units with a VVER-1000 reactor.
The paper presents experience gained in the development and verification of neutron and photoatomic libraries for the specialized computational codes MCPV and MCSS, which are used for the analysis of radiation exposure of VVER reactor pressure vessels, irradiation parameters of reactor internals, and irradiation conditions of surveillance specimens. Approaches to the generation of multigroup neutron libraries with different nuclide compositions and energy coverage, as well as neutron and photoatomic libraries in continuous-energy representation in the ACE format, are discussed. The verification of the developed libraries was performed by comparing calculation results obtained using different Monte Carlo codes in benchmark problems of neutron and photon transport in a simple spherical geometry.
The influence of model parameters for the subcritical assembly core of the subcritical nuclear facility "Neutron Source" and uncertainties of nuclear reaction cross sections on the values of the effective neutron multiplication factor is investigated. The analysis is based on numerical simulation using the international software code MCNP 6.2. The possibility of achieving the design nuclear fuel load of 38 fuel assemblies for the subcritical assembly core with the tungsten neutron-generating target is shown with the justification of nuclear safety.
The article presents a model for comprehensive assessment and improvement of the comparative analysis method for nuclear reactor types in Ukraine, based on the methods proposed in the KIND and CENESO projects. The formation of key and auxiliary sets of indicators for analysis was carried out in accordance with the recommendations of IAEA regulatory documents and taking into account the national characteristics of Ukraine's energy system. The stages of a systematic approach to comparative analysis were formalized, and an evaluation algorithm based on attributes and their indicators was developed. The purpose of improving the method is the need to simultaneously take into account quantitative and qualitative attributes and their indicators, use adequate methods for determining their weights, and develop methods for the comprehensive evaluation of attributes and their indicators. The developed modifications of the analysis methods make it possible to determine the relative values of nuclear reactor types, taking into account expert assessments and the requirements of decision-makers. A weighted "generalized integral value function" was proposed for the comprehensive assessment of nuclear reactor types. The developed improved method is based on a systematic approach, the formation of an array of quantitative and qualitative attributes and their indicators for the corresponding groups of objectives, the method of hierarchy analysis, and the method of multi-criteria optimization. The detailing of the parameters of nuclear reactor types makes it possible to take into account the requirements of decision-makers regarding technical, economic, safety, and other attributes and their indicators.
The DAMA/LIBRA-phase2 experiment was upgraded in 2021 to enhance its sensitivity by lowering the software energy threshold while maintaining a large efficiency. The new configuration, referred to as DAMA/LIBRA-phase2-empowered, collected data for three years. This study extends the investigation of the long-standing, model-independent annual modulation effect pointed out by the DAMA highly radiopure NaI(Tl) experimental setups at the Gran Sasso National Laboratory of the National Institute for Nuclear Physics, using different experimental configurations. The software energy threshold of DAMA/LIBRA-phase2-empowered is below 1 keV, and the exposure is 0.541 t⋅yr. Adding these new results to the previously released DAMA/LIBRA-phase2, the exposure is 2.07 t⋅yr over 11 independent annual cycles, yielding evidence for a signal that fulfills all the requirements of the model-independent Dark Matter annual modulation signature at a confidence level of 13.9 σ in the 1–6 keV energy region. In the 2–6 keV interval, where data from DAMA/NaI and DAMA/LIBRA-phase1 are also available, the combined exposure reaches 3.40 t⋅yr, corresponding to a confidence level of 15.3 σ. No systematic effect or side process capable of simultaneously satisfying all the distinctive features of the exploited Dark Matter annual modulation signature and accounting for the observed modulation amplitude is available.
The article considers the possibility of obtaining new radiation-resistant polystyrene-based plastic scintillators by using high concentrations of activators. 2,5-diphenyloxazole, 2-(4-tert-butyl)phenyl)-5-phenyloxazole-1,3, 2,5-bis(4-(tert-butyl)phenyl)oxazole, 2-(4-tert-butyl)phenyl)-5-phenyl-1,3,4-oxadiazole and N-tolylcarbazole were used as activators. A number of PSs containing from 10 to 40 wt. % of each of the above activators was created, and their radiation resistance was investigated. Using 2,5-diphenyloxazole and its alkyl derivatives, PSs were developed, the light output half-attenuation dose of which reaches 280 kGy.
The value of absolute emission probabilities from the decay of 235U in the energy range of 200-450 keV was refined by using semiconductor gamma spectrometry with a reference material containing highly enriched uranium and mathematical modelling of the measurement geometry. This refinement is essential for the accurate gamma-spectrometric determination of characteristics (signatures) of highly enriched uranium that are crucial for nuclear forensics, such as model age and 228Th impurity. This clarification is also useful from the point of view of fundamental nuclear physics, as it introduces significant changes in the data concerning the 231Th level scheme from the alpha decay of 235U.
For the quantum quartic anharmonic oscillator with Hamiltonian H = ½(p2 + ω2x2) + λx4, our study has been further developed using a convergent expansion of the system's wave function in a modified oscillator basis with an adjustable frequency ω0, i.e., in the complete set of eigenfunctions {φn(ω0;x)} of a reference harmonic Hamiltonian H(0)(ω0) = ½(p2+ω02x2). Our proposed approach enables a significant improvement in the convergence rate of expansions through the additional adaptation of the basis functions to the specific structure of the system being analyzed. Primary attention is given to the rigorous mathematical implementation of the variational scheme, treating the basis frequency ω0 as a true nonlinear variational parameter subject to optimization. Within the framework of the generalized nonlinear Rayleigh - Ritz variational method, the system's energy is minimized with respect to the nonlinear parameter ω0 to accurately determine the optimal value of ω0 for different values of the oscillator coupling constant λ and the variational basis size N. This study provides, for the first time, a fully rigorous numerical implementation of this procedure for the quartic anharmonic oscillator, ensuring precise control and enabling a transition from heuristic parameter selection to a systematic and reproducible algorithmic approach. This rigorous variational justification enables the exploration of the energy functional's structure and the behavior of the nonlinear parameter. It is shown that the proposed method provides standard 10-8 accuracy in energy calculations, employing a remarkably small basis size of N ≃ 6 - 7, while maintaining high efficiency throughout the strong-coupling region - for all values of λ. The behavior of the optimized frequency parameter ω0 with respect to the basis size N was also investigated, along with the identification and interpretation of the important effect of the variational plateau - a broad region of variation in the parameter ω0 where the computed energy remains nearly constant. The system's wave functions were also calculated using the proposed method for a range of λ. The obtained results demonstrate that nonlinear optimization of the basis is a highly effective means of substantially increasing the efficiency of variational calculations, both for energies and for the wave functions.
Wildfires in radioactively contaminated territories in northern Ukraine have intensified over the past decade, raising concerns about the atmospheric resuspension of technogenic radionuclides, particularly 137Cs. Despite numerous studies on this topic, empirical data on radionuclide emissions from burning combustible materials in near-natural environments remain limited. This study provides new estimates of 137Cs release during the combustion of moss, herbaceous vegetation, forest litter layers, and green pine branches collected at six Chornobyl sites representing pine and birch forests as well as meadows. Using a custom-built aerosol filtration system, we quantified 137Cs activity in smoke aerosols and determined its fraction of release relative to both fuel activity and the total ecosystem inventory. The results revealed a clear dependence of the cesium radioisotope release on the vertical position within the pine litter profile during burning: the upper layers (moss and fresh litter) contributed a greater amount to the atmospheric release, despite having a lower total 137Cs activity compared to the deeper humified layer. An increase in moisture content (from 5-13 % to 15-29 %) significantly reduced radionuclide emissions from pine litter (by approximately one order of magnitude), whereas combustion of green pine branches with moisture contents exceeding 100 % had unexpectedly high 137Cs releases (up to 24 %). The mean proportion of cesium radioisotope release increased along the sequence: pine forest - birch forest - meadow (0.075-0.45 %) for mechanically intact and dried above-ground layers of moss/grass vegetation and litter/detritus. The obtained 137Cs release factors relative to its total activity in the studied sites generally align with empirical estimates and modelling results for the spring 2020 Chornobyl wildfires, where this parameter has been estimated to range between 0.01 and 0.4 %. Our materials indicate that 137Cs release in the Chornobyl landscapes is unlikely to exceed 1 % of its gross inventory in ecosystems, even during large-scale wildfires.
The WWR-M research reactor is planned for decommissioning. An essential component of the safety analysis report is the analysis and assessment of potential accident scenarios during decommissioning. This article presents an approach to identifying hazards and possible radiological consequences of the most dangerous initial event. The assessment results show that the radiological consequences will be significantly lower than the established standards.
When solving the problem of spectrum deconvolution, i.e., the problem of eliminating the distorting influence of equipment during the registration of experimental spectrometric data, the choice of the regularization parameter (RP) in the commonly used regularization method is important. In the article, a tool (indicator) for determining the region of favorable values of the RP is proposed. The indicator shows the range of values of the RP for which a balance is observed between the size of a regularized solution and its fit to the given data. The graphical form of the balance range indicator (+S-curve) is convenient for comparing different RP choice methods. In the article own version of RP choice based on the +S-curve is proposed. The new approach is compared with popular RP choice methods such as the discrepancy principle and the L-curve method.
This publication is a continuation of the review on the features and problems of dosimetry of incorporated radionuclides. This part describes and discusses the specifics and methods of biological dosimetry.
Simourg is a software based on the Geant4 toolkit and provides the Monte Carlo simulation of nuclear spectrometric setups with simple geometries for such applications as nuclear decay research, radiation safety, and nuclear medicine. With just a few command lines, users can define simple geometries, materials, and radiation sources to obtain reliable approximations for typical experimental setups. Simourg version 2.0, currently in its prerelease stage, introduces extended functionality for data extraction, geometry configuration, debugging, and visualization.
Using chamber models of the dynamics of 90Sr, 103,106Ru, 134,137Cs, 141,144Се in water masses and plants, the efficiency of extraction of aboveground organs of HELOPHYTES after a single emergency entry of radioactive fallout into fishery reservoirs with varying degrees of overgrowth was assessed. Calculations were performed for 5 hypothetical precipitation time points, which were selected taking into account the routes of radionuclides entering plants and the stage of phytomass development. The most effective method for decontamination of water bodies will be the removal of aboveground plant organs within 1-3 days after the fallout (up to 40 % of each radionuclide that entered the ecosystem) under conditions of ecosystem contamination from July 1 to September 1, i.e., during the period of formation of maximum aboveground phytomass. Over time, the activity of radionuclides concentrated in aboveground organs will rapidly decrease and the removal of plants 10 days after the fallout will allow the removal from the ecosystem of no more than 17 % of 103,106Ru, about 20 % of 90Sr and 134,137Cs, and 27 % of 141,144Сe, after 30 days - no more than 7, 10 and 24 % of the total amount of these radionuclides, respectively.
In this work, within the framework of the Glauber - Sitenko approximation, we present an analysis of the differential cross section for deuteron breakup with proton emission in the reaction H(d, p)X at small proton emission angles (θp < 7 μrad). The study employs several parameterizations of the deuteron wave function, including the single-Gaussian, the multi-Gaussian K2 parameterization, and models based on the Av18 and Nijm I nucleon-nucleon potentials. Particular attention is paid to the effects of small longitudinal components of the transferred momentum (|Qz| ≤ 0.5 GeV/c in the laboratory frame) and the transverse momentum of the proton-neutron pair (p⊥ = (px, 0) ≤ 0.5 GeV/c) in the antilaboratory reference frame. The results are compared with available experimental data, especially in the region of longitudinal momenta kz = p3* = 0.25 – 0.5 GeV/c (in the antilaboratory frame), where quark effects are expected to become significant. Calculations show an increase in the differential cross section with increasing transverse momentum, as well as a small shift – and a noticeable enhancement – of the cross section maximum when the longitudinal component Qz is included.
Accurate gamma-ray spectrometry using High Purity Germanium (HPGe) detectors relies on precise knowledge of detector efficiency, particularly the full energy peak efficiency (FEPE), which can degrade over extended periods of operation due to the growth of the detector's inactive dead layer (DL). Despite this known issue, DL correction is rarely performed in long operating detectors, and manufacturer specifications are often taken as fixed. This study emphasizes the gap by presenting a combined experimental and Monte Carlo modeling approach to re-characterize two planar n-type HPGe detector systems - Sys1 and Sys2 - that have been in continuous operation for nearly three decades. Although the detectors share virtually identical geometrical designs, they exhibit differences in performance, attributed primarily to variations in DL thickness. Gamma-ray measurements using certified point reference sources (59.5-1332.5 keV) were conducted, and corresponding Monte Carlo N-Particle (MCNP5) simulations were performed to evaluate the effect of DL variation on FEPE and on the active detector volume. Additionally, MCNP was used to apply source activity corrections, taking into account geometric and attenuation effects. The results offer a validated framework for modeling and correcting FEPE losses in aging detectors. By optimizing the DL thickness for Sys1 and Sys2 to 2.77 and 2.82 mm, respectively, the deviation between the simulated and experimental FEPE was reduced to below 5 %. Beyond nuclear instrumentation, this work has implications for any application requiring high-accuracy spectrometry over long operational timelines, including nuclear safeguards, radioactive waste assay, environmental monitoring, radiation metrology, and nuclear forensics.
The results of studies of the electro-physical characteristics of GaAsP light-emitting diodes (LEDs) in the temperature range of 77-300 K are presented. The mechanisms of current flow in different regions of the I-V characteristic and the role of screening of internal crystal fields by free carriers are discussed. The formation of a hysteresis loop in the I-V characteristic of the diode within the region of negative differential resistance is revealed, and possible causes for each section are analyzed. The activation energy of the transition process of the LED to the VDO state is determined. It is established that irradiation of GaAsP LEDs is accompanied by an increase in the non-ideality coefficient.
We have analyzed the activities conducted at the WWR-M nuclear research reactor of the Institute for Nuclear Research, NAS of Ukraine, over the past five years, with a focus on nuclear safety and ongoing research efforts. In 2019-2022, preparatory work was carried out for the irradiation of surveillance specimens of nuclear power reactor vessel metals in the vertical channels of the WWR-M reactor, commissioned by National Nuclear Energy Generating Company (NNEC) "Energoatom". To support this effort, vertical channels for sample irradiation were designed and manufactured, and computational analyses were performed to determine the optimal core configuration, the optimal placement of channels within the core, neutron flux distributions, and the required irradiation time. The research presented here is based on computational modeling using the MCNP-4C code, with calculations performed to evaluate neutron fluxes, reactivity parameters, and nuclear safety margins. For each configuration, critical nuclear safety parameters were determined, including the reactivity margin, the control rod worth, the reactivity of the irradiated channels, and that of each fuel assembly. The analysis confirmed the feasibility of the proposed configuration and provided essential insights into optimizing neutron flux distributions and reactivity control. In early 2022, all reactor operations were halted, and the fuel was removed from the core and transferred to storage facilities. As a result, the need arose to improve the nuclear safety justification for the spent nuclear fuel storage facility, taking into account the actual arrangement of fuel assemblies. The present work examines reactor safety considerations and explores approaches to improving the justification of spent fuel storage. It also presents the results of a series of such calculations that were initiated and remain ongoing. Overall, our research contributes to current efforts in nuclear safety assessment and provides a foundation for future investigations in this field.
