1. Supporting trans-national access to key nuclear research infrastructures – OFFERR and JRC OASIS : two complementary projects – one goalCharles Toulemonde, Alice Seibert, Eric Colineau, Leon Cizelj, Raffaella Canu, 2025, izvirni znanstveni članek Povzetek: The OFFER and OASIS projects both provide transnational access to key nuclear research infrastructures. Since September 2022, the OFFERR project, funded by Horizon Europe/Euratom, supports the SNETP Association by providing R&D experts access to key nuclear research infrastructures across Europe. It addresses financial and logistical barriers that hinder nuclear research by offering a platform for financial support and access to more than 230 experimental facilities. Researchers can submit applications through the OFFERR Call Platform, ensuring eligible projects receive necessary funding and access. This initiative aims to accelerate innovation in nuclear energy by bridging the gap between research ideas and advanced facilities, adhering to EU regulations and fostering international collaboration. The OASIS project is funded by an Administrative Arrangement between the Directorate General for Research and Innovation (DG RTD) and JRC since February 2020 and aims at enhancing open access to JRC's nuclear facilities (11 out of 16 are opened) and the associated technical support. So in the OASIS project, JRC makes available its nuclear research infrastructures to external users free of charge while DG RTD provides their financial support to eligible users to cover their travel and subsistence costs. This allows an optimal use of JRC's unique facilities and nuclear materials not available to European scientists at their home institutions and results in scientific excellence in research that could otherwise not be performed. With a large participation of students and young scientists, OASIS also contributes to the training of the next generation of European scientists in various nuclear fields. Whereas the two projects have one goal, they follow complementary approaches.
Ključne besede: nuclear research infracstructure
Objavljeno v DiRROS: 13.01.2026; Ogledov: 146; Prenosov: 110
 Celotno besedilo (2,15 MB)
Gradivo ima več datotek! Več... |
2. Enhanced strain gradient crystal plasticity theory : Evolution of the length scale during deformationAmirhossein Lame Jouybari, Samir El Shawish, Leon Cizelj, 2025, izvirni znanstveni članek Povzetek: An Enhanced Strain Gradient Crystal Plasticity (Enhanced-SGCP) theory, based on the quadratic energy contribution of the Nye tensor, is developed within a thermodynamically consistent framework to accurately capture shear band formation in terms of slip and kink bands within the microstructure. The higher-order modulus in the theory is intrinsically linked to the evolving microstructural properties during applied loading, introducing a physical length scale that governs shear band formation and evolution. It is demonstrated that the Classical-SGCP model (a Gurtin-type nonlocal theory) leads to an increasing width of localization bands, which eventually disappear, resulting in homogeneous deformation within the microstructure. This effect arises from the excessive annihilation of geometrically necessary dislocations, which suppresses localization and may lead to physically meaningless results in the formation of shear bands. To address this issue, the proposed Enhanced-SGCP theory effectively preserves the shear band width and maintains localization throughout the loading process by reducing the higher-order modulus associated with the sweeping away of hardening defects and local softening mechanism. Furthermore, the theory establishes a direct link between lattice curvature in kink bands and the Nye tensor, demonstrating that the kink bands transform into slip bands. Consequently, the Enhanced-SGCP theory breaks the equivalence between slip and kink bands, providing a more accurate physical representation of strain localization mechanisms in irradiated materials. To computationally solve the governing balance equations, a fixed-point algorithm based on the fast Fourier Transform (FFT) method is developed. To validate the algorithm, an analytical solution for the Enhanced-SGCP theory is derived. High-resolution single-crystal simulations confirm that the kink bands transition into regularized slip bands through different physical length scales within the proposed Enhanced-SGCP framework. Furthermore, high resolution simulations are performed on two-dimensional and three-dimensional polycrystalline aggregates, considering different length scales and various higher-order interface conditions at the grain boundaries. The results reveal that the strain gradient effects during applied loading are saturated and stabilized by the Enhanced-SGCP theory, ensuring sustained localization. These findings highlight the capability of the proposed Enhanced-SGCP theory and the developed FFT-algorithm to provide a robust and physically consistent framework for modeling strain localization in crystalline materials. The proposed model offers significant improvements over classical approaches, particularly in preserving localization phenomena and accurately describing the interplay between slip and kink bands.
Objavljeno v DiRROS: 29.05.2025; Ogledov: 597; Prenosov: 198
Celotno besedilo (9,51 MB) |
3. |
4. Robust and intuitive model for COVID-19 epidemic in SloveniaMatjaž Leskovar, Leon Cizelj, 2022, izvirni znanstveni članek Povzetek: The main goal of epidemic modelling is to support the epidemic management through forecasts and analyses of past developments. With this in mind a robust and intuitive SEIR (Susceptible, Exposed, Infectious, Recovered) type model has been developed, applied and verified during the multiple waves of the COVID-19 epidemics in Slovenia since March 2020. The model parameters were based on the general characteristics of the COVID-19 disease reported globally for the entire planet and refined with the aggregate data available mostly on a daily basis in Slovenia, as for example the number of confirmed cases, hospitalized patients, hospitalized patients in intensive care units and deceased. The Slovenian aggregate data was also used to estimate the degree of immunisation due to past infections and vaccination, which reduces the number of susceptible persons for the disease. Examples of the model application are presented to illustrate its robustness and intuitiveness in both the forecasts and analyses of past developments. The analyses of past developments provided specific estimates of modelling parameters for Slovenia and quantified the effects of pharmaceutical and non-pharmaceutical interventions and various events on the development of the epidemics as measured through the reproduction number R. This empirically obtained information was then applied in the forecasts. Accurate forecasts are a great support for decision makers and for hospitals to plan appropriate actions in advance. The inherent uncertainties in the model and data were quantified through intuitive sensitivity analyses represented as different scenarios. The observed accuracy of the forecasts was impressively good also in demanding conditions, when various complex processes influencing the spread of the disease were going on in parallel. This demonstrates the robustness and relevance of the proposed model.
Ključne besede: epidemic, COVID-19, modelling SEIR, reproduction number
Objavljeno v DiRROS: 11.04.2025; Ogledov: 732; Prenosov: 324
Celotno besedilo (2,35 MB)
Gradivo ima več datotek! Več... |
5. |
6. |
7. Towards strategic agenda for European nuclear education, training, and knowledge managementLeon Cizelj, Csilla Pesznyák, Jörg Starflinger, Gabriel Lazaro Pavel, Franck Wastin, Eirini Michailidou, 2024, izvirni znanstveni članek Povzetek: The key elements of the EU-wide strategic agenda for nuclear education, training, and knowledge management are proposed in this paper. They were developed partly within the ENEN+ and ENEN# projects, to support and consolidate the efforts of the nuclear stakeholders to attract, develop, and retain new talents. The paper considers the projections of needs developed by the European Human Resources Observatory-Nuclear (EHRO-N). It builds on the existing national nuclear education strategies in the EU and beyond and more than two decades of experience with the European Nuclear Education Network (ENEN). The paper outlines and substantiates the most important actions and risks related to human resources, which need to be managed successfully for the EU to contribute to the tripling of the nuclear power generation capacity on the planet by 2050 (as announced in COP28) and to retain its leading role in the nuclear power and non-power applications. The sheer complexity of this challenge calls for high-level strategic support, coordination, and partnership between all nuclear stakeholders, especially those involved in the decision-making. The present situation calls for urgent strategic actions with long-term sustainability.
Ključne besede: nuclear education, training, knowledge management, strategic agenda
Objavljeno v DiRROS: 11.04.2025; Ogledov: 664; Prenosov: 338
Celotno besedilo (2,66 MB)
Gradivo ima več datotek! Več... |
8. Fast Fourier transform approach to strain gradient crystal plasticity : regularization of strain localization and size effectAmirhossein Lame Jouybari, Samir El Shawish, Leon Cizelj, 2024, izvirni znanstveni članek Povzetek: The Strain Gradient Crystal Plasticity (SGCP), based on cumulative shear strain, is developed to regularize and simulate the size effect behavior of polycrystalline aggregates, specifically in the formation of localization bands in terms of slip and kink bands, influenced by strain softening during the initial stages of plastic deformation. In this respect, the thermodynamically consistent derivation of the SGCP equations is presented, establishing their connection to the kinematics of classical crystal plasticity (CCP) framework. The governing balance equations are solved using the fixed-point algorithm of the fast Fourier transform (FFT)-homogenization method, involving explicit coupling between the classical and SGCP balance equations. To address this problem, a strong 21-voxel finite difference scheme is established. This scheme is considered to solve the higher order balance equation inherent to SGCP. Additionally, three types of interface conditions are implemented to explore the impact of grain boundaries on the transmission of localization bands. These conditions yield consistent intragranular/transgranular localization patterns in the MicroFree and MicroContinuity cases, while in the MicroHard condition all localization bands are intragranular with stress concentrations appearing at the grain boundaries. Analytical solutions corresponding to different material behaviors are developed and compared with numerical results to validate the numerical implementation of the FFT fixed-point algorithm. It is observed that both the macroscopic behavior and microscopic variables in CCP framework are highly influenced by grid resolutions (non-objective), leading to numerical instabilities arising from the material softening and subsequent formation of localization bands, both in single crystals and polycrystalline aggregates. Remarkably, the developed SGCP model provides results that are independent of grid resolutions (objective) and effectively regularizes the material behavior on local scale. Moreover, the non-local parameter of the model is capable of controlling the localization band widths. Finally, the proposed SGCP model, together with employed MicroHard condition on grain boundaries, is demonstrated to qualitatively reproduce main microstructural features of irradiated polycrystalline materials.
Ključne besede: strain localization A, strain gradient crystal plasticity B, polycrystalline material B, FFT-homogenization method C
Objavljeno v DiRROS: 11.04.2025; Ogledov: 750; Prenosov: 388
Celotno besedilo (9,87 MB)
Gradivo ima več datotek! Več... |
9. Advancing nuclear research and education in Slovenia and EU : From operating the TRIGA reactor to building a new generation facilityJan Malec, Iztok Tiselj, Anže Pungerčič, Tanja Goričanec, Leon Cizelj, Luka Snoj, 2024, izvirni znanstveni članek Povzetek: The TRIGA Mark II research reactor at the Jožef Stefan Institute in Slovenia achieved first criticality in 1966. Since then, the reactor has been playing an important role in developing nuclear technology. The reactor has been mainly used for research, education of university students, training of operators of the Krško nuclear power plant (start of operation in 1983) and other nuclear specialists, isotope production and beam applications. The reactor is experiencing a high level of activity today, engaging in a diverse range of experiments and studies across reactor physics, environmental research, radiation hardness testing as well training and education. The future of nuclear technology in Slovenia is focused on new NPPs, while the research community is looking forward to a possible new nuclear reactor. The basic initiatives are at a very preliminary stage: the primary choice is dual-core pool-type reactor, with a zero-power core and a separate MW-size core, cooled and moderated with light water. Such a dual-core configuration is designed to meet the varied requirements of the European Union member states. Another option would be hosting one or more micro-reactors with electrical and/or heating power producing capability that could offer stronger support toward demonstration of prototype small modular reactors in prototype future electrical grids.
Objavljeno v DiRROS: 10.04.2025; Ogledov: 924; Prenosov: 371
Celotno besedilo (1,56 MB)
Gradivo ima več datotek! Več... |
10. Education, training and mobility : towards a common effort to assure a future workforce in Europe and abroadWalter Ambrosini, Rosa Lo Frano, Leon Cizelj, Pedro Porras Dieguez, Egidijus Urbonavicius, Iskren Cvetkov, Daniela Diaconu, Jan Leen Kloosterman, Rudy J. M. Konings, 2020, pregledni znanstveni članek Objavljeno v DiRROS: 09.04.2025; Ogledov: 530; Prenosov: 181
Celotno besedilo (3,71 MB) |
