The European Journal of Physics N (EPJ-N)
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Synergies in VVER reactor long-term operation and aging: A comprehensive review of CAMIVVER, DELISA-LTO, and EVEREST projects
No full textThis paper reviews the synergies between three Euratom projects–CAMIVVER, DELISA-LTO, and EVEREST–focusing on the long-term operation (LTO) and safety assessment of VVER reactors. These projects address challenges associated with extending the lifespan of VVER reactors with implications to Europe's energy infrastructure.
The CAMIVVER project concentrates on the development of VVER specific computational methods to support their safety assessments. Through the development of advanced simulation tools like APOLLO3® and CATHARE3, CAMIVVER aims to refine thermal-hydraulics and neutronics models for the VVER-1000 reactor type, supporting both existing reactor safety analyses and the qualification of alternative fuel sources. DELISA-LTO focuses on understanding and mitigating material degradation in VVER reactors, especially in the context of thermal aging and swelling. This project emphasizes non-destructive testing (NDT) and experimental validation to identify critical components and extend reactor lifespans safely. In parallel, EVEREST investigates advanced multi-physics approaches to improve the accuracy of reactor pressure vessel fluence assessments. By producing high-resolution experimental data, EVEREST seeks to validate these models for improved safety analysis of both VVER and other pressurized water reactors.
A key synergy across these projects is the integration of experimental data and advanced modelling technics. Additionally, the projects share a focus on knowledge dissemination through workshops, training, and collaborative efforts, aimed at aligning regulatory, and industrial stakeholders with modelling and safety aspects associated with LTO of VVER. Together, CAMIVVER, DELISA-LTO, and EVEREST represent complementary approaches to addressing the aging and sustainability of VVER reactors, thereby contributing to Europe's energy security and decarbonization efforts
Advancing Gas-cooled Fast Reactor Technology: Outcomes of the Euratom SafeG Project on ALLEGRO Research and Development
No full textThe paper describes R&D activities suported by Euratom funded projects (SafeG, TREASURE) focused on advancing the development of the Gas-cooled Fast Reactor (GFR) demonstrator ALLEGRO, a key technology in the Generation IV nuclear reactor systems. With the backing of the Generation IV International Forum (GIF) and European Sustainable Nuclear Industrial Initiative (ESNII) of the Sustainable Nuclear Energy Technology Platform (SNETP), GFR technology promises high efficiency in both electricity and industrial heat production, owing to its ability to achieve high core outlet temperatures and close the fuel cycle. The presented activities revolve around addressing crucial technical challenges linked to the ALLEGRO demonstrator. The described projects have brought together leading European and international experts in GFR and High-Temperature Reactor (HTR) technologies. The key outcomes of the SafeG Project include advancements in core safety (WP1), innovative materials (WP2), passive safety systems (WP3), standardization and codes (WP4), and education and training activities (WP5). The future activities are outlined for the follow-up Project TREASURE
Investigations on the source term of the May 2023 detection event: the most comprehensive one over the last decade in Northern Europe
No full textThe detection of traces of radionuclides in Northern Europe has become more frequent in recent years, although the origin of these emissions has not been officially confirmed by any authorities. IRSN has undertaken investigations to determine the source of the past detections and to understand the origin and the mechanisms that may have led to these releases into the environment (J.J. Ingremeau, O. Saunier, Investigations on the source term of the detection of radionuclides in North of Europe in June 2020, EPJ Nuclear Sci. Technol. 8, 10 (2022), O. Saunier, J.J. Ingremeau, I. Homan, P. Mekarski, J. Yi, A. Botti, Methodology for the investigation of undeclared atmospheric releases of radionuclides: Application to recent radionuclide detections in Northern Europe from 2019 to 2022, Ann. Nucl. Energy 192, 109907 (2023)). Recently, in May 2023, a new detection event was recorded in the same part of Europe, but this is the first time that such a high number of isotopes has been reported. This paper presents the analysis carried out by IRSN to identify the origin of this new release, the most comprehensive one in the last ten years. Using inverse atmospheric dispersion modelling methods, the most likely geographical origin was identified between Estonia and the western part of the Russian Federation, in line with previous releases. The key feature of this event is the simultaneous detection of 46Sc alongside low volatile fission products and actinides, which prompted further investigations. About the origin of 46Sc, it has been shown that it is an activated corrosion product specifically produced in WWER reactors. Although there is no certainty with so few data, this finding reinforces the interpretation from previous studies assuming the release is likely to have originated from a spent primary ion exchange resin of a WWER reactor, possibly involving a fuel cladding failure leading to fuel dispersion within the primary circuit. Finally, a scenario is proposed to explain the atmospheric release which is consistent with all available detection data. However, this scenario is based on highly unlikely assumptions and remains speculative
Corrigendum to Supporting trans-national access to key nuclear research infrastructures – OFFERR and JRC OASIS: two complementary projects – one goal
No full text2024 MCATK Status
No full textThe Monte Carlo Application Toolkit (MCATK) is a C++ component-based Monte Carlo particle transport capability that has been in development by Los Alamos National Laboratory (LANL) since 2008. This paper presents an update on MCATK’s current capabilities, focusing on notable advancements made since the previous status reports (T. Adams, S. Nolen, J. Sweezy, A. Zukaitis, J. Campbell, T. Goorley, S. Greene, R. Aulwes, Ann. Nucl. Energy 82, 41 (2015), T.J. Trahan, T.R. Adams, R.T. Aulwes, S.D. Nolen, J.E. Sweezy, C.J. Werner, Monte Carlo Application ToolKit (MCATK): Advances for 2017, in International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering (Jeju, Korea, 2017). Key enhancements include a Python interface, photon physics, expanded geometry modeling options, improved tallies, and a broader selection of source definitions. Additionally, MCATK now offers stochastic system solvers, shared memory parallelism, and GPU acceleration of ray-tracing tallies. These enhancements have significantly expanded MCATK’s functionality
OperaHPC & SCORPION: accelerated optimization of advanced fuels for Gen-II/III reactors via the synergy of high-performance computing with multiscale material engineering
No full textThe licensing of advanced fuel materials and designs for Gen-II/III reactors requires an extension of the qualification of industrial fuel performance codes to meet the requirements of nuclear safety authorities vis-à-vis the verification, validation, and uncertainties quantification process. To address these requirements, the OperaHPC project works on advanced simulation tools enabling 3D representation of fuel rods. In the first two years of this project, a creep test device for hot cell installation was designed and transmission electron microscopy was used to characterize the microstructure of an irradiated fuel on the nanoscale. In parallel, small-scale simulation and physics-based fuel mechanical modelling were initiated to study dislocation mobility. State-of-the-art fuel and fuel cladding mechanical laws were employed in preparation of advanced mechanical modelling. HPC fuel performance codes are being developed with OFFBEAT/SCIANTIX for macroscale fuel element simulations, and MMM for mesoscale fuel pellet microstructural simulations. The preparation of industrial applications with improved models involves exchanges on machine-learning methods alongside the computation of input data for fuel safety analysis.
SiC/SiC composites are a candidate accident-tolerant fuel cladding material that exhibits inherent refractoriness, pseudo-ductility, and a lack of accelerated oxidation during loss-of-coolant scenarios. Due to its potential for exceptional accident tolerance, this ‘revolutionary’ fuel cladding material concept has claimed large global investments since the 2011 Fukushima Daiichi event. Regrettably, all state-of-the-art variants of the SiC/SiC composite material concept must still overcome shortcomings, such as the inadequate compatibility of SiC with water/steam and its early (> 2 dpa) saturation of radiation-induced swelling during nominal operation. The SCORPION project strives for the radical performance optimization of SiC/SiC composites via multiscale material tailoring, which entails material re-design on the nanoscale (e.g., grain boundary engineering), mesoscale (e.g., fiber/matrix interface), and macroscale (e.g., coating development). In the first two years of this project, candidate coating ceramics and grain boundary engineered/doped SiC were experimentally synthesized and their performance was assessed via autoclave tests, high-temperature steam oxidation tests, and combined proton irradiation/aqueous corrosion tests. The hitherto tested materials performed significantly better than monolithic SiC, highlighting the success of the multiscale material engineering approach.
This article offers a high-level overview of the scope and midterm achievements of the OperaHPC & SCORPION projects, in view of the FISA-EURADWASTE & SNETP Forum 2025, organized in Warshaw, Poland, in the period 12-16 May 2025
NUCOBAM European project: NUclear COmponents based on additive manufacturing
No full textNUCOBAM is an EU-funded project that aimed at developing the qualification process and providing the evaluation of the in-service behaviour allowing the use of Additively Manufactured (AM) components in a nuclear installation. Once qualified, the use of AM allows nuclear industry to tackle component obsolescence challenges and to manufacture and to operate new components with optimized design in order to increase reactor efficiency and safety. To make this ambition a success, NUCOBAM conducted studies to implement AM process in nuclear design codes and standards to manufacture nuclear reactor components. The project was based on two coupled strategies: the first part consists of a collection of the physical, mechanical, and microstructural characterization of the materials from four manufacturers that result from the AM process (using four heat treatments) in order to establish a qualification and codification process. The second part is dedicated to the evaluation of AM material behaviour in-service, especially regarding main degradation mechanisms that occur in Light Water Reactors (LWR) (thermal ageing, irradiation…). Materials are manufactured and some of them submitted to post-treatment (heat treatment or high isostatic pressure). This work allows manufacturers and designers to evaluate and deduce the main parameters required for specification. The project participants involved electricity utilities, operating nuclear assets, component manufactures, design owners, public service experts in nuclear and radiation risks as well as research and competence centres involved in mechanical assessment, metal powder qualification, metallurgical characterization, materials irradiations capabilities and nuclear power research
Properties’ evolution of reactors loaded with MOX-MR fuels in plutonium multi-recycling scenarios in PWR
No full textThis paper studies evolutions of reactor properties when loaded with MOX-MR fuels during dynamical fuel cycle simulations. To do so, artificial neural networks, trained on a dedicated reactor depletion database, are used to estimate reactor irradiation lengths, power factors and burn-up of each discharged assembly during the scenario simulations. The studied scenario is an academic simulation of the French historical fleet that is replaced by 30 new EPRs, a fraction of which are loaded with MOX-MR fuel to balance the plutonium production in UOX fuels. Our simulations, that integrate reactor models based on full core calculations, show that 15 EPRs loaded with 50% MOX-MR assemblies are needed to stabilize the total plutonium inventory. For MOX-MR fuel fabrication, 4 spent fuel blending options at reprocessing are proposed here. Results show that the steady-state plutonium global inventory appears to depend little on spent fuel mixing proportions, which is not the case for spent fuel stockpile, highly dependent to those mixing hypothesis. The simulations also show that some blending options at processing may ensure an acceptable isotopic composition for MOX-MR fuels. Changes in plutonium isotopic quality may occur during the scenario and lead to an approximately 13% deviation of the reactor irradiation length. Consequently, using a fixed-content model for MOX-MR fuels in fuel cycle simulations imposes to control precisely the spent fuel streams at reprocessing to recover plutonium with an acceptable given quality. Unsuitable spent fuel stream flows at reprocessing lead to a strong deviation of the plutonium isotopic vector that should be compensated by an adapted plutonium content in MOX-MR fuels. If not, deviations in reactor cycle length may happen that would question the consistency of scenario simulations. Finally, this paper demonstrates the possibilities and limitations of fixed-fraction fuel fabrication models in fuel cycle simulations. This kind of model induces limited biases when fresh fuel compositions are ensured to be constant among the scenario time. Consequently, two options are viable for fuel cycle simulations : improving fuel fabrication models by adapting the plutonium content to its isotopic composition, or improving the reprocessing modeling by adapting the spent fuel blending to ensure a constant plutonium quality during the scenario simulation
Magic-RR project overview: objectives, methodology and expected results
No full textMost research reactors (RRs) in Europe are over 60 years old, and there are only limited efforts underway (e.g., PALLAS and JHR projects) to partially replace this aging infrastructure. Continued safe operation (CSO) of these reactors is crucial to sustaining the EU’s leadership in nuclear materials development and qualification for advanced reactor designs and to ensuring a steady supply of medical isotopes. Extending the licenses for these reactors to ensure CSO requires comprehensive aging management reviews (AMRs) and time-limited aging analyses (TLAAs) of key structures and components. However, current challenges include a limited understanding of irradiation-induced degradation and corrosion mechanisms, a shortage of data on RR structural materials under high-fluence conditions necessary for CSO, the lack of predictive, physics-based models for irradiation damage in aluminum alloys, and insufficient surveillance specimens for some reactors. Additionally, there are no dedicated design codes for reactor vessels and core structures made of aluminum, and there is no standardized approach in Europe for aging management of operating RRs.
To address these issues, a new project, Research on M
Enhancing severe accident management through research
No full textAfter the Fukushima Daiichi accident, a new wave of research projects aiming at enhancing severe accident (SA) management was launched under different international frameworks. This was the case of MUSA (Management and Uncertainties of Severe Accidents), AMHYCO (Towards and enhanced Accident Management of the H2 and CO combustion risk) and SOCRATES (Assessment of liquid Source Term for accidental post management phase), which under the frame of H2020 and HEUROPE EURATOM were devised to optimize different aspects of Severe Accident management. MUSA explored how bringing uncertainties quantification in the Severe Accident analysis might provide sounder insights into effects and timing of accident management actions. AMHYCO brought new insights into combustion risk management, particularly during the ex-vessel phase of the accident, by combining in a selective manner different analytical approaches and data on recombination and combustion of gas mixtures (i.e., H2/CO/air/steam). SOCRATES is hitting accident management related to liquid source terms, with emphasis in the long-run of the accident. This paper describes the major outcomes of the projects and outlines what should come next for an efficient application of the insights gained in the accident management