The European Journal of Physics N (EPJ-N)
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Using nuclear observations to improve climate research and GHG emission estimates – the NuClim project
No full textProject NuClim (Nuclear observations to improve Climate research and GHG emission estimates) aims to use high-quality measurements of atmospheric radon activity concentration and ambient radioactivity to advance climate science and improve radiation protection and nuclear surveillance capabilities. It is supported by new metrological capabilities developed in the EMPIR project 19ENV01 traceRadon. This work reviews the scientific objectives of project NuClim in terms of both climate science and radiological protection, and provides an overview of the NuClim field campaign and the various nuclear measurements being implemented within the scope of the project
Status of GPU capabilities within the Shift Monte Carlo radiation transport code
No full textShift is a general-purpose Monte Carlo (MC) radiation transport code for fission, fusion, and national security applications. Shift has been adapted to efficiently run on GPUs in order to leverage leadership-class supercomputers. This work presents Shift’s current GPU capabilities. These include core radiation transport capabilities for eigenvalue and fixed-source simulations, and support for non-uniform domain decomposition, Doppler broadening, free-gas elastic scattering, general-purpose geometry, hybrid MC/deterministic transport, and depletion. Transport results demonstrate a 2–5× GPU-to-CPU speedup on a per-node basis for an eigenvalue problem on the Frontier supercomputer and a 28× speedup for a fixed-source problem on the Summit supercomputer
Outcomes of three Euratom projects on cogeneration of electricity, heat and hydrogen
No full textThis paper deals with the assessment of low-carbon energy generation solutions (heat, electricity, hydrogen) provided by nuclear reactors in the general framework of nuclear co-generation addressed by three ongoing Euratom projects, GEMINI 4.0, NPHyCo and TANDEM. It gives a short overview over the three projects, points out the respective objectives and methodologies and describes the current results. Focus is given to the common outcomes of all three projects. The main common outcomes are that low-carbon hydrogen production via nuclear energy is generally feasible and can be done safely. This is easier to be achieved with new-build plants (Small Modular Reactors and High Temperature Reactors) than with existing nuclear power plants in operation. With current price of carbon dioxide certificates and the existing hydrogen infrastructure, low-carbon hydrogen production is not economically competitive compared to hydrogen from fossil sources. Thus, governmental support (national and EU-wide) is needed to foster low-carbon hydrogen production as a means to real decarbonization goals
Link between material properties and integrity assessment of NPP components within EU funded projects APAL, INCEFA-SCALE and FRACTESUS
No full textDeep understanding of aging of the most important nuclear power plant (NPP) components and their material degradation on the one hand and development of advanced methods of the assessment of those components’ integrity and lifetime on the other hand is the only way to ensure safe operation of NPPs for long-term operation (LTO). The most significant degradation mechanisms are fatigue and irradiation embrittlement. Within Euratom research and training programme HORIZON 2020, several projects were running in several past years focussed on the research of the above-mentioned degradation mechanisms and on the way of assessing their impact. Three such projects are described in this paper:
APAL (Advanced PTS Analysis for LTO) project addresses challenges associated with multidisciplinary character of the pressurised thermal shock (PTS) analyses (both deterministic and probabilistic) and quantification of safety margins,
INCEFA-SCALE (INcreasing safety in NPPs by Covering gaps in Environmental Fatigue Assessment – focusing on gaps between laboratory data and component SCALE) aims to improve assessments of fatigue lifetime of nuclear power plant components when subjected to environmentally assisted fatigue (EAF) loading and to provide guidance on the transferability of laboratory scale testing results to component-scale,
FRACTESUS (Fracture mechanics testing of irradiated RPV steels by means of sub-sized specimens) aims to determine the effect of specimen size on the fracture toughness properties. Large inter-laboratory testing is included to prove the repeatability and reproducibility of the small-scale testing of fracture toughness properties. Finite element models (FEM) are used to support the experimental results
Fundamental properties and characteristics of flux distribution tallies using proper orthogonal decomposition
No full textThe flux distribution tallies using the proper orthogonal decomposition (POD) called “the POD tallies” have been developed in our previous study. The POD tallies can achieve dimensionality and statistical uncertainty reduction for a finely discretized flux distribution. Some characteristics of the POD tallies, which are left by our previous work, are revealed in the present study. Firstly, the POD tallies with the track length estimator are newly implemented. Since the statistical uncertainty of the POD tallies is reduced compared with the cell tallies, the POD tallies with the track length estimator can obtain the most precise result among the present implantations. Secondly, the basis vectors obtained by the deterministic and the stochastic methods are compared. The statistical uncertainty of the snapshot data invokes the degradation of the extracted basis vectors. This result indicates that the deterministic method might be more efficient for the snapshot calculation. Finally, the impact of the covariances of expansion coefficients on the statistical uncertainty of expanded flux distribution is investigated. The reconstructed statistical uncertainty considering only the variances of the expansion coefficients differs from the reference. This result reveals that the covariances of the expansion coefficients are important to estimate the statistical uncertainty of the local flux in the flux distribution
In-core thermal and fast neutron measurements with 4H-SiC P+N junction diodes in the JSI TRIGA Mark II research reactor
No full textAccurate online in-core parameter measurements, such as neutron and photon fluxes and nuclear heating rates, are essential for fusion and fission applications. Wide bandgap semiconductors, particularly Silicon Carbide (SiC), have demonstrated strong potential for radiation detection over six decades. Despite this, challenges persist in optimizing detector performance under extreme in-core conditions. Our study focuses on 4H-SiC-based detectors, developed within a joint laboratory between Aix-Marseille University and the CEA, aiming to address these challenges and provide high-precision measurements for advanced nuclear facilities. Following previous measurements in ZPRs and with D-T neutron generators, this paper focuses on in-core experimental results obtained with such detectors in the Triangular Irradiation Channel (TIC) of the TRIGA Mark II-type research reactor at the Jožef Stefan Institute (JSI) in Slovenia. These in-core measurements were done by using two types of diodes. One with a Neutron Converter Layer (NCL) of Boron-10 for thermal neutron detection, and the other one without NCL in order to discriminate thermal and fast neutrons by studying 10B reaction versus scattering. Thanks to various Pulse Shape Analyses (PSA) and count rate studies the influence of bias voltage, NCL and neutron fluence on the detector performances were determined. The highest neutron flux and fluence for these detectors were reached: 1.2 × 1013 cm−2·s−1 and 1.2 × 1017 cm−2, respectively
Identification of European experimental facilities for severe accident research within EU SEAKNOT-project: Analysis and mapping
No full textExperimental facilities play a central role in reactor safety research for both design basis and severe accidents (SA). They are key to demonstrate the effectiveness and appropriateness of specific safety features of reactor designs and providing data for the validation of different models implemented in numerical tools used for safety demonstration. Hence, a well-designed and equipped experimental infrastructures in Europe is a fundamental pillar of European roadmap on reactor safety research. One objective of the EU SEAKNOT (Severe Accident research and KNOwledge management) project, is the analysis and mapping of European severe accident research facilities currently under operation. The responses to a questionnaire sent to European institutions were evaluated and the information collected about each facility was synthesized covering different issues such as age, design features, main phenomena addressed by latest research programs, including advanced technologies like Advanced Technology Fuels (ATFs) and Small Modular Reactors (SMRs). The extensive review of the collected information allowed the identification of critical conditions (human resources; preservation and enhancement of experimental competences, etc. that might jeopardize the current and forthcoming European experimental capabilities for severe accident research, according to the Severe Accident roadmap that is being built in SEAKNOT. This paper describes the methodology and major outcomes of this analysis
GREAPMC: development status, capabilities, and future developments
No full textThis article focuses on the capabilities, performance, and verification of GPU-optimized REActor Physics Monte Carlo (GREAPMC), a multigroup Monte Carlo code, against multigroup simulation on MCS; an in-house, CPU-based, Monte Carlo code. The simulation results for a three-dimensional fuel assembly indicate a superior performance of GREAPMC over the conventional MC codes optimized for CPU with one GPU card equivalent to approximately 13 CPU boards for the hardware employed in this work. The immense potential of GPUs has led to the development of GPU-aware continuous energy capability which is in progress with the target velocity sampling (TVS) part completed. The essence of using GPU for continuous energy MC is quantified by simulating the effect of the number of histories on the execution time for the TVS methods. The results show a remarkable acceleration compared to the CPU. The findings provide a basis for further development in GREAPMC
Direct immobilisation of radioactive liquid organic waste in a geopolymer matrix
No full textManaging and disposing of radioactive liquid organic waste is a complex task due to its hazardous nature and long-term environmental impact. Geopolymer materials, produced through the alkali activation of aluminosilicate precursors, have emerged as promising candidates for immobilising various types of waste, including radioactive waste, due to their chemical stability, mechanical strength, and resistance to degradation. This study investigates the feasibility and effectiveness of the direct conditioning of radioactive liquid organic waste surrogate into a blast furnace slag matrix, focusing on key properties such as mechanical strength, porosity, and durability under various curing conditions. Two experimental series were conducted, using different waste oils as surrogates for radioactive liquid organic waste and various surfactants to evaluate their impact on the geopolymers. Samples were cured under sealed and aerated conditions to assess how these variables influence the resulting material. Several methods, such as UV/Vis spectroscopy, microscopy, porosimetry and compressive strength testing, were utilised to analyse the physical, chemical, and mechanical characteristics of the produced geopolymer waste forms. Compressive strength test results indicate potential suitability for long-term storage and disposal of radioactive liquid organic waste. However, increasing waste oil and surfactant concentrations generally reduced compressive strength and were associated with increased porosity. Additionally, leaching tests were performed to evaluate the potential release of oil and selected elements from the stabilised waste form. The findings demonstrated minimal oil leaching, suggesting a high level of immobilisation efficiency. These findings indicate the potential of geopolymer matrices for encapsulating radioactive liquid organic waste. However, they also highlight the need for careful optimisation of surfactant and waste concentrations to balance the volume of incorporated waste oil and mechanical performance. Further research and optimisation are required to refine these formulations and expand the application to other liquid organic waste types, aiming to develop practical and scalable solutions for radioactive waste management
Re-evaluating the prompt fission neutron spectrum of spontaneously fissioning
No full textThe prompt fission neutron spectrum (PFNS) of spontaneously fissioning 252Cf is a Neutron Data Standards observable. Nearly all fission spectra of actinides were measured relative to it, using efficiencies derived from it, or analyzed with simulations validated by it. The current Standards evaluation was published by W. Mannhart in 1987. It could not be updated because the evaluation input, experimental mean values and covariances, were lost. First, we attempt to reproduce it. However, Mannhart’s evaluation can only be reproduced within its one-σ uncertainties as some of its aspects (e.g., experimental covariances, rejected data points) remain unknown. Therefore, a new evaluation is presented: We revisit all existing experimental 252Cf(sf) PFNS data, including those published after the release of the current Standards evaluation, and re-estimate associated covariances. The newly evaluated 252Cf(sf) PFNS differs distinctly from Mannhart’s below 300 keV and extends it to lower and higher outgoing neutron energies (500 eV–25 MeV). The new evaluated uncertainties are larger from 3–9 MeV and smaller otherwise. Spectrum averaged cross sections of importance to the International Reactor Dosimetry and Fusion File community calculated with the new spectrum are close to those calculated with Mannhart’s evaluation and agree with experimental values well within their uncertainties