Increase of nuclear installations safety by better understanding of materials performance and new testing techniques development (MEACTOS, INCEFA-SCALE, and FRACTESUS H2020 projects)

Research to better understand the phenomena influencing materials and components’ performance is important for increasing the safety of Generation II and III nuclear plants. A crucial step for improving nuclear safety is the development of new experimental techniques that can provide the necessary data. The three H2020 projects presented in this paper, MEACTOS (2017–2022), INCEFA-SCALE (2020–2025), and FRACTESUS (2020–2024), cover the steps needed to realize those safety improvements. The goal of the MEACTOS project is to improve the resistance of critical locations, including welds, to environmentally-assisted cracking through optimizing surface machining and treatments. The project is currently in its final stage, and the complete analysis of the data is finished. The objective of INCEFA-SCALE is to improve predictions of component fatigue lifetime when subjected to Environmentally-Assisted Fatigue (EAF). The strategy consists of producing guidance on how to appropriately accommodate variable amplitude and plant-relevant loading in EAF assessments. Increasing the understanding of the EAF mechanism based on substantial testing, characterization, and analysis program will support the INCEFA-SCALE strategy. The FRACTESUS project will validate the use of miniaturized compact tension specimens by comparing the results of master curve-oriented fracture toughness tests performed with small and large specimens. The round-robin exercises will use irradiated and non-irradiated Reactor Pressure Vessel (RPV) materials. The material selection process is complete in time for the project to enter the testing phase. The output of the project will be beneficial from a long-term operation perspective and a saving in the material amount needed for RPV surveillance programs. Even though each project is devoted to different research areas, common aspects are clearly visible. All three projects investigate phenomena that are relevant to the performance and safe operation of the nuclear plant. Moreover, each project will provide valuable databases and analyses of test results for materials relevant to components in the nuclear plant. The output of these projects will be of great value to the nuclear industry. This paper presents the current progress for each project, emphasizing the common research domains between the projects

Microstructure and mechanical properties of friction stir welded joints made from ultrafine grained aluminium 1050

In order to obtain ultrafine grained structure, commercially pure aluminium (Al 1050) plates were subjected up to 8 passes of Incremental Equal Channel Angular Pressing (IECAP) following route C. Plates in different stages of IECAP were joined using Friction Stir Welding (FSW). All welded samples were investigated to determine their mechanical properties and structure evolution in the joint zone. The joining process reduced mechanical strength of material in the nugget zone, which was explained by the grain growth resulting from temperature rise during FSW. Nevertheless, the obtained results are promising in comparison to other methods of joining aluminium

Multiscale approach including microfibril scale to assess elastic constants of cortical bone based on neural network computation and homogenization method

The complexity and heterogeneity of bone tissue require a multiscale modelling to understand its mechanical behaviour and its remodelling mechanisms. In this paper, a novel multiscale hierarchical approach including microfibril scale based on hybrid neural network computation and homogenisation equations was developed to link nanoscopic and macroscopic scales to estimate the elastic properties of human cortical bone. The multiscale model is divided into three main phases: (i) in step 0, the elastic constants of collagen-water and mineral-water composites are calculated by averaging the upper and lower Hill bounds; (ii) in step 1, the elastic properties of the collagen microfibril are computed using a trained neural network simulation. Finite element (FE) calculation is performed at nanoscopic levels to provide a database to train an in-house neural network program; (iii) in steps 2 to 10 from fibril to continuum cortical bone tissue, homogenisation equations are used to perform the computation at the higher scales. The neural network outputs (elastic properties of the microfibril) are used as inputs for the homogenisation computation to determine the properties of mineralised collagen fibril. The mechanical and geometrical properties of bone constituents (mineral, collagen and cross-links) as well as the porosity were taken in consideration. This paper aims to predict analytically the effective elastic constants of cortical bone by modelling its elastic response at these different scales, ranging from the nanostructural to mesostructural levels. Our findings of the lowest scale's output were well integrated with the other higher levels and serve as inputs for the next higher scale modelling. Good agreement was obtained between our predicted results and literature data.Comment: 2

Digital image correlation utilization in pipeline oriented residual stress estimation

The aim of the paper is to present an idea of the utilization of Digital Image Correlation (DIC) method for industrial pipelines residual stress oriented investigation. For this purpose results of tests performed in laboratory and industrial conditions are presented. Obtained results showed that DIC method gives reliable near drilled hole strain/displacement distribution maps which may be used for accurate residual stress calculations

Metallic foam supported electrodes for molten carbonate fuel cells

This paper demonstrates the benefits of using a metallic foam support within molten carbonate fuel cell (MCFC) cathodes. A state-of-the-art fabrication process based on tape casting has been developed to produce microporous electrodes with a nickel foam scaffold. Surfactant was added to control the depth to which the slurry infiltrated the foam. New cathodes were used as an alternative to the traditional cathode in the single cell assembly and were tested for power density. Mechanical properties were compared with the current state-of-the-art. The results show that the use of metallic foams for high temperature fuel cell electrodes is beneficial from the technological point of view, especially in larger scale production. It was also found that the resultant continuous metallic structure of the microporous electrodes delivered a slight enhancement to fuel cell power density.publishedVersio

Increase of nuclear installations safety by better understanding of materials performance and new testing techniques development (MEACTOS, INCEFA-SCALE, and FRACTESUS H2020 projects)

Research to better understand the phenomena influencing materials and components’ performance is important for increasing the safety of Generation II and III nuclear plants. A crucial step for improving nuclear safety is the development of new experimental techniques that can provide the necessary data. The three H2020 projects presented in this paper, MEACTOS (2017–2022), INCEFA-SCALE (2020–2025), and FRACTESUS (2020–2024), cover the steps needed to realize those safety improvements. The goal of the MEACTOS project is to improve the resistance of critical locations, including welds, to environmentally-assisted cracking through optimizing surface machining and treatments. The project is currently in its final stage, and the complete analysis of the data is finished. The objective of INCEFA-SCALE is to improve predictions of component fatigue lifetime when subjected to Environmentally-Assisted Fatigue (EAF). The strategy consists of producing guidance on how to appropriately accommodate variable amplitude and plant-relevant loading in EAF assessments. Increasing the understanding of the EAF mechanism based on substantial testing, characterization, and analysis program will support the INCEFA-SCALE strategy. The FRACTESUS project will validate the use of miniaturized compact tension specimens by comparing the results of master curve-oriented fracture toughness tests performed with small and large specimens. The round-robin exercises will use irradiated and non-irradiated Reactor Pressure Vessel (RPV) materials. The material selection process is complete in time for the project to enter the testing phase. The output of the project will be beneficial from a long-term operation perspective and a saving in the material amount needed for RPV surveillance programs. Even though each project is devoted to different research areas, common aspects are clearly visible. All three projects investigate phenomena that are relevant to the performance and safe operation of the nuclear plant. Moreover, each project will provide valuable databases and analyses of test results for materials relevant to components in the nuclear plant. The output of these projects will be of great value to the nuclear industry. This paper presents the current progress for each project, emphasizing the common research domains between the projects

Fractesus project:General framework of materials selection and testing processes

The H2020 project entitled “Fracture mechanics testing of irradiated RPV steels by means of sub-sized specimens (FRACTESUS)” started on the 1 st October 2020. The aim of this project is to demonstrate the applicability of miniaturized compact tension specimens in fracture toughness testing of the reactor pressure vessel steels under hot cell conditions. Validation of this method in an industrially-relevant environment will be an important step towards achieving its acceptance by the nuclear authorities, and finally, to induce its prospective usage by the nuclear power plant operators. Successful implementation of a miniaturized specimens testing technique will result, among others, in the optimization of surveillance material usage and savings in irradiated materials testing. The general project overview showing its structure, partners involved and main deliverables was published elsewhere. Here, we focus on some technical aspects being of the utmost importance in the initial stage of the project and which will have a crucial impact on its overall progress. The general consideration on the selection of the best available materials for testing are discussed on the examples of 73W weld, A533B LUS and the WWER-440 base metal 15Kh2MFAA. Moreover, the general scheme of the testing process, which is planned within the project, is briefly presented as well as the basic assumptions about the numerical modeling task aimed for rationalizing experimental findings

Preparation of chitosan/calcium phosphate based injectable system for guided bone regeneration and its properties investigation

The main objective of the work was to design and fabricate an injectable biomaterial with osteoconductive properties that can be used in dental applications in peri-implant therapy concerning guided bone regeneration. For that purpose, a self-setting biomaterial consisting of chitosan/tricalcium phosphate microparticles and sodium alginate was formulated. The obtained material was characterized regarding microsphere and formed agglomerates morphology and microstructure. Physical properties, relating to setting time and mechanical properties, were also investigated. Finally, in vivo response to implanted biomaterial was studied on a rat model and compared with commercially available alloplastic material. The results showed that designed injectable biomaterial fulfi lled main requirements for guided bone regeneration application