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The article is devoted to identifying the concept of the meaning of life in the critical philosophy of A.I. Vvedensky, where special attention is paid to the methodological foundations and the historical and philosophical context. The formulation of the question about the meaning of life is one of the ultimate questions in philosophy, the answer to which makes it possible to determine the motives of human activity. In Vvedenskyʼs philosophy, the problem of goal-setting in life is revealed in the prism of a key research intention – the construction of a scientifically revised worldview based on the principles of criticism. As a result, the question of life and its purpose is reduced to the formulation of the question of the logical permissibility and boundaries of questioning. The article attempts to reconstruct the philosopherʼs reasoning and identify the most significant definitions, which include morality, mental life, and the purpose of life. The disclosure of the concept of life in Vvedenskyʼs philosophy invariably requires consideration of the context in which the development of the philosopherʼs ideas takes place. Based on a comprehensive analysis, it is concluded that the concept of life is an extension of the main goal of Vvedenskyʼs research – the disclosure of the conditions for the formation of a reliable worldview, focused on the principles of scientific knowledge in accordance with moral values. Another important consequence is the provision on the priority of morality in relation to scientific and philosophical knowledge. The foundations of morality, to which the meaning of life belongs, can be presented only in a special form of applicability of critical reason – critical faith. Thus, the question of the specifics of critical metaphysics and the importance of differentiation of types and forms of faith in the work of the Russian neo-Kantian are clarified.

Russian neo-Kantianismʼs status in the history of the development of Russian philosophy is an important, but poorly presented in scientific publications, issue is revealed in the article. With some exceptions, which are represented by a number of few, but informative and informative articles and a monograph, the problem remains without proper reception in the scientific discourse of our time. Russian neo-Kantianism, however, leaving aside the question of what is the phenomenon of Russian neo-Kantianism, it is impossible to productively and consistently actualize the content of Russian neo-Kantians and, moreover, to show their significance in the history of Russian philosophical and socio-humanitarian thought in general. Three key difficulties stand out: 1) the question of originality and the related theme of the independence of the philosophical direction (originality, independence and originality – differ from each other, but are united in their immanent orientation); 2) Russian neo-Kantianism, which in many ways seems to be the most difficult task for researchers engaged in historical and philosophical reconstruction; 3) the question remains ambiguous as to whether Russian neo-Kantianism is a continuation of the German tradition or whether it is a direction of Russian philosophy of thought. Russian neo-Kantianism, the three difficulties identified in the reception of the phenomenon of Russian neo-Kantianism taken as a whole, are consistently revealed in the content of the proposed article, supplemented by a brief overview of the most systemic positions of Russian philosophers, ranked among Russian neo-Kantianism. Overcoming the indicated difficulties, which undoubtedly affect the objective disclosure of the creativity of each representative of Russian neo-Kantianism or thinkers related to them, seems appropriate not only from the standpoint of the history of philosophy, but also for actualizing the heritage of philosophers in the conditions of modern socio-humanitarian pragmatics. Russian neo-Kantianism The author of the article suggests that one of the ways to overcome the ambiguity of the definition of Russian neo-Kantianism in the history of Russian thought may be, firstly, a more detailed consecration of the activities of Russian neo-Kantians in the historical and philosophical literature, and secondly, a comprehensive representation of this direction, including studies of individual personalities and their works. Despite the controversial and polemical nature of the task, its formulation is necessary for the objectivity of the meaning of Russian thought in the global context.

The thermomechanical behavior of titanium beryllide pebble beds was investigated experimentally at ambient temperature in helium. The pebbles consist of a mixture of TiBe12 and Ti2Be17 titanate beryllide phases and a small residual amount of Be phase, denominated as Be-7.7Ti. For purposes of comparison, experiments in air and helium atmosphere were also conducted with Be, Al2O3 and orthosilicate pebble beds. The pebble beds were compressed uniaxially up to 4.5 MPa; the effective thermal conductivity was measured using the hot wire technique. The stress-strain curves do not differ significantly for the different granular materials in contrast to the effective thermal conductivity k. Whereas for Be pebble beds k increases strongly with increasing stress (about 600 % for the uniaxial stress of 4 MPa), the increase is much smaller for the other granular materials (about 60 % for Be-7.7Ti at 4 MPa). The main reason for the large differences is the much lower thermal conductivity of the solid materials. Another influence exists because the other materials are mechanically harder resulting in smaller contact surfaces. As long as the thermal conductivity of other beryllide materials is significantly lower than that of Be, comparable results are expected as for Be-7.7Ti. It is argued that similar results are expected for single phase TiBe12 pebble beds. Because of the harder behavior compared to Be-7.7Ti pebbles, the effective thermal conductivity might be slightly smaller. Although the above reasonings suggest that a phase mixture can be used instead of the single phase TiBe12, this issue has to be investigated in more detail.

Beryllium is considered as a neutron multiplier in the self-sustained fuel cycles of future fusion reactors like ITER and DEMO, thus the retention of tritium generated in transmutation events in beryllium is crucial for the operational safety of such devices. As tritium readily interacts with microstructural defects produced under neutron irradiation, its retention depends on the evolution of the microstructure. Thus, physics-based models to understand and ultimately predict the tritium retention behavior have to comprise the generation and recombination dynamics of such defects. Therefore, the generation and recombination of the most simple defects, i.e. closely correlated as well as separated Frenkel pairs, as produced at the very end of collision cascade branches are considered in this work. To that end, DFT calculations are performed to determine threshold displacement energies, typical closely correlated pair configurations, the volume of spontaneous recombination, and recombination energy barriers. On the basis of these atomic-scale results, rate-based recovery models are derived to simulate electrical resistivity recovery experiments. The proposed models suggest that the principal recovery peak of beryllium is associated with the onset of intra-basal self-interstitial diffusion. This association is found to hold for the principal recovery peak of zirconium as well and it is thus concluded it is likely to generalize to many hcp metals with smaller than ideal c to a ratios.

Beryllium is a proposed neutron multiplier material in future fusion devices like ITER and DEMO. As such, numerous studies of neutron-irradiated beryllium specimen have shown the appearance of facetted bubbles with considerable tritium accumulation at their (0001) surfaces. In this work, we thus simulate hydrogen isotope desorption from (0001) beryllium surfaces using a multiscale modeling approach. We first establish that very fast surface diffusion of hydrogen adsorbed in FCC and HCP sites can be studied independently from the bulk by means of static DFT calculations, as diffusion into the bulk is inhibited by multiple diffusion processes with an accumulated energy barrier of almost 3 eV. Static saddle point searching dimer DFT calculations also reveal energy barriers for associative desorption in a range between 0.94 eV and 1.52 eV due to varying amounts of co-adsorbed hydrogen isotopes in the immediate vicinity of the desorbing pair. A simple rate equation-based desorption model incorporating these associative desorption processes is constructed and compared to thermal programmed desorption (TPD) spectra of earlier exposure experiments. It is found that the simple rate equation-based desorption model seemingly already explains some characteristic aspects of the TPD spectra like a peak shift to lower temperatures by almost 100 K and considerable broadening with increasing coverage. To asses the merit of this model, a refined model effectively taking the repulsion among adsorbed hydrogen isotopes into account by means of relevant correlations from kinetic Monte Carlo (KMC) simulations using a cluster expansion (CE) truncation is considered as well. It is found that the simple model’s reproduction of characteristic features of experimental spectra is the result of error cancellation from considering an incomplete set of desorption processes on one hand and neglecting repulsion among adsorbed hydrogen on the other hand. We conclude that the experimental TPD spectra can not be fully explained by either of the two models and further research particularly considering additional adatoms like oxygen are necessary to understand the TPD spectra of the corresponding experiments.

Neutron multiplier materials are essential for self-sufficient tritium production and are closing the fuel cycle of fusion reactors. Until now, a concept of pebble bed consisting of interchanging layers of beryllium and lithium ceramic pebbles was considered for the Helium-Cooled Pebble Bed (HCPB) tritium-breeding module of the first experimental fusion reactor ITER as well as for the next demonstration fusion reactor DEMO. However, this concept depends on the availability of large amounts of pure beryllium pebbles and is also limited by its material properties like for example the tritium accumulation under irradiation. The results of tritium retention and analytical microstructural studies of beryllium pebbles obtained within the framework of the HIDOBE irradiation campaign suggest that a significant fraction of generated tritium (up to 100% below 500°C) is trapped within helium bubbles. Being negligible in the ITER tritium-breeding module (TBM), the total accumulated tritium inventory imposes severe safety issues and exceeds acceptable limits for the DEMO blanket. Therefore, advanced neutron multiplier materials such as beryllides have to be well characterized for their applicability in the HCPB blanket of DEMO and beyond. The usage of an advanced material with lower volumetric swelling, lower tritium retention, increased irradiation and chemical resistance as well as with higher melting temperature allows to switch from the pebble bed concept to a solid hexagonal block-based one. For the fabrication of titanium beryllide samples both the semi-industrial fabrication route utilizing the hot extrusion of rods and the industrial approach using vacuum hot pressing of a Be-Ti powder mixture were explored. In this contribution, we discuss reasons for the transition from pure beryllium to beryllides, respective changes of the HCPB blanket design and a successful demonstration of the feasibility of a beryllide block fabrication by an industrial method.

The article defines the meaning of the phenomenological approach to the analysis of the concept of intersubjectivity in the context of social and philosophical problems of the balance of the Self and the Other. The discourse is based on the correlation of phenomenological orientation and communicative action in determining the mechanisms of identity of the Self in relation to the Other in the inseparability of social reality. A sequential analysis of prerequisites and research approaches aimed at testing the problem of intersubjectivity is carried out. The focus is placed on social phenomenological research of A. Schutz and the theory of communicative action of J. Habermas, which are aimed at understanding the correlation between the peculiarities of human existence, his life-world and the area of social relations or the inevitability of establishing overindividual patterns. Relevance of the research lies in elaborating the issue of establishing intersubjectivity under the fundamental non-identity of the subjects of communication and their predetermined attitudes. The article concludes by outlining the feasibility of expanding the rational predetermination of the subject-subjective structure of communicative action with the research area of social phenomenology.

According to the recently proposed changes of the HCPB design concept of tritium breeding blanket for the DEMO fusion reactor, massive Be12Ti blocks are considered to be used for neutron multiplication. The paper compares two possible fabrication routes of solid beryllide blocks: combination of hot extrusion with arc melting or with hot isostatic pressing (HIP). Be–Ti composite rods produced by powder extrusion were chosen as a starting material. After arc melting, the ingot had cellular microstructure revealing mixture of Be12Ti and Be10Ti phases with considerable porosity. The powder metallurgy route, including extrusion and HIP, allows to achieve 98.6% of theoretical density and fine-grained Be12Ti microstructure with small amount of residual Be phase. EBSD analysis together with TEM showed that titanium beryllide has a grain size of 0.3–2.5 μm. It was observed that fine BeO particles are distributed along the grain boundaries and can pin them. Titanium beryllide after HIP has high microhardness of 1420 HV and fracture toughness of about 2.4 MPa m1/2 comparable with that of many ceramics. The advantages of Be12Ti blocks manufacturing using extrusion and HIP are discussed.

The paper reviews the current status of development and qualification of the HCPB TBM’s functional materials, namely, Li-ceramic breeder and Be multiplier materials. The main functional and performance requirements for both functional materials are overviewed. The main results and outcomes of the post-irradiation examinations (PIE) of Li-ceramic breeder and Be/beryllides materials irradiated in HIDOBE and HICU irradiation campaigns are presented aiming at determination of the materials’ performance, properties and characteristics under neutron irradiation, like e.g. morphology and microstructure, tritium retention/release characteristics, mechanical properties. Fabrication of the advanced ceramic breeder material, containing lithium orthosilicate with addition of lithium metatitanate phase in order to improve its mechanical properties, is described. Results of characterization of this advanced ceramic breeder in terms of mechanical properties, porosity, morphology and effective thermal conductivity of a pebble bed are overviewed. In addition, results of characterization of the reference 1 mm Be pebbles produced by Rotation Electrode Process are presented in terms of their microstructure, tritium release characteristics and interaction with air and steam. A necessity to realize in the future a new irradiation experiment for the functional materials, LIBERTI experiment, is discussed in the conclusions.

Strengthening of the ODS steels by Y2O3 precipitates permits to increase their operation temperature and radiation resistance, which is important in construction materials for future fusion and advanced fission reactors. Both size and spatial distribution of oxide particles significantly affect mechanical properties and radiation resistance of ODS steels. Addition of the Ti species (present also as a natural impurity atoms in iron lattice) in the particles of Y2O3 powder before their mechanical alloying leads to the formation of YTiO3, Y2TiO5, and Y2Ti2O7 nanoparticles in ODS steels. Modelling of these nanoparticle formation needs detailed knowledge of the energetic interactions between ions. We have performed detailed first principles calculations of the interactions between two Y and O atoms, two Ti and O atoms as well as between Y, Ti, and O atoms which will be used in further kinetic Monte Carlo modelling of the nanoparticle formation.

The effect of hydrogen concentration on principal hexagonal close-packed beryllium surfaces (basal, prismatic type I and II, pyramidal type I and II) at 0 K was studied with the help of ab initio methods. The configurations with critical hydrogen coverage were revealed. Relaxation of outermost atomic layers at critical coverage drastically differs from that found for clean beryllium surfaces. The presence of hydrogen atoms significantly changes the energy of all studied beryllium surfaces except for prismatic type II plane. Influence of hydrogen concentration on equilibrium shape of hydrogen covered voids was investigated by means of construction of Wulff polyhedra. In addition we generalized Gibbs-Wulff approach for accounting of different hydrogen coverages at crystallographic non-equivalent surfaces and temperature effect. The results of the construction were compared with classical Gibbs-Wulff approach as well as the available experimental data on ion or neutron irradiation at elevated temperatures.

Transmission electron microscopy was used to study the effect of heavy-ion irradiation on the structure and the phase state of three oxide dispersion strengthened (ODS) steels: ODS Eurofer, ODS 13.5Cr, and ODS 13.5Cr–0.3Ti (wt %). Samples were irradiated with iron and titanium ions to fluences of 1015 and ~3 × 1015 cm–2 at 300, 573, and 773 K. The study of the region of maximum radiation damage shows that irradiation increases the number density of oxide particles in all samples. The fraction of fine inclusions increases in the particle size distribution. This effect is most pronounced in the ODS 13.5Cr steel irradiated with titanium ions at 300 K to a fluence of 3 × 1015 cm–2. It is demonstrated that oxide inclusions in ODS 13.5Cr–0.3Ti and ODS 13.5Cr steels are more stable upon irradiation at 573 and 773 K than upon irradiation at 300 K.

Beryllium selected as a neutron multiplier material for the tritium breeding blanket of fusion reactor should withstand high doses of fast neutron irradiation. The damage produced by irradiation is usually evaluated assuming that the number of atomic displacements to the threshold displacement energy, Ed, which is considered as an intrinsic material parameter. In this work the value of Ed for hcp beryllium is estimated simultaneously from classical and first-principles molecular dynamics simulations. Quite similar quantitative pictures of defect production are observed in both simulation types, though the predicted displacement threshold values seem to be approximately two times higher in the first-principles approach. We expect that, after more detailed first-principles investigations, this approach can be used for scaling the damage prediction predictions by classical molecular dynamics, opening a way for more consistent calculations of displacement damage in materials.

The helium-cooled pebble bed (HCPB) blanket is one of the two concepts proposed as a driver blanket for the European Union Demonstration Fusion Power Reactor (EU DEMO). In contrast to past conceptual design studies, in the frame of the current Power Plant Physics and Technology of the EUROfusion Consortium, the ongoing EU DEMO preconceptual design activities have adopted a holistic and integrated (i.e., systems engineering) design approach. As a consequence of this new approach, many interfaces and requirements have been identified, some of them driving the design of the blankets. This paper shows the advancements in the HCPB breeding blanket and describes the lessons learned after implementing the new approach. This new set of requirements has led us to reconsider fundamental aspects of the HCPB blanket design, especially in the way of how the heat is extracted from the blanket. Among others, the requirement to achieve a mature balance of plant (BOP) system plays a central role as a key design driver and has forced us to reduce pressure drops in the breeding blanket. In this regard, the blanket has been redesigned, leading to an enhanced concept based on single-module segments with a hexagonal matrix of fuel-breeder pins. Both the fuel-breeder pins and the first wall (FW) are equipped with turbulence promoters (augmented wall roughness in the fuel-breeder pins and V-ribs in the FW), following a similar idea as in the past MAGNOX, Advanced Gas Reactor (AGR), and Gas Cooled Reactor (GCR) programs in fission. This has led to minimizing the pressure drops while maximizing the heat transfer. Also, the blanket outlet temperature has been extended to 520°C, following the same principle as in Generation IV’s GCRs of maximizing the temperature difference across the core to minimize the reactor mass flow rate and thus the circulating power. All these features have led to a remarkably low plant circulating power (80 to 90MW) and the required power per helium blower (5 to 6MW), which potentially solves the key long-standing problem of the BOP technology readiness level for an ≈2.4-GW(thermal) helium-cooled DEMO reactor.

Electron energy loss spectroscopy (EELS) was applied to detect and analyze quantitatively helium (He) and tritium (3H) enclosed inside bubbles in irradiated beryllium. Both gases were formed in beryllium under neutron irradiation as a consequence of neutron-induced transmutation reactions. They were detected for the first time as pronounced peaks at 13.0 eV for 3H and 22.4 eV for He in EELS spectra collected from flat hexagonal bubbles. An adhesion of 3H or formation of thin beryllium hydride layers on the internal basal surfaces was observed. The number densities of both gases were estimated using electron scattering cross-section and intensities obtained from EELS spectra. The number density values estimated for various bubbles fluctuate from 4 to 15 at/nm3 for He and from 4 to 10 molecules/nm3 for 3H2. Lower gas number density was measured inside large bubbles. The observed higher density of tritium at inner walls of bubbles seems to confirm very recent ab initio calculations of the interaction of hydrogen isotopes with beryllium surfaces.

Beryllium and Be12Ti are considered as neutron multiplier materials in various tritium breeding blanket designs for future fusion reactors. Tritium and helium are formed due to neutron-induced nuclear transmutation and accumulated in beryllium-based materials. As a β-radioactive isotope, tritium represents additional safety concern with respect to sudden release during operation or hindering consequent recycling. Therefore, detailed study of its accumulation and release is indispensable. In particular, it is important to reveal which process controls tritium release: binding of tritium with traps or diffusion out of material bulk. Ab initio calculations of solution energies at all non-equivalent hydrogen interstitial sites confirm easier dissolution of tritium in Be12Ti in comparison with pure beryllium. The 17 considered diffusion barriers between adjacent hydrogen interstitial sites are calculated using a dimer method instead of a computationally more expensive nudged elastic band approach. Three possible diffusion paths in Be12Ti were revealed: two of them along the c-axis and another one along the a- and b-axes. Considering calculated hydrogen diffusion barriers in Be12Ti, one can conclude that at low hydrogen concentrations and low temperatures, diffusion occurs preferentially along the c-axis. The rate limiting diffusion barriers in Be12Ti are found to be in the range of 0.4–0.5 eV, which are comparable to 0.42 eV in pure beryllium suggesting that tritium diffusion in both materials proceeds at comparable rates. Therefore, binding of tritium atoms with vacancies and other lattice imperfections are expected to play a crucial role in tritium retention.

Advanced reduced activation ferritic/martensitic steels and oxide dispersion-strengthened steels exhibit significant radiation embrittlement under low temperature neutron irradiation. In this study we focused on atom probe tomography (APT) of Eurofer97 and ODS Eurofer steels irradiated with neutrons and heavy ions at low temperatures. Previous TEM studies revealed dislocation loops in the neutron-irradiated f\m steels. At the same time, our APT showed early stages of solid solution decomposition. High density (1024 m–3) of ∼3–5 nm clusters enriched in chromium, manganese, and silicon atoms were found in Eurofer 97 irradiated in BOR-60 reactor to 32 dpa at 332°C. In this steel irradiated with Fe ions up to the dose of 24 dpa, pair correlation functions calculated using APT data showed the presence of Cr-enriched pre-phases. APT study of ODS Eurofer found a significant change in the nanocluster composition after neutron irradiation to 32 dpa at 330 °C and an increase in cluster number density. APT of ODS steels irradiated with Fe ions at low temperatures revealed similar changes in nanoclusters. These results suggest that irradiation-induced nucleation and evolution of very small precipitates may be the origin of low temperature radiation embrittlement of f\m steels.

Beryllium is proposed to be a neutron multiplier and plasma facing material in future fusion devices. Therefore, it is crucial to acquire an understanding of the microscopic mechanisms of tritium accumulation and release as a result of transmutation processes that Be undergoes under neutron irradiation. A multiscale simulation of ad- and desorption of hydrogen isotopes on the beryllium (0001) surface is developed. It consists of ab initio calculations of certain H adsorption configurations, a suitable cluster expansion approximating the energies of arbitrary configurations, and a kinetic Monte Carlo method for dynamic simulations of adsorption and desorption. The processes implemented in the kinetic Monte Carlo simulation are deduced from further ab initio calculations comprising both, static relaxation as well as molecular dynamics runs. The simulation is used to reproduce experimental data and the results are compared and discussed. Based on the observed results, proposals for a refined model are made.

The paper presents the results of a molecular dynamics simulation of cascade damage production in beryllium caused by self-ion recoils in the energy range of 0.5–3 keV. It is demonstrated that point defects are produced in Be preferentially in well-separated subcascades generated by secondary and higher order recoils. A linear dependence of the point defect number on the primary recoil energy is obtained with the slope that corresponds to formal atom displacement energy of ∼21 eV. Most of the damage is created as single defects and the relatively high part of created point defects (∼50%) survives the correlated recombination following the ballistic cascade stage and becomes freely-migrating.

Ab initio modelling of Y and O impurity atoms as well as VFe vacancies in the fcc-Fe lattice is performed in order to calculate the interactions between these defects, which are important for understanding of nanoparticles’ formation within the oxide dispersed strengthened steels. Large scale parallel calculations based on plane-wave method realised in VASP computer code show that VFe vacancies considerably influence the binding between the impurity atoms. In this study, we present the results of performed calculations providing the detailed information about the binding energies between the defects, the changes of their effective charges as well as displacements of the substitute atoms relatively the host atom positions. The energy barriers for the migration trajectories of impurity atoms have been also found by performing the large-scale calculations within the nudge elastic band method.

The local structure and lattice dynamics in cubic Y2O3were studied at the YK-edge by X-ray absorption spectroscopy in the temperature range from 300 to 1273 K. The temperature dependence of the extended X-ray absorption fine structure was successfully interpreted using classical molecular dynamics and a novel reverse Monte Carlo method, coupled with the evolutionary algorithm. The obtained results allowed the temperature dependence of the yttria atomic structure to be followed up to ∼6 Å and to validate two force-field models.

For the first time, the TiBe12 blocks have been manufactured by powder metallurgy using industrial equipment at the Ulba Metallurgical Plant. Such blocks will be used for neutron multiplication in the helium-cooled breeding blanket for the EU DEMO fusion reactor. The vacuum annealing of a cold-pressed composite of Be and Ti powders at 600–1275 °C approved the conditions for TiBe12 synthesis. After hot isostatic pressing at 1150 °C, a single-phase TiBe12 structure was formed, but the sample fragmented into several pieces. These beryllide pieces were used to manufacture TiBe12 powder. Vacuum hot pressing of the obtained powder resulted in a solid titanium beryllide workpieces of O150 mm × 170 mm. Electrical discharge machining and waterjet cutting were used to machine the external and internal surfaces in accordance with the design requirements. The obtained block has a density of 98.3 % of the theoretical density of TiBe12. Microstructural analysis revealed a bimodal grain size distribution with grains of 5–10 μm and 20–40 μm. Electrical conductivity and thermal expansion coefficient of TiBe12 are similar to other beryllides. To mimic the pulsed operating conditions in DEMO, a sample of titanium beryllide was rapidly heated to 900 °C and cooled with a rate of 12 K/s. After 50 cycles, the sample had no cracks or severe surface oxidation.

The present paper studies the evolving Be microstructure after high-dose neutron irradiation at 660 K, 753 K and 873 K up to 34 dpa and generation of 5524 appm He and 596 appm 3H. At all three temperatures gas bubbles were observed whereby their average size is increasing with the temperature. In addition denuded zones (DZ) formed near grain boundaries. Their width increased with irradiation temperature and was found to be narrower for grains with a random orientation compared to those with a close to basal orientation with respect to the grain boundary. Furthermore, perceptions containing elements such as Al, Cr, Fe, Mg, Si as well as U were found inside single grains, often attached to dislocation lines, and in the vicinity of grain boundaries, mainly at 660 K and 753 K.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Hot isostatic pressing (HIP) has been proposed for manufacturing large hexagonal TiBe12 blocks for neutron multiplication in the new reference design of the DEMO blanket. This paper investigates the effect of HIP at 800 and 900 °C on the microstructure and the properties of extruded Be-Ti composites with the main aim of optimizing HIP parameters. Be-Ti composites produced by powder extrusion at 650 °C consist exclusively of Be and Ti phases. During HIP, they interact forming titanium beryllides with a volume fraction of 70–79%. These beryllides have a very high microhardness of 1130–1680 HV. X-ray diffraction showed that the main beryllide phase is TiBe12. After HIP at 900 °C, it has a very fine-grained microstructure with a mean grain size of 190 nm. Auger electron spectroscopy revealed that the TiBe2 beryllide forms a thin layer surrounding the remaining Ti phase. Ti2Be17 can be found at the prior titanium phase locations in the form of small particles. The titanium and beryllium phase do not dissolve completely during the used HIP process. In addition, the beryllium phase exhibited a higher porosity after HIP. This results in densities as low as 94.4% and 95.9% of the theoretical density of TiBe12 after heat treatment at 800 °C and 900 °C, respectively. Differential scanning calorimetry showed that beryllides are mainly synthesized in the temperature range of 670–740 °C, which can be monitored by the observation of a heat release. To accomplish diffusion processes in the Be-Ti composite, HIP should be carried out at temperatures exceeding 900 °C. Heating rates should be less than 10 K/min to avoid excessive overheating.

The present paper studies the gas bubble distribution in triple beam irradiated (Fe+, He+, H+) EUROFER97, ODS-EUROFER and a 13%Cr ODS-steel. All materials were irradiated at 350 °C, 450 °C and 550 °C up to a displacement damage of 40 dpa, a helium concentration of ∼12.5 appm He/dpa and a final hydrogen content of ∼50 appm H/dpa, respectively. While most of the bubbles, with diameters up to 107 nm, in the 13%Cr ODS-steel were found to be attached to the ODS-particles at all temperatures, they showed a homogenous distribution in EUROFER97 at 350 °C. At 450 °C however, many small clusters with mainly facetted cavities were observed, whereas at 550 °C most of the bubbles were localized at microstructural sinks like grain boundaries, dislocations or precipitates. The largest bubble found in EUROFER97 had a diameter of ∼19 nm. In both materials, the largest bubbles were located in the area where, according to SRIM calculations, superposition of maximum displacement damage and highest gas concentration occurred. This observation suggests that synergetic effects between helium and hydrogen strongly influenced the bubble growth but not the bubble nucleation. Despite exhaustive analysis, no bubbles could be identified in any of the three ODS-EUROFER lamellae. Apparently, bubbles have formed only below the TEM resolution limit or the helium was evenly distributed within the grains or at the particle-matrix interface. In addition, electron energy loss spectroscopy (EELS) was used to confirm the existence of helium and hydrogen inside closed gas bubbles.

Oxide-Dispersion Strengthened (ODS) steels with Y2O3 nanoparticles are promising structural materials for fision and future fusion reactors. A large number of experimental as well as theoretical studies provided valuable information on the ODS particle formation process. However, some important details of this process still remain unexplained. We present the results of ab initio VASP calculations of the initial steps of the ODS particle formation. At these steps Y solute atoms are stabilized in the Fe lattice by vacancies, which create a basis for the future growth of Y2O3-particle. Interaction of multiple vacancies and solution Y and O atoms has been studied in various combinations and configurations.

In the framework of the EUROfusion’s Power Plant Physics and Technology, the working package breeding blanket (BB) aims at investigating four different BB concepts for an EU demonstration fusion reactor (DEMO). One of these concepts is the helium-cooled pebble bed (HCPB) BB, which is based on the use of pebble beds of lithiated ternary compounds and Be or beryllides as tritium breeder and multiplier materials, respectively, EUROFER97 as structural steel and He as coolant. This paper aims at giving an overview of the EU HCPB BB Research and Development (R&D) being developed at KIT, in collaboration with Wigner-RCP, BUTE-INT, and CIEMAT. The paper gives an outline of the HCPB BB design evolution, state-of-the-art basic functionalities, requirements and performances, and the associated R&D activities in the areas of design, functional materials, manufacturing, and testing. In addition, attention is given also to the activities dedicated to the development of heat transfer augmentation techniques for the first wall and the corresponding testing. Due to their nature as design drivers, a brief overview in the R&D of key HCPB interfacing areas is given as well, namely, the tritium extraction and recovery system, the primary heat transfer and power conversion systems, and safety topics, as well as some specific activities regarding the integration of in-vessel systems through the BB. As concluding remarks, an outline of the standing challenges and future R&D plans is summarized.

The paper applies ab initio methods for investigation of possible origin of the easier tritium release from titanium beryllide Be12Ti as compared with that of beryllium. Both materials are considered as neutron multiplier materials in some design concepts of tritium breeding blanket of future fusion reactor. The only stable tetragonal crystal structure of Be12Ti was studied in this work. Hydrogen solution energy in all non-equivalent interstitial positions of Be12Ti was found to be lower than that for beryllium suggesting easier dissolution of hydrogen atoms in Be12Ti. Maximal binding energy of hydrogen atoms in vacancy linearly decreases with the number of hydrogen atoms both in beryllium and Be12Ti. The highest hydrogen binding in a vacancy is 0.4 eV lower in Be12Ti, predicting easier release of hydrogen from beryllide with respect to beryllium. No formation of chemical bonds between hydrogen atoms inside both beryllium and Be12Ti vacancies was observed.

Static ab initio calculations were performed for five principal hexagonal close-packed beryllium surfaces: basal, prismatic (type I and II) and pyramidal (type I and II). The basal plane was found to be the most energetically favorable, while the energies of the prismatic (type I) and pyramidal (type I) planes were slightly higher followed by the type II planes. Beryllium is known to show extreme interlayer distance relaxation near the surface. Up to five outermost atomic layers were involved in surface relaxation. The presence of hydrogen on the beryllium surfaces led to a noticeable reduction of the surface energy.

Beryllium is the reference neutron multiplier material in the Helium Cooled Pebble Bed (HCPB) breeding blanket of fusion power plants. Significant tritium inventory accumulated in beryllium as a result of neutron-induced transmutations could become a safety issue for the operation of such blankets as well as for the nuclear waste utilization. To provide a related materials database, a neutron irradiation campaign of beryllium pebbles with diameters of 0.5 and 1 mm at 686–1006 K, the HIDOBE-01 experiment, has been performed in the HFR in Petten, the Netherlands, producing up to 3020 appm helium and 298 appm tritium. Thermal desorption tests of irradiated unconstrained and constrained beryllium pebbles were performed in a purge gas flow using a quadrupole mass-spectrometer (QMS) and an ionization chamber. Compared to unconstrained pebbles, constrained beryllium pebbles have an enhanced tritium release at all temperatures investigated. Small elongated sub-grains formed under irradiation in the constrained pebbles promote formation of numerous channels for facilitated tritium release.

In fusion reactors, hydrogen isotopes, i.e., tritium and deuterium, will be used as fuel producing energetic neutrons and helium atoms. While deuterium is a stable nuclide frequent in nature, tritium is beta-radioactive. Its half-life time is about 12 years, requiring constant renewal via tritium generation in nuclear reactions. Neutrons produced in fusion reactions should therefore be effectively multiplied. To this end, beryllium is planned to be used in the form of pebble beds in the blanket of a fusion reactor. Unfortunately, helium and tritium are created under neutron irradiation and accumulated in the beryllium matrix, resulting in the formation of gas bubbles, swelling, and, under some circumstances, even in the loss of pebbles’ structural integrity. In this work, beryllium reflector fragments irradiated for 15 years in the research reactor BR2 (SCK-CEN, Mol, Belgium) at temperatures below 120 °C and containing about 2 at.% helium was vacuum annealed at two temperatures and various annealing times. Gas-induced porosity developed after annealing was investigated using synchrotron X-ray micro-tomography. This technique enables a non-destructive and quantitative analysis of the 3D morphology of the gas-induced porosity providing important insights into the kinetics of the gas bubble growth. Using advanced post-processing of the micro-tomography data it has been possible to determine the volume fraction of gas bubbles and their size distribution, and reveal the formation of 3D bubble clusters. The importance of the data obtained for tritium release and relation between microstructure and tritium retention properties are discussed.

The influence of titanium alloying (Ti content of 0, 0.2, 0.3, and 0.4 wt %) on the nanostructure of yttrium oxide (Y2O3) dispersion strengthened steel with a composition Fe-13.5% Cr-2% W-0.3% Y2O3 is investigated. The spatial distribution of chemical elements is analyzed in the investigated volumes. The matrix composition and average size and concentration of nanoscale clusters are compared for different samples. It is shown that the average nanocluster size (∼3 nm) is almost unchanged with increasing Ti concentration, while the cluster concentration grows from ∼1 × 1023 m−3 (for Ti-free steel) to ∼1.5 × 1024 m−3 (for 0.4 wt % Ti alloy).

The nanostructure of the ODS Eurofer steel (9% CrWVTa + 0.5% Y2O3) has been studied after irradiation by iron ions to a damaging dose of 32 dpa. This steel in the initial state is characterized by the presence of a significant amount (∼1024 m−3) of nanosized (2–4 nm) clusters containing atoms of V, Y, O, and N. An analysis of the distribution of various chemical elements in the tested volumes has revealed variations in the composition of the matrix and of the nanosized clusters during irradiation. The data obtained were compared with the results for the ODS Eurofer steel subjected to reactor irradiation to a dose of 32 dpa.

Beryllium pebbles with diameters of 1 mm are considered to be perspective material for the use as neutron multiplier in tritium breeding modules of fusion reactors. Up to now, the design of helium-cooled breeding blanket in ITER project foresees the use of 1 mm beryllium pebbles fabricated by NGK Insulators Ltd., Japan. It is notable that beryllium pebbles from Russian Federation and USA are also available and the possibility of their large-scale fabrication is under study. Presented work is dedicated to a study of characteristics of microstructure and parameters of tritium release of beryllium pebbles produced by Bochvar Institute, Russian Federation, and Materion Corporation, USA.

Beryllium is a promising functional material for several breeder system concepts to be tested within the experimental fusion reactor ITER and, later, implemented in the first commercial demonstrati...