[en] For achieving efficient fusion energy production, the plasma-facing wall materials of the fusion reactor should ensure long time operation. In the next step fusion device, ITER, the first wall region facing the highest heat and particle load, i.e. the divertor area, will mainly consist of tiles based on tungsten. During the reactor operation, the tungsten material is slowly but inevitably saturated with tritium. Tritium is the relatively short-lived hydrogen isotope used in the fusion reaction. The amount of tritium retained in the wall materials should be minimized and its recycling back to the plasma must be unrestrained, otherwise it cannot be used for fueling the plasma. A very expensive and thus economically not viable solution is to replace the first walls quite often. A better solution is to heat the walls to temperatures where tritium is released. Unfortunately, the exact mechanisms of hydrogen release in tungsten are not known. In this thesis both experimental and computational methods have been used for studying the release and retention of hydrogen in tungsten. The experimental work consists of hydrogen implantations into pure polycrystalline tungsten, the determination of the hydrogen concentrations using ion beam analyses (IBA) and monitoring the out-diffused hydrogen gas with thermodesorption spectrometry (TDS) as the tungsten samples are heated at elevated temperatures. Combining IBA methods with TDS, the retained amount of hydrogen is obtained as well as the temperatures needed for the hydrogen release. With computational methods the hydrogen-defect interactions and implantation-induced irradiation damage can be examined at the atomic level. The method of multiscale modelling combines the results obtained from computational methodologies applicable at different length and time scales. Electron density functional theory calculations were used for determining the energetics of the elementary processes of hydrogen in tungsten, such as diffusivity and trapping to vacancies and surfaces. Results from the energetics of pure tungsten defects were used in the development of an classical bond-order potential for describing the tungsten defects to be used in molecular dynamics simulations. The developed potential was utilized in determination of the defect clustering and annihilation properties. These results were further employed in binary collision and rate theory calculations to determine the evolution of large defect clusters that trap hydrogen in the course of implantation. The computational results for the defect and trapped hydrogen concentrations were successfully compared with the experimental results. With the aforedescribed multiscale analysis the experimental results within this thesis and found in the literature were explained both quantitatively and qualitatively. (orig.)

[en] The First Research Coordination Meeting of the Coordinated Research Project on Atomic Data for Vapour Shielding in Fusion Devices was held at the IAEA Headquarters in Vienna on 13 – 15 March 2019. Nine experts representing nine research institutes globally (Australia, China, India, Italy, Netherlands, North Macedonia, Spain, Syria, USA) in the field of atomic collisional physics and vapour formation for magnetic confinement fusion devices met together with the IAEA staff. The participants were theorists and modellers of plasma and vapour particle collisional processes, experimentalists of spectral line properties, and vapour formation and spectral analyses. They described their research background, available experimental methodologies and theories applied in various computational tools. Open issues related to elemental particles formed during vapour evolution and the particle interaction processes were discussed and plans for coordinated research to be performed during the project were made. The proceedings of the meeting are summarized in this report. (author)

[en] A Consultancy Meeting was held on 26–27 September 2019 at IAEA Headquarters in Vienna to review data needs for hydrogen permeation in plasma-facing materials and components in fusion devices and to delimit the scope of a possible coordinated research project on that topic. The proceedings and discussions during the meeting are summarized here. (author)

[en] The Second Research Coordination Meeting of the Coordinated Research Project on Atomic Data for Vapour Shielding in Fusion Devices was held as a virtual meeting on 7 – 9 October 2020. Eight experts representing eight research institutes globally (Australia, China, India, Netherlands, Spain, Syria, USA) in the field of atomic collisional physics and vapour formation for magnetic confinement fusion devices met together with the IAEA staff. Participants were theorists and modellers of plasma and vapour particle collisional processes, experimentalists of spectral line properties, and vapour formation and spectral analyses. They described their research background, available experimental methodologies and theories applied in various computational tools as well as the results obtained. Open issues related to elemental particles formed during vapour evolution and the particle interaction processes were discussed and plans for coordinated research to be performed during the project were made. The proceedings of the meeting are summarized in this report. (author)

[en] The First Research Coordination Meeting of the Coordinated Research Project on Hydrogen Permeation in Fusion-relevant Materials was held on 23 – 27 November 2020 as a virtual meeting due to the global SARS-CoV2 pandemic. 22 Chief Scientific Investigators representing 16 Member States presented their Research Proposals and corresponding activities in the field of nuclear fusion fuel permeation through reactor materials and components. Meeting was attended in total by 51 participants, which comprised of project CSIs, meeting observers and IAEA staff. Open issues related to fusion fuel permeation, retention, solubility, trapping and diffusion were discussed and plans for coordinated research activities to be performed during the project were made. Proceedings of the meeting are summarized in this report. (author)

[en] The 23rd meeting of the Subcommittee on Atomic and Molecular Data of the International Fusion Research Council (IFRC) was held from 16 – 17 May 2022 as a hybrid event, with seven members attending in-person and four participants using video-conferencing software. This follows two shorter, virtual meetings in 2020 and 2021. Activities of the Atomic and Molecular Data Unit for the period June 2021 – May 2022 were reviewed and recommendations were made for continuing activities in 2022 – 2023 and for new projects in the 2024 – 2025 budget cycle. The proceedings, conclusions and recommendations of the Subcommittee meeting are briefly described in this report. (author)

[en] This report details the activities of the Atomic and Molecular Data Unit in the Nuclear Data Section of the IAEA during the period May 2018 – June 2021. The COVID-19 pandemic prohibited the usual biennial meeting of the International Fusion Research Council (IFRC) Subcommittee on Atomic and Molecular Data and an interim report covering the period May 2018 – April 2020 was distributed to committee members and discussed at an online meeting in May 2020. The present report incorporates the material from that interim report and describes the further Virtual Meeting of the IFRC Subcommittee which was held from 14 – 15 June 2021. (author)

[en] This report summarizes the proceedings of the IAEA Technical Meeting on “Technical Aspects of Atomic and Molecular Data Processing and Exchange” (25th Meeting of the A+M Data Centres Network) on 30 September – 2 October 2019. 13 participants representing 12 national data centres in 9 Member States attended the three-day meeting at IAEA Headquarters in Vienna. (author)

[en] The 21^st meeting of the Subcommittee on Atomic and Molecular Data of the International Fusion Research Council (IFRC) was held on 3-4 May 2018 at IAEA Headquarters in Vienna, Austria. Activities of the Atomic and Molecular Data Unit for the period 2016–2018 were reviewed and recommendations were made for continuing activities in 2018–2020 and for possible new projects in the 2020–2021 budget cycle. The proceedings, conclusions and recommendations of the Subcommittee meeting are briefly described in this report. (author)

[en] Properties of small vacancy clusters in tungsten were studied with first-principles calculations. The binding and formation energies of the vacancy clusters increase with the cluster size. Dynamic characteristics of a di-vacancy were specified between room temperature and 700 K with lattice kinetic Monte Carlo calculations, which were parametrised with the present first-principles results for the dissociation barriers. An Arrhenius fit for the di-vacancy diffusion yielded $D=0.04\exp <!--\; ???\; -->(-<!--\; ???\; -->1.65\mathrm{e}\mathrm{V}{\mathrm{k}\mathrm{T}}^{-<!--\; ???\; -->1})$ ${\mathrm{c}\mathrm{m}}^2{\mathrm{s}}^{-<!--\; ???\; -->1}$, and for the mean lifetime, $\mathrm{\tau <!--\; ??\; -->}=0.093\exp <!--\; ???\; -->(1.7\mathrm{e}\mathrm{V}){\mathrm{k}\mathrm{T}}^{-<!--\; ???\; -->1}$ ps. The di-vacancy system was found to be stable up to 500 K, due to the high energy needed for its dissociation. Having a carbon impurity was found to increase the tungsten di-vacancy binding energy. (paper)