Search

International audience; ITER will use beryllium as a plasma-facing material in the main chamber, covering a total surface area of about 620 m. Given the importance of beryllium erosion and co-deposition for tritium retention in ITER, significant efforts have been made to understand the behaviour of beryllium under fusion-relevant conditions with high particle and heat loads. This paper provides a comprehensive report on the state of knowledge of beryllium behaviour under fusion-relevant conditions: the erosion mechanisms and their consequences, beryllium migration in JET, fuel retention and dust generation. The paper reviews basic laboratory studies, advanced computer simulations and experience from laboratory plasma experiments in linear simulators of plasma–wall interactions and in controlled fusion devices using beryllium plasma-facing components. A critical assessment of analytical methods and simulation codes used in beryllium studies is given. The overall objective is to review the existing set of data with a broad literature survey and to identify gaps and research needs to broaden the database for ITER.

Dust generated in JET with the ITER-like wall (ILW) was collected from the divertor by vacuum cleaning and examined with ion and electron beam methods. From totally 1 g retrieved after the third ILW campaign (2015–2016) a number of specimens were prepared using sticky (adhesive) carbon tabs. The aim was to determine the distribution and amounts of constituents: from deuterium (D) to W with particular emphasis on the concentration ratio of D to other species. Two classes of particles containing deuterium were identified: (i) rich in Be and (ii) low-Z matrix without Be, that show large C concentrations with some O contribution and minor contributions from heavier elements. The D content in Be-based particles has been at the level not exceeding ≈2 at %, whereas in the C-rich particles, both in small (10–100 µm) and large conglomerates (>100 µm), the D contribution at the level of about 15 to 20 at % has been detected. W-rich particles are often accompanied by Ni, Cr and Fe and occasionally with Mo. The results clearly indicate that fuel retention in the ILW dust is predominantly associated with residual C, approximately 10–20 times greater retention was found in C-rich objects than in metal-based particles.

Accumulation of dust on the equipment for remotely handled (RH) operations was studied in JET with the ITER-like wall (JET-ILW) during the shutdown period following the third ILW campaign. The topi ...

The paper presents application of pulse plasma sintering method (PPS), developed at the Faculty of the Materials Science and Engineering of Warsaw University of Technology. Unlike other electric-field assisted sintering methods, the PPS method employs pulse high-current electric discharges for heating and activating the material to be sintered. The phenomena, taking place during the high-current pulses, which heat the powder during the PPS treatment and activate the sintering process, are similar to those occurring in SPS technique. However, in PPS, thanks to much higher energy the pulse discharge, these phenomena run much more intensively. The aim of the present study was to fabricate by the PPS a joint between tungsten and Eurofer 97 steel. Because of the large difference in thermal expansion coefficients of the joined materials, stresses are induced at the joint interfaces. To reduce these stresses a thin interlayer was incorporated between the joined materials. Four different materials were tested. The experiments allowed to establish the optimal PPS sintering parameters. It was shown that the interlayers between W and Eurofer 97 steel fabricated at 1000 °C for 10 min were highly dense and no delamination at joint interfaces occurred. The results of the thermocycle tests proved a high strength of the joints produced by PPS.

Metal artworks are subjected to corrosion and oxidation processes due to reactive agents present in the air, water and in the ground that these objects have been in contact with for hundreds of years. This is the case for archaeological metals that are recovered from excavation sites, as well as artefacts exposed to polluted air. Stabilization of the conservation state of these objects needs precise diagnostics of the accrued surface layers and identification of original, historical materials before further protective treatments, including safe laser cleaning of unwanted layers. This paper presents analyses of the chemical composition and stratigraphy of corrosion products with the use of laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy. The discussion of the results is supported by material studies (SEM-EDS, XRF, ion-analyses). The tests were performed on several samples taken from original objects, including copper roofing from Wilanów Palace in Warsaw and Karol Poznański Palace in Łódź, bronze decorative figures from the Wilanów Palace gardens, and four archaeological examples of old jewellery (different copper alloys). Work has been performed as a part of the MATLAS project in the frames of EEA and Norway Grants (www.matlas.eu) and the results enable the comparison of the methodology and to elaborate the joint diagnostic procedures of the three project partner independent laboratories.

The work presents results of a broad TEXTOR dust survey in terms of its composition, structure, distribution and fuel content. The dust particles were collected after final shutdown of TEXTOR in De ...

Tracer techniques were used in the TEXTOR tokamak to determine high-Z metal migration and the deposition of species used for plasma edge cooling or wall conditioning under different types of operat ...

Generation of metal dust in the JET tokamak with the ITER-like wall (ILW) is a topic of vital interest to next-step fusion devices because of safety issues with plasma operation. Simultaneous Nuclear Reaction Analysis (NRA) and Particle-Induced X-ray Emission (PIXE) with a focused four MeV 3He microbeam was used to determine the composition of dust particles related to the JET operation with the ILW. The focus was on “Be-rich particles” collected from the deposition zone on the inner divertor tile. The particles found are composed of a mix of codeposited species up to 120 μm in size with a thickness of 30–40 μm. The main constituents are D from the fusion fuel, Be and W from the main plasma-facing components, and Ni and Cr from the Inconel grills of the antennas for auxiliary plasma heating. Elemental concentrations were estimated by iterative NRA-PIXE analysis. Two types of dust particles were found: (i) larger Be-rich particles with Be concentrations above 90 at% with a deuterium presence of up to 3.4 at% and containing Ni (1–3 at%), Cr (0.4–0.8 at%), W (0.2–0.9 at%), Fe (0.3–0.6 at%), and Cu and Ti in lower concentrations and (ii) small particles rich in Al and/or Si that were in some cases accompanied by other elements, such as Fe, Cu, or Ti or W and Mo.