Papers by Keyword: Plasma Facing Materials

Abstract: The work investigates refractory metals (bulk W, W produced via plasma spraying, W-1% La₂O₃ and Mo) of interest as plasma facing materials in future nuclear fusion reactors. They have been irradiated by a single Nd:YAG laser pulse to simulate the effects of transient thermal loads of high energy occurring in a tokamak under operative conditions and then examined by SEM observations. In all the materials the laser pulse induces a crater in the central area of laser spot surrounded by a ridge due to movement of molten metal while in a more external area a network of cracks is observed. Diameter and depth of the crater, ablated volume and morphological features of the surrounding area exhibit differences depending on the specific metal, its physical and microstructural characteristics which affect vaporization, melting and heat propagation from the irradiated spot.

Abstract: Helium diffusion is a very critical factor for designing a plasma facing components of fusion reactor. Because it not only reduce the thermal conductivity but also degrade the surface morphology of tungsten based materials. In this numerical study the specimens of tungsten, vanadium and tungsten vanadium alloys have been simulated under thermo-diffusion conditions. The finite element commercial software Abaqus was used for simulation to obtain helium diffusion profile at temperature of 800 K for concentration of10²⁴number of atoms in tungsten and vanadium metals. Due to its relatively low helium diffusion coefficient, vanadium has shown better resistance against helium penetration as compared to tungsten. Subsequently the analytical effect of helium diffusion in tungsten, vanadium and different grades of tungsten vanadium alloys has been investigated. To study the distribution of vanadium in tungsten, tungsten vanadium alloys were fabricated by spark plasma sintering technique and its morphology has been analyzed by scanning electron microscopy.

Abstract: Molybdenum has many prominent properties, such as high melting point, good thermal properties, and low erosion rate and so on, which make it promising candidate materials for plasma facing materials in the next fusion reactor. In this paper, Molybdenum coatings were deposited onto the oxygen-free copper substrates by atmospheric plasma spraying. The spraying parameters had been carefully selected. Different interlayers were induced between the substrate and the coating. SEM and XRD were used to investigate the photographs and compositions of these coatings. The micro-hardness and bonding strength were also tested. Thermal behaviors of the coatings were evaluated by thermal shock tests. The coatings with interlayers showed better resistance of thermal shock but lower bonding strength compared to coatings that without interlayers.

Abstract: Tungsten has the highest sputtering threshold of all possible candidates and the highest melting point in metal. It will be the first candidate in selecting divertor materials. Great efforts are made on research and development on W/Cu functionally Graded Materials as high performance divertor material for next generation divertor-mounted Tokamak facilities in China recently. Four different processing technologies are used and compared and some results of evaluation of plasma-relevant characteristics of these materials are reported.

Abstract: To evaluate the performance of plasma facing materials (PFM) and components for future thermonuclear fusion devices under the expected operation conditions, an in-depth material characterization and extensive high heat flux simulation tests are performed routinely in electron beam test facilities. These experiments cover both, thermal fatigue tests with power densities up to approx. 20 MWm-2 and thermal shock loads with deposited energy densities of several MJm-2. In addition, irradiation experiments have been performed in material test reactors to investigate the neutron induced material degradation.