Flow channel inserts (FCIs) are the key elements in the high-temperature dual-coolant lead-lithium blanket, since in this concept the flowing PbLi reaches temperatures near 700 °C and FCIs should provide the necessary thermal and electrical insulations to assure a safe blanket performance. In this paper, the use of a SiCsandwich material for FCIs consisting of a porous SiC core covered by a dense chemical vapor deposition-SiC layer is studied. A fabrication procedure for porous SiC is proposed and the resulting materials are characterized in terms of thermal and electrical conductivities (the latter before and after being subjected to ionizing radiation) and flexural strength. SiC materials with a wide range of porosities are produced; in addition, preliminary results using an alternative route based on the gel-casting technique are also presented, including the fabrication of hollow samples to be part of future lab-scale FCI prototypes. Finally, to study the corrosion resistance of the material in hot PbLi, corrosion tests under static PbLi at 700 °C and under flowing PbLi at ∼10 cm/s and 550 °C, with and without a 1.8-2T magnetic field, were performed to materials coated with a 200-400-µm-thick dense SiC layer, obtaining promising results.

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One of the major bottlenecks in the development of the breeding blanket of the DEMO fusion reactor is the suppression of tritium permeation through structural steels as well as their protection against dissolution-corrosion by interaction with high temperature heavy liquid metals. Reduction of tritium permeation and corrosion of structural steels are crucial issues in order to enhance reactor safety and avoid operational implications. As a solution to these two daunting challenges, we developed multifunctional alumina coatings capable to tackle, at the same time, tritium permeation and Pb-Li corrosion. The coatings are deposited by pulsed laser deposition and are essentially amorphous, with nanocrystalline inclusions. By optimizing the deposition process, we provide experimental evidence that PLD-grown alumina yields a permeation reduction factor for hydrogen and deuterium well above 10 4 , even after electron irradiation, and a suitable protection against corrosion by the Pb-16Li eutectic. Given these results, the multifunctional, PLD-grown alumina coatings stand out as a viable solution to some of the long-lasting issues related to fusion technologies.

h i g h l i g h t s • A wide range of porous SiC materials with different properties were produced. • The produced 50% porous SiC has k ≈ 5 W/m K at 700 • C and ≈ 3 10 −5 S/m at 550 • C. • The produced 50% porous SiC has a flexural strength in the range 50-80 MPa. • A 200 m dense CVD-SiC coating offers reliable protection against static PbLi corrosion. a b s t r a c t Flow Channel Inserts (FCIs) are key elements in a DCLL blanket concept for DEMO, since they provide the required thermal insulation between the He cooled structural steel and the hot liquid PbLi flowing at ≈700 • C, and the necessary electrical insulation to minimize MHD effects. In this work a SiC-based sandwich material is proposed for FCIs, consisting of a porous SiC core covered by a dense CVD-SiC layer. A method to produce the porous SiC core is presented, based on combining a starting mixture of SiC powder with a spherical carbonaceous sacrificial phase, which is removed after sintering by oxidation, in such a way that a microstructure of spherical pores is achieved. Following this technique, a porous SiC material with low thermal and electrical conductivities, but enough mechanical strength was produced. Samples were covered by a 200 m thick CVD-SiC coating to form a SiC-sandwich material. Finally, corrosion tests under static PbLi were performed, showing that such a dense layer offers a reliable protection against static PbLi corrosion.